Complete Package for Chemical Engineers, TICI Training, ACCE, University of Rajshahi.Introduction...

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INTRODUCTION TO PROCESS TECHNOLOGY AND PROCESSES CONTROL TECHNIQUES: This topic covers some terminologies which are generally used in any industrial or manufacturing establishment. Process may be found in activity ranging from individual or group in small or large establishment. The activity is normally executed in a sequence to attain desired product or goal.

PROCESS: A process is any operation or series of operations that causes a physical or chemical change in a substance or a mixture of substances. The material that enters is input or feed to the process and that which leaves is called the output or product. In process, entering feed materials are modified or processes into final materials.

PROCESS UNIT: A process unit is an apparatus/equipment in which one of the operations that constitute a process is carried out. Each process unit has associated with it a set of input and output process streams, which consists of the materials that enter and leave the unit. Reactor, heat exchanger, distillation column etc. are examples of process units.

UNIT OPERATION & UNIT PROCESS: In the process industries, raw materials are changed or processes into useful products. We can break the total process into a series of separate and distinct unit steps called unit operations. The unit steps may be physical, chemical or mechanical. Of these unit operations and unit processes are given below:

Unit operations: Crushing, grinding, drying, distillation, evaporation, conduction etc.

Unit processes: Oxidation, reduction, hydrogenation, polymerization, nitration etc. Although it is important to distinguish between unit operations and unit processes, they are, however, interrelated since no unit process can be carried out in chemical factory without the application of one or more unit operations.

PROCESS TECHNOLOGY: Technology may be defined as the systematic studies of techniques for making and doing things. Process technology is the systematic studies of process and process operation to produce products and the knowledge of physico-chemical properties of the materials. To become an efficient process technologist one should have the clear knowledge about the following:

Process manuals Process diagrams Operating manuals Operation of a process Designing individual process unit and modifying a process design Amounts, compositions and conditions of the materials involved in the process Physical and chemical properties and laws that govern the behavior of process materials Controlling the process variables Calculating material and energy balance Cost involvement Safety awareness and loss prevention

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PROCESS INDUSTRY: The process industry includes all establishments where changes in the nature of materials obtained by physical, chemical or biochemical means in the course of one or more production stages. Example of process industries are:

Chemical industry Metallurgical industry Ceramic industry Food industry etc.

PROCESS PLANT LOCATION AND SITE SELECTION: The location of the plant can have a crucial effect on the profitability of a project and the scope future expansion. Many factors must be considered before selecting a suitable site. The principal factors to be considered are as follows:

Location, with respect to the marketing area. Raw material supply. Transport facilities. Availability of labor. Availability of utilities: water, fuel, power. Availability of suitable land. Environmental impact and effluent disposal. Local community considerations. Climate. Political and strategic considerations.

AUXILIARY MATERIALS OF A PROCESS: Auxiliaries are those substances that are indispensable for carrying out the operations. The known auxiliaries are cooling water, steam, process water, fuel, catalysts, chemicals, electricity etc.

PROCESS VARIABLES AND RATE OF PROCESS: The physical or chemical quantity such as pressure, temperature, concentration, composition etc., the variation of which, will indicate a desirable or undesirable change in the operation of a manufacturing process are called process variables. Unit processes operate at a particular rate and this is influenced by many factors but rate of process is equal to the driving force divided by the resistance. The driving force is that which causes the process to continue e.g. temperature, concentration differences, and pressure differences. Resistance is anything, which opposes the driving force e.g. rust, or scale inside pipes, thickness of stationary liquid film, layers near pipe walls etc. These factors are extremely important to the choice of chemical plant units and the way they are linked up to form the overall process.

STAGES OF CHEMICAL MANUFACTURING PROCESS:

Raw material storage Feed preparation Reaction Product separation Purification Product storage

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PROCESS CLASSIFICATION: Chemical processes may be classified as

Batch

Continuous Semibatch

BATCH PROCESS: Batch processes are designed to operate intermittently. Some or all the process units are being frequently shut down and started up. The feed is charged into the system at the beginning of the process, and the products are removed all at once sometime later. No mass crosses the system boundaries between the time the feed is charged and the time the product is removed. Batch processing is commonly used when relatively small quantities of a product are to be produced on any single occasion.

CONTINUOUS PROCESS: Continuous processes involve the continuous addition of raw material and removal of finished products without stopping the process; these usually involve considerable instrumentation and automatic control. Some down time will be allowed for maintenance and for some processes catalyst regeneration. Continuous processing is better suited to large production rates.

SEMI-BATCH PROCESS: This is any process that is neither batch nor continuous.

PROCESS SYMBLES AND PROCESS DRAWING:

PROCESS: A Process is any operation or series of operations that causes a physical or chemical change in a substance or a mixture of substances. The material that enters a process is referred to as the input or feed to the process and that which leaves is called the output or product. A process unit is an apparatus / equipment in which one of the operations that constitute a process is carried out. Each process unit has associated with it a set of input and output process streams, which consists of the materials that enter and leave the unit. Reactor, heat exchanger, distillation column etc. are examples of process units. In the process industries, raw materials are changed or processed into useful products. We can break the total process into a series of separate and distinct steps called unit operations e.g. distillation, evaporation, absorption etc.

PROCESS SYMBOLS: Process symbols may be defined as the graphical, alphabetical or mathematical representation of instrument, vessel, lines etc. of the process industry. A set of symbols have been adopted by many international organizations. Such as

ISA-The Instrument Society of America BIS-The British Standard Institution JIS-Japanese Industrial Standard ISO-International Standard Organization ANSI-American National Standard Institute DIN-Deutsches Institute for Norming (German)

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To make the drawing of the process more uniform and meaningful, these self-explanatory symbols are used. For identification of instrument, three letters are generally used as under.

1st letter (process variable) 2nd letter(type or function) 3rd letter(additional function)

Level-L Primary Element-E Alarm-A

Conductivity-C Indicating-I Control-C

Density-D Test Point-P Switching-S

Flow-F Recording-R Transmitting-T

Hand Actuated-H Switching-S

Pressure-P Well-W

Speed-S

Temperature-T

DIFFERENT IDENTIFICATION CODES/NUMBERS: Process equipment coding (equipment identification number): Process equipment is coded with one capital letter followed by four digits.

One capital letter: Function/ Name of the equipment

Four digits -1st two digits indicates Section Numbers -2nd two digits indicate Sequence Numbers of Equipment (equipment number). Alphabetical Code Letters: C = Columns D = Dryers E = Electric Motors F = Furnace H = Heat Exchanger

P = Pump Example: V0102 Explanation:

V = Vessel 01 = Section Number 02 = Equipment Number

Pipe line coding: Pipe line is coded with five capital letters followed by seven digits.

1st two digits: Number of process section

Next 4/5 Alphabets /Characters/ Capital letters: -1st two characters = Fluid type or, Name of the fluid flow line. -Others characters = Material of construction of pipe

Next two digits: Sequence no. of pipe

Next one capital: Diameter of the pipe

Finally three digitals: Unit of the Diameter of pipe(D=Diameter) Example: 01WLBA10D100 Explanation:

02 = Section Number SL = Water Line BA = Brass Alloy 10 = Pipe No. D = Diameter of the pipe 100 = Diameter (100 mm)

Codes for fittings: Fittings are coded by two capital letters and two digits.

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1st letter: Type of fittings (e.g. valve, steam trap etc.)

2nd letter: Type of each sort of fitting

Last two digits: No. of fittings Example: ST15 (Steam Trap VALVE) Explanation:

S = Steam T = Trap 15 = Valve No. (Suction No. can be known from pipe line because Steam Trap is set on the

steam pipe line) Instrument identification number (tag number):

1st letter: Process variable (e.g. level, temperature etc.)

2nd letter: Function of the process variable

3rd letter: Additional function

Last digits: Number of the main instrument Example: LIC-326 Explanation:

L = Level I = Indicating C = Controller 326 = Instrument Number

SYMBOLES FOR PIPELINES:

SYMBOLS FOR VALVES & FITTINGS:

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Quick acting Valve

Oblic Valve

Drain Line

SYMBOLS FOR EQUIPMENTS:

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SYMBOLS FOR INSTRUMENTS:

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HEAT TRANSFER AND HEAT EXCHANGER – INDUSTRIAL HEAT TRANSFER EQUIPMENT & THEIR APPLICATION: In process industry, we have to maintain different temperature and pressure at different places of the process line. The temperature of the process fluid has to control at higher or lower level as per requirement. To maintain the desired temperature of the process fluid, different heat transfer equipments are commonly used. The most common heat transfer equipments (apparatus) used in chemical process industries are:

Heat Exchanger

Heater

Vaporizer

Cooler

Chiller

Condenser, Partial & Final condenser

Steam generator

Superheater

Boilers

Waste heat boiler The equipment in which heat transfer takes place from one substance to another is generally called a heat exchanger.

Figure: Heat exchanger

In practice, heat is often exchanged by means of an auxiliary e.g., Steam, Water (cooling & hot), Dowtherm, Oil, Salt solutions. Dowtherm is a clear liquid, consisting of a mixture of organic compounds; Dowtherm is often used as an auxiliary. The advantages of dowtherm over water are considerable since dowtherm has a much higher boiling point. Both the application and removal of heat can be achieved by means of auxiliaries.

To remove heat: 1. Water 2. Air 3. Low B.P. liquid

To apply heat 1. Water (hot) or condensed 2. Steam

Water: When water is used as cooling agent (auxiliary) then it is called cooling water.

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Air: Air coolers are especially used when water does not possess the necessary degree of purity, or where this is necessary for environmental reasons ` Low-Boiling-Point Liquids: lf the end-temperature of the substance to be cooled, is to be lower than that of the available auxiliary, artificial means must be applied e.g.,

Freon 12 (𝐶𝐶𝑙2𝐹2)

Sulfur dioxide (𝑆𝑂2)

Methyl chloride (𝐶𝐻3𝐶𝑙)

Ammonia (𝑁𝐻3) To facilitate process control it is sometimes useful to insert a. second auxiliary between the evaporating liquid and the substance to be cooled. Use is frequently made for this purpose of ethylene glycol (anti-freeze) or a salt solution.

HEAT EXCHANGER EQUIPMENT: CHILLER: Cools a fluid to a temperature below that obtainable. In that case is used as a coolant. It uses a refrigerant such as Ammonia or Freon. CONDENSER: Condensed a vapor or mixture of vapors, either alone or in presence of a non-condensable gas.

Figure: Condenser

When hear is applied by means of an auxiliary. We generally speak of a HEATER or a heater which vaporizes part of the liquid.

Figure: Heater

If the substance to the heater vaporizes through the application of heat we refer to a VAPORISER.

Figure: Vaporizer

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Apparatus for revolving heat by means of an auxiliary is usually called a COOLER. Or, cools liquids or gases by means of water e.g. Oil cooler, interstate cooler, Gland C/W cooler.

Figure: Cooler

CONDENSERS are coolers in which the substance to be cooled condenses as a result of such cooling. It sometimes happens that the heat removed from a high temp. Fluid is used for converting water into steam. A steam boiler is then included in the process, in which feed water is converted into steam. This kind of steam boiler is called a RESIDUAL HEAT BOILER or WASTE HEATBOILER. Example: Ammonia Condenser, Gas condenser.

A. Partial condenser: Condensed Vapor at a high enough to provide a temperature difference sufficient to preheat a cold stream of process fluid. This saves heat and eliminates the need for providing a separate pre-heater.

B. Final Condenser: Condenses the vapor to a final storage temperature of approximately 100°𝐹. It uses water cooling which means the transferred heat is lost from the process.

STEAM GENERATOR: Generates steam for use elsewhere in the plant by using the available high level heat in tar, gas or heavy oil. Example: Auxiliary boiler, Medium pressure boiler. SUPER HEATER: Heats a vapor above the saturation temperature. Example: Steam super heater with boiler, Super heater with 𝐶𝑂2 booster compressor etc. WASTE HEAT BOILER: Produces Steam, similar to steam generator, except that the heating medium is a hot gas. Example: Waste heat boiler in Ammonia Plant.

MECHANICAL ARRANGEMENTS & OPERATIONAL FEATURE OF INDUSTRIAL HEAT EXCHANGER: According to the working features, the heat exchangers are mainly divided into three groups:

1) Recuperative 2) Regenerative 3) Mixed type

The term “Recuperative” applies to the heat transferring method (continuous flow) and “Regenerative" to the heat charging and discharging method (periodic flow).

RECUPERATIVE HEAT EXCHANGER: In this type of heat exchanger variety of cold and hot fluids flow simultaneously through the heat exchanger and the heat is transferred through a wall separating the fluids. All shell-tube heat exchangers are examples of this type.

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REGENERATIVE HEAT EXCHANGER: A regenerative heat exchanger is an apparatus in which one and the same heating surface is alternately exposed to the hot and cold fluids. The heat carried by the hot fluid is taken away and accumulated in the wall of the apparatus, and is then transferred to the cold fluid flowing through the heat exchanger. It is a heat charging and discharging process. Air pre-heater of primary reformer is a regenerative heat exchanger.

MIXED TYPE HEAT EXCHANGER: In heat transfer equipment of direct contact type, the process of heat transfer occurs through direct contact and the mixing of hot and cold fluids. In this case, heat transfer is accompanied by mass transfer. The cooling towers, evaporative condensers in thermal power plants and humidifiers in air-conditioning system are common examples of mixed type or direct contact heat exchangers. According to their construction heat exchangers are of different types. Some of the most common forms with their parts are discussed below:

1) Shell 2) Tribe 3) Tie Rod 4) Spacer 5) Tube sheet 6) Shell cover 7) Baffle plate

SHELL: Types of shell depend on the flow fluid in shell side.

a) One pass shell b) Two pass shell c) Split flow shell d) Double split flow shell e) Divided flow shell

TUBE: It is of two types:

a) Straight tube b) U-tube

TIE ROD: Tie road is used to keep baffle plate. Generally one side of the tie rod is threaded and is held in the hole of tube sheet and another side is fixed with the nut. TUBE SHEET: Tube is covered by tube sheet to be welded. SHELL COVER: It is constructed by the both channel and cover. It is classified as follows:

a) Removable channel and cover b) Integral cover c) Integral with tube shell removable cover

BAFFLE PLATE: Baffle plate is allowed to permit the flow of fluid zig-zug in shell. It is of two types:

a) Longitudinal b) Cross

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PUMP TECHNOLOGY AND OPERATION:

A. CLASSIFICATION AND WORKING PRINCIPLE OF PUMPS: Pumping involves the movement of liquid (fluid) or solution, from a suction source to a discharge point. A pump is a machine, which converts mechanical energy to kinetic energy and potential energy. In another way, a machine that is driven from some external source, lifts or moves fluid from a lower level to higher level. Pumps are classified according to the way energy is imparted to the fluid. The basic methods are:

a) Volumetric Displacement b) Addition of Kinetic Energy and c) Use of Electro-magnetic force

The main classification of pumps is shown below: 1) Dynamic or Kinetic Pumps 2) Positive Displacement Pumps

DYNAMIC OR KINETIC PUMPS: 1. Centrifugal Pump: The term "Centrifugal Pump" is applied generally to all types of pumps with

an impeller having fixed blades housed in a suitable shaped casing, so that when the impeller rotates momentum is applied to liquid in the pump casing transposing it from the inlet to the outlet side. To achieve this it follows that the pump casing has to be full of liquid.

1.1. Axial flow: In axial flow centrifugal pumps, the rotor is a propeller. Fluid flows parallel to the axis of the shaft. Diffusion vanes are located in the discharge port of the pump to eliminate the rotational velocity of the fluid imparted by the propeller.

1.2. Mixed flow, Radial flow: A radial flow pump is commonly referred to as a straight. Diffuser pump: In diffuser pump, after the fluid has left the impeller; it is passed through a ring of fixed vanes that diffuses the liquid, providing a more controlled flow and a more efficient conversion of velocity head into pressure head.

1.3. Peripheral or Regenerative or Turbine pump: The impeller has vanes on both sides of the rim that rotates in a ring like channel in the pump’s casing. The fluid does not discharge freely from the tip of the impeller but is recirculated back to a lower point on the impeller diameter. This recirculation or regeneration increases the head developed. Because of close clearances, regenerative pumps cannot be used to pump liquids containing solid particles. They can pump liquids containing vapors and gases, and in fact they can pump gases provided that they contain sufficient liquid to seal the close clearances.

2. Special Effect Pumps: 2.1. Jet (educator) 2.2. Gas lift 2.3. Hydraulic ram 2.4. Electromagnetic

POSITIVE DISPLACEMENT PUMPS: Positive displacement pumps, which lift a given volume for each cycle of operation, can be divided into two main classes:

(a) Reciprocating and (b) Rotary

3. Reciprocating Pump: A typical reciprocating pump has a ram, plunger, piston or other cylindrical element working backwards and forwards within a cylinder or pump barrel. This motion is usually derived from a crank revolving at uniform speed, and a connecting rod. Automatic valves control the flow of liquids into the cylinder and out again.

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3.1. Piston, Plunger pump: The basic Piston Pump is very simple having just two valves and one stuffing box. In this type of pump, a reciprocating piston is driven back and forth by a rotating mechanism. This piston pump uses suction to raise water into the chamber. The lower valve can be placed below water level. The piston must be within about 25 feet of the water level, but the water can then be raised quite high.

3.2. Diaphragm pump: The action of a diaphragm pump is similar to that of a piston pump in which the piston is replaced by a pulsating flexible diaphragm. This overcomes the disadvantages of having piston packing in contact with the fluid being pumped. As in the case of piston pumps, fluid enters and leaves the pump through check valves. The diaphragm may be actuated mechanically by a piston directly attached to the diaphragm or by a fluid such as compressed air or oil.

4. Rotary Pump: Single Rotor:

4.1. Vane pump: Sliding Vane Pump: In this type of pump, a rotor is mounted off—center. Rectangular vanes are positioned at regular intervals around curved surface of the rotor. Each vane is free to move in a slot. The centrifugal force from the rotation throws the vanes outward to form a seal against the fixed casing. As the rotor revolves, a partial vacuum is created at the suction side of the pump, drawing in fluid. The fluid is then transferred to the other side of the pump in the space between the rotor and the fixed casing. At the discharge side, the available volume is decreased, and the resultant increase in pressure forces the fluid into the outlet line; the pumping rate can be varied by changing the degree of concentricity of the rotor. Vane pumps do not need inlet and outlet check valves; they can pump liquids containing vapors or gases but are not suitable for pumping liquids containing solid particles. Vane pumps deliver a constant output with negligible pulsation for a given rotor speed. They are robust, and their vanes, easily replaced, are self-compensating for wear. Pumping capacity is not affected until the vanes are badly worn.

4.2. Screw pump: In a screw pump, a helical screw rotor revolves in a fixed casing that is shaped so that cavities formed at the intake move toward the discharge as the screw rotates. As a cavity forms, a partial vacuum is created, which draws fluid into the pump. This fluid is then transferred to the other side of the pump inside the progressing cavity. The shape of the fixed casing is such that at the discharge end of the pump the cavity closes, generating an increase in pressure that force the fluid into the outlet line.

Multiple Rotors: 4.3. Gear: In gear pump, one of the gears is driven and the other runs free. A partial vacuum,

created by the unmeshing of the rotating gears, draws fluids into the pump. This fluid is then transferred to the other side of the pump between the rotating gear teeth and the fixed casing. As the rotating gears mesh together, they generate an increase in pressure that forces the fluid into the outlet line. A gear pump can discharge fluid in either direction, depending on the direction of the gear rotation.

4.4. Lobe: Lobe pumps resemble external gear pumps, but have rotors with two, three or four lobes in place of gears; the two rotors are both driven. Lobe pumps have a more pulsating output than external gear pumps and are less subject to wear. Lobe-type compressors are also used to pump gases; each rotor has two lobes.

B. CONSTRUCTIONAL PARTS OF PUMP AND THEIR FUNCTION: 1. Major Components of Centrifugal Pump

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Figure: Components of centrifugal pump

A centrifugal pump has two main components:

I. A stationary component comprised of a casing, casing cover, and bearings. II. A rotating component comprised of an impeller and a shaft

The general components, both stationary and rotary, are depicted in figure. The main components are discussed in brief below. STATIONARY COMPONENTS: Casing: Casings are generally of two types: volute and circular. The impellers are fitted inside the casings.

i. Volute casings build a higher head. ii. Circular casings circular casings are used for low head and high capacity.

