Refinery Report

8/8/2019 Refinery Report

1/29


2/29

1. BRIEF OVERVIEW OF GUWAHATI REFINERY

2. FIRE AND SAFETY TRAINING

3. MECHANICAL MAINTENANCE

THERMAL POWER STATION(TPS)

MECHANICAL WORKSHOP

PLANT

4. CONCLUSION

2


3/29

Crude oil is refined into products such as gasoline, asphalt, and waxes by a processcalled fractional distillation. During the process, the parts, or fractions, of crude oil are

divided out successively by their increasing molecular weight. For instance, gasoline hasa low molecular weight and vaporizes at a fairly low temperature. This means that at the

appropriate temperature, while all of the rest of the oil is still in liquid form, gasoline maybe separated out. The remaining oil goes through the same process at a slightly highertemperature, and jet fuel is divided out. Repeating the distillation process several times

will separate out several constituents of crude oil, which are then processed and put to a

wide range of uses.

3


4/29

A BRIEF OVERVIEW

The oil sector can be broadly divided into 3 major divisions, viz.

1. Drilling and extraction of crude oil: In India, mostly done by Oil India

Limited (OIL) and Oil and Natural Gas Commission (ONGC). In most cases thetransportation to the refining site is carried out through pipelines which are

handled by these organizations only.

2. Refining: The next phase of refining of the crude oil into suitable products like

petrol, kerosene, diesel, ATF etc is carried out by IOCL( which is the only

government sector undertaking) and by companies like Reliance, BPCL etc in theprivate sector.

3. Marketing: After the crude oil has been refined it is then transported to the

different outlets and marketed by various companies like BP, HP, IBB etc.

Before the advent of the 1962 Indo-China aggression, India was

completely dependent upon MNCs for entirely managing the oil sector but thewar among its numerous repercussions brought about the establishment of

companies like IOCL, OIL etc.

Guwahati Refinery:

Guwahati refinery was built and commissioned on 1st January 1962 with

Rumanian assistance.

Originally designed to process 0.75 MMTPA of Assam crude.

Revamped in 1986 to a capacity of 1 MMTPA.

Revamped in 2000 to a capacity of 1.3 MMTPA.

The distillate yield (85.4%) is the highest amongst all refineries in the

country(1999-2000)

For Quality Management System the refinery received ISO 9001 accreditationin September 1995.

For Environment Management System received ISO 14001 in August 1997.

Also the refinery has been accredited OHSAS 18001 in April 1999 & ISRSlevel-6 in March 2000.

Over the years, the refinery has been revamped and modernized by adding

new facilities like :

LPG production(1971)

Effluent Treatment Plant(ETP) (1976)

New 27km long treated effluent discharge pipeline to River Brahmaputra

(1984).

Naptha splitting facilities (1984).

4


5/29

Circulating water system (1986).

New turbo generator (1986).

Demineralised water plant (1993).

Digital Distributive Control System- Unit Control Room (1994).

Digital Distributive Control System- OM&S Control Room (1994).

Crude Distillation Unit Delayed Coker Unit revamp (2000). Project facilities like Hydrogen Unit, Hydrotreater Unit, ISOSIV Unit,

Sulpher recovery Unit, Nitrogen Unit .

Commissioning of two new boilers (2004).

BG unloading facility for tank wagon (2005).

5


6/29

FIRE & SAFETY:

Safety, health and environment (S, H&E) efficiency is given prime importancein todays industrial ventures. The value of life and property necessitates

precautionary measures that have to be taken by employees at workplace as well at

their homes.

Fire-safety:

A fire breaks out when the three elements; fuel, oxygen and heat come together.

Thus, it can be kept away cautionary measures:a) storing of inflammables away from sparks and heat.

b) avoiding throwing of cigarette butts here and there.

c) keeping workplaces clean from thrash.

d) not wearing synthetic inflammable material clothing.

There are mainly four types of fire-extinguishers:

1) soda-acid2) foam type

3) dry chemical: this is an all purpose fire extinguisher.

4) carbon-dioxide: this type is mostly found at homes.

Different Extinguishing Agents:

The Extinguishing Agents, which are suitable for different types of fire and their

extinguishing action, are as below:-

(i) Water: Water is the most effective, cheapest and readily available for fightingthe fire and it has the highest heat of vaporization. Water is used in therefinery fire as cooling agent and also for the production of foam required for

fighting the oil fire. To achieve this objective, sufficient quantity of water is

made available in the refinery premises.

