9
Watson McDaniel Company
PMPNT Manual 2605100 Rev A
System Troubleshooting
PROBLEM
POSSIBLE
CAUSE CORRECTION
1. Pump fails to operate
on startup.
a) Motive pressure line closed
a) Open valves to supply motive pressure to
pump
b) Motive pressure insufficient to
overcome backpressure
b) Check motive pressure and backpressure.
Adjust motive pressure to 10 psi (min.)
higher than the backpressure
c) Liquid inlet line closed
c) Open all valves to supply liquid to the
pump
d) Liquid discharge line closed
d) Open all valves on the discharge side of
the pump
e) Pump vapor-locked
e) Break vent connection at pump cover.
Stand clear of vent connection. If pump
begins to cycle, vapor locking has
occurred. Re-check that the exhaust tie-
back line is unobstructed and completely
self-draining to a lower pressure area
with sufficient vapor space
f) Insufficient fill head to allow pump
to trip
f) Check that fill head is large enough for
condensate to drain freely by gravity into
the pump properly. Raise condensate
source or lower pump to achieve required
filling head
2. Liquid backup and
equipment flooded, but
pump appears to cycle
normally
a) Motive pressure is too low to
achieve required capacity
a) Check motive pressure setting and
maximum backpressure during operation.
Check against sizing table. Increase
motive pressure as required
b) Insufficient filling head to achieve
required capacity
b) Verify required filling head is large
enough for condensate to drain freely by
gravity into the pump properly. Raise
condensate source or lower pump to
achieve required filling head
c) Restriction in liquid inlet line
c) Check that only full ported fittings are
used. Clean the strainer. Verify that all
valves are fully open
d) Inlet check valve stuck open
d) Isolate inlet check valve and relieve
pressure. Remove cap and visually
inspect for debris. Clean seating surfaces
and reinstall or replace, if necessary
e) Pump undersized
e) Verify rated capacity in the sizing capacity
table. Increase check valve size or install
additional pump as required
3. Liquid backup and
equipment flooded, and
pump has stopped
cycling
a) Motive pressure low
a) If motive pressure is below backpressure,
increase motive pressure setting to 10 psi
(min.) above backpressure. Do not
exceed rated pressure limits of equipment
b) Discharge line closed via valve
blocked with debris
b) Compare motive pressure and
backpressure. If backpressure is higher
or equal, a closed or blocked discharge
line is possible. Check valves
downstream of pump
