Pump is the equipment to move fluid (liquid) from one point to other point by increasing pressure of that liquid. Increasing the pressure of liquid is used to overcome flow resistance. The flow resistances can be caused by difference pressure, different height or friction resistance. Pump can be generally classified as two types, namely: positive displacement pump and non positive displacement pump. One of non displacement pump type is centrifugal pump which has working principal to convert kinetic energy of liquid to potential energy (dynamic) through an impeller which rotates in the casing.
In the steam boiler, type pump which is mostly used is centrifugal pump type because its simplicity and low cost. Steam boiler need feedwater pump to supply water into steam drum. Centrifugal force is a force which occur because a particle move through circle way. The advantage of centrifugal pump than type positive displacement pump is the impeller can run continuously so the flow will be soft and do not produce bubble. Other advantages of centrifugal pump are can operate in high speed rotation, can be coupled electric motor or small scale steam turbine so only need small and light room, and low cost for installation and maintenance.