(ii) Mechanical Foam : Mechanical Foam is one of the suitable fire-fighting

agents to tackle the refinery fire. Foam is protein based compound and

insoluble in the hydrocarbon products. Foam is nothing but air filled bubbles,

so it floats on the surface of the oil and forms a blanket covering the surface ofthe burning liquid.

(iii) Dry Chemical Powder: Dry Chemical Powder is universal fire fighting agentto tackle all classes of fire. The basic ingredients of the powder are sodiumbicarbonate with metallic stearate and additives.

6


7/29

Road-safety:

Road accidents can be avoided if pedestrians as well as people on vehicles follow

traffic rules.

Safety at home:

Careful use of gas-stoves and cylinders, proper earthlings of power points etc.

can prevent a lot of hazards that occur at homes.

Personal protection equipments (PPE):

The use of PPE at work places is a must for safety. The PPE generally used atwork places are:

helmet

shoes

gas-masks

gloves

The gloves used may be of different types based on the type of work handled,

such as : PVC gloves for safety from electric shock, chemical gloves when handling

toxic chemicals, acid gloves etc.

7


8/29

THERMAL POWER STATION (TPS):

MAINTENANCE PLANT: - we went to the Maintenance Unit of the ThermalPower Station. The main function of this unit is to see that the boilers, turbines,

compressors and generators are in good working conditions it is this unit only which ismainly responsible for the production of electricity and afterwards distributing it among

the various units as per their requirements.

BOILERS: - there are four single drum boilers and there is a bi-drum boiler as well.

These boilers are oil/gas filled and are steel cased designed for natural circulation suitablefor outdoor installation. The specifications are enlisted below-

Fuel: LSHS/Coking fuel/Hydrocarbon gasesSteam Temperatures: 450+5 degrees

Peak Evaporation:45MT per hour

Working process:39 kgf per sq cmNumber of Burners: 2 nos.

Oil Consumption: 2959 kg per hr

Efficiency: Gross on G.C.V at MCR(oil) is 89.6 + 0.6%Tubs: 51 mm outside diameter, 4.06 mm thick seamless from the outside wall root

and sidewalls, roof.

The boiler is a vertical one with accessories like economizer, air pre heater, super heaters

(both primary & secondary.), a deaerator and attemperator (desuperheater). The boiler

drums have been safeguarded by the use of spring loaded safety valves, which were

replacements of dead weight safety valves, which were previously installed. The feedwater to the boiler is fed by the feed water pump at a pressure much greater than the

boiler pressure i.e, 50 kgf per sq cm. Thee is a feed check valve which is non-return.

Valves and there are no other mountings common to any other boiler such as the blow off

chuck, the manholes, the furnace gates etc.

The steam thus produced is sent to the turbo generator run turbines and a part of it isalso sent to the steam atomizer, which in turn sends steam to the combustion chambersfor effective ignition of the furnace. To monitor the different boilers under working

conditions there is a boiler control room with digital instruments. Among the

maintenance work that is done in the TPS is the maintenance of the boilers, thereciprocating compressors, centrifugal pumps, turbines etc.

8


9/29

MAINTENANCE OF BOILERS:- Technical inspection meets both inside &outside inspection. Outside inspection: this includes all the operations including

inspection of all factors involved for safe, economical operation. They are:-

1. Clearance of boiler room & plant properly.2. Existence of journals & training of he attendant for each boiler

3. Inspection of all visual ports of the boiler & auxiliary equipments

such as water gauges, pressure gauges, safety valve feeding heads etc.

Inside inspection:- this shall be carried out with boiler shut down for a limited period, at

a date established by the official inspector. During internal inspection the boiler has tocomply with all the requirements with regard to cleaning, venting, temperature, light are

done. All valves should be removed and the state of metallic surfaces should be checked

for possible defects. Internal corrosion, thermal cracks must be inspected & the bucklingof the boiler tubes should also be inspected.