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Casing wear pings act as the seal between the casing and the impeller. Seal Chamber and Stuffing Box: Seal chamber and Stuffing box both refer to a chamber, either integral with and separate from the pump case housing that form the region between the shaft and casing where sealing media are installed. When the sealing is achieved by means of a mechanical seal, the chamber is commonly referred to as a Seal Chamber. When the sealing is achieved by means of packing, the chamber is referred to as a Stuffing Box. Bearing housing: The bearing housing encloses the bearings mounted on the shaft. The bearings keep the shaft or rotor incorrect alignment with the stationary parts under the action of radial and transverse loads. ROTATING COMPONENTS: Impeller: The impeller is the main rotating part that provides the centrifugal acceleration to the fluid. They are often classified in many ways.

Based on major direction of flow in reference to the axis of rotation o Radial flow o Axial flow o Mixed flow

Based on suction type o Single-suction: Liquid inlet on one side. o Double-suction: Liquid inlet to the impeller symmetrically from both sides.

Based on mechanical construction o Closed: Shrouds or side-wall enclosing the vanes. o Open: No shrouds or wall to enclose the vanes. o Semi-open or vortex type A

Wear rings: Wear ring provides an easily and economically renewable leakage joint between the impeller and the casing. Clearance becomes too large the pump efficiency will be lowered causing heat and vibration problems. Shaft: The basic purpose of a centrifugal pump shaft is to transmit the torque encountered when starting and during operation while supporting the impeller and other rotating parts. Shaft Sleeve: Pump shafts are usually protected from erosion, corrosion, and wear at the seal chambers, leakage joints, internal bearings, and in the waterways by renewable sleeves. Coupling: Couplings can compensate for axial growth of the shaft and transmit torque to the impeller. Shaft couplings can be broadly classified into two groups: rigid and flexible. AUXILIARY COMPONENTS:

Seal flushing, cooling, quenching systems Seal drains and vents Bearing lubrication, cooling systems Seal chamber or stuffing box cooling, heating systems Pump pedestal-cooling systems etc.

2. Major Components of Reciprocating Pump

Reciprocating pump comprises two major segments: a) Liquid end b) Power end

Liquid and segment consists of the following parts: Cylinder: It is the major pressure retaining part and usually contains and supports all other liquid end components. Piston or Plunger: A piston is a cylindrical disc, mounted on a rod (called piston rod) and normally contains a sealing ring such as piston ring or packing. The function of the piston is to transmit the force that develops the pressure to the liquid.

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Piston ring: Piston rings serve as seal and minimize leakage from the high-pressure side of the piston to the low-pressure side. Valves: The valves of a reciprocating pump are simply check valves. They are opened by liquid differential pressure only. The function of valves is to control the flow of the liquid. Stuffing box: The stuffing box of a pump consists of a box, lower and upper bushing, packing and gland. The function of stuffing box is to seal around the reciprocating piston rod or plunger. Manifold: These are the chambers where liquid is dispersed or collected for uniform distribution (flow) before or after passing through the cylinder. ' Liner: To absorb wear from the sealing element, most of the cylinders are equipped with replaceable liner. This is a cylindrical sleeve, which is fastened to the cylinder by an interference fit or by bolting. The liner is often made of iron or bronze. Power and segment consists of the following parts: Crankshaft: It drives the connecting rods and absorbs the loads from the rod and driver. It is made of ductile iron, cast steel and forged steel. Connecting rod: The connecting rod transmits the power from the crankshaft to the crosshead. The crankshaft moves in pure rotary motion, the crosshead in pure reciprocating motion. The connecting rod is the link between the two, with one end in pure rotary motion, and the other in pure reciprocating motion. Connecting rod is made of iron, steel and aluminum. Crosshead and Pin: The crosshead pin is driven by the connecting rod, transmitting the force to the crosshead. On some pumps, the pin is locked in the crosshead. On others, the pin is locked in the connecting rod and rotates in the crosshead. The crosshead absorbs the force from the crosshead pin and transmits it to the extension. In addition to absorbing the total axial force being transmitted from the connecting rod to the liquid end, the crosshead must also absorb the side load from the connecting rod. Crosshead is made of iron, steel and aluminum. Crosshead Guide: Crosshead guide is the surface on which the crosshead reciprocates. Bearing: Bearing supports the crankshaft and absorbs all of the loads imposed on the crankshaft. Bearings used in reciprocating pumps are of sleeve type, roller type or in smaller pumps, ball type.

3. Major Components of Rotary Pump Rotary pump consists of the following main constructional parts: Casing or Housing: The casing is that part of the pump, which surrounds the boundaries of the pumping chamber. The pumping chamber is generally defined as all the space inside the pump that may contain the pumped fluid while the pump is operating. Suction and Discharge Ports: Fluids enter the pumping chamber through one or more suction ports and leave through one or more discharge ports, all of which usually include arrangements for liquid-tight and airtight connections to external fluid system. Rotor: Rotor is the specific part of the rotating assembly, which rotates in the pumping chamber. Rotors may be given specific names in specific types of rotary pumps; they may be called gears, lobes, screws etc. Shaft: Most rotary pumps have driven shaft, which accepts driving torque from a power source. Seal: Two types of seals are generally used in rotary pump, i.e. Static and moving seal. Static seals provide a liquid-tight and airtight seal between demountable stationary parts of the pumping chamber, and moving seals are used at pumping chamber boundary locations through which moving elements extend, usually shaft. Bearing: Bearing supports the rotor and absorbs all the loads imposed on the rotor.

C. PUMP CHARACTERISTICS AND CHARACTERISTIC CURVES:

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A centrifugal pump can give a flow rate from zero to maximum value during operation at any speed. Each pump motor combination can deliver specified maximum quantity of energy and therefore, can carry out a specific quantity of work. The key performance parameters of centrifugal pumps are capacity, head, BHP (Brake Horsepower), BEP (Best efficiency point) etc. The pump curves provide the operating window within which these parameters can be varied for satisfactory pump operation. CAPACITY: Capacity means the flow rate with which liquid is moved or pushed by the pump to the desired point in the process. It is commonly measured in either Gallons per minute (𝑔𝑝𝑚) or Cubic meters per hour (𝑚3/ℎ𝑟). The capacity usually changes with the changes in operation of the process. The capacitydepends on a number of factors like:

Process liquid characteristics i.e. density, viscosity

Size of the pump and its inlet and outlet sections

Impeller size

Impeller rotational speed (RPM)

Size and shape of cavities between the varies

Pump suction and discharge temperature and pressure conditions As liquids are essentially incompressible, the-capacity is directly related with the velocity of flow in the suction pipe. This relationship is as follows:

𝑄 = 449 × 𝑉 × 𝐴 Where,

𝑄 =Capacity in gallons per minute (𝑔𝑝𝑚) 𝑉 =Velocity of fluid in 𝑓𝑡/𝑠𝑒𝑐 𝐴 = Area of pipe in 𝑓𝑡2

HEAD AND PRESSURE: Pressure can be measured in terms of the height of the column of liquid exerting that pressure on the horizontal liquid surface at the bottom of the column. It is independent of the cross—section of the column and thus can be expressed as a single linear quantity e.g. meters or feet. PRESSURE TO HEAD CONVERSION FORMULA: The static head corresponding to any specific pressure is dependent upon the weight of the liquid according to the following formula:

Head(𝑓𝑡) =Pressure(𝑝𝑠𝑖) × 2.31

Specific gravity

The various head terms are discussed below: STATIC HEAD: The height above a given point of a column or body of water at rest (the weight of the water causing pressure) is termed Static head. With respect to pump operation, the head is measured from the center point of the pump outlet connection. STATIC LIFT: The height to which atmospheric pressure causes a column of water to rise above the source of supply to restore equilibrium is termed Static lift. The weight of the column of water (1 𝑠𝑞. 𝑖𝑛. ofcross-sectional area) required to restore equilibrium is equal to the pressure exerted by the atmosphere (𝑙𝑏. 𝑝𝑒𝑟 𝑠𝑞. 𝑖𝑛.). The maximum height to which water at standard temperature (62° 𝐹) can be lifted is determined by the barometric pressure. Water rises to a height of 34.1 𝑓𝑡 whenthe barometric pressure is 30 𝑖𝑛𝑐ℎ𝑒𝑠. DYNAMIC HEAD: M The dynamic head of water is an equivalent or virtual head of water in motion which represents the resultant pressure necessary to force the water from a given point to a given height and to

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overcome all frictional resistance. The dynamic head causing flow of liquid is divided into three parts:

o Velocity head o Entry head and o Friction head

Velocity Head: The height through which a body must fall in a vacuum to acquire the velocity with which the water flows into the pipe is equal to (𝑣2/2𝑔), in which 𝑣is velocity in 𝑓𝑡 per second and 2𝑔 = 64.32. Entry head: This is the head required to overcome the frictional resistance to entrance to the pipe. With a sharp-edge entrance, the entry head is equal to approximately one-half the velocity head; with a smooth, rounded entrance, the entry head is negligible. Friction Head: Friction head is the equivalent head, expressed in feet of the liquid pumped, that is necessary to overcome the friction losses caused by the flow of liquid through the piping, including all the fittings. The friction head varies with:

1) The quantity of flow 2) The size, type and condition of the piping and fittings, and 3) The character of the liquid pumped

DYNAMIC LIFT: The dynamic lift of water is an equivalent or virtual lift of water in motion which represents the resultant pressure necessary to lift the water from a given point to a given height and to overcome all frictional resistance. The practical limit of actual lift in pump operation ranges from 20 to 25 𝑓𝑒𝑒𝑡. When the water is warm, the height to which it can be lifted decreases, due to increased vapor pressure. TOTAL COLUMN: The term Total Column means head plus lift. The Static total column is the static lift plus the static head. The height or distance from the level of supply to the level in the tank, in feet, is termed the Static Total Column. It is the column that is causing pressure resulting from its weight. The dynamic total column is the dynamic lift plus the dynamic head, or the equivalent total column of water in motion. It represents the pressure resulting from the static total column plus the resistance to flow caused by friction. Friction of water in pipes results in loss of pressure and reduced volume of water per minute delivered. NET POSITIVE SUCTION HEAD (NPSH): To avoid Cavitation, the pressure at the pump inlet must exceed the vapor pressure of the liquid at the corresponding temperature by a certain value, called the positive suction head or NPSH. The Net Positive Suction Head or NPSH is the total head at the suction flange of the pump less the vapor pressure converted to fluid column height of the liquid expressed in feet or meter. Cavitation: An important factor in satisfactory operation of a pump is the avoidance of cavitation, both for the sake of good efficiency and for the prevention of impeller damage. The term cavitation refers to conditions within the pump where, owing to a local pressure drop below the vapor pressure of the liquid at the corresponding temperature, cavities filled with water vapors are formed; these cavities collapse as soon as the vapor bubbles reach the region of high pressure on their way through the pump. POWER AND EFFICIENCY: Break Horse power: The work performed by a pump is a function of the total head and the weight of the liquid pumped in a given time period. Pump input or Brake Horse Power (BHP) is the actual horsepower delivered to the pump shaft. Pump output or Hydraulic or Water Horse Power (WHP) is the liquid horse power delivered by the pump.

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These two terms are defined by the following formulas:

𝐵𝐻𝑃 =𝑄 × 𝐻𝑇 × Sp. Gr.

3960 × Efficiency

Where, 𝑄 = Capacity in gallons per minute (𝑔𝑝𝑚) 𝐻𝑇 = Total Differential Head, 𝑓𝑡 Sp. Gr. = Specific Gravity of the liquid Efficiency = Pump efficiency, %

𝑊𝐻𝑃 =𝑄 × 𝐻𝑇 × Sp. Gr.

3960

The constant 3960 is obtained by dividing the number of foot-pounds for one horse power (33,000) by the weight of 1 𝑔𝑎𝑙𝑙𝑜𝑛 of water (8.33 𝑝𝑜𝑢𝑛𝑑). The brake horse power or input to the pump is greater than the hydraulic horse power or output due to the mechanical and hydraulic losses incurred in the pump. Therefore, the Pump Efficiency is the ratio of these two values.

Pump efficiency =𝑊𝐻𝑃

𝐵𝐻𝑃

INDUSTRIAL WATER TREATMENT: Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from raw water. The goal is to produce water fit for a specific purpose. Most water is purified for human consumption (drinking water) but water purification may also be designed for a variety of other purposes, including meeting the requirements of medical, pharmacology, chemical and industrial applications. In general the methods used include physical process such as filtration and sedimentation, biological processes such as slow sand filters or activated sludge, chemical process such as flocculation and chlorination and the use of electromagnetic radiation such as ultraviolet light. The purification process of water may reduce the concentration of particulate matter including suspended particles, parasites, bacteria, algae, viruses, fungi; and a range of dissolved and particulate material derived from the surfaces that water may have made contact with after falling as rain. Impurities in water: The major impurities in water are summarized as follows:

Ionic and dissolved Non-ionic and un-dissolved Gaseous

Cationic Anionic Calcium Magnesium Sodium Potassium Ammonium Iron Manganese

Bicarbonate Carbonate Sulfate Chloride Nitrate Phosphate Silica Organic matter

Turbidity, silt, mud, dirt and other suspended matter Color Organic matter Colloidal silica Microorganisms Bacteria Oil Corrosion product

Carbon dioxide Hydrogen sulfide Ammonia Methane Oxygen Chlorine

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The raw water treatment may consist of the following steps to remove impurities from raw water. These may be mechanical, chemical, biological or combination of these.

Screening

Pre-sedimentation

Clarification

Filtration

Disinfection SCREENING: In rivers or lakes where the water transports debris such as leaves, branches, logs, and similar objects, it is necessary to provide screening facilities before water is withdrawn for treatment. When substantial amount of debris are present, mechanically cleaned screens should be considered. Most water intakes include protective screens, or bar racks, those are not mechanically cleaned, and only remove the largest pieces of debris. Micro screens are also used as a pre-treatment process, to remove finer material such as filamentous algae. Screening media are generally stainless steel or polyester. Media opening can be as small as 1 𝑚𝑖𝑐𝑟𝑜𝑛 but are typically 20 to 30 𝑚𝑖𝑐𝑟𝑜𝑛𝑠. Micro screens typically are located at the treatment plant, and are used only when the water source is very turbid. PRE-SEDIMENTATION: Pre-sedimentation is a pretreatment process for control of silt load on subsequent treatment units. Pre-sedimentation is a unit process almost solely associated with river supplies and more specially, only for those river supplies that carry heavy silt loads. If pre-sedimentation is not provided, the heavy turbidities will require increased chemical doses. Pre-sedimentation basins should have hopper bottoms and/or be equipped with continuous mechanical sludge removal apparatus specially selected or designed to remove heavy silt or sand. CLARIFICATION: Coagulation: Coagulation is defined as the process that causes a reduction of repulsion forces between particles or the neutralization of the charges on particles. Multivalent cations (𝐴𝐿3+, 𝐹𝑒3+ etc.) when added to water exert a direct influence on the rigid layer, to decrease the zeta potential and this lead to effective coagulation. The coagulation takes place in the rapid mixing basin in clarifier. Coagulation reagents: The most common coagulants are alum (𝐴𝑙2(𝑆𝑂4)3 ∙ 18𝐻2𝑂) and iron salt (𝐹𝑒𝑆𝑂4 ∙ 7𝐻2𝑂). When alum is dissolved in water, hydrolysis takes place, aluminum hydroxide and sulfuric acid is produced, as a result, 𝑝𝐻 of water decreases.

𝐴𝑙2(𝑆𝑂4)3 + 6𝐻2𝑂 = 2𝐴𝑙(𝑂𝐻)3 + 3𝐻2𝑆𝑂4 (Insoluble)

If natural alkalinity is present, then 𝐴𝑙2(𝑆𝑂4)3 + 3𝐶𝑎(𝐻𝐶𝑂3)2 = 3𝐶𝑎𝑆𝑂4 + 2𝐴𝑙(𝑂𝐻)3 + 6𝐶𝑂2

(Insoluble) If natural alkalinity is insufficient, then lime or soda ash can be added.

𝐴𝑙2(𝑆𝑂4)3 + 3𝐶𝑎(𝑂𝐻)2 = 3𝐶𝑎𝑆𝑂4 + 2𝐴𝑙(𝑂𝐻)3 (Insoluble)

𝐴𝑙2(𝑆𝑂4)3 + 3𝑁𝑎2𝐶𝑂3 + 3𝐻2𝑂 = 2𝐴𝑙(𝑂𝐻)3 + 3𝑁𝑎2𝑆𝑂4 + 3𝐶𝑂2 (Insoluble)

If iron vitriol (𝐹𝑒𝑆𝑂4 ∙ 7𝐻2𝑂) is added for coagulation, 𝐹𝑒𝑆𝑂4 + 𝐶𝑎(𝐻𝐶𝑂3)2 = 𝐶𝑎𝑆𝑂4 + 𝐹𝑒(𝐻𝐶𝑂3)2 𝐹𝑒(𝐻𝐶𝑂3)2 = 𝐹𝑒(𝑂𝐻)2 + 𝐶𝑂2 4𝐹𝑒(𝑂𝐻)2 + 𝑂2 + 2𝐻2𝑂 = 4𝐹𝑒(𝑂𝐻)3

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(Insoluble) The 𝑝𝐻 must be controlled to established optimum conditions for coagulation. Flocculation: Flocculation is defined as the aggregation of destabilized particles into larger elements. Flocculation (transport) step requires more time for development of large flocs. Ideally flocculation colloidal particles should settle rapidly and be strong enough to resist shearing forces. Often the flocs do not posses these characteristics and a coagulant aid is then added to improve floc properties. Coagulant aids that have been used include clays, activated silica and polymers. The polymers help to promote large floc particles by a bridging mechanism, after the colloidal particles have been destabilized by a coagulant such as alum. Flocculation takes place in flocculation basin in clarifier. Sedimentation: Sedimentation takes place in settling or sedimentation basin in clarifier. A major portion of the solids can be removed from the water by gravity settling following coagulation and flocculation. FILTRATION: Filtration accomplishes polishing of water and is required for almost every water. Filtration follows sedimentation it is provided. Water moves through a tank that contains sand and other types of media. Pine solid that did not settle out in a sedimentation basin will be entrapped in filter. There also will be significant removal of bacteria in a filter but not enough to provide safe water. Larger microorganisms such as protozoan are completely removed in a properly operated filter. There are two filtration alternatives in common use. Slow sand filters have only sand media. They are cleaned b scraping off the top layer of media on a periodic basis as filter clogs. Rapid filters are sand filters or multimedia filters that have anthracite, sand, and possibly other media in them. Loading rates of rapid filters are much higher than slow sand filters. Rapid filters are cleaned by back washing. Flow through rapid and slow sand filters is due to gravity. WATER DISINFECTION PROCESS: Disinfection is the destruction of pathogenic microorganisms in water. Pathogens are defined as any type of microorganisms capable of producing disease. Disinfection of water may be done by the application of the following:

1. Physical treatment by application of heat. 2. Chemical oxidants, such as chlorine, bromine, iodine, ozone, chlorine dioxide. 3. Different chlorine compounds such as bleaching powder, hypochlorite.

CHLORINATION: When chlorine is dissolved in water at temperatures between 49℉ and 212℉, it reacts to form hypochlorous and hydrochloric acids:

𝐶𝑙2 + 𝑂2 = 𝐻𝑂𝐶𝑙 + 𝐻+ + 𝐶𝑙− The hypochlorous acid ionizes or dissociates practically instantaneously into hydrogen and hypochlorite ions:

𝐻𝑂𝐶𝑙 = 𝐻+ + 𝑂𝐶𝑙− These reactions represent the basis for the use of chlorine in most sanitary application. The dissociation of 𝐻𝑂𝐶𝑙 is also temperature and 𝑝𝐻 dependent. At 𝑝𝐻 5.0 and below, almost all chlorine is in the form of 𝐻𝑂𝐶𝑙. At 𝑝𝐻 10.0 and above, almost all chlorine is in the forms of 𝑂𝐶𝑙−. 𝐻𝑂𝐶𝑙 is very strong disinfectant, about 80~200 times as strong as 𝑂𝐶𝑙−, therefore, 𝑝𝐻 exerts a strong influence on the effectiveness of chlorine. 𝐻𝑂𝐶𝑙 reacts with the enzymes essential to the metabolic process of living cells.

