Checklist for Overhauling Centrifugal Pumps

After all, Prevention is the Best Cure and it Applies to your Centrifugal Pumps too To ensure that your centrifugal pump works with utmost efficiency and minimal repairs, it’s essential to set up a sound maintenance program. And, this checklist will help you do precisely that. Whether your centrifugal pump operates in mild, external conditions or harsh environments, the surroundings can place a great deal of stress on your pump equipment. Pumps generally have to run 365 days a year, with downtime being extremely costly. Hence, it’s essential that your centrifugal pumps run at optimum performance. Why is it crucial that a Pump operates near and left of BEP? You get the most out of the system, when your pumps operate at BEP (Best Efficiency Point) – the point at which the unbalanced load is at a minimum. If your pump runs at a point different from the actual BEP, then it leads to an overall increase in the unbalanced load. This affects the pump’s performance, drastically reducing the efficiency and reliability. This is where the role of a routine maintenance program is vital. It helps in extending the life of your pump by reducing repair frequency and cost. In this article, we outline a basic checklist that will help you in preventive maintenance of centrifugal pumps. Steps involved in the Removal of Centrifugal Pumps for Maintenance and Inspection

1. Switch off the power supply to the pump from the control room. Isolate the breaker with masking tape and put up a safety board that says, “Do not operate machinery. Men at Work.”
2. The next step is to cut off the supply from the local panel. Once done, isolate it with masking tape and place a similar safety board on top of the panel.
3. Close the inlet (suction) and outlet (discharge) valves and tie them with rope.
4. The next step is to drain the water remaining in the suction pipe. Make sure that water is not entering the system. Then, loosen up the joints and make sure that the pump is safe for opening.
5. Fix a chain block. Make sure the length of the cable is adequate, and it has sufficient strength.
6. Mark on the point of casings and couplings with a temporary marker and then remove the bolts.
7. Next, make a note of the motor input wiring and disconnect it as per the circuit drawing.
8. Lift the motor with the help of the chain block.
9. Disconnect all the external casings and fittings including the pressure gauge, cooling pipe, and purging cock.
10. Remove the top cover.
11. Jack, it to ease removal.
12. Lift up the pump shaft along with the impeller.
13. Dismantle the impeller and liner.
14. Remove the wear ring.
15. Finally, remove the gland packing.

Now, you have successfully disassembled the pump and made it ready for inspection and maintenance. Inspection Procedure for Routine Maintenance of Centrifugal Pumps Let’s take a closer look at the centrifugal pump inspection procedure.

1. Check the pump shaft, impeller and casing for any signs of erosion, wear downs, or pitting.
2. If you spot any troublesome signs, rectify the defects with the help of brass putty.
3. If some parts are worn down beyond repair, then replace them with new ones.
4. The next step is to inspect the wear levels of the ring clearance. The general procedure is that the rings are replaced with new rings during every inspection.
5. Next, check the shaft trueness. If needed, remove the sleeve from the shaft and replace the ‘O’ ring.
6. Ensure that the key, key slots, nuts, and threads are all in perfect condition.
7. Once you have inspected all these components, you can begin assembling the parts of the centrifugal pump.

How to Restart the Pump?

1. Open up all the inlet and outlet valves.
2. Remove air from the suction line and prime it up.
3. Ensure that the pump shafts are free to rotate and turn the shaft couplings in the right position.
4. Connect the motor wires R, Y and B.
5. The final step is to turn on the motor. Check the current drawn by the pump while starting and during running. Note down the values and feel the casing for any unusual vibrations, noise or rise in temperature.

Troubleshooting Centrifugal Pump Operation One of the biggest problems with centrifugal pumps is in figuring out what has gone wrong exactly. For instance, your pump may run, but the output may falter. The reason for this is many. Here, in this section of the article, we give you some common errors with centrifugal pumps and the reasons behind it.

• Error 1: Does not Pump out any Liquid

Possible Causes:

• Inadequate pumping speed
• Insufficient priming liquid
• Excessive pressure in the discharge due to a partially closed valve or any other block on the discharge outlet
• Rotation in the wrong direction
• Loss of suction pressure
• Clogged impellers or suction screen
• Torn/broken suction line
• Excessive suction lift

• Error 2: A crackling noise from the casing and/or lowered pump capacity

Possible Causes:

• Leakage of air in the suction line
• Inadequate pump speed
• Clogged impellers
• Excessive suction lift and discharge pressure
• Mechanical defects like worn down rings, sleeves, impellers and stuffing box packing

• Error 3: Not enough discharge pressure

Possible Causes:

• Inadequate pump speed
• Air or gas mixed with the displaced liquid
• Mechanical causes like worn impellers, wearing rings, and leaking sleeves and seals

• Error 4: Pump works for a short while after which it fails to pump the liquid

Possible Causes:

• Air entry into the suction line
• Air leakage from the stuffing boxes
• Blocked water seals
• Inadequate liquid on the inlets (suction side)
• Excessive temperature of the pumped liquid

• Error 5: Overheating of the motor due to too much power

Possible Causes:

• Pump is continuously operated at excess capacity
• Misalignment of the shafts or bent shafts
• Worn down wearing rings and other mechanical defects
• Excess tight stuffing in the packing
• Inadequate discharge pressure

• Error 6: Vibration of the Pump Casing

Possible Causes:

• Misalignment of the shafts or bent shafts
• Foundation is not rigid
• Inadequate suction pressure
• Fluctuations in the discharge pressure
• Inadequate venting

The Last Word Regular overhauling of your centrifugal pump is essential to prolong the life and to avoid costly downtime, repairs, and replacement. Make use of this handy checklist to overhaul and inspect the working of your pump periodically and ensure that it’s in perfect condition. If you have any further queries on how to handle pump overhauling or if you’re looking for the right centrifugal pumps for your industry, then get in touch with our Sintech pumps care experts who provide you with expert guidance. Just give us a call at +91-120-4176000 or drop in a line at sales@sintechpumps.com.