MAINTENANCE OF FIRING UNIT:-

Frequent inspection of atomizing nozzles and of the heads of fuel oil burners is

compulsory. Damaged parts should be replaced immediately.The spare parts of all firing equipments are:

1. 9 internal burners with head & nozzles2. 4 staring burners complete with head & nozzles3. 12 spare heads & nozzles for normal burners

4. 288 seats for flexible hoses. In pairs

5. 8 diffusers for injectors

MAINTENANCE OF BOILER MOUNTINGS & ACCESSORIES:

The boiler mountings are safety valves, water level indicator, pressure gauge, stopvalve, feed check valve, blow cock, inspector testing gauge, man hole & mud hole. The

maintenance of the mountings is of the following types:-1. Calibration(Zero based, suppressed base, elevated zero)2. Component alignment

3. Measuring element replacement

4. Periodic service

5. Daily check6. Correction of trouble shooting

9


10/29

Among the boiler accessories the main are-feed pump, injector, economizer, air pre

heater, super heater, steam separator & steam pump. The maintenance of accessories

includes:

1. The links, packages & piston should be checked

2. The injector path should be cleaned from time to time3. Valve spindle should be lubricated properly

MAINTENANCE OF TURBINES:-

The turbines mainly consist of couplings, turbo gears, pumps and D.C motors. Itsmaintenance includes:

a) Coupling maintenance: It is limited to periodic cleaning &

checking. They must be properly aligned & lightly fixed. b) Turbo gear maintenance: Inspection gear tooth contact,

bearing, assembling of gear box, replacement of damaged gear

and protection of gear against corrosion must be inspected.c) Pump maintenance: The pumps are dial, periodically and

annual checked. Their discharge rate, bearing temperature &

lubrication must be checked.d) DC motor: The interior & exterior of the machine must befree from moisture, oil dust, dirt etc.

MAINTENANCE OF COMPRESSORS:

The compressor is used in the refinery to control the different air operating system.Here maintenance of component include piston, cylinder, inter cooler, lubrication of drive

mechanism air filter, air receiver & the entire unit.

We had gone to the De-Mineralization plant as well. This plant is mainly responsible

for the supply of water that is required to be fed into the boilers. The water that is to enter

must have certain properties failing which some kind of anomalies might crop up. The

De-Mineralization plant serves the purpose of brining the water up to the desired properties. This plant removes the unwanted minerals & discharges the water at a

required pH.

10


11/29


12/29

Therm

12


13/29

MECHANICAL MAINTENANCE & PLANNING:

A. Rotary section:

It deals mainly with the construction and repairing of pumps.

PUMPS:

Some of the pumps found in the workshop are :

1) centrifugal2) reciprocating

3) duplex

1) Centrifugal:

The various parts of the centrifugal pump are :

i. Gland plate

ii. Shaft sleeve

(which is

also knownas rotary

part)

iii. Carbon ringor mating

ring.

iv. Compression

unit to

prevent leak.v. Rubber

oaring or

packing.

Also mechanical shielding is

provided for highly

inflammable contents. This is

13


14/29

single stage pump. For multistage pump both side shielding called double shielding is

provided to give additional property of better leak proofness.

Pumps also consist of stuffing box, bearing house, impeller and casing.

These pumps basically consist of an impeller and a casing. The impeller is the rotating

part andthe casing is the stationary part. The liquid that enters at the centre at suctionpressure is pushed through a path of increasing cross-section, adding hydraulic energy to

the liquid.

These centrifugal pumps are again of two types, single stage and multi stage. Thecasings are placed one after the other

concentrically in multi staged pumps where

each stage adds extra energy .The water first

enters the first impeller, then through thediffuser and out to the casing from where it

goes to the second impeller.[Fig-a]

Impellers are of three types:

box-type: the impelleris completely closed on

both sides.

semi-closed : the impeller is closed on one side.

open

2) Reciprocating :

Reciprocating pumps have lesser efficiency than centrifugal pumps and are

increasingly being replaced by centrifugal ones.

3)Duplex:The duplex pumps are used for pumping thick crude oil or such unprocessed

liquids. These consist of two pistons, one for suction and the other for discharge

.

BEARINGS:

The rotating parts of machinery require bearings for the purpose of free movement atthe ends with minimum friction, to increase the life-span of the main shaft.

Bearings are basically of three types:

1) roller2) ball

14


15/29

3) journal

Roller bearings:

In this type the outer and inner parts are separate, i.e. the cage holding the roller and the

outer ring move independently. Generally this bearing can take more load than ballbearings.

Roller bearings are classified as follows:

a) cylindricalb) taper

c) needle

d) spherical

a) Cylindrical: The rollers are cylindrical and these are used in rolling mills or in

bearing units for rail vehicles.

b) Taper: The rollers are slightly tapered and found in passenger cars and trucks,

propeller shafts and differentials.c) Needle: These are thin rollers capable of taking radial loads mostly.

d) Spherical: These bearings allow slight misalignments of the rotating shaft, as theplane of the outer and the inner rings can have relative angular movement. They are

found in railway axle boxes , and in stationary transmission.