ADVANCED WATER TREATMENT: DEMINERALIZATION: The very term demineralization refers to the removal of minerals from water. But this process involves removal or reduction of both minerals and acid part remaining in water. The method of

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removing or reducing the ionic impurities present in water is known as demineralization. Sometimes it is also known as deionization. In this process ion exchange resins are used which are insoluble material carrying exchangeable cation and anions. Resins are mostly made by first forming an insoluble, infusible polymer into which active acidic or basic groups are introduced by suitable chemical reactions. RESIN: The carriers of the exchangeable cations and anions are called cation and anion resin or exchanger. The ionic groups that are generally associated with the cations are the nuclear sulfonic −𝑆𝑂3𝐻, the methylene sulfonic −𝐶𝐻2𝑆𝑂3𝐻, carboxylic −𝐶𝑂𝑂𝐻, the phenolic −𝑂𝐻. With anions the ionic groups are the quaternary ammonium −𝑁𝑅3, the primary amine −𝑁𝑅2, the secondary amine −𝑁𝐻𝑅 and the tertiary amine −𝑁𝑅2. Of the resins there are mainly strong acid cations with sulfonic group, weak acid cation with carboxylic, strong base anion with quaternary ammonium, weak base with secondary/tertiary ammine. A number of commercial ion exchangers are based upon matrix composed of copolymer having a major proportion of styrene and a minor portion of divinyl benzene (DVB). These copolymers are generally prepared in bead form by suspension polymerization. The cross linked polystyrene matrix is converted to a strong acid cation exchanger by sulfonation and to a strong base anion- exchanger by chloromethylation and amination as under: Water demineralization: For demineralization i.e. removal of all ions from water, it may be treated with cation exchanger in the hydrogen form and anion exchanger in hydroxyl form. The simplest way to achieve this is a two column process in which water is first passed over a strong acid cation exchanger and then over a strong base anion exchanger. The reactions that take place in the exchange tower or vessel are as under: Cation Exchanger:

𝐶𝑎(𝐻𝐶𝑂3)2

𝑀𝑔𝐶𝑙2

𝑁𝑎2𝑆𝑂4

+ 𝑅𝐻 →𝐶𝑎𝑀𝑔𝑁𝑎

} 𝑅 + 𝐻𝑛 {𝐻𝐶𝑂3

𝐶𝑙𝑆𝑂4

Where n = 1 or2 Anion Exchanger:

𝐻𝑛 {𝐻𝐶𝑂3

𝐶𝑙𝑆𝑂4

+ 𝑅𝑂𝐻 → 𝑅 {𝐻𝐶𝑂3

𝐶𝑙𝑆𝑂4

+ 𝐻2𝑂

Regeneration: Catton resin:

𝐶𝑎𝑀𝑔𝑁𝑎

} 𝑅 + 𝐻2𝑆𝑂4 → 𝑅𝐻 +𝐶𝑎𝑀𝑔𝑁𝑎

} 𝑆𝑂4

Anion resin:

𝑅 {𝐻𝐶𝑂3

𝐶𝑙𝑆𝑂4

+ 𝑁𝑎𝑂𝐻 → 𝑅𝑂𝐻 + 𝑁𝑎 {𝐻𝐶𝑂3

𝐶𝑙𝑆𝑂4

During regeneration sulfuric acid with lower concentration is first used then a bit higher concentration of sulfuric acid is used. Otherwise a thick precipitate of 𝐶𝑎𝑆𝑂4 will form on resin surface leading to lose activity. 𝐻𝐶𝐼 may also be employed for regeneration of cation resin. Sulfuric acid with 4 − 5% and 𝐻𝐶𝐼 with 5 − 10% are used for regeneration. For anion resin 𝑁𝑎𝑂𝐻 is used for regeneration. Temperature rise up to 50°𝐶 of caustic soda is required to elute silica from resin during regeneration. Mixed Bed Polisher:

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In the mixed bed, the strongly acidic cation exchanger in the 𝐻+ form and strongly basic anion exchanger in 𝑂𝐻− form are present side by side throughout the bed so that an infinite chain of full deionization units are formed. Consequently better deionization sequence of cation exchanger and anion exchanger units will take place. The mixed bed is regenerated after exhaustion with 4 − 5% acid and alkali respectively after separating the resin. DEGASSER: The function of the degasser is to remove free 𝐶𝑂2. The residual 𝐶𝑂2 in degassed water corresponds to the solubility of 𝐶𝑂2 in water at that temperature. Carbon dioxide is formed in cation tower from bicarbonate according to the reaction.

𝐻𝐶𝑂3− + 𝐻+ = 𝐻2𝑂 + 𝐶𝑂2

Air is blown from bottom to upward which causes 𝐶𝑂2 release until it is in equilibrium with 𝐶𝑂2 content of the air i.e., to about 0.5 − 1 𝑚𝑔/𝑙.

BOILER WATER TREATMENT: Problems caused by water in boiler: Water is a universal solvent. It has tendency to retain suspended solids and minerals, gases in dissolved condition. The impurities like any suspended solid, mineral and gas if allowed to accompany any boiler will cause detrimental effects to pre—boiler, boiler and after boiler system. Main problems caused by water in boiler are enumerated below:

Causes of problems Effects Remedy

Dissolved gases 𝑂2, 𝐶𝑂2, 𝑁𝐻3 etc.

Corrosion of pre-boiler, boiler and after boiler

Removal of the gases

Priming Carryover of the boiler water to system

Loss of heat content

Damage of post boiler equipment

Damage to process

Boiler water level to be maintained at normal

Steam generation should be maintained at its design capacity

Foaming Carryover of boiler water into the system

Minimum level of suspended solids to be maintained

Proper alkalinity to be ensured

Dissolved solids to be removed

Reduction of contaminating substance causing foam

Proper blow down

Silica carryover deposition

Silica enters steam at high temperature causing deposition

Forms scale in the steam generation system

Loss of efficiency

Damage of equipment

Removal of silica from water

Periodical blow down

Proper demineralization of water

COOLING WATER TREATMENT: Cooling water system:

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Water after receiving heat from hotter zone gets its temperature rise. The reuse of this water with higher temperature is less effective or in some cases not effective in exchanging heat. So to retain the effectiveness of cooling water it is required to release hot water in the environment or to reuse the same for cooling purpose. For recirculation or reuse it is then cooled down by removing unwanted heat from its mass. Based on the mode of system it is divided into three classes:

1. Open recirculating 2. Closed recirculating 3. Once through system.

Cooling Water Treatment: Problem in cooling water system takes place in the form of (i) Corrosion (ii) Scale or deposition (iii) Microbiological growth. This can reduce operating efficiency, life of the equipment and increase the cost of plant maintenance. An effective, well-designed cooling water treatment program can reduce many of the problems incurred. This has led the plant authority to adopt cooling water treatment program. Corrosion and its prevention: Corrosion is an electrochemical process in which a difference in electrical potential develops between two metals or between two parts of a single metal. Corrosion happens due to low 𝑝𝐻, dissolved salts – salts of chloride and sulfate, dissolved gases – 𝑂2, 𝐻2𝑆, 𝑆𝑂2, Microorganism – Algae, Fungus Corrosion inhibition: Corrosion inhibitor is added to cooling water inhibition usually results from one or more of three general mechanisms. In the first, the inhibitor molecule is adsorbed on the metal surface by the process of chemisorption, forming a thin protective film either by itself or in conjunction with metallic ions. The second method —some inhibitors merely cause a metal to form its own protective film of metal oxides, thereby increasing its resistance. In the third, the inhibitor reacts with a potentially corrosive substance in the - water. Choice is determined by the cooling system design parameters and water composition. Scale formation and its prevention: Scales form in cooling water due to many reasons. These scales deposit in the heat exchanger and impair resistance to the phenomenon of heat exchange. This effect of resistance ultimately retards process activity. Scale formation: The solute exists ion the form of ion, complex ion, and simple molecule in a diluted solution, many molecules combine together and form a crystal nucleus in a super saturated solution. Crystal than having low ionic charge tend to coagulate. The deposits in the cooling water are normally found as 𝐶𝑎𝐶𝑂3, 𝐶𝑎𝑆𝑂4, Silicate, Silica, Iron salts, water borne foulants and 𝐶𝑎 & 𝑀𝑔 sulphate. Scale Control:

i. Prevention of formation of crystal nuclei ii. Prevention of growth of crystal

iii. Dispersion of the crystal Scale Inhibitors:

i. Phosphates (aminotrimethylene phosphanate, Phospheno butane tricarboxylates) ii. Polymers

a. Acryl acid homopolymer b. Acryl acid based ter polymer c. Maleic anhydride homopolymers & copolymers

Microbiological growth and its control: Microbiological life affects cooling water system and many industrial processes. So it needs control to retain cooling water quality.

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Microbes: Algae, Fungus, Bacteria. Problems caused by microbial activity:

Corrosion

Deposition

Deterioratien of cooling tower lumber

Odors & environmental pollution Microbiocides: Microbiocides inhibit microorganism in a variety of ways. Some alter the permeability of cell walls, thereby interfering with the vital life processes. Heavy metals penetrate the cell wall and enter the cytoplasm, destroying protein groups essential for life. Chlorine as biocide: Chorine has long been used as a disinfectant for domestic water supply and for removal of taste and odor from water.

BOILER AND STEAM SYSTEM:

CLASSIFICATION OF BOILER: Based on construction:

A) Water tube boiler: Here water circulates through the tube, which is surrounded by flame and hot gases. Generally high-pressure boilers are of water tube design.

B) Fire tube boiler: Here the hot products of combustion of fuel (flame or hot gases) pass through the tube, which are surrounded by water

Based on the application of heat: A) Direct fire boiler: e. g. Water tube boiler, Fire tube boiler B) Indirect fire boiler: e. g. Waste heat boiler

Based on- the method of circulation of water: A) Natural circulation boiler: Boiler water circulates naturally (by density difference). B) Assisted forced circulation boiler: Boiler water is circulated by the action of a pump. C) Once through forced circulation boiler: Here, a pump feeds the water at one end and forces

the steam through the other end of the boiler. Based on steam generation:

A) Low pressure steam boiler (< 20 𝐾𝑔) B) Medium pressure steam boiler (< 40 𝐾𝑔) C) High pressure boiler (> 40 𝐾𝑔)

Types of fuels: A variety of fuels are used for heating of boilers. Fuels may be classified as follows:

Solid fuels i.e., Wood, Coals, Bagasse, cokes, etc.

Liquid Fuels i.e., Alcohol, Petroleum oil, Furnace oil, Tar, etc.

Gaseous Fuels i.e., Natural gas, Coal gas, Producer gas, etc.

Steam and Steam generation (evaporation of water): Steam is a good conveyor of heat and pressure energy. When heat energy is transferred to water, its enthalpy and physical state change (liquid to vapor). The vapor thus formed is known as steam. As heating takes place the temperature of water rises and generally its density decreases. When

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water is placed in a container and heated up under a constant pressure, the water temperature gradually rises. When the water temperature reaches a certain level with respect to the pressure being applied, the temperature rise stops and the water begins to boil. This level of temperature is called a saturated temperature with respect to the pressure applied. And this is called a saturated pressure with respect to the temperature. As the pressure in the boiler rises, the boiling point of the water in the boiler also rises. For each pressure there is a corresponding boiling temperature. The required pressure at which boiler must operate is determined by the temperature required in the process work and the pressure required to transmit the steam. When 1 𝐾𝑔 of water is heated at atmospheric pressure from 0℃ to 100℃, this temperature is reached with the addition of 100 𝐾𝑐𝑎𝑙 heat The water begins to boil and this point is known as the boiling point (at atm. pressure). With further addition of heat, there is no rise in temperature, the heat being used for evaporation of the water (change of state).

Classification of steam: Steam may be classified into two categories:

Saturated steam

Superheated steam

Uses of steam: i. Power generation

ii. Steam engines or Steam Turbines iii. Heating iv. Heat Exchangers: Heaters, Evaporators, Re-boilers etc. v. Room heater/ Radiator

vi. Utilization in process industries such as Ammonia manufacturing vii. Sizing and bleaching in textile industries

Enthalpy or heat content of water & steam: When a quantity of heat applied to a substance is consumed in raising the substance’s temperature, that heat is called sensible heat. When a substance is heated and its state is changed such as evaporation or melting, by the heat applied under constant temperature that heat is called latent heat. For example, when water evaporates, the applied heat is consumed in evaporation, leaving the water temperature unchanged. In such a case, the heat is used to change only the state of water and is called latent heat or heat of vaporization. The latent heat of water is 539 kcal per kilogram of water under standard atmospheric pressure. The sum of sensible heat and latent heat is called total heat. Enthalpy of liquid/sensible heat: The amount of heat energy in 𝐾𝑐𝑎𝑙, necessary to rise 1 𝐾𝑔 of water from a temperature of 0℃ to its temperature of boiling, at a given absolute pressure, is the enthalpy of liquid/sensible heat. Enthalpy of evaporation/latent heat: The heat energy, in 𝐾𝑐𝑎𝑙, necessary to convert 1 𝐾𝑔 of water into dry steam at the constant temperature and pressure, is the enthalpy of evaporation/latent heat. Enthalpy of steam: Total enthalpy (𝐻𝑠) of 1 𝐾𝑔 of dry saturated steam, reckoned above 0℃, is the sum of enthalpy of liquid (𝐻𝑙) and the enthalpy of evaporation (𝐻𝑒).

𝐻𝑠 = 𝐻𝑙 + 𝐻𝑒 CONSTRUCTION SYSTEM OF NATURAL CIRCULATION TYPE BOILER: The constituents of a boiler system may be classified as follows:

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i. Major constructional parts ii. Auxiliary equipment

iii. Mountings iv. Measuring and control Instrument v. Electrical equipment

vi. Piping Major constructional parts of boiler: A boiler consists of the following major constructional parts:

i. Boiler shell ii. Furnace / Combustion chamber

iii. Burner iv. Steam drum & Water drum/mud drum v. Down comer & Riser

Auxiliary equipment: These are the devices which form an integral part of a boiler but are not mounted on it. Boilers need accessories & auxiliaries to operate the boiler efficiently and safely. This includes:

i. Deaerator ii. Feed water pump

iii. Feed water heater/economizer & Air heater iv. Super heater & Desuperheater v. IDF (Induced draft fan)

vi. FDF (forced draft fan) vii. Stack

Mounting: These are fittings, which are mounted on the boiler for its proper functioning. To operate a boiler smoothly and safely, some mountings are required which are as follows:

i. Water level indicator ii. Pressure gage

iii. Safety valve iv. Steam supply valve v. Blow-down valve

vi. Feed water check valve Measuring and control Instrument: These items attached to a boiler give an indication to the operator of the conditions that exist within the oiler and thus enable him to ensure that these are within the safety limits and operational parameters or which the boiler was designed. Examples of indicated quantities are operating pressures, temperatures, flows and water levels. Control items carry out the function of regulating the various quantities indicated by the instruments and which can be arranged, with interlocks, to shut the plant down if any values pass outside the allowable operating range. Boiler control systems can Manual as well as Automatic.

BOILER: COMBUSTION, AIR-FUEL RATIO & BOILER EFFICIENCY: Combustion: Combustion is a chemical reaction involving the combination of fuel and oxygen to produce heat and combustion products. Boiler requires fuel to produce steam, which may be in the form of gas, liquid and solid. Fossil fuel, utilized for the generation of steam is generally burned directly in the furnace of boiler. The convenient source of oxygen is that which forms almost 21% of atmospheric air. Fuel has a definite intrinsic heat content, which is released by combustion. Complete

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combustion occurs when the fuel is fully oxidized and all the energy released. Incomplete combustion may result from

Insufficient oxygen

Poor mixing of fuel and oxygen

A temperature too low to support combustion Principles of combustion in boiler:

1) Fuel is forced through the burner port into the furnace at a certain velocity depend9ing on the characteristics of the fuel and the required firing rate.

2) The fuel mixes with the air entering the furnace around the burner tip for combustion. This air is secondary air, if ‘primary’ air has already been mixed with the fuel before it enters the burner tip.

3) Combustion is initiated by ignition. 4) Within the proper range of fuel-air mixture, a stable flame is established.

Combustion calculations: The combustible elements present in all fossil fuel, coal, oil and natural gas, are carbon, hydrogen and in some cases, sulfur. The analyses of solid and liquid fuels are based on the masses of the combustible substances present as chemical elements. But the analyses of gaseous fuels are done on the basis of volumetric proportions of constituent gases. The most common gas used in boilers is natural gas. The main combustible constituent in natural gas is methane but there are others, notably ethane, propane, butane, pentane and some higher hydrocarbons, in decreasing order of proportion. There may also be other non-combustible gases such as nitrogen and carbon dioxide. The combustion reaction of natural gas can be represented by way of a chemical equation for each constituent present in it. This enables the theoretical air to gas ratio to be determined together with the volumes of combustion products produced. Let us consider the combustion reaction of natural gas found in Bangladesh, the constituent of which is given in table.

Constituent % by volume Proportion by volume

Methane 96.80 0.968

Ethane 1.77 0.0177

Propane 0.40 0.004

Butane 0.15 0.0015

Pentane 0.05 0.0005

Carbon dioxide 0.38 0.0038

Nitrogen 0.45 0.0045

Totals 100.00 1.00

The chemical reactions of the combustible gases with oxygen are as follows on a volume basis. Methane 96.80% by volume:

𝐶𝐻4 + 2𝑂2 = 𝐶𝑂2 + 2𝐻2𝑂 + 212.8 𝐾𝑐𝑎𝑙/𝑚𝑜𝑙𝑒 Multiplying through by 0.968, the proportion by volume becomes,

0.968 volumes of 𝐶𝐻4 + 1.936 volumes of 𝑂2 produce 0.968 volumes of 𝐶𝑂2 + 1.936 volumes of 𝐻2𝑂

Ethane 1.77% by volume: 𝐶2𝐻6 + 3.5𝑂2 = 2𝐶𝑂2 + 3𝐻2𝑂

Multiplying through by 0.0177, the proportion by volume becomes, 0.0177 volumes of 𝐶2𝐻6 + 0.06195 volumes of 𝑂2 produce 0.0354 volumes of 𝐶𝑂2 +0.0531 volumes of 𝐻2𝑂

Propane 0.40% by volume: 𝐶3𝐻8 + 5𝑂2 = 3𝐶𝑂2 + 4𝐻2𝑂

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Multiplying through by 0.004, the proportion by volume becomes, 0.004 volumes of 𝐶𝐻4 + 0.02 volumes of 𝑂2 produce 0.012 volumes of 𝐶𝑂2 + 0.016 volumes of 𝐻2𝑂

Butane 0.15% by volume: 𝐶4𝐻10 + 6.5𝑂2 = 4𝐶𝑂2 + 5𝐻2𝑂


Pentane 0.05% by volume: 𝐶5𝐻12 + 8𝑂2 = 5𝐶𝑂2 + 6𝐻2𝑂


Constituent gas

Proportion by volume

𝑶𝟐 required Products of combustion with 𝑶𝟐

𝑪𝑶𝟐 𝑯𝟐𝑶 𝑵𝟐 𝐶𝐻4 0.968 1.936 0.968 1.936 − 𝐶2𝐻6 0.0177 0.06195 0.0354 0.0531 − 𝐶3𝐻8 0.004 0.02 0.012 0.016 − 𝐶4𝐻10 0.0015 0.00975 0.006 0.0075 − 𝐶5𝐻12 0.0005 0.004 0.0025 0.003 − 𝐶𝑂2 0.0038 − 0.0038 − − 𝑁2 0.0045 − − − 0.0045

1.00 2.0317 1.0277 2.0156 0.0045

Air consists of 21% by volume of oxygen and 79% by volume of nitrogen. Stoichiometric air requirements to supply 2.0317 volumes of oxygen are given by:

2.0317 𝑂2 + 7.6431 𝑁2 = 9.6748 volumes of air. Air requirements including 10% excess air are:

2.235 𝑂2 + 8.407 𝑁2 = 10.642 volumes of air The total products of combustion (wet) with 10% excess air including nitrogen from the fuel are as follows:

(2.235 − 2.0137)𝑂2 + (8.407 + 0.0045)𝑁2 + 1.0277 𝐶𝑂2 + 2.0156 𝐻2𝑂 = 11.676 volumes/volume of fuel

The total products of combustion (dry) with 10% excess air including nitrogen from the fuel, (2.235 − 2.0137)𝑂2 + (8.407 + 0.0045)𝑁2 + 1.0277 𝐶𝑂2 = 9.6604 volumes/volume of fuel

Hence, a Flue gas is produced that contains the combustion products (𝐶𝑂2, 𝐻2𝑂) plus the excess oxygen and nitrogen contained in the combustion air. The flue gas contains the heat generated by combustion in the form of sensible heat at a high temperature. This heat is transferred to the water via the heat exchange surfaces.

BURNER MANAGEMENT: Burner management is a systematic approach, which encompasses activities to light burner with fuel and to actuate trip just by cutting the flow of fuel for boiler and human safety. It ensures the safe startup, run, trip of the boiler. To- manage this, sequential control systems are incorporated. These control systems are subdivided under the purview of management. Steps of Burner management: The ignition of boiler is very critical. It must be done step by step. The burner management system consists of Furnace purge, Burner startup and Burner trip sub divisions.

