IN THIS eBOOK You may not know it... But, you may be setting your pump up to self-destruct! Check out these 36 common ways pumps are inadvertently destroyed, and be sure not to make the same mistakes.
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About the Author Kurt Schwei is a Field Sales Manager for Crane Engineering with a long history of pumping experience. He has designed fluid-handling systems, controls & components for a variety of industries including Pulp & Paper, Food, Beverage, and General Industry. Kurt strives for continuous improvements, and provides a high level of technical expertise and professional support to his customers and team members.
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36 WAYS TO KILL YOUR PUMP 1. PIPE STRAIN Any time a pipe pulls on a pump, pipe strain occurs. The pull of the pipe on the pump can be caused by improperly supported pipes, or misalignment between the pipe and the pump. Connecting a pump to a pipe that is too high can cause base plate damage, pulling the threads out of the base plate, along with nozzle breakage, casing damage, and premature impeller, stuffing box, and casing wear. 2. POOR PIPING DESIGN AND/OR INSTALLATION Having a poor piping design can have a big effect on how the pump will perform. Designs with inverted “U”s on the suction side can trap air, while designs with a 90° immediately before the pump can cause turbulence inside the pump. Both result in suction problems and pump cavitation.
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3. ALLOWING THE PUMP TO RUN DRY Allowing your pump to run dry can be very damaging. Doing this leads to pump cavitation and mechanical seal damage. In fact, a mechanical seal can experience thermal shock (getting too hot), under the right conditions it can shatter within about 30 seconds.
Evidence of suction cavitation due to running a pump dry.
4. ISSUES WITH NPSHA Causes pump cavitation, erratic flow, impeller & case damage, and loss of performance. 5. ENTRAINED VAPOR Entrained vapor can be caused by a number of factors. Vortexing in the tank, insufficient water source, or steam injection, for example. Entrained vapor causes loss of performance, wear to the impeller and cutwater, and dry running of the seal due to vapor between the faces.
Helpful Hint:
There’s more information about cavitation on Crane’s Fluid Connection Blog!
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6. PUMPING SOLIDS & ABRASIVES WITH THE WRONG TYPE OF PUMP & OTHER EQUIPMENT It’s extremely important to select the right type of pump and materials to move solids and abrasives. If improperly selected, expect to see shortened life on nearly all liquid end components (casing, impeller, stuffing box, etc.), impeller imbalances, and a serious drop off in efficiency. 7. USING THE WRONG SIZED IMPELLER Using the wrong sized impeller for the
Pick up tube from Roto-Jet impeller. Left side shows severe abrasion wear.
pump causes the pump to produce too much, or too little flow, running off its best efficiency point (BEP). If the impeller is too big, the pump motor has to work harder to pump the fluid, eventually causing it to burn out. An impeller that’s too small will most likely not generate enough flow or head. 8. INCORRECTLY ADJUSTING THE IMPELLER Incorrect impeller adjustment can lead to increased slippage in the pump, creating more turbulence inside the pump, lowering its efficiency, and increasing stuffing box pressures. 9. VANES BENT AND OUT OF PLANE Trying to remove or install an impeller without the proper tools (like A HAMMER!) can cause damage to the impeller. A damaged impeller will cause insufficient head and/or capacity, hydraulic imbalance, and pressure pulses.
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10. INCORRECT WEAR RING CLEARANCE A wear ring separates the high pressure zones of the pump from the low pressure zones. When clearances open up, the pump experiences increased slippage, and the high pressure liquid seeps back into the low pressure areas, causing a loss in efficiency. When clearances are too tight on the other hand, the wear ring will cause
Wear ring from large split case pump. Ridges indicate excessive wear.
galling and seizing of the pump. 11. IMPROPER AXIAL ADJUSTMENT Improper axial adjustment causes a drop in head and capacity and low stuffing box pressure, resulting in dry running of the seal and premature bearing failure. 12. PLUGGED VANES OR BALANCE HOLES Plugged vanes or balance holes are caused by blockages from solids that have been pulled into the pump that are too large for the pump capacity. Plugged valves lead to a decrease in performance, priming issues, impeller imbalance, and high vibration, finally resulting in bearing and seal damage.