Ball bearings:

Here the rotating moves smoothly over some steel balls fitted onto the cage of thebearing. They are classified as follows:

a) deep groove

b) angular contactc) self aligning

a) Deep groove: These are capable of taking both radial and axial loads. They are foundin electrical machinery, air, sea and land vehicles. Miniature ones are used in instruments

and computers while the large ones can be seen in rolling mills.

b) Angular Contact: These can take high axial loads, particularly the four-contact point

one. These can be seen in machine tool spindles, in gear-boxes and passenger car-wheels.c) Self aligning: These consist of a pressed steel cage and are found in agricultural

machinery and ventilators.

Journal bearings:

Journal bearings are of two types : the slip and the split type. The inner

surfaces of these bearings have a layer of white metal. This material being soft

can be given fine finishing and hence causes less friction. Also the bearing

undergoes wear and tear instead of the shaft.

15


16/29

B. The Valve Section:

An altogether of eight types of valves was seen in this section.

These are:

1) safety v.2) gate v.

3) glove v.

4) N.R.V.(non-return valve )5) angle v.

6) ball v.

7) audco v.8) foot v.

Some of these are discussed below:

1) Safety v.: safety valves are necessary part of boilers , vessels etc. which prevent thepressure inside them to exceed a limit determined by the material strength of the boiler.

These are again of two kinds:

a) Dead-weight : the valve remains closed until pressure due to the weight

kept on the seat cover is exceeded by the pressure inside. After the excess steamor air escapes through the open valve and inside pressure comes to the safe limit,

the valve automatically closes.

b)Spring-loaded : the operation of this type is similar to that of dead-

weight ,except that instead of a weight a compressed spring is kept, the lock nutof which is adjusted with the help of safety-valve testing bench*.

*safety-valve testing bench:This testing bench basically consists of an air or water chamber where air

or water is sucked in. The valve body is fixed on top of the chamber with the seat-

cover subjected to the desired pressure through a hole in the chamber. Thepressure exerting at the seat cover and that inside the chamber is indicated by

pressure gauges.

2) Gate valve: These are manually operated valves. The valve can be closed or opened by

turning the wheel in the clockwise and anticlockwise way respectively.[Fig-1]

16


17/29

3) Glove valve: These are similar to gate valves but differ only in internal structure.[Fig-

2]

4) Non-return valve: These are only one-way valves.

5) Angular valves: Angular valves have angular seats and are generally placed in the

bends of boilers.

6) Audco valves: These valves are fast closing valves. They can be shut in about 1/2 a

sec. They are operated by a handle and are generally used to prevent over flow while

filling tankers with oil in the stations.

C. Fabrication section:

The two main fabrication processes seen in this section are welding and heat expansion

process.

17


18/29

1) welding:

The main types of welding done are:

a) gas welding: oxy-acetylene gas is used in the process . Gas cuttingcan be done only in the case of M.S. and not for C.S. or S.S.

b) arc-welding: this gives much stronger weld than gas welding.

c) TIG welding: a very effective method of welding is the tungsten

inert gas (TIG) welding. Here the welding rod consists of 99.95% pure

tungsten and thoria or zirconia is also used.the use of filler rod isoptional in the process.

2) Heat-expansion process:

In the workshop, this method is used for the purpose of fitting pipes in flanges

of heat exchangers**.

The expanding machine which consists of an electronic torque control unit and

a mandrel does this. [Fig-3]

The mandrel has a main rod which has its cross section decreasing in a direction. Rollers

rolling over this rod move in the outward direction as they are pushed towards the largercross-sectional side. So, this outward movement of the rollers and heat generated due to

the friction caused by the rolling action causes the pipe to expand and fit securely onto

the flange.

18


19/29

The electronic torque control unit controls the forward and reverse movement

of the mandrel.