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Before any fuel firing can take place, a satisfactory furnace purge cycle must be completed. The furnace purge cycle is to be proceeded as follows: Pre conditions of purging:

i. Power to the furnace safeguard supervisory system (F.S.S.S.), the combustion control system and the related equipment

ii. The boiler drum water level is satisfactory & FD fan is running iii. Instrument air pressure is not low & the furnace pressure is not high iv. The gas pressure is satisfactory v. Fuel gas block valves are closed

vi. Fuel gas vent valves are opened vii. Ignition gas pressure is correct & No flames are present in furnace

When the foregoing is correct, the boiler is available for purging. i. Air damper is opened

ii. Purging of the combustion chamber and flue passage should be done with four times as much air as the combustion chamber and the flue passage volume

iii. Purging is done for 5 − 10 minutes Burner startup: Prior to start up ether burner:

i. "Purge complete" condition remain satisfied ii. The air flow must be above 25%

iii. The burner interlocks must be satisfied iv. The ignition gas pressure must be satisfactory v. When it is certain that there are no faults, the pilot burner is ignited

A satisfactory ignition flame will,

i. Close the gas burner vent valves and then open the block valves ii. Initiate the main flame start timer

iii. When the main flame start timer has timed out, the ignition gas block valves will close its vent open

iv. The main flame is them established v. lf the main flame is not on when its timer has timed out an alarm will be raised and the

burner goes into its trip sequences Burner trip: Gas burner will trip if any of the following conditions occur.

i. FD fan stopped or airflow below required amount ii. Boiler drum level low low or high high

iii. Instrument air pressure low low iv. Furnace pressure high high v. Emergency trip push button operated

vi. Gas pressure becomes low low or high high

SEALS AND GASKETS:

1.0 INTRODUCTION A seal is basically a device for closing (sealing) a gap or making a joint fluid-tight (the fluid in

this case being either a gas or liquid).

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Seals are used to form a barrier between two spaces in the machine or equipment.

Generally speaking, one of these spaces will communicate with the outside air and there will be a pressure in the other space greater than atmospheric pressure.

However there are also cases where spaces with a pressure of less than 1 𝑏𝑎𝑟 (vacuum) have to be sealed off.

2.0 TYPE OF SEALS: 2.1 Static seals: When the seal and the surface to be sealed off virtually do not move against

each other are known as static seal i.e., machine casing seals, Flange connection seals, Cylinder covers seals etc.

2.2 Dynamic seals: When the seal itself and surface to be sealed) off can be reciprocate or rotate in relation to one another i.e., Gland packing seal, Mechanical seal, Oil seal etc. Further dynamic seal can be classified into contact type and non con-contact type seal.

3.0 DIFFERENT TYPES OF SEALS & THEIR PLACE OF USE 3.1 Gasket:

i. A gasket is a material or combination of materials clamped between two separable members of a mechanical joint.

ii. Its function is to affect a seal between the members and maintain the seal for a prolonged period.

iii. The gasket must be capable of sealing the mating surfaces, impervious and resistant to the medium being sealed, and able to withstand the application temperature and pressure.

iv. Gaskets are used in between machine casings, flanges, valve bonnet joints etc. v. It is made of Asbestos, Rubber, Teflon, Leather, Metal etc.

3.2 O-Ring seals: i. They are used as both dynamic and static seals.

ii. In the case of dynamic seals, the O-ring seals by friction. The movement can be either rotating or reciprocating.

iii. With rotating shafts or spindles, the peripheral speed must not exceed 30 𝑚/𝑚𝑖𝑛, because this speeds the O-ring may be twisted or broken down.

iv. Satisfactory performance however depends on the material characteristics, suitable mating groove geometry with close tolerance and smooth surface finish on mating surfaces.

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3.3 V-ring: i. V-ring is the shaft bearing seal made entirely of rubber.

ii. The V-ring seal can be used with both grease and oil lubrication. iii. The elastic rubber ring of the seal firmly grips the shaft and rotates with it. iv. For grease lubrication the seal is generally arranged outside the housing and with oil

lubrication it is placed inside the housing. v. They are simple to mount and it is not affected if the shaft is out of alignment.

3.4 V-packing: i. It is used between the plunger and stuffing box of reciprocating machine.

ii. It is mainly made of Teflon. iii. A solid adopter is pushed on the V-packing; as a result ID of the packing decreased, so

effective sealing takes place.

3.5 Lip-type oil seal:

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i. The lip—type oil seal is a circular element forming a seal between a stationary machine part and a rotating shaft.

ii. It is used to prevent oil leakage from oil chamber, gear box etc. iii. The bore of the seal housing should have a smooth finish beveling to 15° for 2 − 3 𝑚𝑚.

3.6 Gland packing: i. A good functional seal at the point where the shaft, spindle or plunger projects from the

housing is one of the main conditions of the effective operation of pumps, valves or compressor.

ii. This type of seal with packing fitted into a space between the stationary and moving components is also called stuffing box seal and is used for both rotating and reciprocating shafts.

3.7 Mechanical seal: i. Mechanical seals comprise rotating and stationary elements in rubbing contact to form a

sealing face. ii. Successful operation depends on achieving the right conditions at the face, the faces

themselves being lubricated by a thin hydrodynamic film. iii. The majority of mechanical seals are used as pump shaft seal. iv. Other significant applications include centrifugal compressors, stirring mechanism and

marine propeller shaft seal. v. They have a specific application at high pressure and for combustible, precious, high volatile

and corrosive media, i.e. where no leakage at all is permissible.

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Advantages over stuffing box seals are: Require minimum maintenance (if properly install and used) There is no friction between seals and the shafts Operation does not cause shaft wear The risk of pollution is reduced Long operating life lf in good condition does not leak along the shaft (provides 100% scaling) Handle all types of fluids (acids, salts, abrasive particles) Disadvantages of mechanical seals are: Requires more space than radial lip seals, etc. Cannot handle axial end play Sealing faces must be finished smooth (0.08 to 0.4 um) and can be easily damage High initial cost

3.8 Labyrinth seal: i. A labyrinth seal is a series of bushings joined together in such a way that the fluid must

change directions as it flows from the sump to the atmosphere. ii. The directional changes result in a longer path within a given space and additional pressure

drops occur wherever the fluid changes direction. iii. They are used to seal gases in turbine, or turbo-compressor applications and also act as a

seals for rolling bearings, machine spindles, and other applications where some leakage can be tolerated.

iv. The fluid then expands into the chamber beyond the constriction. Turbulence results and a pressure drop occur.

v. The knife tip will usually have a width of 0.12 to 0.35 mm with a root width of 3.5 to 5.0 mm. The angle of the knife sides is typically 8 to 120.

vi. It is made of brass, Leaded nickel-tin bronze, Aluminum bronze, Soft stainless steel etc.

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BEARING:

1.0 INTRODUCTION Bearing is a vital mechanical part of a mechanism which rotates, oscillates, or reciprocates easily. The main function of Bearing is:

To carry the load of rotating part (Shaft)

To help the shaft for easy movement

To reduce friction

To hold the shaft

Figure: Deep groove ball bearing

2.0 TYPE OF BEARING

All of the above bearings are also classified according to load:

Radial bearing (Can take load along the radius of the shaft)

Thrust bearing (Can take Axial/thrust Load along the axis of the shall)

Bearing

Rolling

Ball

1. Deep groove

2. Angular contact

3. Self aligning

Roller

1. Cylindrical

2. Taper

3. Spherical

Plain

1. Bush

2. Split

3. Tilting pad

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Angular contact Self aligning

Cylindrical roller Taper roller Spherical roller

Bush type Split type Tilting type

3.0 CONSTRUCTION OF BALL BEARING Ball Bearing is point contact Bearing. Deep groove: The race way (groove) is too much deep, two rings is similar. Angular contact: Balls of this bearing contact at an angle with the central line, Thickness of

each ring is thick at ball-seat side and thin at other side. Self aligning: Balls (Double row) are fixed on inner ring, outer ring can move with respect to

inner ring, outer race is smooth curved surface.

PIPE FITTINGS AND VALVES:

1.0 PIPE:

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A tube with a round cross section conforming to the dimensional requirements for nominal pipe size as tabulated in ASME/ANSI B 36.10 and B 36.19.

Practically there is no plant, factory or workshop without its network of pipes for supplying and moving liquid, gases, vapors, semi-solid or even solids. These 'arteries' are of vital importance in Industries as well as for all social utilities.

2.0 PIPE FITTINGS: The components which are used to fabricate a pipe line network are known as pipe fittings. Following are the most common pipe fittings used in piping network:

2.1 Flanges: Flanges are round discs welded or threaded to the pipe ends having bolt hole to connect

two pieces of pipe end to end. Many types of flange are used in industry according to pressure rating some of them are:

flat face, raised face, serrated face, ring joint, lapped joint, maIe-female, tongue-groove flange etc.

Flange Socket

2.2 Socket:

In order to connect two pieces of pipe in a straight line socket is used. It has internal thread in both ends. If the two sections of pipe to be jointed do not have the same diameter a reducing socket

is used. 2.3 Reducer

To reduce the fluid flow it is necessary to connect two dissimilar diameter pipe ends to end. In that case reducer is used. It is commonly welded type.

Reducers are two types: concentric and eccentric reducer.

Concentric reducer Eccentric reducer

2.4 Union socket:

It is also used to connect two pieces of pipes end to end in a straight line. It offers maintenance facilities to the long pipelines. So, for this purpose union socket is

intentionally introduced to the pipeline instead of socket. 2.5 Tee-joint:

When a pipe is to be connected at right angles to the main pipeline a tee-joint is used. 2.6 Cross-joint:

When two pipes are to be connected at right angles to the both sides of main pipeline, a cross-joint is used.

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Union socket Tee-joint Cross-joint Hexagonal nipple

2.7 Hexagonal nipple: In order to fasten a tee, cross etc to a threaded flange, a hexagonal nipple is used.

2.8 Expansion Joints: Expansion joints are used in piping system to absorb thermal expansion and contraction

where the use of expansion loops is undesirable or impractical. Expansion joints are available in slip, ball, metal bellows and rubber bellows

configurations.

90° below Bend Metal bellows

2.9 90° Elbow:

In order to connect two pieces of pipes at right angles, 90° elbow is used. 2.10 Bend:

Bend is also used to connect two pieces pipe at right angle. But its arc radius is larger and frictional loss is less than 90° elbow.

2.11 Cap& Plug: A pipe section can be sealed off temporarily with the aid of a cap or a plug. A cap is used on an external thread and a plug, whose thread is tapered, on an internal

thread.

Cap Plug

2.12 Nut & bolt:

In order to connect two flange jointed pipe ends, nut & bolt are used. Mainly two types of bolt used: machine bolt and stud bolt.

Nut Machine bolt Stud bolt

3.0 VALVES:

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Valve is a mechanical device which has movable mechanism and capable of opening & closing the passage in order to pass, stop & control the fluid flow in pipeline, equipment and machine.

Rules applies to all valves; “Turn right to close, left to open”. 3.1 Gate Valve:

Gate valve is used to fully open or shut down the fluid flow in a pipeline, equipment or vessel.

When the valve is completely open, the fluid is flow without any restriction. Pressure drop is very nominal in this valve. This valve is less suitable for throttling the liquid flow because when it is partially opened

the liquid meets strong resistance (turbulent flow etc.). Gate valve is most commonly used in liquid system.

3.2 Globe Valve: This valve consists of a spherical body with flange or threaded ends. The sealing capacity of these valves is therefore potentially high. The body contains a partition with an opening, which can be sealed off by a disc or plug. Always flow direction is marked on the valve body. Due to change the direction of flow through the valve opening, considerable pressure loss

will occur. This valve is suitable for throttling.

3.3 Ball Valve: It consists of a through pass hole ball. The seats between which the ball is located are generally made of Teflon (PTFE). Used for opening or closing the fluid flow rapidly. It is also used to control fluid flow moderately. It needs only 90° rotation from fully open to fully close. Pressure loss is very negligible.

3.4 Plug Valves: Plug valves are rotary valves in which a plug-shaped closure member is rotated through

increments of 90° to open and close a port hole or holes in the plug with the port in the valve body.

The shape of the plug may be cylindrical or taper. The shape of the port is commonly rectangular in parallel plugs and truncated triangular in

taper plugs. When the plug is open, there is almost no pressure loss. Used in low pressure services where a flow may have to be stopped or started quickly. Capable of handling fluids with solids in suspension. Plug valves are not designed for regulation of flow. An important characteristic of the plug valve is its adaptability to multiport construction. When designed in a three, four or five way configuration, the multiport plug valve can be

used to replace as many as conventional shutoff valves. 3.5 Check Valves:

Check valves are automatic valves, which open with forward flow and close against reverse flow.

This mode of flow regulation is required to prevent return flow, to maintain prime after the pump has stopped, to enable reciprocating pumps and compressors to function.

Check valves, also known as ‘Non-return’ valves or reflex valves. 3.6 Butterfly Valves:

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Butterfly valves are rotary valves in which a disc-shaped closure member is rotated through 90° or about to open or close the flow passage.

These valves are used for throttling purposes. It is not intended for tight shut-off. Easy to operate both manually and by power. Only suitable for low—pressure service. Pressure drop is negligible.

3.7 Diaphragm Valves: Diaphragm valves are used for on-off and throttling service. The major components of the diaphragm valve are the body, diaphragm and stem &

bonnet assembly. There is no valve seat, because the body itself acts as a seat. The gas or liquid is shut off by the flexible diaphragm which, is pressed onto a seat in the

body by the spindle. The diaphragm is made of different elastomeric material (natural and synthetic rubber)

and PTFE (polytetrafluoroethylene). Diaphragm valves are frequently used in services with highly corrosive atmospheres (i.e.,

acidic and caustic). The diaphragm valve is excellent for handling slurries and for low-pressure service. There are no packing glands to maintain and no possibility of stem leakage as long as the

diaphragm does not rupture. The diaphragm valve is distinguished from all valves by its closed hand wheel. Its reasons are, to ensure that no tools (wheel key) are used to close the valve, the

diaphragm would then be damaged or broken and if the diaphragm ruptures, the closed hand wheel prevents the medium from spouting straight up and injured personnel. Thus, this arrangement is also a safety precaution.

3.8 Safety Valves: Safety valves are automatic pressure—relieving mechanical devices used for overpressure

protection of piping and equipment. Safety valves are generally used in gas or vapor service. Safety valve saves pipeline or vessel from pressure greater than the allowable one. Under normal operating pressure, the valve disk is held against the valve seat by a

preloaded spring. It must open when the pressure reached beyond the preset pressure (e.g. 10% above

normal) and release the excess pressure. The body is connected at the underside to the pipe or pressure vessel to be protected.

INSULATION AND HIGH TEMPERATURE REFRACTORIES:

1.0 INTRODUCTION: Heat transfer losses through conduction can be sharply reduced by means of insulation. Insulating material is therefore designed particularly against this kind of heat loss. Refractories resist heat and various forms of corrosion. Materials having a refractoriness of more than 1580℃.

2.0 TYPES OF INSULATING MATERIALS:

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The most common types of Insulating materials are Glass wool, Mineral wool, Cork, Calcium silicate, Vermiculite, Asbestos, Blanket etc.

2.1 Properties of insulating materials: Low heat conductivity, Low water absorption factor, Combustibility and heat resistance,

Elasticity and resilience, Easy workability, No heat contraction, Good chemical stability, High temperature resistance, Low specific heat etc.

2.2 Application of insulating materials: Reduce energy losses, Prevent gain or loss of heat, Avoid condensation in steam pipes,

Avoid freezing or solidification, Prevent heat radiation in a working environment for safety reasons etc.

2.3 Form of insulating materials:

Loose fill: Powers, Bubbles, fibers, flakes, granules etc.

Flexible: Blankets, batting, multi-layer sheets etc.

Rigid: Brick, block, board, castomolded, sheet and pipe covering etc.

Foam: Fiber materials mixed with liquid binder etc.

3.0 HOT & COLD INSULATION: Hot insulation: The heat flow is inhibited from inside to outwards. Cold insulation: The heat flow is inhibited from outside to inwards.

3.1 Hot Insulation: It is generally applied to equipment and piping at 80℃ and above except for the case where

heat loss is desired. Hot Insulating materials are:

Calcium silicate – for equipment & piping 650℃ and below except S.S.

Perlite – for equipment & piping 650℃ and below for S.S.

Mineral wool – for expansion joint of towers, vessels, flanges, valves and irregular surface of equipment 600℃ and below.

Glass wool: up to 700℃, Asbestos: up to 450℃, Glass fiber: up to 538℃, Alumina bubbles: up to 700℃, Aluminum silica fiber: up to 700℃, Reinforced bonded colloidal silica: 1090℃, vermiculate: 1200℃ to 1300℃, Zirconia fibers: 1640℃, Carbon and Graphite fiber: 2480℃, Microw quartz fibers: 1370℃, Fiberous potassium titanate: 1040℃ etc.

3.2 Cold Insulation: It is generally applied to equipment and piping at 10℃ and below except for full

refrigeration where heat gained to be restricted. Anti sweat cold insulation shall be applied to equipment and piping operating at 20℃ and

below if surface condensation of moisture would give adverse effect. Cold Insulating materials are:

Tempex polystyrene – for equipment & piping −150℃ to +130℃.

Cellular glass: −268℃ and below.

Rigid cellular polyurethane for equipment and piping; −180℃ to 180℃.

Mineral wool – for expansion joint of towers, vessels, flanges, valves, flanges and piping for irregular surfaces etc.: −180℃ to +600℃.

Cork: −200℃ to +100℃.

Polyurethane foam: −120℃ and below etc.

4.0 HIGH TEMPERATURE REFRACTORY: High temperature refractories are composed of metallic substances that are resistant to

heat and resistant to various forms of corrosion.

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Materials with a melting point above 1580℃ are called refractory.

It is required for furnace above 1790℃ is called highly refractory.

The function of refractory is to isolate or form a barrier by means of resisting material in the form of a lining with in structure in such a way that the maximum possible amount the initial heat input will be contained and passed only to the workload.

Japan industrial standard defines refractories as materials having a refractoriness of more than 1580℃.

4.1 Classification of Refractory materials: General Refractories: These are produced mainly in the form of standard firebricks and are required for their

strength and abrasion resisting qualities on hearths, the lower areas of side walls and doors. Because of their poor insulating properties, they are confined mainly to the inner course.

Insulating Refractories: These consist of insulating firebrick on high porosity. They are commonly used as inside face

linings of furnaces and as backing insulation to firebrick and are known as hot face insulation. Low temperature insulation: These are light in weight have a low thermal capacity and a low crushing strength. Monolithic Refractories: These are very wide and flexible range of refractory concrete materials, which are suitable

for the production of shapes, especially in new or existing structures and in burner manufacture. Three basic forms are Castable, Moldable & Ramming mixtures. Ceramic fiber insulation: The current use of this form of furnace lining. The following properties and compatibilities should prove helpful:

Very low thermal conductivity, Good resistant to thermal expansion, low density compared to insulating fire brick, Good chemical stability, Available in three main grades: 1200℃, 1400℃ & 1600℃.

4.2 Important Properties of Refractory materials: Thermal conductivity, Coefficient of thermal expansion, Permanent linear change, Modules

of rupture, Influence of mixing conditions, High resistance to wear, chemical resistance to slag, resistance to corrosion, Heat shock resistance, Effect of freezing on curing etc.

5.0 AUXILIARY MATERIALS OF INSULATION It is used for joint fitting, waterproofing, sealing, coating & reinforcing.

HI and CI mastic: for all opening used as sealing material & water proofing.

Hard setting cement: for bent pipe and heads.

Glass cloth: for reinforcement of mastic.

Silver paint: for finishing work etc.

6.0 CONCLUSION: For smooth operation of process plant i.e., Boiler, Reformer etc. periodic checking of Hot & Cold

insulation, High temperature refractory materials inlet/outlet fluids (temp. & press) etc. is necessary otherwise leakage, damage may occur.

