Fluid Power Engineering (2151903)

GANDHINAGAR INSTITUTE OF

TECHNOLOGY

Topic:-Pump

Presented By: Upadhyay Ayush. 150123119053

WHAT IS THE PUMP?WHAT IS THE PUMP?

A hydrodynamic pump machine is a device for converting the energy held by mechanical energy into fluid

Pumps enable a liquid to:

1. Flow from a region or low pressure to one of high pressure.

2. Flow from a low level to a higher level.

3. Flow at a faster rate.

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There are two main categories of pump:

• Rotodynamic pumps.

• Positive displacement pumps.

Diaphragm

Piston

Plunger

Reciprocating Rotary

Mixed flow Gear

Lobe

Sliding Vane

Screw

Axial flow

Centrifugal

Rotodynamic

Turbine

Positive displacement

PUMPPUMP

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WHAT IS CENTRIFUGAL PUMP?

WORKING MECHANISM OF A CENTRIFUGAL PUMP

ADVANTEGAES AND DISADVANTAGES OF

CENTRIFUGAL PUMPS

CENTRIFUGAL PUMP

Centrifugal pump works on the principle that when a certain mass of liquid is made to rotate along the impeller from the central axis of rotation, it impresses a centrifugal head. It causes the water to move radially outwards at higher velocity and causes the water to rise to a higher level. The motion of water is restricted by casing of pump, it result into pressure build up. In addition , the change in angular momentum of liquid during its flow results into increase in pressure head.

The steps involved in operation of centrifugal pump are as follows :

1.The delivery valve is closed.

2.The priming of the pump is carried out. Priming involves the filling the liquid in suction pipe and casing up to the level of delivery valve so that no air pockets are left in the system. if any air or gas pockets are left in this portion of pump, it may result into no delivery of liquid by the pump.

Working of centrifugal pump

3.The pump shaft and impeller is now rotated with the help of an external source of power like a motor or any other prime mover.

The rotation of impeller inside a casing full of liquid produces a forced vortex which is responsible in imparting the centrifugal head to the liquid. It creates a vacuum at the eye of impeller and causes liquid to rise into suction pipe from the sump.

4.The speed of impeller should be sufficient to produce the centrifugal head such that it can initiate discharge from delivery pipe.

5. Now the delivery valve is opened and the liquid is lifted and discharge through the delivery pipe due to its high pressure.

Thus the liquid is continuously sucked from the sump to impeller eye and it is delivered from the casing of pump through the delivery pipe.

6. Before stopping the pump, it is necessary to close the delivery pipe otherwise the back flow of liquid may take place from the high head reservoir.

In case the priming of pump is not done and the pump is not done and the pump is not under the operation, the water present in the pump and suction pipe will flow back to the sump. The space occupied by water will be filled by air.

If the pump is now started, the air pockets inside the impeller may give rise to vortices and cause the discontinuity of flow. Under these condition, the flow of fluid does not commence and the pump runs dry. It causes the rubbing and seizing of the wearing rings, increases noise level and vibrations and finally may cause the serious damage to pump.

The priming in reciprocating pumps is not required since the pumping is done by positively moving the fluid out of the cylinder by the piston. Hence, the air will be displaced from the casing when the pump starts and it will get a suction pressure which will draw the fluid from the sump.

Priming for small pumps is done by hand

A foot valve is essential at the bottom of suction pipe

A funnel or priming cup is provided to fill the water by hand. An air vent is provided in the casing of pump. When the water is filled, the air escapes through the air vent. It is closed once the priming is completed

The operation of filling the casing , impeller and suction pipe and the portion of delivery pump up to delivery valve is called priming.

Priming of Centrifugal Pump

WHAT IS CENTRIFUGAL PUMP ?

Convert the mechanical energy into hydraulic energy by centrifugal force on the liquid

Constitute the most common type of pumping machinery

Used to move liquids through a piping system

Has two main components:

1. Stationary componets, casing, casing cover and bearings

2. Rotating components, impeller and shaft

Classified into three categories ; Radial Flow, Mixed Flow, Axial Flows

WORKING MECHANISM OF A CENTRIFUGAL PUMP

Simplest piece of equipment in any process plant

Energy changes occur by virtue of impeller and volute

Liquid is fed into the pump at the center of a rotating impeller and thrown outward by centrifugal force

The conversion of kinetic energy into pressure energy supplies the pressure difference between the suction side and delivery side of the pump

Liquid flow path inside a centrifugal pump

ADVANTAGES Simple in construction and cheap

Handle liquid with large amounts of solids

No metal to metal fits

No valves involved in pump operation

Maintenance costs are lower

Cannot handle highly viscous fluids efficientlyCannot be operated at high headsMaximum efficiency holds over a narrow range of conditions

DISADVANTAGES

POWER AND EFFICIENCY CALCULATIONS

The power supplied to the pump:

Where m=mass flow rate, kg/s ∆H= total discharge head, N.m/k

η=efficiency

…………(1)

The power delivered to the fluid:

…………(2)

From equations (1) and (2) efficiency:

Specific speed that is used to classify pumps

nq is the specific speed for a unit machine that is geometric similar to a machine with the head Hq = 1 m and flow rate Q = 1 m3/s

43q H

Qnn ⋅=

qs nn ⋅= 55,51

What is a centrifugal pump?

Three basic components:

Volute, casing, bodyor Diffuser

Impelleror impellers

Driver (motor)

Pump Impeller types

Open

Semi-open

Closed

• Single suction

• Double suction

Non-clogging

Axial flow

Mixed flow

Parameter Centrifugal Pumps Reciprocating Pumps Rotary Pumps

Optimum Flow and Pressure Applications

Medium/High Capacity,Low/Medium Pressure

Low Capacity,High Pressure

Low/Medium Capacity,Low/Medium Pressure

Maximum Flow Rate 100,000+ GPM 10,000+ GPM 10,000+ GPM

Low Flow Rate Capability No Yes Yes

Maximum Pressure 6,000+ PSI 100,000+ PSI 4,000+ PSI

Requires Relief Valve No Yes Yes

Smooth or Pulsating Flow Smooth Pulsating Smooth

Variable or Constant Flow Variable Constant Constant

Self-priming No Yes Yes

Space Considerations Requires Less Space Requires More Space Requires Less Space

Costs Lower InitialLower Maintenance

Higher Power

Higher InitialHigher Maintenance

Lower Power

Lower InitialLower Maintenance

Lower Power

Fluid Handling Suitable for a wide range including clean, clear, non-abrasive fluids to fluids with abrasive, high-solid content.

Not suitable for high viscosity

fluids

Lower tolerance for entrained gases

Suitable for clean, clear, non-abrasive fluids. Specially-fitted pumps suitable for abrasive-slurry service.

Suitable for high viscosity

fluids

Higher tolerance for entrained gases

Requires clean, clear, non-abrasive fluid due to close

tolerances

Optimum performance with high viscosity fluids

Higher tolerance for entrained

gases

Difference between Centrifugal Reciprocating Rotary pumps

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1 Casing:-

II. Circular casings for low head and high capacity.

A volute is a curved funnel increasing in area to the discharge port.

Volute

SuctionImpeller

Construction of Centrifugal Pumps

Casing generally are two types:

I. Volute casings for a higher head.

Have stationary diffusion vanes surrounding the impeller periphery that convert velocity energy to pressure energy. 6

Radial flow Axial flow

Mixed flow

2 Impeller

Three main categories of centrifugal pumps exist

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Thanks for listening