**Heat- exchangers:

The heat exchangers consist of a casing which holds around a couple of

hundred brass or cast-iron tubes . Thepipes are held onto the casing by iron

flanges. These pipes carry the fluid that

has to be either heated or cooled to aparticular temperature. Incase of cooling,

cold water and incase of heating hot

steam runs around the casing. The

conduction of heat through the outersurface of these pipes brings the desired

effect.[Fig-4]

D. Machine-shop:

The machines in this section are:

a) lathe

b) milling machinec) shaper

d) drilling machine

a) Lathe: the lathes seen the workshop are used for step-cutting, thread-cutting,facing etc. The half nut is used for the purpose of locking and unlocking the lead

screw (provides necessary feed during thread-cutting). The largest among these isone ten feet long used for the cutting of flanges having a large chuck.Tools and accessories of the lathe:

i. cutting tool. [Fig-5]ii. lathe centers. [Fig-7]

iii. guides.[Fig-6]

19


20/29

b) Milling machine: the various functions like facing , gear cutting, slotting , sawingetc. is done on the machine. Generally, the milling cutter , angle cutter and the

like are fitted onto the arbor (an over-hanging rotating shaft ). More than onecutter can be fitted on it to work simultaneously. Gear cutting is done with the

help of the index plate#.

c) Shaper: in the shaper, the reciprocating arm is driven by a crank and slottedmechanism. This reciprocating arm is held onto the base by a dovetail .

d) Drilling machine: two of types of drilling machines are the radial and the axialdrilling machines.

The radial type has two motors, one for the drill jig and the other for the up and

down motion of the radial arm. The work- piece remains fixed .

The axial type has a single motor for the motion of the drill jig.

e) Grinding machine: grinding machines are used for various purposes, such as

tool sharpening, finishing of machined articles etc. The material of the grains of thewheel differed in each case.

# Index plate:The index plate is used to cut gear teeth according to the required module. The

no. of teeth for the given diameter and module is calculated.

The index plate containing a no of holes is fitted in a way so that the work-piecefeeding mechanism of the machine rotates the piece accordingly.

E. Compressors:

The compressors used in the refinery consist of the following parts :

motor

reciprocating mechanism with pistons

compression chamber

F. Vibrations:

Maintenance of the machinery in the refinery is of utmost importance for thesmooth running of the plants. For example efficiency will suffer if parts are not

aligned properly. Failure to align properly can cause:-

a) Increased vibrationb) Shaft seal failure

c) Accelerated failure of close clearance machine parts

d) Bearing overload/failuree) Coupling failure

20


21/29

f) Shaft fretting/failure

Types of misalignment:

a) Parallel misalignmentb) Angular misalignment

c) Combination(Parallel & Angular) misalignment

Dial indicators are used to quantify or measure the misalignment between parts.

Dial indicators are of two types. These are:-

a) Balanced type :- Figures are read in both directions(positive & negative)from zero.

b) Continuous reading type :- Figures are read only clockwise from zero.

MECHANICAL MAINTENANCE OF PLANT

Mechanical maintenance is done by two methods:

a) Breakdown maintenanceb) Preventive maintenance

a.) Breakdown maintenance: This method is basically applied in case ofhousehold appliances and other cases where maintenance cost is considerable

compared to capital cost. This method was earlier also employed in factories.

b) Preventive maintenance: Preventive maintenance is done when the

following conditions satisfy: the maintenance cost is negligible compared to thecapital cost of the machinery and equipments.

The shutdown of plant cannot be afforded due to

heavy loss in production time.

The breakdown involves safety hazards.

***Total Preventive Maintenance (TPM):

This is a revolutionary step taken up by IOCL . By this process all thevarious machineries and parts of the refinery are kept under constant observation

so as breakdown of any part is completely avoided. Each part of the refinery, such

as a pump or a boiler, is to be looked after by an employee, be he a mechanic oran officer of any rank. They are to perform their daily duties of maintaining the

cleanliness and health of the assigned part of the refinery.

Generally, there are 4 major divisions in the maintenance section, namely,

1. Mechanical division.

2. Electrical division.

21


22/29

3. Instrumentation division.

4. Miscellaneous division ( mostly concerned with civil equipment and handling)

Mechanical maintenance in an oil refinery is of paramount importance and is one of the

main factors which determine whether it is running at a profit or loss. However in a

refinery, breakdown maintenance is rarely if ever carried out. We shall go through a briefoverview of these aspects in the following segment of the report.

Breakdown maintenance:

This is the type of maintenance which is carried out when the equipment breaks down

and is non-operative. It is only possible under the following circumstances,

1. Cost: When replacement of the equipment incurs lesser cost than

maintenance.

2. Safety hazard: When the equipment poses no safety hazard during its

operation after damage has set in and it is on the verge of breakdown.3. Time: When the time factor for maintenance is not detrimental to the

profitability of the venture.

In order to carry out mechanical maintenance in the refinery it is very much necessary

to observe the operation of the different machineries. This is carried out by observationand analysis of the vibrations of the various machineries in the units.