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COMPRESSORS AND COMPRESSORS SYSTEM OPERATION:

COMPRESSION: Compression is defined as increasing the pressure and density of compressible fluid (either gas or vapor and can have a wide molecular weight range) Types of Compression

Isothermal Compression

Adiabatic Compression Isothermal compression: The Compression at which heat is removed or reduced through interstage cooler is called isothermal compression. Adiabatic compression: The Compression at which no heat is removed or added during the process is called adiabatic compressor. Theory of compression: In any compression process the product of absolute pressure P and V is a constant i.e.,

𝑃𝑉𝑛 = Constant … … … … … … … … … … … … … … . . (1) Temperature rise due to compression: For adiabatic change, the expression for temperature rises 𝑇2 due to compression, may be derived as

𝑇2 = 𝑇1(𝑃2/𝑃1)(𝛾−1)/𝛾 𝑃1 = Suction pressure 𝑃2 = Discharge pressure 𝑇1 = Suction temperature 𝑇2 = Discharge temperature

COMPRESSOR: Compressor is a mechanical device that does work to increase the pressure of compressible fluid (gas or vapor). The inlet and outlet pressure are related corresponding with the type of compressor and its configuration. During compression, the speed of the gas molecule also increases which causes an increasing in gas temperature. The amount of temperature increases depends on the nature of the gas (fluid), the suction temperature and the amount of compression ratio.

Compression ratio =Discharge ratio

Suction pressure

Purpose of Compressor: Compressors are commonly used in the process industries and gas transport or distribution industries; typical applications include:

i. Ammonia plant: Feed gas, Synthesis gas, Refrigeration and Air compression ii. Urea plant: Carbon dioxide compression

iii. Refining: Hydro-cracking, Hydrogen make up, recycle, air services and other hydrogen and hydrocarbon mixtures.

iv. Air separation: Nitrogen feed, recycle and air services v. Oil production: Gas lift and reinjection

vi. Gas production: Gathering, Liquid production, Pipe line boosting services. Working principles of Compressor: All compressors work on either of the following two principles:

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Positive displacement principle: Pressure is increased by physically squeezing the volume of gas. Compressors working on this principle are known as positive displacement compressors e.g., Reciprocating compressor, Screw compressor, Rotary compressor etc.

Turbo/Hydrodynamic principle: Pressure is increased by increasing speed of gas molecules. Compressors working on this principle are known as Dynamic or Centrifugal compressor. Axial flow, Radial flow or Centrifugal compressor etc.

Types of Compressor: Compression machinery can be separated into two broad categories: Dynamic and Positive Displacement. Centrifugal compressor is a dynamic type this compressor do their work by using inertial forces applied to the gas by means of rotating bladed impellers, whereas Positive Displacement compressors trap gas by the action of mechanical components and restrict its escape as compression takes place through direct volume reduction. Each of these two broad categories can be further subdivided as shown in the following figure.

Positive displacement compressor: Pressure is increased by physically squeezing the volume of gas. Compressors working on this principle are known as positive displacement compressors e.g., Reciprocating compressor. Screw compressor, Rotary compressor etc. Reciprocating compressor: Reciprocating compressor is a positive displacement compressor, in which pressure is increased by squeezing the volume of gas. In reciprocating compressor, gas is compressed by the back and forth motion of the piston. Rotary Compressor: Rotary compressors impart energy to the gas being compressed by way of an input shaft moving a single or multiple rotating. Sliding vane compressor: The sliding vane type compressor consists of a cylindrical rotor in an eccentric casing. Thin, flat vanes (8 to 30) located in slots along radii of the rotor slide in and out as the rotor turns. Centrifugal forces drives the vanes outward; contact with the eccentric casing inner surface drives the vanes back inward as rotation gradually decreases the rotor center to cylinder inner-diameter radius. Rotation within the eccentric casing gradually reduces the volume in chambers trapped by the sliding vanes, thus raising the pressure.

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Liquid ring compressor: The liquid ring compressor is a unique type of rotary machine which utilizes a liquid annulus held by centrifugal force around the inside of a casing by a single impeller to compress vapor. It has the low cost per unit volume capacity characteristic of the rotary class and is thus competitive for vacuum ad other low-pressure air and gas services. It is ideally suited to handling gases sensitive to temperature rise, such as acetylene, because the liquid compressing provides continuous contact cooling, allowing the compression to follow a nearly isothermal path. The discharge temperature is typically only 10 to 15℉ higher than the compressing liquid inlet temperature. Screw compressor: The rotary screw compressor is a positive displacement type machine in which compression is carried out by the intermeshing of two helically formed rotors. The rotors are designated as the male rotor and female rotor. The male rotor has convex lobes while the female rotor has concave flutes. The gas to be compressed is admitted through a properly located inlet port and completely fills one of the flutes in the female rotor. The discharge ends of the rotor are sealed by the compressor end plate. As the rotors rotate, the male rotor lobe enters the pocket in the female rotor, decreasing its volume and compressing the trapped gas. When the desired amount of compression is achieved, the discharge port is uncovered and the compressed gas is expelled. The process is repeated for each successive interlobal space. Straight lobe compressor: One of the oldest and simplest types of rotary compressors is the "Roots" or straight lobe "blower". This type employs two identical ductile iron rotors, each with two rounded lobes, if giving the rotors a figure like shape in cross section. The rotor lobes intermesh and are held apart by timing gears. They are straight with respect to the shaft axis, like rounded teeth on a spur gear. As the rotors turn, gas is swept between the rotor and the casing wall toward the discharge, with no volume reduction. Compression take place as the discharge port is uncovered. Gas from the discharge line then flow backwards into the casing until the pressure in the cavity reaches discharge line pressure. Further rotor turning sweeps the mixture back into the discharge line. It is similar to the helical lobe machine but is much less sophisticated. As name implies, it has two untwisted or straight lobe rotors which intermesh as they rotate. Normally each rotor pair has a two lobe rotor configuration, although a three lobe version is available. Gas is trapped in the open area of the lobes as the lobe pair crosses the inlet port. Four cycle of compression take place in the period of one shaft rotation on the two lobe version. Dynamic compressor: In dynamic compressors energy is transferred from a moving set of blades to the gas. The energy takes the form of velocity in the rotating element and converted to pressure in the stationary part of the compressor e.g., Centrifugal compressor. Here pressure is developed by increasing the speed of gas molecule through centrifugal action. It is widely used in process industries. Centrifugal compressor: The compressor by which pressure of gases is increased by increasing speed of gas molecules is called centrifugal compressor. In centrifugal compressor, gas molecules receive higher energy while passing through the rotating impeller. This high energy gas molecules when enter into the stationary confined diffuser and then it strikes at diffuser wall at higher rate & with higher momentum. Summation of these striking forces per unit area of the diffuser wall, give rise to higher pressure. Axial flow compressor:

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Axial compressors are large volume compressors that are characterized by the axial direction of the flow passing through the machine. The energy from the rotor is transferred to the gas by blades. The rotor consists of multiple rows of unshrouded blades. Major components of the centrifugal compressor:

Rotor o Shaft o Impellers

Impeller disc Counter disc Impeller eye Impeller vane

o Thrust collar o Balance drum o Seal

Gland seal Impeller tip seal Stage seal

Casing o Horizontal split casing o Vertical split casing

Diaphragm & diffuser

Bearing o Radial bearing o Thrust bearing

Major components of vane type compressor:

Rotor

Vane

Casing

Suction port

Discharge port Major components of lobe type compressor:

Lobe

Casing

Shaft

Seal

Bearing

Gear Major components of reciprocating compressor:

Cylinder

Piston

Piston rod

Cross rod

Connection rod

Crankshaft

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Stuffing box/rod packing

Valves Major components of screw compressor:

Casing

Rotor

Suction port

Discharge port

Bearing

Seals

INDUSTRIAL TURBINES:

1. INTRODUCTION: Turbine is a machine which converts the pressure , velocity and heat energy i.e., decrease the head of energy level of the working fluids passing through them to the rotational energy i.e., mechanical energy of the machine is utilized to drive different turbo machinery like generator, pump, compressor etc.

2. TYPES OF STEAM TURBINE: Steam turbine is steady flow machine in which steam enters nozzle and expands to a lower pressure. Steam Jet develops a high velocity and part of the kinetic energy delivered to the blades of the turbine in the same manner that a jet of water can deliver energy water to the buckets of water wheel.

2.1 Condensing turbine Where all the exhaust steams are passed to a condenser.

2.2 Back pressure turbine/non-condensing turbine Which has no condenser. The exhaust steam, at an appropriate pressure, is generally used

for heating purpose. 2.3 Extraction turbine

In this case steam is extracted for process work at one or more stages of the expansion, the remainder being expanded down to condenser pressure.

2.4 Mixed pressure turbine In which steam is supplied from two or more sources at different pressures.

3. MAJOR COMPONENT OF STEAM TURBINE: Casing: Casing consists of different sections naming steam chest, rotor chamber, exhaust hood. It surrounds the steam path components and supports the stationary parts. Casing is of the center support type allowing expanding freely with their centers precisely. Casing supports are designed to permit thermal expansion without disturbing shaft alignment, with enough strength and arrangement allow reasonable connecting pipe forces and moments. Rotor: The rotor disks are forged and machined as an integral part of the shaft. Attached to the steam or high pressure end of the rotor are thrust.

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Bearing housing: The bearing housing is supported on pedestal at shaft height, independently of the turbine casing. The relative location of the pedestal to the outer casing is conveniently adjusted by means of screw adjusting device. The thermal expansion of turbine takes place freely on the guide-way. Journal Bearing: Turbines are equipped with two types of bearing, those are Journal bearing & Thrust bearing. The journal bearing are used to take the radial load which may be split type (pressure dam sleeve bearing) or tilting pad type. Thrust bearing: The thrust bearing, which is of the tilting pad type, is designed for taking up the residual axial thrust in positive or negative direction axially. Thrust bearing maintains the proper axial rotor clearances and absorb the rotor thrust. Nozzle: The expansion channels in which the potential energy present in the steam is transformed into kinetic energy. The nozzle ring contains nozzles which expands the steam and direct it against the rotating blades. Guide blade: Redirect the steam at proper angle to the next moving blade stage. Its function is conversion of potential to kinetic energy (for reaction turbine). Diaphragm: Stationary diaphragms containing the nozzles/guide blades expand the steam and direct it against the following rows of rotating blades. The diaphragms are located in the casing groove by shims at the bottom of the grooves and laterally by means of adjusting screws. The upper halves of the diaphragms are fixed in the casing by the same arrangement and lift with the casing cover. The diaphragms are adjusted on assembly to allow for rotor deflection and assure that the packing is concentric with the shaft. Moving blade: Kinetic energy of steam is converted into mechanical energy (rotational energy) or work during passing through the moving blades. The moving blades are mounted (inserted) on the disc of rotor. Shroud: Shroud is riveted to the tips of the blades. Shroud supports the blades and also prevents the steam from being cast off radially. Rotor Chamber: The space within which the rotor runs is called rotor chamber. Gland seal (front & rear): The gland seal consist of large number of labyrinth chamber. The chambers are divided into three sections (usually). Labyrinth seal strips, fitted to the outer casing of them turbine go into these chambers to seal steam from going out and/or mixing with oil in the bearing section. After the front seal gland, the shaft contains a stepping there is another set of labyrinth chamber, on to which the labyrinth strips, fitted to outer casing, take three positions to seal high pressure steam. Bearing seal ring: Bearing seal rings may be a flat disk integral to shaft or it may be a stepping in the shaft. This disc impedes the normal flow oil along the shaft towards casing. There is oil labyrinth after the ring which seals oil from flowing towards casing.

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INDUSTRIAL SAFETY:

INDUSTRIAL SAFETY: Industrial safety is the term consisting of some precautionary measures that are observed by people at the time of performing a job inside the factory with the help of some machine or equipment designed in such a manner that can check the accident that happen with a ultimate view to achieve the possible higher productivity. Some safety related terminologies: Safety: Freedom from unacceptable risk. Hazard: A Situation that may give rise personal or environmental injury. Danger: A state or condition in which personal injury is reasonably foreseeable. Risk: Combination of probability of injury and degree of injury. Accident: Unplanned or undesired event giving rise to death, illness, injury, damage or loss. Causes of Industrial Accidents:

Poor planning

Unsafe working conditions

Unsafe acts

Inadequate and ineffective supervision

Lack of knowledge of consequence of hazards

SAFETY SIGNS & COLOURS: The purpose of a system of safety colors and safety signs is to draw attention to objects and situations which affect, or could affect, health or safety. There are no specific safety signs and color regulations in Bangladesh. In most of the cases, we follow the British standard (Safety sign regulations 1980). According to BS, safety related different terms are defined as follows: Safety color: A color to which a specific health of safety meaning or purpose is assigned. Safety Sign: A sign that gives a message about health or safety by a combination of geometric form, safety color and symbol or text (i.e. words, letter, numbers) or both.

GENERAL MEANING ASSIGNED TO SAFETY COLOURS (BS): Safety color

Meaning of purpose

Examples of use Contrasting color (if

required)

Symbol color

Red Stop/Prohibition

Stop signs: Identification and color of emergency shutdown devices; Prohibition signs.

White Black

Yellow Caution/Risk of danger

Identifications of hazards (fire, explosion, radiation, chemical etc.); Warning sign; Identification of thresholds, dangerous passages, obstacles.

Black Black

Blue Mandatory action

Obligation to wear personal safety equipment; Mandatory signs.

white White

Green Safe condition Identification of safety showers, first aid posts and rescue points; Emergency exit signs.

White White

SAFETY SIGN:

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Safety signs are classified in four groups: 1. Prohibition sign 2. Warning sign 3. Mandatory sign 4. Safe condition sign

Prohibited sign:

Background color shall be white.

Circular band and cross bar shall be red.

The symbol shall be black and placed centrally the background, and shall not obliterate the cross bar.

Red shall cover at least 35% of the area of safety sign.

Warning sign:

Background color shall be yellow.

Triangular band shall be black.

The symbol or text shall be black and placed centrally on the background.

Yellow shall cover at least 50% of the area of safety sign.

Mandatory sign:

Background color shall be blue.

The symbol of text shall be white and placed centrally on the background.

Blue shall cover at least 50% of the area of safety sign.

Safe condition sign:

Background color shall be green.

The symbol of text shall be white. The shape of the sign shall be oblong or square as necessary to accommodate the symbol or text.

Green shall cover at least 50% of the area of safety sign.

PERSONAL PROTECTIVE EQUIPMENT: Personal protective equipment (PPE) means all attires & equipment (including clothing affording protection against the weather), which is intended to be worn or held by a person at work and which protects him against one or more risks to his health. It also helps person to work confidently against risk. Purposes of PPE: The main purposes of PPE are as follows:

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i) To protect the people in working place ii) To maintain safe operation of the plant iii) To reduce accidents iv) To enhance the awareness of process safety

Classification of PPE:

Example of PPE

Head protective equipment Safety helmets & hats

Eye protecting equipment Safety spectacles, eye shield, safety goggles, welding filter/goggles, welding helmet

Face protective equipment Plastic face shield, metal screen face shield, welding helmets, etc.

Ear protective equipment Insert type ear protector (Ear plug) and Muff type ear protector (Ear muff)

Respiratory protective equipment Chemical cartridge respirator, gas mask, nose mask, Air-line respirator, self contained breathing apparatus

Hand and finger protective equipment Rubber gloves, leather gloves, PVC gloves, linen gloves etc.

Foot protective equipment Safety shoes

Special clothing Fire resistant clothing, liquid and gas tight clothing, apron, rainwear, shocks, overall jacket etc.

Personal buoyancy equipment Life-jacket or buoyancy aids

Miscellaneous Safety belts, harnesses and safety ropes

INTRODUCTION TO INDUSTRIAL INSTRUMENTATION:

1. PROCESS PARAMETERS: The physical variables which is measured and sometime controlled are the process parameters.

Pressure, level, flow, temperature are the main parameters measured in the industry 𝑝𝐻, conductivity, humidity, density, turbidity, vibration, 𝐶𝑂,𝐶𝑂2, 𝐻2, 𝑂2 etc. are also

measured Necessity of Measurement: It is necessary to measure different variables for better control of the process and to get best product/output.

2. INSTRUMENTS & CONTROL: Instrument: A device used directly or indirectly to measure or control a variable or both. Instrumentation: When a machine or a process is furnished with instruments for measurement and control is called instrumentation. In fact, instrumentation is the application of instruments. Types of Industrial Instruments:

Measuring Instruments o Measuring instruments with indicating system o Measuring instruments with recording system o Measuring instruments with counting system

Controlling instruments

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Safety & interlock instruments Control: By control we mean that the physical variables are kept constant as the desired value. This is generally done by measuring the instantaneous value of physical variable, comparing it with the desired value and using the difference to make a correction, which reduces this difference. Control Technology: The knowledge, way and system of controlling the parameters of a process are the control technology and by control technology we mean that the process would be controlled automatically or semi-automatically. MANUAL & AUTOMATIC CONTROL: Manual Control: When the corrective action is carried out by the operator to operate the process to a desired condition, then it is manual control. Automatic Control: When the corrective action is carried out by the instruments, then it is automatic control. Types of Automatic Control:

Open loop control

Close loop control Types of Close Loop Control:

Feed-Forward control

Feed-back control Advantages of Automatic Control:

Increased production A

Improved quality

Greater product uniformity

Saving in raw material

Saving in energy

Saving in manpower

Increased safety Control Loop: An arrangement of instruments connected to control a physical variable to the desired value, constitutes a control loop. Elements of Control Loop:

Process; a variable of which has to be controlled Sensing / measuring system; measures the physical variable Transmitter; transmits measured signal to the controller Controller; generates control command according to the desired value Correcting element; carries out the control command Connecting cables & tubes, allows to pass the signals

3. DIFFERENT METHODS OF CONTROL TECHNIQUE: Conventional Control System: In this system the control components are permanently connected with each other according to the requirement of the process. For continuous control of the process parameters different instruments such as measuring, indicating, transmitting. Controlling instruments are physically connected with each other to control the process. On the other hand, ON-OFF control, sequential logic operation, process operation and safety is done by permanently connecting the electrical/electronic/pneumatic/hydraulic relays, timers, counters, switches and actuators.

Advantages: o All components can be checked physically o All interconnections can be checked physically

Disadvantages:

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o Difficult to change the control program of the process, because it is clone by physical cable

o High cost, low speed, low reliability Computer Control System: Now days, powerful low cost micro—computers are available, and are often used in both continuous control sequential logic operation of the process. Except field connections, the instruments and logic connections can be done by software program. For continuous control of the process, Distributed Control System (DCS), etc. are used. On the other hand, automation, sequential logic operation and safety of the process can be done by Programmable Logic Controller (PLC).

Advantages: o Not difficult to check/ calibrate of the control components while it is in use o Not difficult to change control program, because program is done by software o Low cost, high speed & high reliability

Disadvantages: o Control components & their interconnections cannot be checked o For maintenance & programming, needs trained manpower

Distributed Control System (DCS): DCS is the computer control process operation system in which the control is distributed in computer modules containing one or more microprocessor based controller and each controller is capable to control several instrument loops. Every controller or computer modules are connected by single high speed data link, called data high-way and connected with central console. Central console consists of CRT display, keyboards, printers, memory and communication interfaces. Programmable Logic Controller (PLC): The programmable logic controller is the replacement of conventional sequence system such as electromechanical relays, timers, counters etc. A PLC is a digital electronic system designed for use in automatic control system. The system comprises of programmable memory for the internal storage of instructions for implementing specific functions The PLC can execute functions like logic and sequential control of process, timing, counting and mathematical functions.

3. RANGE, SPAN AND ACCURACY Range: Range is the region between two extreme values (lowest and highest) of the relevant parameter, which the meter is capable of measuring. Span: Span is that part of range, which is actually used. So, span is the part of a range. Span can be maximum equal to the range but can’t exceed the range. Accuracy:

Accuracy = ±(Instrumental reading-Actual reading) × 100%

Span

4. INDICATING INSTRUMENT A measuring instrument in which only the present value of the measured variable is visually indicated is called indicating instrument. Types of Indicating Instruments:

Pointer type indicator Digital type indicator

Types of Pointers: Lance type pointer Knife-edge pointer A Actual measuring system

Types of scale plates:

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Square plate Circular plate Rectangular plate Arc plate

RECORDING INSTRUMENT: A measuring instrument in which the values of the measured variable are recorded continuously is called recording instrument. Recording instrument continuously registers the measured parameter with respect to time. Recording may be in the term of hard copy (in chart paper) or soft copy (data in disk). As a result more information is obtained about the actual production process and the nature and extent of deviations. This makes it possible to take appropriate action and keep the process well under control. Types of chart papers:

Strip chart Circular chart

Recording pen and ink: Instrument ink contains glycerin and attracts water so that it does not dry up in the pen and the recorded lines remain wet for slightly longer than ordinary ink. Ordinary ink must not be used even in cases of emergency. This would only lead to clogging.

