Preventive Maintenance Pumps

PREVENTIVE MAINTENANCE FOR PUMPS P034

Preventive maintenance programs are fun to talk about, but we seldom find people using a sensible schedule. A good preventive maintenance program for pumps would include:

  • Dynamically balance the rotating components.
  • Do a proper pump to driver alignment or use a “C or D” frame adapter.
  • Reduce pipe strain where ever possible.
  • Specify a low L3/D4 pump shaft
  • Make impeller adjustments as necessary to stop vibration problems.
  • There should be at least 10 diameters of pipe between the suction of the pump and the first elbow. This is especially critical in double-ended pump designs as the turbulent inlet flow can cause shaft thrusting, and subsequent bearing problems. If an elbow must be installed be sure it is in a plane at right angles to the pump shaft to prevent an uneven flow to both sides of a double suction impeller.
  • Be sure you have the correct amount of lubricant in the bearings. Over lubrication is just as bad as under lubrication
  • Set the open impeller clearance when the pump is hot.
  • Check to be sure the shaft is not bent.
  • Try to operate as close to the best efficiency point as possible. Sometimes it is just a matter of trimming an impeller.
  • Eliminate as much vibration as possible:
  • Dynamically balance the rotating components.
  • Stop any cavitation that might be occurring.
  • Check that the pump foundation is at least five times the mass of the hardware sitting on it.
  • Up to 500 horsepower (375 kw), the foundation must be 3 inches (76 mm.) wider than the base plate all around. Above 500 horsepower (375 kw) the foundation should be a minimum of 6 inches (150 mm.) wider.
  • Imaginary lines extended downward 30 degrees to either side of a vertical through the pump shaft should pass through the bottom of the foundation and not the sides.
  • Be sure the pump is leveled before it is aligned or the bearing oil level will be incorrect.
  • If you are going to be pumping hot liquid, you should specify a centerline pump to eliminate the pipe strain problems caused by the wet end of the pump expanding in only one direction. A good rule of thumb says that each inch of stainless steel metal will expand 0.001 inches with each 100°F of temperature increase, The metric expansion is each millimeter will expand 0.001 millimeters with every 50°C increase in temperature.

See: Monitoring the centrifugal pump M026

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  • On February 16, 2018