Centrifugal Pump: Faults & Overhauling (An Idiot's Guide Series Presentation)

All About CENTRIFUGAL PUMP: Faults & Overhauling!

(An Idiot's Guide Series Presentation)

Centrifugal Pump Overhaul

1. Switch off supply from the control room and isolate breaker with masking tape and place a safety board (Men at work).

2. Switch off supply from local panel and isolate by masking tape, place a safety board on the panel (Men at work).

3. Close suction and discharge valves and lash them with rope.

4. Drain the suction pipe and ensure water is not coming, then loosen or crack open the joints and ensure that pump is safe for opening .

5. Fix chain block and ensure its cable length and strength is satisfactory.

6. Mark on coupling and casings and then remove the coupling bolts.

7. Now motor input supply wire can be marked and disconnected as per drawing.

8. Motor can be lifted by chain block.

9. Disconnect all external fittings and pump casing e.g. cooling pipe, pressure gauge, purging cock.

10. Remove top cover and jack it for removal.

11. Now the pump shaft with impeller can be lifted.

12. Dismantle the impeller, liner and remove the wear ring.

13. Remove the gland packing.

INSPECTION PROCEDURE

1. Impeller, pump shaft and casing to be inspected for erosion, pitting and wear down etc.

pic courtesy: pumpfundamentals.com

2. If required rectify defects with brass putty.

3. Excess worn out parts can be replaced with new ones.

4. Check wear down ring clearance, general practise is to replace with new ring.

5. Check shaft trueness, remove sleeve from the shaft replace sleeve with ‘o’ ring if required.

6. Check key, key slots, nuts and its threads are ok.

7. Assemble all the pump parts.

PROCEDURE TO START THE PUMP

1. Open inlet and out let valves.

2. Purge air and prime the suction line.

3. Turn the shaft coupling and ensure shaft is free to rotate.

4. Connect motor wire R, Y, B.

5. Start and check current drawn by the motor while staring and running.note down the pr and feel the pump casing for any noise or rise in temp of motor.

Fault Finding & Trouble Shooting

• Does not deliver any liquid

Insufficient priming liquid

Insufficient pump speed

Excessive discharge pressure (such as a partially closed valve or some other obstruction in the discharge line)

Excessive suction lift Clogged impeller passages

Wrong direction of rotation

Clogged suction screen (if used)

Ruptured suction line

Loss of suction pressure

• Insufficient capacity and Crackling noise from the pump casing

Air leakage into the suction line

Insufficient speed of the pump

Excessive suction lift

Clogged impeller passages

Excessive discharge pressure

Mechanical defects (such as worn wearing rings, impellers, stuffing box packing,or sleeves)

• Does not develop enough discharge pressure

Insufficient speed of the pump

Air or gas in the liquid being pumped

Mechanical defects (such as worn wearing rings, impellers, leaking mechanical seals, and sleeves)

• Works for a while and then fails to deliver liquid

Air leakage into the suction line

Air leakage in the stuffing boxes

Clogged water seal passages

Insufficient liquid on the suction side

Excessive heat in the liquid being pumped

• Takes too much power and the motor overheats

Operation of the pump at excess capacity and insufficient discharge pressure

Misalignment

Bent shaft

Excessively tight stuffing box packing

Worn wearing rings

Other mechanical defects

• Vibration

Misalignment

Bent shaft

Clogged, eroded, or other-wise unbalanced impeller

Lack of rigidity in the foundation

Insufficient venting (Positive suction head)

Insufficient suction pressure may also cause vibration, as well as noisy operation and fluctuating discharge pressure

Downloads & Must Visit Section

Must Read:

Learn About various precautions & tips about Centrifugal Pumps, here @ pumpfundas!

Must Download:

Best Centrifugal Pump Guide Book (.pdf), Download Here!

That's All Folks :)

Get Social,

Like us on Facebook: FB/MEOSUCCESS

Follow on Twitter: Twitter/MEOSUCCESS