Frequently asked Questions...

Q: Does the arrow on my submersible pump refer to direction of impeller rotation or kick direction?

A: Usually, a red arrow on the pump refers to direction of kick, a green arrow refers to direction of impeller rotation.  However, it is advisable to check the operation manual whilst wiring up a submersible pump.

 

Q: Can I use recycled water through my high pressure pump for wash down applications? 

A: It’s not best practice as high pressure pumps are designed for clean water only. It depends how clean the water is, however you will have to be prepared for mechanical seals and or pumps to be replaced regularly. It’s best to exhaust all fresh water options first. If there is no other option then we’d recommend a centrifugal end suction pump over a vertical multistage pump as they’re easier to maintain and repair.

 

Q: Can cavitation be an issue with centrifugal pumps even if I have a far greater NPSHa than NPSHr?

A: Yes, you can still have discharge cavitation if the required differential pressure is greater than the pump can provide.

 

Q: The pump isn’t giving me the pressure/flow I need, compared to what you specified it to do. Why would this be?

A: If the pump has a 3 phase motor, check it is wired in correctly. If the phases are wired in incorrectly, the pump may run in reverse. This will then only provide up to 60% of the specified performance depending on the type of pump.

 

Q: What approximate flow of water is required for a typical 4mm dust suppression nozzle?

A: It depends on the pressure, but at a typical 3 bar, they use approximately 1 cubic meter of water per hour each.

 

Q: Why is my pump giving reduced flow?

A: This could be caused by a number of things:

 

  • Worn impeller: As the impeller wears out it become less and less efficient and the flow rate will drop.
  • Blocked discharge lines: If you have a long discharge line a drop in flow rate due to a worn impeller could allow solids to settle out in the line.
  • Rubber pipe lining collapsed: If the rubber liner in steel pipework becomes unstuck from the pipe wall it can partically block the suction line and reduce flow rate.
  • Cyclone liner collapsed: A worn cyclone liner can become unstuck from the cyclone and restrict the flow into the cyclone which limits pump flow.

 

Q: Why is the pump discharge surging?

A: This could be due to a number of reasons:

 

1) The pump could be losing its prime. Check suction pipework and the level in the feed tank if pump is flooded suction.

 

2) Solids could be settling out in the discharge pipeline causing it to surge.

 

3) The pump impeller could be worn and struggling to get up to pressure.

 

Q: Why is water spewing out of the throat?

A: This happens on rubber lined pumps when the discharge pipework isn’t straight. The throatbush can get pushed out of line, which leaves a gap between the cover plate liner and the throatbush. Water then comes out where the cotter pins are.

 

Q: Why is my slurry pump steaming?

A: This happens where the pump is running too much to the left of the curve. Power is constantly going into the pump, so if it can’t pump as fast as it would like, the energy turns into heat. When left for a long time, the water actually boils, and the pump cavitates and steams.

 

Q: Why is the bearing housing on my slurry pump extremely hot?

A: This can indicate a few potential issues.  

 

1) The bearings have been incorrectly shimmed which causes them to run hot.  
2) The bearings have not been greased for an extended period of time.  
3) The pump is running faster than the maximum recommended speed.  

 

New built-up SlurryPro pumps include provision for an automatic greasing system as standard. Once fitted, this ensures consistent reliable lubrication of the bearings and seals for maximum service life. 

 

Find out about SlurryPro Automatic Greaser here.

 

Q: Why does my slurry pump sound like it’s pumping marbles?

A: This is a sure sign of cavitation and there can be a few reasons for this:

 

1) The discharge heads too great for the pump. This could be due to a valve on the discharge being closed or the wrong pump for the application.


2) The suction heads too great. This is when you’re trying to draw the fluid up too far or the suction pipe has blocked.

 
3) If you are pumping from a tank, ensure the fluid level is not dropping below the level of the inlet pipe as it will start to draw in air.

 

All of the above will result in damage to the pump, especially the impeller.

 

Q: Why does the impeller is pitted around the outside

A: This will be due to cavitation, and the fact it is around the outside means it is discharge cavitation rather than suction cavitation. This is almost exclusively a high chrome issue. To resolve the problem, check for blockages, closed valves and check the application.

 

Q: Why does our rubber impeller / liners look melted?

A: This can be due to a number of reasons:

 

1. Cavitation with a rubber impeller. Rubber does not pit in the same way that high chrome does.

 

2. The pump is turning too fast which makes the tip speed too high. When the max tip speed is exceeded, the rubber starts to delaminate and disintegrate.

 

3. The discharge head is too great or a valve is closed. The fluid thrashes around inside the pump which causes a build-up of heat and can lead to the rubber melting.

 

4. If the impeller is incorrectly adjusted, it can rub against the liner which causes both to heat up and disintegrate.