For the sake of mechanical maintenance the machine parts in the refinery are broadly

divided into 3 divisions:

1. Critical : where the observations are carried out on a daily basis.

2. Semi-critical : where the observations are carried out on a weekly basis.3. Sub-critical : where the observations are carried out after a certified period of time.

Repairing of jobs by the mechanical maintenance department is carried outin the following manner:

1. The department of production informs the maintenance departmentabout the damaged part by giving a job request.

2. The defect is then identified and necessary steps are taken in orderto remove the defect at the site.

3. If the above steps fail, then in case it is a hot job then clearance is

sought from the Fire and Safety Department and also from the ProductionDepartment.

4. Then the damaged part is dismantled and carried to the requiredplace, usually the maintenance workshop by the transportation department

22


23/29

5. After the job has been completed then the mechanical workshop

informs the maintenance department which in turn informs the

transportation department which transports the part back to its originalsite.

6. The repaired part is boxed up and the production department isinformed that the job assigned has been completed.

Brief descriptions of some of the units visited are given in the following

lines:

1. Crude Distillation Unit (CDU):

The mother unit, the unit where the raw crude oil with all its impurities makes its

entry into the refinery. The crude oil is bought from Oil India Limited and stored instorage tanks. These tanks are insulated. The crude oil in the storage tanks is kept warm

with the help of steam coils. The main function of this unit is to separate the crude oil

into its various components by the means of 2 fractionating columns CL1 and CL3. The

oil is circulated throughout the unit by various pumps starting from P1 (the initial inputsuction pump). The raw crude oil is firstly passed through 2 strainers, one of which is idle

and the other running with the purpose of separating some of the impurities present in the

crude. Then the crude is passed into a heat exchanger and then is passed into the different

fractionating columns. The fractionating column separates the crude into its variouscomponents which collects on the different trays set at different heights placed in it on

the basis of their volatility and boiling points. The heavy waste which is at the bottom ofthe columns are pumped out by P9 pump & heated in the burner. These pass through the

heating coils and are heated by the hot gases outside. The number of burners used

depends on the amount of heating required. There are six chulhas each having three

burners. A steam line and an oil line goes to each of the chulhas. The oil is burnt at themouth of the burner. Steam is added for better burning of the oil.

2. Delayed Coking Unit (DCU):

The main process which is carried out in this unit is thermal cracking which yields

products such as coker gases, coker gasoline, coker gas oil, coker fuel oil, refined fuel oil

and raw petroleum coke. Coker gases are fed from the LPG Recovery Unit (LRU) andother products obtained from the CDU and KTU to form motor spirit, high speed diesel,

light diesel oil, furnace oil and low sulphur heavy stack. This unit is called delayed

cooking unit since it envisages the production of coke by allowing high resistance time to

cracking for liquid phase cracking in the reaction chamber operated on alternate days

23


24/29

with a gap of 24 hours in between. The feed to this unit basically comprises of reduced

crude oil (RCO) and coke gas oil. The cracking process consists of decomposition to

lighter hydrocarbons. (In the fractionating column in DCU (CL2), there are 3 types ofcondensate: light, medium and heavy. Cracking is the process of converting the groups of

heavy hydrocarbon mixtures into lighter ones by the application of mostly heat). Except

for the coke, the rest of the products of this unit are transported to different units forfurther refining. The solid, heated coke formed after cooking for 24hours is cut or

broken up into smaller pieces by highly pressurised water which is fed at into the

chamber at around 120kgf/cm squares initially and then further broken into smallerpieces in the second and third cuts by water fed at a pressure of 80kgf/ cm squares.

The importance of mechanical maintenance is illustrated by the analysis and solution of

a case encountered in the DCU:

There are 3 pumps operating in the DCU to supply water for the cutting process ofcoke: P19, P19a and P19B. Pump 19a supplies water at 120kgf/cm squares whereas the

other two pumps supply water at 80kgf/cm square. All the pumps have a separate inlet forwater suction and a separate outlet for water discharge. However all the outlets are

connected to a discharge pipe via separate non-returning valves (NRVs). Now a situation

so arises that the pump 19a starts supplying water at 50kgf/cm square instead of 120kgf/

cm square although its record indicates that the pump has not been plagued by problemsof any kind since its setting up (it is a relatively new pump) and the other two pumps are

operating according to expectation. From which source could have the problem arisen?

