Pump Maintenance Tips
Lubrication, seals, clearances, alignment and what to hold on the shelf.
Bearing Lubrication
- Grease lubricated bearings, as used on the KCP and VNP series, are regreased at the interval and the quantity in the manual. More grease is not better — an overfilled housing churns and runs hot.
- Use one grease type. Mixing thickeners can break the grease down.
- A bearing temperature that climbs steadily after regreasing is usually a sign of too much grease, not too little.
Mechanical Seals and Packing
- A single mechanical seal, as fitted to the CN, CI and KCP series, is a wear part. When it starts to leak, replace it rather than tightening anything.
- Do not run a mechanical seal dry, even briefly, when filling or draining the pump.
- Gland packing, optional on the FA series, is adjusted to a slow steady drip. Nipping the gland down to stop the drip burns the packing and scores the sleeve.
- The VNP series uses a labyrinth or lip ring seal rather than a face seal in the liquid, so there is no seal face to lap or replace.
Impeller Clearance and Wear
- On a full open impeller, as used on the CN series, performance depends on the running clearance between the impeller and the casing. That clearance can normally be reset as it wears, which recovers head and efficiency without new parts.
- On a closed impeller, wear shows at the wear rings. Replace them when the clearance has opened up.
- A slow loss of head at the same speed and the same suction condition is usually clearance, not the motor.
Re Alignment
- Re check the coupling alignment after any pipework change, after any work on the foundation and after the first period at working temperature.
- A coupling that keeps failing is a symptom. The cause is usually alignment or piping strain, not the coupling element.
Back Pull Out Overhaul
- The CN, CI, KCP, FA and VNP series all use a back pull out construction. The bearing frame, shaft, seal and impeller come out of the drive end as one assembly.
- The casing stays bolted into the pipework, so an overhaul does not mean breaking and remaking the flanged joints.
- Where downtime matters, hold a complete spare rotating assembly. Swapping it is far faster than rebuilding in place.
Recommended Spares
- Mechanical seal or a set of gland packing
- Bearings and the bearing housing seals
- Wear rings on closed impeller pumps, or a gasket and shim set on open impeller pumps
- Casing gasket or O ring
- Coupling element
- A complete rotating assembly for critical duty
Maintenance Tips FAQ
How often should bearings be regreased
At the interval given in the manual for the pump and the duty. Both the interval and the quantity matter.
Can a leaking mechanical seal be tightened
No. A mechanical seal has no adjustment. When it leaks, it is replaced.
Why is the head dropping on an old pump
Usually internal clearance. On an open impeller pump the clearance can often be reset. On a closed impeller pump the wear rings are replaced.
What does back pull out mean for maintenance
The rotating element is withdrawn from the drive end while the casing stays bolted to the pipework, so the flanged joints are not disturbed.
What spares should we keep on the shelf
Seal or packing, bearings, wear rings or shims, casing gasket and a coupling element. For critical duty, a complete spare rotating assembly.
Which series does not have a mechanical seal in the liquid
The VNP vertical sump pump, which uses a labyrinth seal or a lip ring seal.
Question About Maintenance Tips
Send the pump series, the size and what you are seeing on site and we will come back to you.