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13. PUMP IMBALANCE Unbalance creates issues like structural problems, reduced machine and bearing life, increased vibration, and many more. Vibration hurts your equipment!
Resonance Misalignment Bearing Failure Looseness Unbalance
14. OPERATING THE PUMP AT SHUT-OFF When the discharge side valve is partially or completely closed to manually control flow, it causes 100% of input energy to be destructive. Heat, high radial loads cause shaft deflection, heat and increased pressure, vibration, auto shut-off, increased energy use, and low amps. 15. OPERATING THE PUMP TOO FAR BACK ON THE CURVE Running the pump off its best efficiency point causes excess recirculation, heat, radial loads, vibration, high seal temperatures, and lowered efficiency.
Helpful Hint:
Learn more about how to read a centrifugal pump curve on Crane’s Fluid Connection blog!
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16. TRAPPING VAPOR IN THE STUFFING BOX This occurs most often in a vertical installation, where the stuffing box is at the highest point on the pump. If the seal flush becomes plugged or shut-off, any vapor in the pump will work its way up to the highest point, the stuffing box. If the vapor is not properly bled off or vented, the pump is susceptible to partial dry running, until the
Pitting due to the seal running dry causing gases to escape, imploding on the seal face.
vapor releases through the seal to atmosphere. 17. TRAPPING SOLIDS IN THE STUFFING BOX When product gets into the stuffing box and isn’t properly flushed out, expect to see shortened seal life. 18. INSTALLING THE STUFFING BOX FACE NOT PERPENDICULAR TO THE SHAFT Improper installation will cause excessive seal movement and shortened life. Including, fretting corrosion, o-ring and drive wear. 19. USING A DAMAGED STUFFING BOX OR WORN & DAMAGED FITS Results in seal misalignment, leakage, and decreased pump efficiency. 20. BENT SHAFT Shafts are sometimes bent by solids getting caught in the pump. A bent shaft causes vibration, internal parts contact, bearing damage and premature failure, coupling damage, coupling misalignment, and very short seal life. Page 9
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21. USING A PIPE WRENCH ON SHAFT OR IMPELLER Pipe wrenches are for pipes! Using a
Helpful Hint:
ALWAYS use an impeller wrench!
pipe wrench on shafts and impellers can cause coupling end damage and bent vanes on the impeller (see #9!). 22. SLEEVE RUN OUT Sleeve run out is basically an improperly fitted sleeve on a shaft. The wrong fit causes excess movement under the seal and leads to shorter seal life. 23. LIP SEAL GROOVES IN THE SHAFT Contaminates can enter the bearing housing through the grooves destroy the bearings. If contaminates can enter, that also means lubricants can exit, leading to bearing failure and a complete pump failure. 24. POOR SURFACE FINISH ON SHAFT SLEEVE OR SHAFT If the surface finish isn’t smooth, the packing will fail, leading to leaking between the shaft or sleeve & shaft o-ring seal.
Shaft sleeve shows deep grooves, excessive wear from packing.
25. IMPROPER BEARING FITS Every time a bearing is replaced, or the shaft is cleaned, just a tiny fraction of the material on the surface is removed. Over time, a little adds up to a lot and can really affect the bearing clearance on the shaft. When this happens, expect the bearings to spin within the housing, or on the shaft.
