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IOM Manual: IOM-0000-CST
Series CST: Submersible Turbine
01/01/2018 - Edition 1A
PROBLEM
POSSIBLE CAUSE
RECOMMENDED REMEDY
Problem #1
Pump not reaching design flow rate.
1.1
Insufficient NPSH
A
. (Noise may not be
present)
Recalculate NPSH available. It must
be greater than the NPSH required by
pump at desired flow. If not, redesign
suction piping, holding number of
elbows and number of planes to a mini-
mum to avoid adverse flow rotation as it
approaches the impeller.
1.2
System head greater than anticipated.
Reduce system head by increasing pipe
size and/ than or reducing number of
fittings. Increase impeller diameter.
NOTE: Increasing impeller diameter
may require use of a larger motor.
1.3
Entrained air.
Air leak from atmosphere on suction
side.
1. Check suction line gaskets and
threads for tightness.
2. If vortex formation is observed in suc-
tion tank, install vortex breaker.
3. Check for minimum submergence.
1.4
Entrained gas from process.
Process generated gases may require
larger pumps.
1.5
Speed too low.
Check motor speed against design
speed.
1.6
Direction of rotation wrong.
After confirming wrong rotation,
reverse any two of three leads on a three
phase motor. The pump should be
disassembled and inspected before it is
restarted.
1.7
Impeller too small.
Replace with proper diameter impeller.
NOTE: Increasing impeller diameter
may require use of a larger motor.
1.8
Impeller clearance too large.
Replace impeller and/or case wear rings.
1.9
Plugged impeller, suction line or casing
which may be due to large solids.
1. Reduce length of suction when pos-
sible.
2. Reduce solids in the process fluid
when possible.
3. Consider larger pump.
1.10
Wet end parts (bowl, impeller) worn,
corroded or missing.
Replace part or parts.
Problem #2.0
Pump not reaching design head
(TDH).
2.1
Refer to possible causes under Problem
#1.0.
Refer to remedies listed under Problem
#1.0 and #3.0.
Problem #3.0
No discharge or flow
3.1
Not properly primed.
Repeat priming operation, recheck
instructions. If pump has run dry, disas-
semble and inspect the pump before
operation.
