Appendix F—Troubleshooting Guide
F. Troubleshooting Guide
Symptom
Probable Cause
Remedy
Low Capacity
Pump speed too low
Wrong electric motor
Check the RPM of the electric motor.
High differential pressure
Remove the restrictions in the discharge piping/hose, or increase
their sizes.
Vapor lock
Regenerative turbine pumps “vapor- lock” when reaching their
maximum differential pressure capability. See above for high
differential pressure.
By-Pass valve stuck open
or set too low
Readjust, repair or replace the by-pass valve
Clogged strainer
Clean strainer screen.
Worn impeller
Replace the impeller.
Suction pipe too small or
restricted
Indicated by pump’s inlet pressure dropping when the pump is
started. Remove restrictions and/or increase pipe size.
Pump runs but
no flow
Valve closed
Check valves and make sure they are in the open position.
Excess flow valve
slugged or closed
Stop pump until the excess flow valve opens. If the problem
continues, install a new or larger capacity excess flow valve.
Wrong rotation
Check the rotation of the electric motor and change the rotation.
Suction pipe too small or
restricted
Indicated by pump’s inlet pressure dropping when the pump is
started. Remove restrictions and/or increase pipe size.
Pump will not
turn — locked
Foreign matter in the
pump
Clean out the pump—inspect the strainer screen.
Bearing seized
Replace the pump’s bearings —grease bearing every three months,
using a ball bearing grease.
Moisture in the pump
Thaw and break loose carefully. Check with the product supplier
if the product contains water. Properly remove the moisture from
the product.
Pump will not
build pressure
Poor suction conditions
Check the storage tank excess flow valve—clean filter screen. The
suction pipe might be too small or restricted. Remove restrictions
and/or increase pipe size.
By-pass valve set too low Set the valve for higher pressure (see valve’s instructions).
Too much impeller
clearance
Do a performance test on the pump (see preventive
maintenance program).
Noise or
vibration in the
pump
Cavitation from poor
suction conditions
Make sure all valves are open, look for restrictions on the suction
piping and clean the strainer screen.
Coupling misaligned
Align the coupling.
Coupling or coupling
guard loose
Tighten the coupling and its guard.
Coupling rubber insert
worn or damaged
Replace the rubber insert and check coupling alignment.
Worn bearings
Replace if necessary—Lubricate every three months.
In diagnosing pump and “system” troubles, the following information is essential:
1. Pump model and serial number
2. Electric motor; hp and RPM
3. Product specific gravity
4. Product temperature
5. Pressure at pump’s suction port
6. Pressure at pump’s discharge port
7. Pressure in the storage tank
8. Pressure in the tank being filled
9. Size and length of the discharge pipe and hose
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