MEASURING DEVICES/SENSORS AND TRANSMITTERS:

INTRODUCTION: If an industrial process is to be truly controlled, it is essential that certain system variables to be monitored. That is, conditions within the system must be constantly measured and converted to other forms of signal. So integral parts of any industrial process control system are those elements or subsystems that are capable of sensing the system conditions. These elements can be classified into two parts; input transducers and sensors, in many cases, treating the two groups as one is acceptable. Variable to be measured in a point of a system called measurement point. Measurement point consists of measuring element or primary element. Primary element is also called transducer or sensing element.

PRIMARY ELEMENTS: Primary element for pressure measurement:

o Pressure gauge with liquid elements: Mercury barometer U tube manometer

o Pressure gauge with elastic elements: Bourdon tubes Bellows Diaphragm Diaphragm capsule

o Pressure measuring transducer: Electrical resistance strain gauge/transducer Capacitate pressure transducer Piezoelectric force/pressure transducer LVDT (linear variable differential transducer)

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o Different pressure measurement: Orifice plate Venture tube Flow nozzle Pilot tube Elbow-wire target

Primary element for level measurement: Float type level sensor Displacer type level sensor Hydrostatic pressure for level measurement Air bubble or purge system level measuring sensor Capacitive type level sensor Ultrasonic level sensor/transducer The nuclear radiation level sensor

Primary element for temperature measurement: Resistance temperature detector (RTD) Thermistor Thermocouples Bimetallic temperature sensors Liquid/gas filled thermometers

Primary element for flow measurement: o Displacement

Positive displacement Turbine meter

o Velocity Magnetic flow-meter Vortex flow-meter

o Mass flow-meter Weight type

Pressure sensing and measuring elements:

C-bourdon Spiral bourdon

Diaphragm Diaphragm capsule Bellows

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Level sensing and measurement elements:

TRANSMITTER: INTRODUCTION: Transmitters are the instruments those are used to transfer measurement data rapidly and accurately from the measurement point to the central control room in the industry. The receiver receives the measurement variables and displays those measurement variables. Transmitters &Receivers are interconnected by transmission line. This is usually an air pipe, electric cable or optical fiber but there is also wireless transmission systems designed to cover very large distances. Receiver can be designed as an indicating, Recording or Counting instrument. The scale is calibrated in the desired units as in 𝑏𝑎𝑟, 𝑘𝑔𝑓/𝑐𝑚2, °𝐶 etc. Advantage of using Transmitter and Receiver:

1. Gives a clear view of process at a glance from the control room. So it is easy to control the process very precisely.

2. Inexpensive and simple. 3. Greater safety and reliability.

CLASSIFICATION OF TRANSMITTERS: Depending on driving power transmitter may be classified as follows:

1. Pneumatic Transmitter 2. Electrical/Electronic transmitter: -Analog, -Digital, -SMART 3. Hydraulic transmitter

According to function transmitter may be classified as: 1. Pressure Transmitter 2. Volume flow transmitter 3. Level transmitter 4. Temperature transmitter 5. 𝑝𝐻 transmitter 6. Conductivity transmitter etc.

According to operating principle pneumatic transmitter are classified as follows: 1. Motion balance type 2. Force balance type 3. Torque balance type

DEFINITION OF PNEUMETIC TRANSMITTER:

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Pneumatic transmitter converts the measured value into an air pressure signal using pure, oil tree and dry compressed air. The supply pressure of the compressed air is 1.4 𝑘𝑔𝑓/𝑐𝑚2 andoutput of the pneumatic transmitter is 0.2 𝑘𝑔𝑓/𝑐𝑚2to 1.0 𝑘𝑔𝑓/𝑐𝑚2. PNEUMATIC TRANSMITTER OPERATES AS FOLLOWS:

1. A measured value of pressure, flow, level or temperature is fed to the transmitter. 2. The transmitter converts the measured value into an output air pressure. The compressed

air being supplied(1.4 𝑘𝑔𝑓/𝑐𝑚2) to the transmitter. 3. The output pressure of the transmitter is linear with the measured value for 0.2to

0.1 𝑘𝑔𝑓/𝑐𝑚2. THE FLAPPER-NOZZLE SYSTEM: A pneumatic transmitter uses flapper nozzle arrangement. The flapper nozzle system is shown in figure. Here it converts the mechanical movement of the measuring element into a change of air pressure. The output pressure variations for different clearances between flapper and nozzle are shown in l*`ig.16. The relation between output and clearance is not exactly linear. If a variable force is given to it in such a way that the clearance changes from 0.075 𝑚𝑚 to 0.125𝑚𝑚, then one can consider a linear relation between the output and clearance. Assume, in this case, the output changes from 0.8 𝑏𝑎𝑟 to 0.4 𝑏𝑎𝑟. An amplifier may be used to amplify this output range 0.8 ~ 0.4 𝑏𝑎𝑟 into 1.0 ~ 0.2 𝑏𝑎𝑟. Electrical transmitter: The operating principle of the electrical transmitter is illustrated in figure. If the measured pressure increases, the soft-iron core will move further away from the coil. The current through the coil will now rise and the output current of the amplifier will also rise. Due to this increase in current the opposing force will also increase and move the lever back until it is in equilibrium with the measuring force.

CONTROLLERS AND CONTROL LOOPS:

A controller is an instrument which can measure or control a process variable to a desired value.

The measured value is compared with the desired value and generates control signal for the correcting element / control valve, so that the PV& DV remains same.

CONTROLLER FACILITIES:

Indications o Measured value o Set/Desired value o Output

Auto/Manual operation

Local/Remote set value

Control action adjustment

Direct/Reverse operation Controller Classification:

According to Auxiliary Power o Pneumatic controller o Electronic or Programmable controller

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o Hydraulic controller

According to the Method of Control o ON-OFF controller o Proportional (P) controller o Proportional + Integral (Pl) controller o Proportional + Derivative (PD) controller o Proportional +Integral + Derivative (PID) controller

According to the Output o Direct acting controller o Reverse acting controller

CONSTRUCTION: Controller operates with three units

Sensing element / measuring system Error detector compares MV & SV Control element generates control signal according to deviation

ON-OFF CONTROLLER: Application of ON-OFF Controller:

Precise control must not be needed Process must have sufficient capacity to allow the final operator to keep up with

measurement cycle, which is RC time constant of the process is large Disadvantages of ON-OFF Controller:

Controller output is either maximum or minimum Valve or final driver is either open or close ` Measured value always oscillates about the set value

PROPORTIONAL (P) CONTROLLER: In the proportional controller the output variation is proportional to the deviation between the measured value (MV) and the desired value (DV) and having a continuous output value.

𝑃0 ∝ 𝑒 𝑃0 = 𝐾𝑒

Where, 𝑃0 = Change in output 𝑒 =Deviation between the MV & DV 𝐾 = Constant factor and known as amplification factor of the controller andadjustable

between certain limit Because 𝑃0 is the change in output, so output of controller is

𝑃𝑜𝑢𝑡 = 𝑃0 + 𝐵𝑒𝑓𝑜𝑟𝑒 𝑃𝑜𝑢𝑡 = 𝐾𝑒 + 𝐵𝑒𝑓𝑜𝑟𝑒 𝑃𝑜𝑢𝑡 = (𝑀𝑉 − 𝐷𝑉) + 𝐵𝑒𝑓𝑜𝑟𝑒 (for direct acting controller) 𝑃𝑜𝑢𝑡 = (𝐷𝑉 − 𝑀𝑉) + 𝐵𝑒𝑓𝑜𝑟𝑒 (for reverse acting controller)

Proportional Band: The proportional band (PB) is the amount of variation of the measured values expressed in percentage of the scale on both sides of the set point which is needed to change the output from maximum to minimum or minimum to maximum. Relationship between Gain & PB:

𝑃𝐵% = 100/Gain Gain = 100/𝑃𝐵% Adjustable PB Value: 0 ~ 500 % Disadvantage of P Controller: Remains offset Reduction of Offset:

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Increasing the gain Changing the value of the load spring

PROPORTIONAL + INTEGRAL (Pl) CONTROLLER: Features of Pl Controller:

i. Load spring is replaced by a reset bellows ii. It is done by connecting the reset bellows from the output via a variable restrictor

iii. Variable restrictor is a needle valve and the dial is graduated in terms of time iv. Time graduation scale is from 0 to 50 minutes v. Integral controller is always in combination with P controller

vi. Output of Pl controller, 𝑃0 = 𝐾 ∙ 𝑒 + 𝐾 /𝑇𝑖 ∫ 𝑒𝑑𝑡 vii. Continue to change the output until there exist deviation, because of I action

viii. Ultimately there is no offset Different Conditions of Reset Restrictor:

Restrictor fully close (P controller) Restrictor fully open (ON—OFF controller) Restrictor partially open (Pl controller)

Reset / Integral Time: Reset or integral time is the time required to change the output of the controller due to integral action which is equal to the same amount of change due to the proportional action. PROPORTIONAL + DERIVATIVE (PD) CONTROLLER: Application of Derivative Controller:

Derivative action of the controller is introduced where the process variable may overshoots or undershoots due to sudden change in load

Lagging in sensing of process variable Features of PD Controller:

i. Derivative controller is always in combination with P controller ii. Controller is proportional to the deviation plus the rate of change of deviation

iii. Derivative action can be activated by placing a variable restriction in the connecting pipe of the feed-back bellows

iv. Variable restrictor is a needle valve and the dial is graduated in terms of time v. Time graduation scale is from 0 to 50 𝑚𝑖𝑛𝑢𝑡𝑒𝑠

vi. Output of Pl controller, 𝑃0 = 𝐾 ∙ 𝑒 + 𝑇𝑑 ∙ 𝐾𝑑𝑒/𝑑𝑡 Different Conditions of Derivative Restrictor:

Restrictor fully close (ON—OFF controller) Restrictor fully open (P controller) Restrictor partially open (PD controller)

Derivative Time: Derivative time is the time required to reduce the output of the controller by 63.2% fromthe peak value which was caused by the derivative action. PROPORTIONAL + INTEGRAL + DERIVATIVE (PID) CONTROLLER: Output of PID Controller:

𝑃0 = 𝐾 ∙ 𝑒 + 𝐾 /𝑇𝑖 ∫ 𝑒𝑑𝑡 + 𝑇𝑑 ∙ 𝐾𝑑𝑒/𝑑𝑡

Control Loops: The arrangement of instruments connects to control a physical variable to the desired value constitute a control loop.

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Elements of Control Loop: i. The process; a variable of which has to be controlled ·

ii. The measuring system;-measures the physical variable iii. The transmitter; transmits measured signal to the controller - iv. The controller; which generates the control command according to the desired value v. The correcting element (final control element); which carried out the control command

vi. The connecting tubes and pipes; which passes the signals

Figure: Block diagram of control loop

Types of Control Loop:

Open Loop Control

Closed Loop Control Open Loop Control: Open loop control simply involves making an estimate of the form or quantity of action necessary to accomplish a desired objective. Its basis is in prediction. In open loop control, no check is made to determine whether or not the corrective action taken has accomplished the desired objective.

Figure: Block diagram of open control loop

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Closed Loop Control: In closed loop control, a measurement is made of the process and is compared with the desired value or reference point and then according to the difference or deviation between the measured value and the desired value generates corrective signal to minimize the deviation.

Figure: Block diagram of closed loop control

CASCADE CONTROL LOOP: In cascade control two control loops are coupled to each other. The output of one controller being the set—point for another controller. The cascade control loop is often called "Master-slave" control. The cascade control loop consists of the followings:

Two measuring systems/transmitters Two controllers; one is master and another is slave One control valve

Operation: For a particular set-value of the master controller TIC (PID controller), if the temperature of the hot water increased the output of TIC is feeding as remote set-point of FIC also increased causing the control valve to close. At the same time the steam flow will decrease and the slave controller FIC will get sense through FT. Ultimately the temperature will decrease and control at set value. During decrease of hot water temperature, reverse operation will happen. Start-up and Shutdown of Cascade Control Loop: Start-up:

Switch the master (TIC) and slave (FIC) to manual. Operate the slave controller (FIC) manually to obtain the desired temperature in TIC. Operate the master controller (TIC) manually and set the slave controller (FIC) remote set

equal to the measured value of FIC. Switch the FIC controller to automatic, Set the TIC controller set-point equal to the measured value. Switch the master controller (TIC) to automatic.

Shutdown: Switch the master controller to manual (bumpless transfer). Switch the slave controller to manual (bumpless transfer).

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Figure: Block diagram of cascade control loop

Advantage of Cascade Control Loop:

Better Control of the Primary Variable Primary variable less affected by disturbances Faster recovery from disturbances Increase the natural frequency of the system Reduce the effective magnitude of a time-lag Improve dynamic performance Provide limits on the secondary variable

CONTROL VALVE: Definition of control valve: A valve with a pneumatic, hydraulic, electric or other externally powered actuator that automatically opens or closes the valve fully or partially by signals received from controlling instruments is called control valve. Functions of control valve: Control valve controls fluid flow to control other process parameter such as pressure, temperature, level, flow etc. A control valve functions as variable resistance in a pipeline. Control valve directly controls the fluid flow and because of that it is called final control element. CLASSIFICATION OF CONTROL VALVE: Classification based on operating power:

Pneumatically operated control valve Hydraulically operated control valve Electrically operated control valve

Pneumatically operated control valves are most popular in use for reliability and effective control. Classification based on valve body construction:

Globe valve Diaphragm (Saunders) valve

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Three-way valve Butterfly valve Angle valve Ball/Rotary valve

Classification based on control action: Signal to open: It is called normally closed (NC) control valve. It closes at 0.2 𝑘𝑔/𝑐𝑚2

andopens at 1 𝑘𝑔/𝑐𝑚2. Signal to close: It is called normally open (NO) control valve. It closes at 1.0 𝑘𝑔/𝑐𝑚2 and

opens at 0.2 𝑘𝑔/𝑐𝑚2.

Figure: Flow characteristics of control valve

Classification based on flow characteristics: Linear flow characteristics control valve Quick opening flow characteristics control valve Equal percentage flow characteristics control valve

Different Parts of a Pneumatic Control Valve: The main parts of a pneumatic control valve are the followings:

(i) Valve actuator (ii) Valve body (iii) Bonnet

VALVE ACTUATOR: Valve actuator is operated by controller signal. The function of actuator is to open or close the control valve appropriately by using the signal that comes from controller. Sometimes control valves are operated manually. In that case a hand wheel is associated with an actuator. Valve is closed or opened as per requirement with the help of the hand wheel. Different Types of Actuator: Actuator Based on Action:

Direct acting actuator: Input increases, actuator stem moves outward.

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Reverse acting actuator: Input increases; actuator stem moves inward.

Figure: Different parts of a pneumatic control valve

Piston Cylinder Actuator: The piston cylinder actuator consists of a hollow cylinder tube that is divided into two parts by a movable piston. The cylinder itself is sealed at both ends except for signal connection it has a power take-off shafts. Piston cylinder actuator can be of two types:

Single acting cylinder with spring Double acting cylinder without spring

In single acting cylinder with spring, the diaphragm is replaced by a piston. The piston is placed in a cylinder whose one side acts as signal chamber and the other side has a spring. Pneumatic signal is applied in signal chamber and the force is balanced by the spring in opposite side. This type of piston actuator may have a greater stroke than that of diaphragm type actuator. The main parts of piston cylinder actuator are cylinder, piston, actuator stern, piston ring, spring (actuator with spring) etc. In double acting cylinder without spring, two different signals are applied on opposite sides of the piston and the valve is controlled by the force exerted on the piston due to differences of signals on it. Figure shows a piston-cylinder type actuator. Control Valve Accessories: Some accessories are used with the control valve to the valve stroke, i.e., closing or opening. These are as follows:

i. Valve positioner ii. Limit switch

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iii. Booster relay iv. Air Lock relay v. Solenoid valve

vi. Hand wheel Valve Positioner: Valve Positioner is auxiliary devices attached to the control valve to ensure the valve position corresponding to the controller signal. When a positioner is applied to a valve, the valve is no longer operated directly by the controller output pressure. The positioner utilizes the instrument (controller) output pressure only as a signal and controls an independent pressure supply to apply whatever pressure is required to force the valve stem to the correct position. Thus the positioner is a relay capable of applying maximum force to position the valve stem correctly. Functions of Positioner:

i. Positioning the control valve precisely in accordance with the controller output pressure. ii. Eliminate valve hysteresis i.e. to overcome stuffing box friction with the stem, spring

hysteresis etc. iii. Split range control of two or three valves can be obtained by using positioner without

changing the bench range of the actuator. iv. Positioner can change the valve flow characteristic through the use of cam. v. By using a positioner with non-standard output, it is possible to operate a non-standard

control valve (say 5 ~ 25 𝑝𝑠𝑖) with a standard controller output. vi. Positioner greatly increases the speed of response when the distance between controller

and valve is long. Types of Positioner:

Pneumatic Positioner Electro-pneumatic positioner

Main Components of a Pneumatic Positioner: i. Input bellows, which receives the output of the controller

ii. Adjustable spring, which counteracts the input, bellows iii. Flapper nozzle system iv. Amplifier v. Cam

vi. Feedback lever

Figure: Pneumatic positioner

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Working principle of a pneumatic positioner: Pneumatic valve positioner is a single acting single stage force balance type control instrument (servo device). It utilizes an auxiliary air supply and a feedback cam to position the control valve in accordance with the air signal from a controller. Utilizing the force balance principle the positioner feeds air to the valve actuator until the force control signal is in balance with the force created by the valve stem movement on a feedback cam.

Figure: Electro-pneumatic positioner

INTRODUCTION TO SEQUENTIAL LOGIC CONTROL: CONCEPT ON SEQUENTIAL LOGIC INSTRUMENTATION: The manner of operating a machine or equipment by feeding the steps into a particular order for safe start-up, operation, annunciation and shutdown is called sequence. Sequential control improves the quality of control as well as safety of machine and plant. An example will make it clear. For smooth running of a compressor lubrication is necessary. A lube oil pump supplies oil to the bearing of the compressor to protect it nom overheating. To save the compressor, lube oil pump is to be started first before starting the compressor, the compressor and the pump can be interlocked (electrical) so that without starting the lube oil pump operator cannot start the compressor. This type of protection system of a machine by proper instrumentation is called interlocking. There are two types of sequence system:

(i) By electromagnetic relay (ii) By Programmable Logic Controller (PLC)

In the conventional sequence system electromagnetic or solid state relays, timers, counters etc. are used as switching element. On the other hand in the computerized control system electromagnetic or solid state relays, timers, counters etc. are replaced by microprocessor based Programmable Logic Controller(PLC). COMPONENTS OF CONVENTIONAL SEQUENCE SYSTEM:

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The main components of a conventional sequence system are switches, relays, timers, solenoid valves etc. Switch: The electric switch is a device that is used for making, breaking or rerouting connection in an electrical circuit to operate the load. This switching is accomplished by the opening or closing of two metal surfaces. Types of Switch: Mainly switches are of three types:

• Momentary action switch • Maintained action switch

Momentary action Switch: When actuated power is applied to the switch, it changes its position, but if the power is withdrawn, the switching position will be returned to the previous position. This type of switch is called the momentary contact switch. Example: Push button switch, Limit switch, Level switch, Pressure switch etc. Maintained action Switch: When the actuated power is applied to the switch, it changes its position, but if the power is withdrawn, the switching position will remain unchanged. This type of switch is called the maintained contact switch. Example: Normal on-off switch, change over switch, toggle switch, slide switch etc. Relay: Relay is an electrically controlled device that can open or closes several contact paths simultaneously when its coil is energized by electric power. By using a low level of control energy in the relays, it is possible to switch high power levels and actuate several contacts at the same time. Functional components: Electro-magnetic relays are consists of the following:

i. Coil ii. Iron core

iii. Armature iv. Contacts v. Spring

Principle of Operation: The solenoid coil of a relay remains in de-energized position if no power is applied. In this case, the spring 5 pulls the armature 3 away from the iron core. When power is applied, the solenoid coil becomes energized and the armature 3 is pulled towards the iron core. As a result the normally open (NO) contacts will close and normally close (NC) contacts will open. Concept on NO and NC Contact: If the contact of a switch or relay remains close on actuated force free condition, the contact is called NC contact. Actuated force may be mechanical, electrical, hydraulic or any other means. On the other hand, if the contact of a switch or relay remains open on actuated force free condition, the contact is called NO contact. A relay may have several sets of NO and NC contact. In every set of contact, there is a common (COM) terminal.

Figure: Relay (shown de-energized)

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Figure: Self-hold system of relay

Sequential Operation of a Typical Level Control Loop: We want to control the liquid level of a tank in such a way that when the liquid level goes below 20 %, ‘level low’ alarm appears and pump starts by level switch low (LSL) and continuous to run till high level appears. When the level of liquid reaches 80 %, ‘level high’ alarm appears and pump stops automatically by high level switch (LSH). It remains stop until level low alarm appears. For the above automatic operation, selector switch must be positioned in 'AUTO' mode. The pump should have the facility of starting and stopping manually at any time. In that case the selector switch must be positioned in ‘MAN’ mode.

