Pumps

These are such devices which are used to transfer of liquid from one place to another place (e.g. water from an underground aquifer into a water storage tank) and to circulate liquid around a system (e.g. cooling water or lubricants through machines and equipment).

The main components of a pumping system are:

�� Pumps

�� Prime movers: electric motors diesel engines or air system.

�� Piping, used to carry the fluid.

�� Valves, used to control the flow in the system.

�� Other fittings, controls and instrumentation.

�� End-use equipment, which have different requirements (e.g. pressure, flow) and therefore determine the pumping system components and configuration. Examples include heat exchangers, tanks and hydraulic machines.

The pump and the prime mover are typically the most energy inefficient components.

 

Types of pumps:-

Pumps come in a variety of sizes for a wide range of applications. They can be classified according to their basic operating principle as dynamic or positive displacement pumps.

In principle, any liquid can be handled by any of the pump designs. Where different pump designs could be used, the centrifugal pump is generally the most economical followed by rotary and reciprocating pumps. Although, positive displacement pumps are generally more efficient than centrifugal pumps, the benefit of higher efficiency tends to be offset by increased maintenance costs.

Positive displacement pumps:

Positive displacement pumps are distinguished by the way they operate: liquid is taken from one end and positively discharged at the other end for every revolution. Positive displacement pumps are widely used for pumping fluids other than water, mostly viscous fluids.

Positive displacement pumps are further classified based upon the mode of displacement:

�� Reciprocating pump if the displacement is by reciprocation of a piston plunger. Reciprocating pumps are used only for pumping viscous liquids and oil wells.

�� Rotary pumps if the displacement is by rotary action of a gear, cam or vanes in a chamber of diaphragm in a fixed casing. Rotary pumps are further classified such as internal gear, external gear, lobe and slide vane etc. These pumps are used for special services with particular conditions existing in industrial sites.

In all positive displacement type pumps, a fixed quantity of liquid is pumped after each revolution. So if the delivery pipe is blocked, the pressure rises to a very high value, which can damage the pump.

Dynamic pumps:

Dynamic pumps are also characterized by their mode of operation: a rotating impeller converts kinetic energy into pressure or velocity that is needed to pump the fluid.

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There are two types of dynamic pumps:

�� Centrifugal pumps are the most common pumps used for pumping water in industrial applications. Typically, more than 75% of the pumps installed in an industry are centrifugal pumps. For this reason, this pump is further described below.

�� Special effect pumps are particularly used for specialized conditions at an industrial site.