Solution: One of the non-returning valves in the unaffected pumps had been causing theproblem. It is defective and has been allowing water from the common discharge line to

seep through its gates. This generates a back pressure which translates into movement of

the blades of that pump even in non-operative condition and thus reduces the line pressure of the discharged water. The problem can be detected by observing the

movement of one of the pumps even when it is not in operating state. This problem is

fixed by either replacing the non returning valves or by repairing it.

3. ISOSIV unit:

Another unit which we visited during the course of our vocational training was the

ISSOSIV unit. The feed for the ISSOSIV unit is light naptha from the CDU and fromstorage tanks (the advantage of the second means that storage results in sedimentation of

some of the heavier impurities present in the light naptha which results in purer feed).The main function of the ISSOSIV is to separate the normal naptha from the iso-naptha.This is done using a process akin to sieving based on the principle of adsorption.

A brief description of the process carried out in the ISSOSIV unit follows:

The light naptha is firstly sucked into a vessel from either the CDU or the storage tank.

It is then passed through a heat exchanger before being passed through a furnace. The

24


25/29

output from the furnace is then passed via 2 feed lines to 4 adsorption chambers. The

adsorption chamber contains a zeolite based adsorbent. The adsorbent is a specially

prepared 5A molecular sieve with a pore diameter tailored so that normal paraffin canpass through the pores and into the cavities within the crystalline structure, while others

such as isoparaffins, napthalenes and aromatics are excluded. The separation is achieved

in the vapour phase. Cycle time is 260 seconds. These chambers contain hydrogen gas asthe medium. Hydrogen is supplied and taken out from the adsorption chambers through

inlets and outlets interconnected between them. The adsorbent contains miniscule pockets

which are just sufficiently large to trap the normal naptha hydrocarbons but not theisonaptha hydrocarbons. Thus against a feed of mixture of normal and isonaptha the

output only comprises of the isonaptha hydrocarbons. After the isonaptha hydrocarbons

have been collected, the trapped normal naptha hydrocarbons are blown out from the

pockets by blowing hydrogen through the inlet. The temperature of the naptha feed is 288degree C. The iso component is not trapped in the pores of the sieves and these pass

through the top of the adsorber to the V03 and from there to the C01 to V07. Iso product

to storage is sent from the C01 at 13872 kg/hr. The normal component goes through V04

to C02 to V08. The normal product is sent to the storage at 2088 kg/hr. This is the lowoctane product. Normal paraffins are used as reaction solvents due to their inherent

stability The isonaptha, normal naptha hydrocarbons are then processed in the unit itselffor further purity. Pure hydrogen is recovered and recirculated in the unit.

4. Kerosene Treating Unit (KTU):

Straight run kerosene is a mixture of parafinnic, napthanic and aromatic close boilingpoint mixture. The purpose of the KTU is to remove the aromatic hydrocarbons abnd

thereby improve the smoking point. The feed and sulphur dioxide are contacted at -20

degree Celsius in a column packed with resching rings (to provide larger surface area).

The extract phase so created contains about 80% and 20% aromatic and the raffinatephase contains about 80% non-aromatics as solvent.

5. LPG recovery unit:The basic purpose of recovering coker off gases is to absorb heavier components of

compressed gas with stabilized naphtha(lean oil) in a rectified absorber and separation ofthe LPG components from unstabilized naphtha(rich oil) in a stabilizer. Stabilized

naphtha and LPG are caustic treated before being transported to their respective storages.

6. Nitrogen unit:

In the Nitrogen plant, 99.9% pure nitrogen is extracted from air and supplied to theother units wherever required. There are three centrifugal air compressors in the plant. At

a time only one or when requirement is more two compressors are run and the other iskept as back-up. The compressed air is kept in a surge vessel. Some of this air is used as

plant air. A part of it sent to the drier section. Remaining part is sent through a moisture

separator to a refrigerating component where it is at 9-15degree C. This cool air goesthrough an Air Purifier Unit to the Cold Box. The cold box has an MP Column. From the

cold box gaseous nitrogen goes to the header for supply and liquid nitrogen is stored in

25


26/29

two 50000L storage tanks. In case there is a power failure then this liquid nitrogen is

passed through heat exchangers where it is converted to gaseous form and this is supplied

to the other plants.

