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.
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| 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
Misalignment
Bent shaft
Excessively tight stuffing box packing
Worn wearing rings
Other mechanical defects
- Vibration
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 :)
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