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INTRODUCTION TO DISTRIBUTED CONTROL SYSTEM (DCS):

INTRODUCTION: Distributed Control System is one kind of Computer control system, in which the control is distribute to computer modules containing one or more microprocessors—based controller & each controller have capabilities to control several instrument loops. Every controllers or computer modules are connected together by a single high-speed data link, called a Data Highway, which permitting communications between each of the microprocessor-based modules and the central control console. Control console is basically consists with CRT for process status looking, Two/three—level Keyboard for process operation & System configuration, Printer for process status hardcopy representation and also its own memory to store data in its microprocessors to process data, and its own communications interface for being tied to the data highway etc.

DCS is a very broad term used in a variety of industries, to monitor and control different Process:

1) Electrical Power grids and Electrical generation Plants 2) Environmental control systems 3) Traffic signals 4) Water management systems 5) Oil refining plants 6) Chemical plants 7) Pharmaceutical manufacturing

The main features and advantages of DCS:

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(a) The system is reliability & speedy. (b) If any microprocessor is fail, only one portion of the overall system will be out of control, not

the whole assembly. (c) Similarly, if Station fails, whole field units should be alive. (d) It is much easier to make software changes to the distributed system. (e) The availability of color CRT based operator control centers provides more information and

guidance to the operator for his actions. (f) Control rooms are simplified, as all information is available on CRT. (g) Extensive diagnostic schemes are available. (h) Redundancy and fail—safe techniques incorporated permit high reliability and availability of

the system.

PLANTSCAPE SYSTEM (Windows based-DCS): PlantScape is one kind of Distributed Control System for process plant. The PlantScape Server, Stations & Operator Interface provide an operator ‘window’ to the plant or process. With PlantScape the user only needs to configure the system, allowing the user to concentrate more on the application. There are three different types of PlantScape system available:

(a) PlantScape Vista: Use on small systems using Honeywell UDC controller and similar. (b) PlantScape SCADA: For use with SCADA systems using a wide variety of Honeywell and 3rd

party controllers &PLCs. (c) PlantScape Process: Same as PlantScape SCADA but also fully integrated with the PlantScape

Hybrid controller (Present at TICI). PlantScape system hardware is consisted with:

(a) Process Units a. Process equipment/Instruments b. UMC 800 (Microprocessor-based multi-loop controller) c. Networking devices

(b) Management Units a. PlantScape Server b. PlantScape Workstations c. Networking devices d. Printer etc.

Process equipment/Instruments: Like Conventional Control System, DCS also have Held or process equipment or instruments as Flow meters, D/P transmitter, T/C, RTD, Analyzers, Control valves, Recorders, Pumps, SV, Limit SW, Motor, Smart transmitter, PLCs etc. UM-C 800 Controller: The Universal Multi loop Controller (UMC 800) is a modular controller designed to address the analog and digital control requirements of small unit processes. With up to I6 analog control loops, four set point programmers, and an extensive assortment of analog and digital control algorithms, the UMC8OO is an ideal control solution for furnace, environmental chambers, ovens, reactors, cookers, freeze dryers, extruders, and other processes with similar control requirements. Figure shows the UMCSOO connection diagram. The operator interface uses a color graphic LCD display to provide a variety of display presentations for viewing control loops, set point programs, and other analog and digital status. A separate "Control Bui1der"configuration software program is used for system configuration that operates on a Windows95/98 or NT-based PC.

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PlantScape Server: The Computer on which the PlantScape database software runs. The PlantScape Server provides an operator’s window to the plant or process. The major functions provided by the PlantScape Server are:

i. Fully integrated with the PlantScape Hybrid controller. ii. Interface to other Honeywell and 3rd party controllers.

iii. Distributed server architecture enabling data sharing with other PlantScape. iv. Acquisition and control Algorithms. v. Historical Data Collection Display.

vi. Reports. vii. PC based Operator Stations.

viii. Alarm and Event Management. Station: The main operator interface to PlantScape. Stations may run on either a remote computer through a serial or LAN link, or on the server computer. When station is running on the PlantScape server computer, it is often referred as a server station. When it is running on a machine other than the server, it is often referred to as an operator station. Networking: Computers are usually connected together on a network so that the applications (programs) running in each of the computers are able to pass information to each other. The Network hardware’s that PlantScape uses are Ethernet and different protocols are used to transfer information into different stations. PlantScape server uses TCP/IP to transfer data to connected stations.

DATA STORAGE PHILOSOPHY OF DCS: Process Data Storage Media: In this system, there data may be saved on Hard disk or ZIP drive Floppy disk at writable CD in CD-ROM drive. By using these disk drives we can up-load or download the system programs & also storage on that disk. This type storage device is called auxiliary memory. It is also possible to print start-up log, shutdown log, and previous events from above media. As for example, operator message, process alarms system status etc. Semiconductor Memory: A semiconductor is a microscopic component such as transistor or diode. In semiconductor storage, thousands of the miniature components are combined on a tiny silicon chip. Metal oxide Semiconductor (MOS), Complementary MOS (CMOS) and bipolar semiconductors are the major technologies used in semiconductor memories. Semiconductor storage devices are

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called Integrated Circuits (IC), since all the storage components & address decoding are integrated on a single chip. Semiconductor storage is available in different types. They are RAMs, ROMs, PROMs, EPROMS, IEEPROMS & dynamics RAMs. The most commonly used & cheap semiconductor storage is Battery backup RAM (because they are Volatile). RAM is high-memory capacity & used as working memory. On the other hand, ROMs are used in applications in which the programs or data in ROM are not to be changed (because they are non-volatile). EPROMs are mostly used.

REDUNDANCY SYSTEM: Many manufacturers, depending on process emergency, offer system with built-in back-up features so that the failure of one part of the DCS does not affect the system performance at all. There are several ways of providing these features. Partly or whole part may be back up or redundant. Redundant mode may be selected through by manual switch or auto system. Below figure shows a typical redundancy system.

DIAGNOSTICS & TROUBLESHOOTING: Different types of problem arise during plant running or off conditions. DCS system has facilities to monitor & End out the message / events through different menu / icons on DCS screen. These menu/icons may be: Alarm icons: When any event occurs due to process abnormality or system fault, then Alarm icon will be flashed with "Red" color & audio "Sound". By selecting this Alarm icon, we can get the details causes & identifications of problems. Logic or interlock diagram menu: Logical or on / off events can be identify through this menu so that where is the problem to start / stop of a device. Monitor mode in process configuration menu: In this mode we can observe the on / off status of input /output devices & other parameters. For test the devices, we can make force on / off of devices for loop / logic checking. Software of PlantScape system: The PlantScape Server software is divided into functional subsystems. Each subsystem consists of task groups to execute and manage data flow. All task groups have access to the Server Real-time Database. The Database is located solely in the PlantScape Server and is not distributed. Operating Software & application- software used in PlantScape system is shown in below Table:

Name device Type of software used

Function of software Operating software Application software

PlantScape Server Windows NT Control builder, Display Builder, Quick Builder, On line documentation Station software

System configuration, Upload/Download, save, edit etc.

PlantScape Station Windows 95/98

UMC 800 Controller Leader line control builder – Run on Windows NT/95/98 based PC

Pilot Plant Areas: There is only one area in the TICI DCS Pilot Plant & is configured as AREA-01. Under Area—01, there is 3-unit. Unit 01 is Pressure control loop (Process—P300), Unit 02 is Flow control loop (process—P800) & Unit 03 is Furnace temperature control loop (Process—T1100). Figures show the TICI Pilot Plant area’s schematic diagram &Pressure control Loop. Again there may be sub-units under every unit.

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UV – VISIBLE SPECTROSCOPY Spectroscopy is the study of absorption or emission of radiation by atoms or molecules. When electromagnetic radiation passed through a substance the electrons from the lower energy state promoted to the higher energy state by absorbing the electromagnetic radiation, after a while it jumps back to the lower energy state by emitting the absorbed energy. This is known as electronic transition. Electronic transition accompanied with vibrational and rotational transition. UV/Visible spectroscopy deals with that absorbed or emitted energy. Electromagnetic radiation can be divided in seven distinct regions:

1. Gamma ray : 1𝑝𝑚~100𝑝𝑚 2. X-ray : 100 𝑝𝑚 ~ 10 𝑛𝑚 3. Ultra-Violet ray : 10 𝑛𝑚~ 400 𝑛𝑚 4. Visible : 400 𝑛𝑚 ~ 800 𝑛𝑚 5. Infrared : 800 𝑛𝑚 ~ 1000 𝑝𝑚 6. Micro wave : 1000 𝑝𝑚 ~ 30 𝑐𝑚 7. Radio wave : 30 𝑐𝑚 ~ 10 𝑚

Range of UV- visible radiation are 10 𝑛𝑚 ~ 400 𝑛𝑚 and 400 𝑛𝑚 ~ 800 𝑛𝑚.

INSTRUMENTATION: Spectrophotometer is a device, which measures the absorbance as well as transmittance of electromagnetic radiation, when radiation applied through a sample. UV- Visible Spectrophotometer is of two types: -

1. Single beam Spectrophotometer 2. Double beam Spectrophotometer

In single beam spectrophotometer the light radiation follows a single continuous path between light source and detector. In double beam spectrophotometer, light (radiation) emerges from the monochromator splitted into two alternating pulse trains, one of which passes through the reference and the other passes through the sample. Either the beams may have their own detector or they can combine before reach a single detector.

PARTS OF SPECTROPHOTOMETER: 1. Light source:

a. Hydrogen lamp; wave length range 185 ~ 400 nm. b. Deuterium lamp: wave length range as hydrogen lamp but higher stability. c. Tungsten filament lamp: wavelength range 350nm ~ 800nm. d. Tungsten halogen lamp: wavelength range as tungsten filament lamp but the life time is

double than that of tungsten filament lamp. 2. Mirrors: Transfer the light or radiation. 3. Monochromator: The purpose of monochromator is to separate the required wavelength

radiation(monochromatic radiation) from the source radiation. Monochromator consists of:

i. Entrance slit ii. Filters

iii. Grating iv. Exit slit

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Slits: Entrance slit reduces the source radiation to small suitable area. Exit slit selects the required wave length which is presented to the sample. Filters: Filters are used to isolate the desired spectral region by absorbing the undesired wave length spectra. They consist of gelatin containing dyes or colored glass or metal film. Diffraction grating: The purpose of grating is to produce a spectrum of radiation by diffraction. The grating consists of a large number of slits or grooved formed on glass or metal. When light falls on the metal grating it enters each grooved and reflected. The undesired wave lengths thus are blocked by using filters.

4. Cell/cuvettes: To measure the absorption of radiation the sample solution must be placed into a container or vessel, which is called cell or cuvette. Cell may be made of glass, plastic or quartz. Standard cell path length is 10 𝑚𝑚.

5. Detector: It is fused to measure the intensity of the radiation and hence the absorption.

APPLICATIONS: a. Quantitative chemical analysis b. Identification of compounds c. Impurities detection etc.

OPERATION & USE OF ATOMIC ABSORPTION SPECTROPHOTOMETER

PRINCIPLE: The sample containing metal element is heated on high temperature produces metal atoms after evaporation of solvent. The gaseous metal atoms may absorb energy in the form of radiation of characteristic wavelength. The sequential steps for the production of gaseous metal atoms are as follows:

Ultraviolet, visible and X-ray atomic spectra are obtained by atomization. The absorption, emission and fluorescence spectrum of atomized species serves as the basis of analysis Absorption spectra: Metallic atoms absorb radiation of certain wavelength and electronic transition is occurred to get excited state. Emission spectra: Metallic atoms & ions in excited state can release energy in the form of radiation when electrons back to its original position. Fluorescence spectra: Atoms absorb radiation and electrons are promoted to higher energy levels. After a moment they can irradiate more intensely radiation of particular wavelength.

ATOMIZATION OF SAMPLES:

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Flame atomization: A solution of sample is sprayed into a flame by means of a nebulizer.

Fuel Oxidants Temperature ℃ Natural gas Air 1700 − 1900

Natural gas Oxygen 2700 − 2800

Hydrogen Air 2000 − 2100

Hydrogen Oxygen 2500 − 2700

Acetylene Air 2100 − 2400

Acetylene Oxygen 3050 − 3150

Acetylene Nitrous oxide 2600 − 2800

Flameless atomization: There are two types of flameless atomizer (1) Electro-thermal and (2) Graphite cup atomizer.

RADIATION SOURCES FOR ATOMIC ABSORPTION: The absorption & emission of radiation in atomic state occur within the band of 0.002to0.005 𝑛𝑚. So line source is required for this purpose. Hollow cathode lamps: The cathode is a hollow cylinder made of pure element of which we require the spectrum and the anode is of tungsten. The anode and cathode are scaled into a glass tube that is filled with neon or argon gas. It has restricted life. Electrodeless discharge lamps: A small amount of element is sealed in a small quartz globule. Neon or argon is used as the filler gas. The bead is enclosed with a ceramic cylinder which is coiled and high frequency electric field is applied for emission of radiation.

INSTRUMENTATION:

ANALYTICAL TECHNIQUES: Preparation of sample: In the flame spectroscopic method, sample is introduced into excitation source as a solution, most commonly an aqueous one. So most of the samples require extensive preliminary treatment. In most methods mineral acids are used for decomposing the sample. Combustion in oxygen bomb, high temperature Fusion with boric acid, 𝑁𝑎2𝐶𝑂3, 𝑁2𝑂2, 𝐾2𝑆2𝑂8 etc. are also employed. In some cases Electro-thermal atomization is more advantageous. Nebulization & aspiration: In flame atomization, sample solution is sucked by a capillary tube of air ejector which produces mist in the nebulizer box. Ultimately the solution mist falls into the flame. Hydride generation techniques: 𝐴𝑠, 𝐵𝑖, 𝑆𝑒, 𝐺𝑒, 𝑆𝑏, 𝑆𝑛 etc. produce gaseous hydride on action of reducing agent with their solution. The hydrides are directly aspirated into the flame. Cold vapor technique: Mercury ion is reduced quantitatively to 𝐻𝑔-vapor by 𝐻𝐶𝑙, 𝐻𝑁𝑂3and 𝑆𝑛𝐶𝑙2 or sodium borohydride solution. 𝐻𝑔-vapor absorbs radiation from𝐻𝑔-hollow cathode lamp.

APPLICATION OF ATOMIC ABSORPTION SPECTROSCOPY:

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Atomic absorption is useful for the determination of a large number of metals, particularly at trace level. It is widely used in such fields as water, pharmaceutical, plant & animal tissue analysis, and in metallurgy. The exact conditions required for a given determination are quite critical unless one prepared to undertake a lengthy methods/research. It is essential to obtain specific directions and to follow them carefully.

OPERATION & USE OF GAS CHROMATOGRAPH

INTRODUCTION: In the year of 1906 a Russian Botanist, Mikhil, Tswett invented the technique of separation of chlorophylls in plant extract. He used a glass burette packed with chalk powder and flow of solvent through the column for separation work and introduced the subject ’chromatography’ in the analytical realm. He saw different bands of color developed indifferent zones of the column. The name of subject ‘Chromatography’ comes from the Greek word chrome means color and graph means to write. The way of identification of separated components was done from the color and hence the name.

PRINCIPLE OF CHROMATOGRAPHY: Chromatography is separation technique based on the difference in distribution coefficients of a component into two phases; one stationary and other is mobile phase. In this process, the mobile phase carries the sample components through the stationary phase. The speed of the components is retarded by the stationary phase on the basis of different affinity for stationary phase. As a result of selective affinity retardation is brought about. The components of the mixture will travel through the column at different speed causing separation of components.

ADVANTAGES IN CHROMATOGRAPHIC METHODS: Rapid analytical procedure Very small amount of sample can be used Sample can be subjected to both qualitative and quantitative analysis The process can be readily automated In most cases the test is non-destructive Members of homologous series can be separated & analyzed easily Suitable for analysis of isomeric compounds as well

CLASSIFICATION OF CHROMATOGRAPHIC METHODS: On the basis of physical state of mobile and stationary phases the chromatographic methods can also be classified into following groups:

Sl. No. Mobile phase Stationary phase Types of chromatography 01 Gas Solid Gas-solid chromatography (GSC)

GC 02 Gas Liquid Gas-liquid chromatography (GLC)

03 Liquid Solid Liquid-solid chromatography (LSC) LC

04 Liquid Liquid Liquid-liquid chromatography (LLC)

GAS CHROMATOGRAPH (GC): The stationary phase in a gas chromatograph should have sorption active property while the gaseous mobile phase with high purity carries samples i.e. the sample components through the

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column. The stationary phase reacts on each component with different strength of affinity and reduces the mobile speed of the components causing separation of the sample components.

ESSENTIAL PARTS OF A GAS CHROMATOGRAPH: 1) Reservoir wit/1 control device of carrier gas- Helium, Nitrogen, Argon 2) Sample injection device — Gas sampler / Liquid injection port 3) Columns — Packed, Capillary, Wide bore capillary etc. 4) Detector — Thermal conductivity (TCD), F lame ionization (PID), Mass spectrometric 5) Thermostat for injection block, column block and for detector 6) Read out device — Recorder/Computer system data integration

BASIC COMPONENTS OF A GAS CHROMATOGRAPHIC SYSTEM:

OPERATION MODE: Isothermal, Programmed temperature, Programmed Pressure/flow

CHROMATOGRAM: The detector signal is recorded by an analog recorder digital integrator or by a computer system. The paper runs at a certain speed (𝑐𝑚/𝑚𝑖𝑛) through x-axis and detector signal (𝑚𝑉) is reproduced on the y-axis. A computer system collects the detector signals and subsequently represents this data in various ways. When computer or integrator is used, it is important for all the necessary parameters to be set correctly. Generally detector signal is recorded graphically and such graph is known as chromatogram. Both qualitative & quantitative calculation can be done from the analysis of chromatograms.

USE AND APPLICATION OF GC: The volatile and gaseous components of samples are determined suitably by a GC. Mostly organic samples are employed for analysis.

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PRACTICAL ASSIGNMENT SHEET Flow Assembly

Tasks:

01. Practical on start-up, normalization and shutdown procedure of the unit 02. Rotameter calibration 03. Determination of pressure drop for different flow rate of liquid with different restrictions

A. Experimental data: Table-1: Calibration of rotameter:

Obs. No. Rotameter reading (%) Time (second) Amount of water (ml) Flow rate (lit/hr)

01 10 5 330 237.6 02 20 5 570 410.4 03 30 5 910 655.2 04 40 5 1260 907.2 05 50 5 1550 1116 06 60 5 1780 1281.6 07 70 5.5 2270 1485.8

Table-2: Pressure drop for different flow rate of liquid with different restrictions:

Obs. No.

Rotameter reading (%)

Flow rate

(lit/hr)

Differential pressure (∆𝑃), Bar

Gate valve

Glove valve

Oblique valve

Orifice Bend with

fittings

Bend without fittings

01 10 237.6 0.018 0.038 0.1 0.05 0.01 0.02 02 20 410.4 0.02 0.10 0.12 0.07 0.025 0.025 03 30 655.2 0.03 0.22 0.14 0.1 0.04 0.03 04 40 907.2 0.035 0.34 0.16 0.14 0.65 0.032 05 50 1116 0.045 0.46 0.18 0.18 0.1 0.035 06 60 1281.6 0.053 0.59 0.21 0.25 0.14 0.04 07 70 1485.8 0.06 0.255 0.34 0.19 0.045

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237.6

410.4

655.2

907.2

1116

1281.6

1485.8

50

250

450

650

850

1050

1250

1450

1650

0 10 20 30 40 50 60 70 80

Flo

w r

ate

(lit

/hr)


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 10 20 30 40 50 60 70 80

Flo

w r

ate

(lit

/hr)


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Study of process response for level control loop using different size liquid tank Tasks:

01. Practice on start-up, normalization and shutdown procedure of the level control loop. 02. Determination of process response for level control loop.

Experimental data:

PB (%) Reset time

(minute) Obs. No.

