How is the pressure in the seal chamber of a centrifugal pump determined?
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For centrifugal pump impellers, including those with secondary vanes, those without wear rings but with balance holes, and those with wear rings as well as balance holes, how is the pressure in the sealing chamber determined?
The most accurate approach is to install a pressure gauge at the sealed chamber; otherwise, this pressure is calculated by the centrifugal pump manufacturer.
For pumps with a rear cover equipped with back blades and no balance holes at the impeller inlet, the formula for estimating the pressure in the sealing chamber is as follows. The values of Pm, the pressure in the sealing chamber, for different types of pumps are provided for reference:
Pump type | Estimation formula
--- | ---
Rear cover with back blades or a sealing ring | Pm = Ps + 0.25(Pd – PS)
Rear cover with balance holes | Pm = Ps + 0.10(Pd – PS)
Rear cover with both back blades and balance holes | Pm = Ps
Rear cover without balance holes but with a sealing ring | Pm = Ps + 1.8 bar
Open-type impeller, without a rear cover or balance holes | Pm = Ps + C(Pd – PS)
Note: C = 0.1 when the impeller is at its maximum diameter, and C = 0.3 when it is at its minimum diameter.
Rear cover without a sealing ring or balance holes (for vertical pumps) | Pm = Ps (this is the case for most vertical pumps).
Double-suction pump | Pm = Ps
Where Ps is the pressure at the pump inlet, and Pd is the pressure at the pump outlet
Pump type | Estimation formula
--- | ---
Rear cover with back blades or a sealing ring | Pm = Ps + 0.25(Pd – PS)
Rear cover with balance holes | Pm = Ps + 0.10(Pd – PS)
Rear cover with both back blades and balance holes | Pm = Ps
Rear cover without balance holes but with a sealing ring | Pm = Ps + 1.8 bar
Open-type impeller, without a rear cover or balance holes | Pm = Ps + C(Pd – PS)
Note: C = 0.1 when the impeller is at its maximum diameter, and C = 0.3 when it is at its minimum diameter.
Rear cover without a sealing ring or balance holes (for vertical pumps) | Pm = Ps (this is the case for most vertical pumps).
Double-suction pump | Pm = Ps
Where Ps is the pressure at the pump inlet, and Pd is the pressure at the pump outlet