MIL-HDBK-1164
Table 12 (Continued)
Symptom
Possible Cause
Suction valve only partially open.
Discharge valve only partially open.
Speed too low.
Total head of system higher than design head of
pump.
Parallel operation of pumps unsuitable for such
operation.
Foreign matter in impeller.
Wearing rings worn.
Impeller damaged.
Casing gasket defective, permitting internal
leakage.
Insufficient pressure developed.
Excessive amount of air or gas in water.
Speed too low.
Wrong direction of rotation.
Total head of system higher than design head of
pump.
Parallel operation of pumps unsuitable for existing
conditions.
Wearing rings worn.
Impeller damaged.
Casing gasket defective, permitting internal
leakage.
Pump loses prime after starting.
Pump or suction pipe not completely filled with
water.
Suction lift too high.
Excessive amount of air or gas in water.
Air pocket in suction line.
Air leaks into suction line.
80
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