Centrifugal Pump User’s Guidebook

Centrifugal Pump User’s Guidebook – Problems and Solutions
Sam Yedidiah
Contents
Preface Vii
Part I. Introduction 1
Chapter 1. Rotodynamic Pumps 3
Chapter 2. Performance Chracteristics of Centrifugal Pumps
Chapter 3. Classification of Centrifugal Pumps
Part Ii. Performance Factors 29
Effects of Free Air in the Pumped Liquid 31
Cavitation 33
Cavitation in Centrifugal Pumps 45
Losses of Energy 61
Effects of Temperature and Viscosity on Pump Performance 75
Recirculation 79
Axial and Radial Thrust and Balancing 97
Miscellaneous Factors That Affect Pump Performance Iii
Problems Encountered With Centrifugal Pumps
Testing
Pump Performance at Reduced Npsh
Pumping System Layout
Installation. Handling, and Operation of Pumps and
Pumping Systems
Problems With Bearings
Sealing Rotating Parts
Miscellaneous Studies
Problems Related to Specific Circumstances
Special Cases That Have Proven Very Difficult to Solve
Part Iv.
Solving Pump Problems
Solving Problems Prior to Visiting the Site
Conclusions Drawn From Visual Inspection of Failed Parts
On-site Inspection and Testing
Part V. Eliminating Pump Problems and Modifying
Performance
Remedial Methods
The Effects of Speed and Impeller Od on Pump Performance
The Effects of Reducing the Impeller Width
Moditying the Casing Geometry
Various Methods of Altering Pump Performance
A Glimpse of the Future
New Findings Concerning the Mode of Operation
Of Rotodynamic Impellers
Some Future Applications of the Presented Theory
Appendix a. Checklist of Problems With Centrifugal Pumps and
Their Causes
1. Pump Does Not Develop Any Head, Nor Does It Deliver Liquid
2. Pump Develops Some Pressure, but Delivers No Liquid
3. Pump Delivers Less Liquid Than Expected
4. Pump Does Not Develop Enough Pressure
5. Shape of Head-capacity Curve Differs From Rated Curve
6. Pump Consumes Too Much Power
7. Pump Does Not Perform Satisfactorily, Although Nothing
Appears to Be Wrong With Pumping Unit or System
8. Pump Operates Satisfactorily During Start, but Performance
Deteriorates in a Relatively Short Time
9. Pump is Operating With Noise, Vibrations, or Both
10. Stuffing Box Leaks Excessively
11. Packing Has Short Life
12. Mechanical Seal Has Short Life
13. Mechanical Seal Leaks Excessively
14. Bearings Have Short Life
35415. Bearings Overheat
16. Bearings Operate With Noise
17. Pump Overheats, Seizes, or Both
18. Impeller or Casing, or Both, Has Short Life
19. Loud Blow is Heard Each Time Pump is Started or Stopped
20. Casing Bursts Each Time Pump is Started or Stopped
21. Gaskets Leak During Pump Operation
22. Flow-rate Periodically Decreases, or Stops Completely, Then
Returns to Normal
23. Pump Develops Cavitation When the Available Npsh is
Increased
Appendix B. Tables
Vapor Pressures of Water at Different Temperatures
Gall Resistance of Material Combinations
Packing Selections
Tables of Chemical Compatibility of Materials
Bibliography
Index
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