Page 233 - Intro Predictive Maintenance

224 An Introduction to Predictive Maintenance

Table 10–3 Common Failure Modes of Reciprocating Positive-Displacement Pumps

THE PROBLEM

No Liquid Delivery Insufficient Capacity Short Packing Life Excessive Wear Liquid End Excessive Wear Power End Excessive Heat Power End Excessive Vibration and Noise Persistent Knocking Motor Trips

THE CAUSES
Abrasives or Corrosives in Liquid
Broken Valve Springs
Cylinders Not Filling
Drive-Train Problems
Excessive Suction Lift
Gear Drive Problem
Improper Packing Selection
Inadequate Lubrication
Liquid Entry into Power End of Pump
Loose Cross-Head Pin or Crank Pin
Loose Piston or Rod
Low Volumetric Efficiency
Misalignment of Rod or Packing
Non-Condensables (Air) in Liquid
Not Enough Suction Pressure
Obstructions in Lines
One or More Cylinders Not Operating
Other Mechanical Problems: Wear, Rusted, etc.
Overloading
Pump Speed Incorrect
Pump Valve(s) Stuck Open
Relief or Bypass Valve(s) Leaking
Scored Rod or Plunger
Supply Tank Empty
Worn Cross-Head or Guides
Worn Valves, Seats, Liners, Rods, or Plungers
Source: Integrated Systems, Inc.

Because of the close tolerances between the pistons and the cylinder walls, rec-
iprocating pumps cannot tolerate contaminated liquid in their suction-supply system.
Many of the failure modes associated with this type of pump are caused by
contamination (e.g., dirt, grit, and other solids) that enters the suction-side of the