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26. DEFLECTION DURING THE HARD START OF OPERATION BACK ON THE CURVE With a hard start, the pump tries to pump liquid from the get-go. The pressure inside the pump causes the shaft to deflect towards the low pressure side of the pump, causing the shaft to contact the stuffing box, and the impeller to contact the casing. The misalignment will then
Helpful Hint:
Centrifugal pumps should have a soft start with the suction valve wide open.
cause seal failure. 27. USING TOO LITTLE, TOO MUCH, OR THE INCORRECT LUBRICANT Lubrication is the #1 cause of premature bearing failure. Using too little lubricant can cause the bearings to seize, while too much lubricant retains heat inside the bearing, and also causes oil leakage. 28. CONTAMINATION OF THE BEARING HOUSING Sometimes contaminates get inside the bearing housing. This can happen during wash down duties, or sometimes particulates left over from repairs will remain inside. Contaminates will destroy the bearings, housings, fits, and also cause shaft damage. 29. HAMMERING COUPLINGS ONTO THE SHAFT When it comes to pumps, hammers are not friends! Pounding couplings onto shafts will damage the thrust bearing and mechanical seal. Carbon mechanical seals can crack if struck with a hammer.
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Bearing Damage Coupling Damage
premature seal and bearing failures,
DAMAGE
SA
I
ment. This means increased vibration,
MACHINE
M
chinery is directly related to misalign-
Seal Wear
CAUSES OF
T
Up to 50% of damage to rotating ma-
Machine Vibration
LIG N ME
N
30. IMPROPER ALIGNMENT
OTHERS
and increased power consumption. 31. NOT FOLLOWING INITIAL STARTUP PROCEDURES NOTED IN THE PUMP MANUAL Improperly starting up the pump can cause the motor to trip and the shaft to twist causing orbital movement - directly related to internal parts contact, seal failure, and shortened bearing life.
Crane Engineering service technician performs laser alignment on a “bad actor” pump.
32. MECHANICAL SEAL INSTALLATION ERRORS Improperly installing the mechanical seal will cause damage to elastomers (o-rings or boots), among a wide variety of other issues. Mechanical seals can be very sensitive as the faces are incredibly flat. Even a small amount of dirt or oil (such as fingerprints) can cause the faces to not align properly.
Chips and cracks in seal rings can be caused by mishandling of parts, or improper installation.
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33. IMPROPER USE OF OR COMPLETELY OMITTING MECHANICAL SEAL FLUSH PLANS It is critical that a mechanical seal flush plan is properly in place. Not having one sets up a scenario where dewatered product and contaminates can build up, the seal experiences excessive heat, and ultimately shortens its life. 34. SELECTING THE WRONG MECHANICAL SEAL OR SEAL MATERIALS DUE
Heat checking occurs with an inadequate amount of face lubrication, causing the seal to experience excessive heat.
TO LACK OF KNOWLEDGE Lack of knowledge and information accounts for the majority of mechanical seal installation errors. Consider normal operating conditions, potential for off-design excursions and nonprocess activities, such as cleaning, steaming, acid and caustic flushes.
Helpful Hint:
Learn more about single mechanical seal flush plans on Crane’s Fluid Connection blog!
An example of a poor material choice for an abrasive liquid.
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35. INCOMPLETE FAILURE ANALYSIS OR OMITTED ENTIRELY Always try to get the root of the problem when making pump repairs. Oftentimes, forces outside the pump are causing it to fail. By only fixing the symptoms and not addressing the system as a whole, you may end up making the same repair on the pump again. 36. OPERATORS RELYING HEAVILY ON REACTIVE MAINTENANCE, RATHER THAN PREVENTATIVE OR PREDICTIVE MAINTENANCE MEASURES Reactive maintenance accounts for unnecessary equipment downtime, increased costs, and equipment instability. Consider a preventative maintenance program with a schedule of maintenance to be performed, laser alignment and balancing, or a predictive maintenance program using technology like vibration analysis, to get ahead of problems before they happen.
Helpful Hint:
Organize a “bad actor” team of Engineering, Maintenance, and Operations personnel to watch for seal problems.
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CONCLUSION When it comes to fluid process pumps, be aware of your actions! Energy usage and pump maintenance account for MORE THAN than 50% of the pump’s total cost of ownership. The main culprits of rotating equipment failure are caused by the sealing device, couplings, hydraulics, static joints, and bearings. Don’t let your pump be the next statistic! Read the pump manual, train your operators, and identify the “bad actors” in your facility to help prevent costly pump repair.
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