TROUBLESHOOT

Troubleshooting

The troubleshooting guide below allows you to review and diagnose potential problems that may be encountered with Trishul’s range of pumps. The guide outlines common pumping problems and failures with probable causes and procedures for checking and correcting possible faults.

Between regular maintenance inspections, be alert for signs of motor or pump trouble. Correct any trouble immediately to AVOID COSTLY REPAIR AND SHUTDOWN.

 

No liquid delivery

Sr.

Causes

Cures

1.1

Lack of prime

Fill pump and suction pipe completely with liquid.

1.2

Loss of prime

Check for leaks in suction pipe joints and fittings; vent casing to remove accumulated air.

1.3

Suction lift too high

If no obstruction at inlet, check for pipe friction losses. However, static lift may be too great. Measure which mercury column or vacuum gauge while pump operates. If static lift is too high, liquid to be pumped must be raised or pump lowered.

1.4

Discharge system head too high

Check pipe friction losses. Larger discharge piping may correct condition. Check that valves are wide open.

1.5

Speed too low

Check whether motor is directly across-the-line and receiving full voltage. Alternatively, frequency may be too low; motor may have an open phase.

1.6

Wrong direction of rotation

Check motor rotation with directional arrow on pump casing. Wrong rotation will cause pump damage.

1.7

Impeller completely plugged

Dismantle pump or use piping hand hole to clean impeller.

Not enough liquid delivery

Sr.

Causes

Cures

2.1

Air leaks in suction piping

If liquid pumped is water or other non-explosive, and explosive gas or dust is not present, test flanges for leakage with flame or match. For such liquids as gasoline, suction line can be tested by shutting off or plugging inlet and putting line under pressure.  A gauge will indicate a leak with a drop of pressure.

2.2

Air leaks in stuffing box

Increase seal lubricant pressure to above atmosphere.

2.3

Speed too low

See item 1.5.

2.4

Discharge system head too high

See item 1.4.

2.5

Suction lift too high

See item 1.3.

2.6

Impeller partially plugged

See item 1.7.

2.7

Cavitation; insufficient NPSH (depending on installation)

a) Increase positive suction head on pump by lowering pump or increasing suction pipe size or raising fluid level.
b) Sub-cool suction piping at inlet to lower entering liquid temperature.
c) Pressurize suction vessel.

2.8

Defective impeller

Inspect impeller. Replace if damaged or van sections badly eroded.

2.9

Defective packing.

Replace packing and sleeves if badly worn.

2.10

 Foot valve too small or partially obstructed

Area through ports of valve should be at least as large as area of suction pipe- preferably 1½ times.  If strainer is used, net clear area should be3 to 4 times area of suction pipe.

2.11

Suction inlet not immersed deep enough

If inlet cannot be lowered, or if eddies through which air is sucked persist when it lowered, chain a board to suction pipe. It will be drawn into eddies smothering the vortex.

2.12

Wrong direction of rotation

Compare rotation of motor with directional arrow on pump casing. Wrong rotation will cause pump damage.

2.13

Impeller diameter too small (probable cause if none of above)

Check with factory to see if a larger impeller can be used; otherwise, cut pipe losses or increase speed, or both, as needed.  But be careful not to seriously overload drive.

2.14

Speed too low

See item 1.5.

2.15

Air leaks in suction piping

See item 2.1.

2.16

Mechanical defects

See item 2.8, 2.9, and 2.10.

2.17

Obstruction in liquid passages

Dismantle pump and inspect passages of impeller and casing.  Remove obstruction.

2.18

Air or gases in liquid (Test in laboratory, reducing pressure on liquid to pressure in suction line.  Watch for bubble formation.)

May be possible to over rate pump to point where it will provide adequate pressure despite condition.  Better to provide gas separation chamber on suction line near pump, and periodically exhaust accumulated gas. See item 2.7.

2.19

Excessive impeller clearance

Adjust impeller clearance.

2.20

Impeller diameter too small (Probable cause if none of above)

See item 2.13.

Pump operates for short time, then stops

Sr.

Causes

Cures

3.1

Incomplete priming

Free pump, piping and valves of all air.  If high points in suction line prevent this, they need correcting. See item 1.5.

3.2

Suction lift too high

See item 1.3.

3.3

Air leaks in suction piping

See item 2.1.

3.4

Air leaks in stuffing box

See item 2.2.

3.5

Air or gases in liquid

See item 2.18.

Pump takes too much power

Sr.

Causes

Cures

4.1

Head lower than rating; thereby pumping too much liquid

Machine impeller's OD to size advised by factory.

4.2

Cavitation

See item 2.7.

4.3

Mechanical defects

See item 2.8, 2.9, and 2.10.

4.4

Suction inlet not immersed enough

See item 2.11.

4.5

Liquid heavier (in either viscosity or specific gravity) than allowed for

Use larger driver. Consult factory for recommended size. Test liquid for viscosity and specific gravity.

4.6

Wrong direction of rotation

See item 1.6.

4.7

Stuffing box too tight (Packing)

Release gland pressure. Tighten reasonably. If sealing liquid does not flow while pump operates, replace packing.  If packing is wearing too quickly, replace scored shaft sleeves and keep liquid seeping for lubrication.

4.8

Casing distorted by excessive strains from suction or discharge piping

Check alignment.  Examine pump for friction between impeller and casing. Replace damaged parts.  Check for pipe strain.

4.9

Shaft bent due to damage - through shipment, operation, or overhaul

Dismantle pump and inspect shaft.

4.10

Mechanical failure of critical pump parts

Check bearings and impeller for damage.  Any irregularity in these parts will cause a drag on shaft.

4.11

Misalignment

Realign pump and driver.

4.12

Speed may be too high (brake hp of pump varies as the cube of the speed; therefore, any increase in speed means considerable increase in power demand)

Check voltage on motor.

4.13

Electric defects

The voltage and frequency of the electrical current may be lower than that for which motor was built or there may be defects in motor.  The motor may not be ventilated properly due to a poor location.

4.14

Mechanical defects in turbine, engine, or other type of drive exclusive of motor

If trouble cannot be located, consult factory.

 

 

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