7. IndMax unit/SRU:

Indane maximization is known as the Indmax unit. Indane is the brand name of the

LPG marketed by the IOCL. The main product of this unit is LPG. Here the feed consistsof coker gasoline and RCO + coker fuel oil. These are sent to a riser. There is a catalyst

present in a regenerator. The riser is connected to a reactor. From the reactor the raw

material goes through the main chamber and TCO stripper and forms the productTCO(diesel). Clarified oil can be had from the main chamber. Also the main chamber

connects to a primary absorber and then to the sponge absorber and finally we get fuel

gas. From the main column through stripper and stabilizer, LPG and gasoline isproduced.

a. ARU/ATU:- Diethnol amine when saturated with H2S iscalled rich amine. The source of H2S is sour water and off gases

received from HDTU, Indmax unit and off gas from DCU is

processed in the ARU to separate H2S and amine solution (leanamine) which is obtained as bottom product from ARU. H2S &

other light components present in rich amine are separated out as

sweet gas. The top gas from regeneration section as acid gas sentto SRU for sulphur recovery.

b. SWS(Sour Water Stripping):- Sour water originatesmainly from Indmax unit. It contains NH3, H2S plus phenols,

CO2, cyanides, chlorides & hydrocarbons. Principle of sour waterstripping is based on the application of heat to reduce stability of

NH4+ & HS- in water phase plus the dilution & depletion of

gaseous NH3 & H2S by raising steam vapour. Net result isequilibrium is forced to leave. But NH3 is extremely soluble in

water some amine salt will persist in SW. Residual ammonia

present as NH4Cl can be removed by injection of NaOH. This feedammonia can then be stripped away.

Storage of crude oil:

The storage of crude oil is of prime concern to the oil sector in order to deal with

demand and supply situation as well as for circulation to different units within the

refinery. This has necessitated the construction of storage tanks within the refinery itself.

Before the tank is constructed, the bearing strength of the soil in the selected site is tested.If the strength of the soil is found to be lesser the required strength then a process known

as piling is carried out. In this process the strength of the soil is increased by

26


27/29

constructing underground columns in a geometric pattern. Firstly the soil is dug up to the

point of the rock soil strata. After the rock soil strata has been reached, alternate layers of

bentonite solution and soil are poured onto the dug out space and ramming is carried outuntil the initial ground level is reached. A ring shaped base is constructed around the

proposed design of the tan which takes care of the hoop stress. The base is constructed in

a manner which leaves a taper thus easing the delivery and discharge of the crude oil.The three basic parts of a storage tank are:

1. Tank bottom2. Shell courses

3. Roof.

Based on the type of roof the tanks are classified into different types which are used to

store different types of liquid fuels. These tanks are usually constructed based on theparameters of construction expenditure, storage capacity required and the fuel to be

stored. They are:

1. Open roof tanks : These are used for storing liquids whose properties are notaffected with time and which are not adversely affected by evaporation. Thelimitation of such a tank makes it suitable mostly for the storage of water required

in the refinery.

2. Fixed roof tanks : These tanks as their name suggests have immoveable roofs.There is a definite clearance between the roof height and the height of the storedfuel. They are mostly used for the storage of fuels like high speed diesel, kerosene

which have low volatility and are not greatly affected by evaporation.

3. Floating roof tanks : These tanks are used to store highly volatile fuels like ATF

and petrol. In these types of tanks, the height of the tank roof is not fixed at adefinite height but adjusted along with the height up to which the oil is filled in

the tank so as to create a very small vapour space i.e the space between the roof

and the oil. This leads to minimum vaporisation and cuts back losses.

4. Combination of floating and fixed roof tanks.

27


28/29

Maintenance Workshop

Layout

Fabrication Section

Lathe, shaper, boring, milling& drilling m/c

Rotary section

Valve section

Unfinished jobs

28


29/29

CONCLUSION:

If you want to find out anything from the theoretical physicists about the methods they

use, I advise you to stick closely to one principle: Don't listen to their words, fix yourattention on their deeds. Albert Einstein (1879 - 1955)

In a changing industrial world with changing perspectives, the gap between theoretical

knowledge and analysis and practical skill and application has widened. This gap canonly be bridged by greater interaction between the industry and educational institutions

imparting technical know-how. This short vocational training was no doubt a big leap for

a technical student like me. It was the first time I have been provided with theopportunity to set foot inside a PROCESS INDUSTRY and it has been truly a great

learning experience for me.

The nuts, bolts and machinery of which we were familiar with in only black and whiteare no longer only fragments of our imagination, for in the course of this training we have

become perhaps not fully but substantially acquainted with them. Overall it was one of

the best practical experiences that I have ever had and I am sure it will of immense helpto any of my future endeavor.

(JYOTI PRASAD DEKA)

Refinery Report

Documents

Transcript of Refinery Report