Please see our main Centrifugal Pump article for more information.
Boiler feedwater from the deaerator is drawn into the pump through this pipe.
The type of bearing used depends upon the pump design. Due to the usage of multiple impellers, some axial thrust is transferred to the bearings. Thus a suitable bearing should be chosen to handle both axial and radial thrusts.
Mechanical seals are used to seal the space between the pump shaft and casing. The seal prevents boiler feedwater leaking out of the intended flow area.
The pump shaft is installed through the centre axis of the pump. The impellers, mechanical seals and bearings are all installed onto the shaft. Shaft keys are used to mechanically connect each impeller to the shaft.
1st Stage Impeller
The first centrifugal impeller that the feedwater comes into contact with is referred to as the 1st stage impeller. This pump has five impellers (five stages).
The casing must withstand the high system pressures to which it is subjected, as well as high temperatures. A boiler feedwater pump will typically discharge at pressures exceeding several hundred bar (>2900 psi), the casing must be able to withstand this pressure.
After passing through several centrifugal pump impeller stages, boiler feedwater is discharged through this pipe.