Vertical Multistage Pump Introduction
A vertical multistage pump is a special centrifugal pump that has multi-stage configurations and uses multiple impellers on a single shaft to generate high pressures that would be required for higher head (pressure) at ground level or in very deep wells. It is primarily designed to draw water from a reservoir or well that is deep underground.
This pump contains various stages in the piping system where pressure is applied to the liquid being pumped. Each stage has an impeller and its accompanying diffusion devices. Most centrifugal pumps are generally known by the term multistage. In most cases, the pump is referred to with respect to the number of stages it contains. For instance, a pump with three stages might be called a vertical three-stage pump.
How it Works
A vertical multi-stage pump is normally powered by an AC electric induction motor or a diesel engine in a right angle drive. It consists of several spinning impellers that are all attached to one shaft and guides the well water into a bowl known as a diffuser casing.
The pump works when water passes into the pump at the base via a bell-shaped device known as a suction bell. The water then moves into the first stage impeller that increases the velocity of the water. It then enters the diffuser casing/bowl located directly above the impeller and the high velocity energy is transformed into higher pressure. The diffuser casing also guides the water into the subsequent impeller which is located directly above the diffuser casing. This process is repeated through each stage in the pump.
After leaving the final diffuser casing, the water goes through a long vertical pipe/column and rises up from the well toward the surface. The rotating shaft within the vertical column/pipe is supported at 3 or 5 foot intervals that have sleeve bushes which are fitted within the vertical pipe and lubricated as the water moves past them. There is a pump discharge head at the surface which enables the flow’s direction to change toward the discharge pipe. The discharge head has a vertical high thrust AC motor that is mounted above it.
The vertical multistage pump is used in many liquid and industrial treatment facilities where there is a need to move fluids for large distances at high pressure. In a majority of such instances, the only means of achieving high pressure is to use a pump with several impellers.