Rise or fall time (second) at corresponding MV

Maximum value MV = SV Minimum value

50

0.02

𝑀𝑉 (%) 𝑇𝑖𝑚𝑒 (𝑠) 𝑀𝑉 (%) 𝑇𝑖𝑚𝑒 (𝑠) 𝑀𝑉 (%) 𝑇𝑖𝑚𝑒 (𝑠) 01 50 00 02 60 05 03 64 09 60 12 57 20 04 60 23 05 61 27 60 29 59 31 06 60 32 07

0.05

01 50 00 02 60 05 03 63 09 60 13 59 17 04 60 23 05 06 07

25

0.02

01 50 00 02 60 03 03 63 05 60 10 58 13 04 60 15 05 06 07

0.05

01 50 00 02 60 04 03 63 07 60 11 04 05 06 07

Conclusion: i. When proportional band decreases, the measured value becomes stable

quickly. ii. When reset time increases, the measured value does less fluctuation.

So it is proved that decreasing the proportional and increasing the reset time are the best practice for controlling process variable.

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50

52

54

56

58

60

62

64

66

0 5 10 15 20 25 30 35

Mea

sure

d v

alu

e

Time (second)

Process response for Time vs. Measured value%PB = 50 & Reset time = 0.02

50

52

54

56

58

60

62

64

0 5 10 15 20 25 30 35

Me

asu

red

val

ue

Time (second)


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50

52

54

56

58

60

62

64

0 5 10 15 20 25 30

Me

asu

red

val

ue

Time (second)


50

52

54

56

58

60

62

64

0 5 10 15 20 25 30

Me

asu

red

val

ue

Time (second)


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Pump arrangement Tasks:

01. To draw the flow diagram of pump arrangement unit 02. To establish the relationship between capacity (Q) and head (H) of centrifugal pump 03. To establish the relationship between speed (N) and head (H) of centrifugal pump 04. To establish the relationship between speed (N) and capacity (Q) of centrifugal pump 05. To compare the energy consumption at constant delivery of pump through pipelines having

different diameters 06. To observe the influence of bubbles, suction head etc. on pump capacity

A. Experimental data: Table-1 (02): Relation between flow rate and head of centrifugal pump:

Obs. No. Speed (rpm) Rotameter reading (%) Liquid flow rate (lit/hr) Head (bar)

01

2470

0 0 1.65 02 10 64 1.6 03 20 130 1.58 04 30 190 1.54 05 40 260 1.50 06 50 320 1.46 07 60 380 1.40 08 70 445 1.34 09 80 515 1.25

B. Result and conclusion (02): In 𝑄 − 𝐻 curve, the nature of curve is parabolic. Conclusion:

i. In case of maximum head the flow rate is zero. ii. Head is decreased with capacity.

iii. The curve is flat. So the variation of head is not too much with caoacity. Table-2: Relation between speed and head of centrifugal pump (03) and Relation between speed and capacity of centrifugal pump (04):

Obs. No. Speed (N) (rpm) Head (H) (bar) Flow rate (%) Capacity (Q) (l/hr)

01 400 0.40 10 64 02 670 0.44 20 130 03 890 0.48 30 190 04 1168 0.55 40 260 05 1460 0.65 50 320 06 1720 0.75 60 380 07 1960 0.88 70 445 08 2238 1.04 80 515 09 2500 1.20 90 580

C. Results and conclusion (03 and 04): i. In 𝑁 − 𝐻 curve, the nature of curve is parabolic. Here the head is increased with speed.

ii. In 𝑁 − 𝑄 curve, the line is straight line. Capacity is increased with speed.

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Table-3 (05): Comparing the energy consumption at constant delivery of pump through pipelines having different diameters:

Obs. No. Pipelines

(mm) Valve

positions Rotameter reading (%)

Speed (rpm)

Head (bar) Current

consumption (amp)

01 14 Full open

50 1450 0.63 0.4

70 1982 0.87 0.7

20 Full close − − − − − − − − − − − −

02 14 Full close − − − − − − − − − − − −

20 Full open 50 1340 0.57 0.35

70 1853 0.76 0.6

D. Results and conclusions: If the flow rate is kept constant, the speed of pump is decreased with increasing diameter of pipe. It is decreased with increasing diameter of pipe. It is also seen that head and current consumption are also decreased with increasing diameter of pipe at constant flow rate. Table-4 (06): influence of bubbles, suction head, and discharge head pump capacity:

Observation Suction head (bar) Rotameter reading (capacity) Discharge head

(bar) (%) Lit/hr

Before introducing bubbles 0.26 51 325 0.57 After introducing bubbles Not stable.

E. Conclusion (06): We can easily measure the suction head, discharge head before introducing bubbles. But after introducing bubble the indicator of the flow meter becomes unstable and the pointers in suction head and discharge head fluctuate. It means that the pump capacity and head is unstable.

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1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

0 100 200 300 400 500 600

He

ad, H

(b

ar)

Flow rate (lit/hr))

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 500 1000 1500 2000 2500 3000

He

ad, H

(b

ar)

Speed, N (rpm)

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0

100

200

300

400

500

600

700

0 500 1000 1500 2000 2500 3000

Cap

acit

y, Q

(lit

/hr)

Speed, N (rpm)

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Heat exchange Tasks:

01. Practice on start-up, normalization and shutdown procedure of the unit 02. Calibration of rotameter 03. Study of heat exchange for parallel and counter flow, using a shell-tube heat exchanger

A. Experimental data: Table-1: Calibration of rotameter for cold water-flow:

Obs. No. Rotameter reading (%) Time (sec) Amount of water (ml) Flow rate (lit/hr)

01 10 90 550 22 02 20 90 1045 41.8 03 30 60 1085 65.1 04 40 60 1600 96 05 50 30 950 114 06 60 30 1150 138 07 70 30 1350 162 08 80 15 775 186 09 90 15 875 210

Table-2: Calibration of rotameter for hot water-flow:

Obs. No. Rotameter reading (%) Time (sec) Amount of water (ml) Flow rate (lit/hr)

01 10 90 550 22 02 20 90 1045 41.8 03 30 60 1085 65.1 04 40 60 1600 96 05 50 30 950 114 06 60 30 1150 138 07 70 30 1350 162 08 80 15 775 186 09 90 15 875 210

Table-3: Heat exchange data for parallel and counter current flows:

Obs. No. Flow

circulation

Flow rate (lit/hr) Temperature (℃)

Cold water

Hot water Cold water Hot water

Inlet Outlet Inlet Outlet

01 Parallel

50 50 35 72 91 79 02 100 100 35 65 88 75 03

Counter 50 50 35 38 95 42

04 100 100 35 40 90 45

B. Calculations: (i) For parallel flow:

a. Flow rate reading (cold water and hot water) 50 liter/hour and 50 liter/hour:

𝐿𝑀𝑇𝐷 =(91 − 35) − (79 − 72)

ln91−35

79−72

= 23.56

b. Flow rate reading (cold water and hot water) 100 liter/hour and 100 liter/hour:

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𝐿𝑀𝑇𝐷 =(88 − 35) − (75 − 65)

ln88−35

75−65

= 25.90

(ii) For counter flow:

a. Flow rate reading (cold water and hot water) 50 liter/hour and 50 liter/hour:

𝐿𝑀𝑇𝐷 =(95 − 38) − (42 − 35)

ln57

7

= 23.92

b. Flow rate reading (cold water and hot water) 100 liter/hour and 100 liter/hour:

𝐿𝑀𝑇𝐷 =(90 − 40) − (45 − 35)

ln90−40

45−35

= 25

C. Result and conclusions: In heat exchange operation normally 𝐿𝑀𝑇𝐷 of counter current flow system is greater than parallel one. In this pilot plant, in case of 50 − 50 parallel and counter is predictable but on the other hand in case of 100 − 100 parallel and counter is unpredictable because of cavitation in line, air pocketing in the pump suction, and malfunction in temperature indicator. All other parameters and equipment functions are well done.

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0

50

100

150

200

250

0 10 20 30 40 50 60 70 80 90 100

Flo

w r

ate

(lit

/hr)


Cold water calibration

0

50

100

150

200

250

0 10 20 30 40 50 60 70 80 90 100

Flo

w r

ate

(lit

/hr)


Hot water calibration

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Water treatment – lime-soda process Tasks:

01. Practice on start-up, normalization and shutdown procedure of the unit 02. Reduction of hardness of water by soda and lime process 03. Determination of total hardness of water 04. Determination of temporary hardness of water

A. Experimental data: Table-1: Determination of total hardness of water by EDTA solution before treatment:

Obs. No. Sample volume

(ml) Burette reading, EDTA (ml) Average volume

of EDTA (ml) Total hardness

(ppm as 𝐶𝑎𝐶𝑂3) Initial Final Difference

01 25 20 23.7 3.7 3.7 148 02 25 23.7 27.0 3.7

03 Table-2: Determination of temporary hardness of water by 𝐻𝐶𝑙 solution before treatment:


(ml) Burette reading, 𝐻𝐶𝑙 (ml) Average volume

of 𝐻𝐶𝑙 (ml) Total hardness


01 25 20 27.3 7.3 7.3 146 02 25 27.3 34.6 7.3

03 Table-3: Determination of total hardness of water by EDTA solution after treatment:


(ml) Burette reading, EDTA (ml) Average volume

of EDTA (ml) Total hardness


01 25 26.4 29.2 2.8 2.8 112 02 25 29.2 31.4 2.8

03 Table-4: Determination of temporary hardness of water by 𝐻𝐶𝑙 solution after treatment:


(ml) Burette reading, 𝐻𝐶𝑙 (ml) Average volume

of 𝐻𝐶𝑙 (ml) Total hardness


01 25 20 25 5

5 100 02 25 25 30 5

03

B. Calculations: Before treatment:

Total hardness =𝐴 × 𝐹 × 100 × 1000

Sample taken ppm of 𝐶𝑎𝐶𝑂3

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Temporary hardness =𝐴 × 𝐹 × 100 × 1000

Sample taken ppm of 𝐶𝑎𝐶𝑂3

Permanent hardness = Total hardness − Temporary hardness

= 148 − 146 = 2 𝑝𝑝𝑚 as 𝐶𝑎𝐶𝑂3 Chemical dosages: Lime requirement = 𝑔𝑟𝑎𝑚𝑠

(Lime requirement (𝑚𝑔) = 0.74 𝑚𝑔 𝐶𝑎(𝑂𝐻)2/𝑙𝑖𝑡𝑒𝑟 raw water having temporary hardness 1 𝑚𝑔/𝑙𝑖𝑡𝑒𝑟 as 𝐶𝑎𝐶𝑂3.

Soda requirement = 𝑔𝑟𝑎𝑚𝑠 (Soda requirement (𝑚𝑔) = 1.06 𝑚𝑔 𝑁𝑎2𝐶𝑂3/𝑙𝑖𝑡𝑒𝑟 raw water having permanent hardness 1 𝑚𝑔/𝑙𝑖𝑡𝑒𝑟 as 𝐶𝑎𝐶𝑂3.

After treatment: Total hardness = 112 ppm of 𝐶𝑎𝐶𝑂3 Temporary hardness = 100 ppm of 𝐶𝑎𝐶𝑂3 Permanent hardness = 12 ppm of 𝐶𝑎𝐶𝑂3

C. Conclusion:

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Evaporation and crystallization Tasks:

01. Practical on start-up, normalization and shutdown procedure of the unit 02. Production of crystalline ammonium sulfate by evaporation and crystallization of dilute

ammonium sulfate solution 03. Drawing a diagram of the unit

A. Log sheet for evaporation and crystallization of ammonium sulfate solution Feed (𝑁𝐻4)2𝑆𝑂4 solution: Specific gravity: Concentration (%):

Time (30

minute interval)

Solution flow rate (%)

Steam pressure

Temperature (℃) S

level (%)

Evaporated solution

FI-601

(feed)

FI-602

(recir)

PIC-602 (%)

PI-601 (bar)

E S JC MLT Sp. Gr.

Conc. (%)

TR601-1

TR601-2

TR601-3

TR601-4

09.30 100 0 0 0 30 30 30 30 0 1.04 8

10.00 100 60 35 1.4 100 120 110 60 70

10.30 100 60 40 1.6 100 120 95 50 70

11.00 100 60 40 1.6 100 125 105 60 70

11.30 100 60 40 1.6 100 125 105 65 70

12.00 100 60 35 1.4 100 120 100 60 70 1.09 18

Crystallizer and crystal separation:

a. Crystal formation time : 2 hour 30 min b. Set RPM of centrifuge : c. Amount of separated product :

B. Result and conclusion: The specific gravity and concentration of final evaporated solution is 1.09 and 18 % respectively.

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Determination of 𝑷𝑶𝟒𝟑− in water sample

Working principle: Ammonium molybdate reacts with phosphate to form molybdophosphoric acid, which then reacts with ANSA (1-amino 2-naphthol 4-sulfonic acid) to form a blue colored complex. The color intensity is proportional to the phosphate concentration in the sample and is measured at a wavelength 700 𝑛𝑚. Method: Spectrophotometric/photometric. Reagent: 𝑃𝑂4

3− standard solution, ammonium molybdate, ANSA (1-amino 2-naphthol 4-sulfonic acid). Procedure:

i. 30 𝑚𝑙 sample was taken in a 100 𝑚𝑙 volumetric flask. ii. 2 𝑚𝑙 𝑃𝑂4

3− standard solution (100 𝑝𝑝𝑚) was taken in another 100 𝑚𝑙 volumetric flask. iii. A blank titration was performed. iv. Some distilled water taken in the each of the flask. v. 1 𝑚𝑙 ammonia molybdate was added in each of the flasks.

vi. 1 𝑚𝑙 of ANSA solution was added in each of the flasks. vii. The flasks were made up to the mark with distilled water.

viii. The absorbance was measured in 700 𝑛𝑚. Observation:

Obs. No. Sample Absorbance Result

01 Blank 100

02 Standard 83 100 𝑚𝑔/𝑙

03 Test sample 68 13.77 𝑚𝑔/𝑙

Calculation:

For standard, 𝐼0 = 100 and 𝐼𝑡 = 83 Therefore,

𝐴 = log𝐼0

𝐼𝑡= log

100

83= 0.0809

For sample, 𝐼0 = 100 and 𝐼𝑡 = 68 Therefore,

𝐴 = log𝐼0

𝐼𝑡= log

100

68= 0.167

For standard, 1000 𝑚𝑙 solution ≡ 100 𝑚𝑔 𝑃𝑂4

3− 2 𝑚𝑙 solution ≡ 0.2 𝑚𝑔 𝑃𝑂4

3− Then,

𝐴 0.0809 ≡ 0.2 𝑚𝑔 𝑃𝑂43−

𝐴 0.167 ≡ 0.2 × 0.167/0.0809 𝑚𝑔 𝑃𝑂43− = 0.413 𝑚𝑔 𝑃𝑂4

3− Again,

30 𝑚𝑙 solution ≡ 0.413 𝑚𝑔 𝑃𝑂43−

1000 𝑚𝑙 solution ≡ 0.413 × 1000/30 𝑚𝑔 𝑃𝑂43− = 13.77 𝑚𝑔 𝑃𝑂4

3− Therefore,

𝑃𝑂43− concentration in the sample = 13.77 𝑝𝑝𝑚 or 13.77 𝑚𝑔/𝑙

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Determination of calcium and magnesium in water sample by AAS

A. Determination of calcium by absorption mode: 01. Sample preparation: As usual 02. Method setting:

Wave length: 422.7 𝑛𝑚 Lamp current: 4 𝑚𝐴 Slit: 2 Gain: 6 Fuel flow: 3.3 Air flow: 6 𝑁2𝑂 flow: Burner height: 6

03. Table of observation:

Obs. No. Sample tag Analyte Sample abs. Std. conc. & Abs. Result (𝒎𝒈/𝒍)

01 Standard 𝐶𝑎2+ 10 𝑝𝑝𝑚 and 526

02 Tap water 𝐶𝑎2+ 549 10.44

03 Tube-well water 𝐶𝑎2+ 211 4.01

B. Determination of magnesium by absorption/emission mode: 04. Sample preparation: 10 times diluted 05. Method setting:

Wave length: 285.2 𝑛𝑚 Lamp current: 3 𝑚𝐴 Slit: 2 Gain: 5 Fuel flow: 2.8 Air flow: 6 𝑁2𝑂 flow: Burner height: 7

06. Table of observation:

Obs. No. Sample tag M-Reading Reading of Std. Result (𝒎𝒈/𝒍)

01 Standard 728

02 Tap water 892 12.3

03 Tube-well water 387 5.32

C. Calculation: 𝐶𝑎2+ concentration determination:

Standard solution conc. 10 𝑝𝑝𝑚 and absorption 526. For tap water,

𝐴 526 ≡ 10 𝑝𝑝𝑚 𝐶𝑎2+

𝐴 549 ≡10 × 549

526𝑝𝑝𝑚 𝐶𝑎2+ = 10.44 𝑝𝑝𝑚 𝐶𝑎2+

For tube-well water, 𝐴 526 ≡ 10 𝑝𝑝𝑚 𝐶𝑎2+

𝐴 211 ≡10 × 211

526𝑝𝑝𝑚 𝐶𝑎2+ = 4.01 𝑝𝑝𝑚 𝐶𝑎2+

𝑀𝑔2+ concentration determination: Standard solution conc. 1 𝑝𝑝𝑚 and absorption 728. For tap water,

𝐴 728 ≡ 1 𝑝𝑝𝑚 𝑀𝑔2+

𝐴 892 ≡1 × 892

728𝑝𝑝𝑚 𝑀𝑔2+ = 1.23 𝑝𝑝𝑚 𝑀𝑔2+

Therefore, actual concentration of 𝑀𝑔2+ = 1.23 × 10 = 12.3 𝑝𝑝𝑚 For tube-well water,

𝐴 728 ≡ 1 𝑝𝑝𝑚 𝑀𝑔2+

𝐴 387 ≡1 × 387

728𝑝𝑝𝑚 𝑀𝑔2+ = 0.532 𝑝𝑝𝑚 𝑀𝑔2+

Therefore, actual concentration of 𝑀𝑔2+ = 0.532 × 10 = 5.32 𝑝𝑝𝑚

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SOP of Gas Chromatograph (GC-17A, Shimadzu)

Carrier gas (He) 1. Record cylinder pressure : 12000 𝑘𝑃𝑎 2. Set deliver pressure : 600 𝑘𝑃𝑎 3. Set primary pressure : 600 𝑘𝑃𝑎 4. Set auxiliary pressure : 60 𝑘𝑃𝑎

System start-up 1. Turn switch on & push system key ……..... 2. Set start time to : 1 𝑚𝑖𝑛 3. Set stop time to : 2 𝑚𝑖𝑛 4. Set flow off time to : 5 𝑚𝑖𝑛

Isothermal prog. (file-1) 1. Injection port temp : 120 ℃ 2. Detector temp : 140 ℃ 3. Col. Initial temp : 60 ℃ 4. Increment rate : 0 ℃ 5. Equilibrium time : ……………..……. min

Combustion gases (air & 𝑯𝟐) Compressed air:

1. Turn air compressor on : …….. 2. Set delivery pressure : 2 k𝑔/𝑐𝑚2 3. Set inst. Gauge pressure: 50 𝑘𝑃𝑎

hydrogen 1. Record cylinder pressure : 8750 𝑘𝑃𝑎 2. Set delivery pressure : 600 𝑘𝑃𝑎 3. Set inst. Gauge pressure : 75 𝑘𝑃𝑎 4. Ignite : ……….

Gas sample analysis 4. Select column 1 Sample volume: 5 𝑚𝑙 5. Set column pressure/flow : 60 𝑘𝑃𝑎 6. Set intg. range to : 3 7. Turn integrator on & analyze a blank ………….. 8. Inject & start : …………..

Shut down 1. Push system key & off key : ……….. 2. After flow off time turn inst. off : ……….. 3. Close all gas valves & air compressor : ………..

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Calculation: Standard gas composition: 𝐶𝐻4 = 42.5%, 𝐶2𝐻6 = 4.6%, 𝐶3𝐻8 = 1.3% Standard:

Retention time Area Conc. (%)

𝐶𝐻4 1.985 2713572 80.2202 𝐶2𝐻6 2.582 477209 14.1075 𝐶3𝐻8 3.980 191873 5.6723

Response time of 𝐶𝐻4 = Conc.Area⁄ = 80.2202

2713572⁄ = 2.956 × 10−5

Sample:

Retention time Area Conc. (%)

𝐶𝐻4 1.938 2173270 100

Response time of 𝐶𝐻4 = Conc.Area⁄ = 100

2173270⁄ = 4.60 × 10−5

Therefore, composition of 𝐶𝐻4 in sample = 42.5 × 4.60 × 10−5

2.956 × 10−5⁄

= 66.14%

Complete Package for Chemical Engineers, TICI Training, ACCE, University of Rajshahi.Introduction...

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Transcript of Complete Package for Chemical Engineers, TICI Training, ACCE, University of Rajshahi.Introduction...