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PROCESS ROTATING EQUIPMENT

(CENTRIFUGAL PUMPS )

CENTRIFUGAL PUMPS

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� Pumps can be divided into two main groups:

• Displacement pumps

• Dynamic pumps

CENTRIFUGAL PUMPS

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Axial horizontal split case pump

BASIC CENTRIFUGAL PUMP PARTS

Casing

CENTRIFUGAL PUMPS

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Multistage axial horizontal split case Pump

CENTRIFUGAL PUMPS

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Single stage axial vertical split case pump

CENTRIFUGAL PUMPS

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Barrel casing

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Impellers

CENTRIFUGAL PUMPS

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Shafts

CENTRIFUGAL PUMPS

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Bearings

Partially filled

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Bearings

Grease lubricated

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Bearings

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Spherical bearings

CENTRIFUGAL PUMPS

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Sleeve bearings

CENTRIFUGAL PUMPS

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Thrust bearings

CENTRIFUGAL PUMPS

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Stuffing Boxes

CENTRIFUGAL PUMPS

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Packing and seals

CENTRIFUGAL PUMPS

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Packing and seals

CENTRIFUGAL PUMPS

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Mechanical seal

CENTRIFUGAL PUMPS

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Wearing Rings:

CENTRIFUGAL PUMPS

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Couplings

Chain coupling

CENTRIFUGAL PUMPS

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Diaphragm coupling

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Elastomeric coupling:

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Flexible Disc coupling:

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Flexible link coupling:

CENTRIFUGAL PUMPS

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Gear coupling

CENTRIFUGAL PUMPS

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Leaf spring coupling:

CENTRIFUGAL PUMPS

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Metallic Grid coupling:

CENTRIFUGAL PUMPS

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Metallic Grid coupling:

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Pin Drive Coupling:

CENTRIFUGAL PUMPS

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TYPES OF CENTRIFUGAL PUMPS

Volute

Diffuser

Regenerative - Turbine

Mixed-flow

Axial-flow (propeller)

Single stage

Multi stage

Submersible

Can

Horizontal

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Volute- type pumps:

CENTRIFUGAL PUMPS

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Diffuser-type pump

CENTRIFUGAL PUMPS

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Turbine-type pumps

CENTRIFUGAL PUMPS

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Mixed flow type pumps

CENTRIFUGAL PUMPS

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Axial flow type pumps

CENTRIFUGAL PUMPS

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Single stage and multistage pumps

� There are three common types of multistage

pumps:

- Submersible

- Can

- Horizontal

CENTRIFUGAL PUMPS

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Vertical pumps (submersible)

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Can type pumps

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Horizontal

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HEAD ON A PUMP

� The amount of energy transferred to the fluid in a

centrifugal pump is called the head of the pump.

� Head is not the same as pressure. This is a very

important concept, which will be explained in the

following paragraphs

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Terms and Definitions

� Pressure:

• Three pressure terms commonly arise in

pumping problems-absolute, barometric,

and gauge pressure.

• A fourth term, vacuum, is used with

installations operating below atmospheric

pressure, but it is not a pressure term in the

same sense as the first three.

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� Absolute pressure

• is the pressure above absolute zero.

It may be above or below the atmospheric pressure

existing at the point under consideration.

• Barometric pressure is the atmospheric pressure at

the locality being studied and varies with altitude

and climatic conditions.

• Gauge pressure is the pressure above atmospheric

at the locality where it is measured.

• A vacuum is a negative gauge pressure

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� Head:

• a column of water or other liquid in a vertical pipe exerts a certain pressure (force per unit area) on the horizontal surface at the bottom of the pipe.

• This pressure can be expressed in pounds per square inch (psi) or as the number of feet of liquid, which exert an equal pressure on the same surface.

• The weight of the column of liquid producing the pressure in question is known as the head on the surface.

• Note that is the weight of the liquid acting on the surface that produces the pressure.

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CENTRIFUGAL PUMPS

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� Static Head:

• In pump application the height of a column of liquid acting on the pump suction or discharge is often termed the static head on the inlet or outlet and is expressed as a certain number of feet of the liquid.

• Static head is a difference in elevation and can be computed for a variety of conditions surrounding a pump installation.

CENTRIFUGAL PUMPS

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�Vapour Pressure:

• Every liquid at any temperature above its freezing point exerts a pressure due to formation of vapour at its free surface.

• This pressure, known as the vapour pressure of the liquid, is afunction of the temperature of the liquid the higher the temperature, the higher the vapour pressure.

• Vapour pressure is an important factor in the suction conditions of pumps handling liquids of all types.

• In any pumping system the pressure at any point should never be reduced below the vapour pressure corresponding to the temperature of the liquid because the liquid will form vapour, which will partially or completely stop liquid flow into the pump.

CENTRIFUGAL PUMPS

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� Static Suction Lift:

• This is the vertical distance, in feet, from the liquid supply level to the pump centreline, the pump above the supply level.

• Horizontal runs are not considered as part of the static suction lift, so far as lift is concerned

CENTRIFUGAL PUMPS

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� Static Suction Head:

• Where the pump is below the liquid supply level a static suction head exists.

• Numerically, it is the vertical distance, in feet, between the liquid supply level and the pump centreline.

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� Static Discharge Head:

• This is the vertical distance, in feet, from the pump centre line to the point of free delivery of the liquid

• Care must be exercised to see that the point of free delivery is used when computing static discharge head.

• In some layouts the exact point may be difficult to determine. This is discussed in greater detail later in this chapter.

CENTRIFUGAL PUMPS

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� Total Static Head

• Total static head on a pump is the vertical distance, in feet, between the supply level and the discharge level of the liquid being handled.

� Friction Head:

• Measured in feet of the liquid handled, this is the equivalent head needed to overcome the resistance of the pipe, valves, and fitting in the pumping system, friction head exists on both the suction and discharge sides of a pump, and varies with liquid flow rate, pipe size, interior condition of the pipe, type of pipe, and nature of the liquid being handled.

CENTRIFUGAL PUMPS

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� NPSH definition:

Total inlet pressure, in meters or feet of liquid pumped determined at the pump suction connection (i.e. suction flange), minus the vapour pressure of the liquid pumped in meters or feet of liquid pumped at pumping temperature.

� Two NPSH definitions are used in pumping systems :

Net Positive Suction Head available (NPSHa),

Net Positive Suction Head required (NPSHr).

CENTRIFUGAL PUMPS

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�Cavitaion

CENTRIFUGAL PUMPS

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Pitting accompanying cavitation in a Centrifugal pump