Table of Contents
Advertisement
POSSIBLE CAUSES
1
There may be air existing in pump or piping.
Ingress of air through shaft seal, suction pipe
2
or suction port. Pump lifts liquid with air.
3
Air pocket in the suction pipe.
4
There is air in liquid.
5
Too much suction lift.
6
Pump is working at cavitation conditions.
7
Insufficient manometric head.
8
Increase at total manometric head.
9
Pump is operating at lower manometric head.
10
Reverse rotation.
11
Speed is too low.
12
Speed is too high.
13
Impeller or check valve or strainer is clogged.
14
Impeller or strainer is clogged partially.
15
Partially clogged impeller.
16
Worn out and defected impeller.
17
Mechanical frictions inside the pumps.
18
Excess tightened soft packing.
19
Bad coupling aligment.
20
Bearing covers are too tight.
The pumped flow is less than the minimum
21
flow required.
22
Existence of excess grease.
23
Oblique shaft.
Insufficient lubrication or lubricating grease
24
dirty, contamined.
25
Unbalanced rotating parts.
26
Pump runs out of duty range.
The density or viscosity of the liquid pumped is
27
higher than that originally specified.
28
Defects in motor.
REMEDIES
Fill pump and piping completely with liquid and repeat the priming
procedure.
Check for leaks in suction pipe joints and fittings. Check shaft seal if
necessary increase the pressure of sealing liquid. Check the dept of suction
pipe or foot valve in the liquid and if necessary increase the depth of them.
Check the slope of the suction line make sure that there is no reason for
formation of air pockets.
Suction pipe is not submerged enough creating vortex. Check liquid level in
suction tank or increase the depth of suction pipe or foot valve in the liquid.
If no obstruction at inlet check the friction losses of suction line, larger piping
may correct condition. If static lift is too high, the liquid level in the suction
tank must be raised or the pump lowered.
NPSH available is too low. Check liquid level in suction tank, check suction
line for excessive friction losses. Check isolating valve in suction line to make
sure it is completely open. If necessary increase suction head on pump by
lowering the pump.
The actual total head is higher than that originally specified. Check the
geodetic total head and friction losses in the discharge line. Larger piping
may correct the condition. Check that valves are fully open.
Check that valves are fully open. Check that there is any obstruction in
piping.
The actual total head is lower than that originally specified. Machine impeller
outer diameter to size advised by supplier.
Check motor rotation with directional arrow on pump casing or nameplate.
Check the supply voltage and frequency or motor may have open phase.
If possible decrease the pump rotational speed or turn down the impeller
outer diameter to size advised by supplier.
Clean the impeller or check valve or strainer.
Clean the impeller or strainer.
Clean the impeller.
Replace impeller.
Check pump rotor for any rotor obstruction or deflection.
Loosen the nuts of the packing gland.
Check the coupling rubber and realign the coupling.
Check and make necessary modification on the cover.
Increase the flow. If necessary use by-pass recirculating valve or line.
Remove excess grease.
Check the shaft and replace it if necessary.
Check the amount of grease. Clean the bearings and bearing housing and
relubricate
Check the balance of the rotating parts.
Check the values of operating point.
Use a more powerful motor.
Check any motor defects. The motor may not be ventilated properly due to a
poor location.
Table 7
24
Advertisement
Table of Contents
