PUMPS AND PUMPING

PUMPING:

Pumping is the addition of energy to a fluid to move it from one point to another. Since energy is capacity to do work, the addition of energy to a fluid causes it to do work, such as flowing through a pipe or rising to a higher level.

BASIC TYPES OF PUMPS ON FLOW CONSIDERATION :

The direction of the fluid flow, in relation to the plane of the axis of the rotating element, distinguishes the basic types of pumps.

If the flow is radial, the pump is a Centrifugal type.

If the flow is along the axis of rotation, the pump is an Axial Flow type.

If the flow is partly axial and partly radial, then they are called hybrid or Mixed Flow pumps.

MAIN TYPES OF MARINE USE PUMPS :

Marine pumps fall into the two broad classes of being either displacement or rotodynamic.

Displacement: The liquid or gas is displaced from the suction to the discharge by the mechanical variation of the volume of a chamber or chambers. Displacement pumps can be subdivided into two classes. Reciprocating pumps, in which a plunger or piston is mechanically reciprocated in a liquid cylinder and Rotary Pumps, where the liquid is forced through the pump cylinder or casing by means of screws or gears. Positive dis­placement rotary pumps rely on fine clearances between moving parts for their efficient operation.

Rotodynamic: Rotodynamic pumps are either centrifugal pumps or axial flow pumps, in which the flow through the pump is induced by the centrifugal force imparted to the liquid by rotation of an impeller. Whereas an axial flow pump is one in which a screw propeller is used to create an increase in pressure by causing an axial accelaration of liquid within its blades. The incidental rotation imparted to the liquid is converted into straight axial movement by suitably shaped outlet guide vanes.

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