News

The more the number of stages of the pump, the greater the outlet discharge pressure. These pumps have the outstanding ability to produce higher pressures after adding in each stage, but the range of the flow always remains constant at a certain speed. Each stage comprises a rotor, a diffuser, and directional return blades (often combined with a diffuser), all in one and the same stage housing.

The pressure head of a single-stage centrifugal pump is considerably adjusted by the impeller type and the circumferential speed. If the rotational speed must be constant due to operating conditions, a larger impeller diameter leads to very low specific speeds and uneconomical efficiencies. So, installing multiple stages in series can be an economical choice to increase the head. If the number of stages is changed at fixed dimensions and speeds, the flow rate of the multistage pump does not alter, but the power input and head increase proportionally to the number of the stages.​

In multi-stage pumps, the fluid flows through multiple impellers installed in series. The fluid enters the first chamber (or stage) under pressure in the suction line and drains at a certain elevated pressure. After leaving the first stage, the fluid enters the second stage, in which the pressure increases again.

Using multi-stage pumps is an economical way to reach higher pressure ranges in the pump series selection diagrams. However, one drawback in using too many stages is the increased sensitivity of the rotor to external or natural vibrations.

An example of a pump with multi-stage casings of the same type arranged in tandem is the ring-section pump. This pump type is usually applied in power stations, such as a boiler feedwater pump, and for industrial purposes that require high pressures.

The distinct stages of a multi-stage centrifugal pump do not necessarily have to be fitted in tandem.  The balancing of axial force can be improved by putting the stages back to back in pairs or groups. A common example is the pipeline pump.

The inlet housing with the axial or radial inlet nozzle is located before the first stage, regardless of the number of stages, and the last stage is positioned in the outlet housing, including the balancing tools and the shaft seal. Only the pump shaft, tie rods, and base plate should be arranged to accommodate the needed number of steps.