• (918) 437-8800
Trouble Possible Causes
Low volumetric efficiency (failure to deliver rated capacity and pressure)
  1. Air or vapor pocket in inlet line
  2. Capacity of charge pump less than capacity of power pump
  3. Air or vapor trapped in or above inlet manifold
  4. Air leak in liquid supply piping system
  5. Loose bolts in pump inlet manifold
  6. Air or gases entrained in liquid
  7. Foreign object holding pump inlet or discharge valve(s) open
  8. Incorrect drive ratio
  9. Loose belts
  10. Incorrect motor or engine speed
  11. Loose valve covers or cylinder head
  12. Worn valves and seats
  13. Safety relief valve partially open, or not holding pressure
  14. Worn liners, piston rings or plungers
  15. Bypass valve open, or not holding pressure
  16. Blown liner gasket
  17. NPSHA not sufficient
  18. Liquid bypassing internally
  19. Foreign object blocking liquid passage
  20. Vortex in supply tank
  21. Insufficient power delivered by motor
  1. Inlet line partially clogged
  2. Liquid vapor pressure too high
  3. Liquid pumping temperature too high
  4. Restricted inlet pipe fittings
  5. Inlet line too long
  6. Too many pipe fittings
  7. Too small inlet line
  8. Too low static inlet head
  9. Too low atmospheric pressure
Liquid Not Delivered
  1. Pump not primed
  2. Air or vapor pocket in inlet line
  3. Clogged inlet line
  4. All inlet valves propped open
  5. All discharge valves propped open
  6. Loose bolts in pump inlet manifold
  7. Too high valve velocities


Trouble Possible Causes
  1. NPSHA too low
  2. Liquid NOT Delivered to Pump Inlet Connection
  3. Excessive Stuffing Box Leakage
  4. NPSHR too high
Leak at Cylinder Head or Valve Cover
  1. Over Recommended Pressure
  2. Loose Cylinder Head/Valve Cover
  3. Damaged Gasket/O-ring
Water in Crankcase/Oil
  1. Water Condensation
  2. Worn seals
  3. Clogged Air Breather(s)
  4. Worn Crankcase Packing
  5. Loose Covers
Oil Leakage from Crankcase
  1. Oil Level/Temperture Too High
  2. Worn seals
  3. Worn Crankcase Packing
  4. Loose Crankcase Cover
Excessive Heat in Power End
  1. Pump Running Backward/RPM too low
  2. Insufficient Oil in Power End
  3. Excessive Oil in Power End
  4. Incorrect Oil Viscosity
  5. Operating Pump above Recommended Pressure
  6. Main Bearings too Tight
  7. Drive Misaligned
  8. Belts too Tight
  9. Discharge Valve, one or more, Stuck Open
  10. Insufficient Cooling
  11. Pump RPM too Low
  12. Inadequate Ventilation
  13. Liquid End Packing Adjusted too Tight (adjustable style packing only)
Pump Overloads Driver
  1. 1) Pump RPM too High
  2. 2) Low Voltage or other Electrical Trouble
  3. 3) Trouble with Engine, Turbine, Gear Reducer or other Related Equipment
  4. 4) Excessive Discharge Line Pressure
  5. 5) Clogged Discharge Line
  6. 6) Closed/Throttled Valve in Discharge Line
  7. 7) Incorrect Plunger/Piston Size for Application
  8. 8) Improper Bypass Conditions
  9. 9) Over-tightened Stuffing Box Glands on Adjustable Packing


Trouble Possible Causes
Stuffing Box Leakage
  1. Worn Packing
  2. Worn rods or plunger
  3. Worn stuffing boxes
  4. Wrong size packing
  5. Worn O-ring seal (replaceable boxes)
Stud Failure
  1. Excessive discharge pressure
  2. Improper torquing of nuts
  3. Shock overload caused by pump cavitation
Excessive Valve Noise
  1. Broken or weak valve spring
  2. Pump cavitation
  3. Air leak in inlet piping or loose bolts in pump inlet manifold
  4. Air trapped above inlet valve
Inlet or Discharge Line Vibration
  1. Piping inadequately supported
  2. Inlet line too long or too small in diameter
  3. Too many bends in inlet line
  4. Multiple pump installations operating in phase
  5. Obstruction Under Valve(s)
  6. Packing Worn
  7. Operating Above Recommended Pressure or RPM
  8. Low NPSHA
Noisy Operation (Be sure to differentiate between liquid knock and mechanical knock – very few knocks are mechanical on new installations.)
  1. Piston or plunger loose
  2. Valve noise amplified through power end
  3. Pump cavitation
  4. Liquid knock
  5. Air leak in inlet piping
  6. Loose bolts in pump inlet manifold
  7. Hydraulic noise in liquid end
  8. Loose or worn crosshead pins and bushings
  9. Loose connecting rod cap bolt
  10. Worn connecting rod bearings
  11. Worn crosshead
  12. Main bearing end play excessive
  13. Worn gears or chains
  14. Gears or chains out of line
  15. Pump running backward
  16. Partial loss of prime
  17. Shocks in piping system
  18. Water in power end crankcase
  19. Poorly supported piping, abrupt turns in piping, piping misaligned, pipe size too small


Trouble Possible Causes
Broken shafts, bent, stripped threads and other catastrophic failures
  1. Start-up against closed gate valve in discharge line. If valve seats are discovered driven too deeply after operationof the pump, look for the following pattern of driven seats, indicative of start-up or run against a closed discharge line valve:
      • Triplex single acting plunger pump:
          • 2 inlets and 1 discharge valve seat
          • 1 inlet and 2 discharge valve seats
      • Quintuplex single acting plunger pump:
          • 3 inlets and 2 discharge valve seats
          • 2 inlets and 3 discharge valve seats
      • Duplex double acting piston pumps:
          • 2 inlets and 2 discharge valve seats
  2. 2) Low oil level
  3. 3) Contaminated oil
  4. 4) Main bearing failure
  5. 5) Piston or plunger striking cylinder head
  6. 6) Disintegration of worn valves
  7. 7) Frozen liquid in liquid body
  8. 8) Air leak in liquid supply system
  9. 9) Loose bolts in pump inlet manifold
Packing Failure
  1. Normal wear
  2. Improper material
  3. Improper lubrication
  4. Adjustable packing – gland tightened excessively
  5. Dirty liquid
  6. Plunger or piston rod misalignment
  7. Dirty environment
Valve Failure
  1. Normal wear
  2. Pump cavitation
  3. Abrasives in fluid
  4. Incompatibility of valve components to corrosive liquid
  5. Electrolysis
  6. Incorrect installation – driving on the valve stem, improper torque on jam nut, valve seat and valve deck not thoroughly clean and dry when seat installed.
Plunger Failure
  1. Thermal shock (cold water hitting hot ceramic plunger)
  2. Packing too tight
  3. Inlet valve dislocated/disassembled during pump operation
  4. Stuffing box gland rubbing on plunger due to improper tightening procedure
  5. Dirty liquid
  6. Dirty environment