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Wednesday, December 26, 2007

Introduction of Pump

A. Introduction
Pump is a machine or mechanic equipment which is required to lift liquid from low level to high level or to flow liquid from low pressure area to high pressure area and also as a debit booster in a piping network system. This is reached by making a low pressure at suction side of pump and a high pressure at discharge side of pump.
Principally, pump converts mechanic energy of motor into fluid flow energy. Energy which is received by fluid will be used to lift pressure and to bridge over resistances which are exists in the line that passed.
Pump also can be used in process that requires a high hydraulic pressure. This can be seen in heavy duty equipments. In the operation, heavy duty equipment requires a high discharge pressure and a low suction pressure. Due to low pressure at suction side of pump, so fluid will lift from certain depth, whereas due to high pressure at discharge side of pump, so it will push fluid to lift until reach desired height.

B. Classification of Pump
Pump can be classified into two categories, i.e.:
1. Positive displacement pump
2. Dynamic pump

B.1. Positive displacement pump
In positive displacement pump, energy is periodically added by application of force to one or more movable boundaries of any desired number of enclosed, fluid-containing volumes, resulting in direct increase in pressure up to the value required to moves the fluid through vales or ports into the discharge line. Positive displacement pump divided into three:
a. Reciprocating pump
b. Rotary pump
c. Diaphragm pump

B.1.1. Reciprocating pump
Reciprocating pump is a pump where mechanic energy of pump drive is converted into fluid flow energy which is transferred by using an element that moves reciprocating in a cylinder. Fluid enters through suction valve and leaves through discharge valve with high pressure. This pump delivery liquid in limited volume with output debit depends on rotation and the stroke of the piston. Liquid volume which is transferred during one piston stroke will be equal to multiplication of piston area and piston stroke.
B.1.2. Rotary pump
Rotary pump is a pump which transfers energy from drive to liquid by using an element that moves rotate in casing. Fluid is sucked from reservoir through suction side and then pushed away through closed casing to discharge side at high pressure. How much fluid pressure that will leave the pump depends on the pressure and the resistance of flow system, whereas output debit depends on rotation speed of rotary element, the rotary element is usually called rotor.
B.1.3 Diaphragm pump
Diaphragm pump is a pump that transfers energy from drive to liquid through drive rod that moves reciprocating to move diaphragm, so then suction and discharge appear by rotation between suction valve and discharge valve. The advantage of this diaphragm pump is just on the diaphragm that touches transferred fluid, so then reducing the contamination with other part especially driver part.

B.2. Dynamic pump
Dynamic pump is consist of one or more impeller which is completed by blades, which is installed on moving shafts and receive energy from pump motor and it is covered by a casing. Energize fluid enters impeller axially, and then fluid leaves impeller with relative high speed and collected in volute or diffuser, after fluid collected in volute or diffuser, the conversion of velocity head to pressure head occur, which is followed by velocity decreasing. After this conversion process has done and then fluid out of pump through discharge valve. Dynamic pump can be divided into some types:
a. Centrifugal pump
According to flow direction n the impeller, centrifugal pump divided into:
- Radial flow
- Axial flow
- Mixed flow
b. Special effect pump
- Jet pump
- Gas lift pump
- Hydraulic ram

B.2.1. Centrifugal pump
This pump is moved by motor. The power of the motor is given to pump shaft to rotate impeller which is installed on the shaft. Resulting in impeller rotation that cause centrifugal force, so liquid will flow from the center of the impeller and exit through line between blades and leaves impeller with high velocity.
The liquid that leaves impeller with high velocity, it through the line that the area is getting wide which is called volute, so then the conversion of velocity head to pressure head will occur, so total head of the liquid out of the discharge flange of the pump will get high. Whereas suction process occurs because after the liquid delivered by impeller, space between blades become vacuum, so then the liquid will be sucked into the impeller.
The total head of the liquid difference between discharge flange and suction flange is called pump total head, so then it can be said that centrifugal pump has function to convert motor mechanic energy into fluid flow energy. This is the energy that causes pressure head, potential head and velocity head addition continuously.
The advantage of the centrifugal pump compared with other type pump:
a. At the same head and capacity, centrifugal pump usage is the cheapest.
b. Has the cheapest operational.
c. Has smooth and uniform flow.
d. Reliable in operation.
e. Has low maintenance cost.
Centrifugal pump can be classified into some types:
a. According to capacity:
- Low capacity (<> 60 m3/hour)
b. According to output pressure:
- Low pressure (<> 50 kg/cm2)
c. According to specific speed:
- Low speed
- Medium speed
- High speed
- Mixed flow pump
- Axial flow pump
d. According to the number of the impeller with the stage:
- Single stage pump
- Multi stage pump
e. According to suction side of impeller:
- Single suction
- Double suction
f. According to casing design:
- Volute
- Diffuser
g. According to shaft position:
- Horizontal shaft pump
- Vertical shaft pump
h. According to drive system:
- Direct coupled to drive unit
- Through some various types of transmission

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