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Pump Wisdom: Problem Solving for Operators and Specialists

Pump Wisdom: Problem Solving for Operators and Specialists

Heinz P. Bloch

ISBN: 978-1-118-05674-5 April 2011 224 Pages

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Description

An accessible guide to the main reasons pumps fail—and what can be done about it

Workhorses in many different industries, including the oil industry, water industry, chemical industry, food industry, and pharmaceutical industry to name a few, pumps are a vital contributor to maintaining and increasing the flow of production. In fact, the pump industry itself is a multi-billion dollar global business.

Taking the unique approach of addressing both pump operators and pump designers, Pump Wisdom explains the causes of failure in centrifugal pump function—whether it's pump selection, overlooked installation criteria, or the accumulation of small deviations—and maps out remedies with well defined methods that target specific issues, rather than focusing on technical generalities and theory. Clearly written and concise, Pump Wisdom relies on proven tactics for reducing pump vulnerabilities and correcting imbalances between hydraulic assembly and mechanical assembly. In addition, it supplies sound tips for detecting and rectifying risky shortcuts taken by pump designers and manufacturers. Pump Wisdom also:

  • Provides a concise explanation of how pumps function
  • Details the specifications to be considered when purchasing a pump
  • Provides tips on the installation of centrifugal pumps in process plants
  • Written in concise language that avoids excessive mathematical treatment
  • Explains pump hydraulics in easy to understand terms
  • Emphasizes the mechanical aspects of pumps with coverage on bearings, seals, impeller trimming, lubricant application, lubricant types, and more

Pump Wisdom sheds light on the techniques for stabilizing pump performance and maximizing pump efficiency. Its concise format allows readers to strike directly at the heart of the problem—and helps them devise strategies to prevent costly failures before they occur.

1 Principles of Centrifugal Process Pumps 1

Pump performance: Head and Flow

Operation at zero flow

Impellers and rotors

The meaning of specific speed

Process pump types

Process pump mechanical response to flow changes

Recirculation and cavitation

The importance of suction specific speed

What we have learned

References

2 Pump Selection and Industrial Standards 15

Why insist on better pumps

ANSI and ISO vs API pumps

What we have learned

References

3 Foundations and Base Plates 23

Securing pumps in place—with one exception

Why not to install pump sets in the as-shipped condition

Conventional vs pre-filled base plate installations

Epoxy pre-filled base plates

How to proceed if there is no access to specialist firms

What we have learned: Checklist of foundation and base plate topics

References

4 Piping, Stationary Seals, and Gasketing 35

Pipe installation and support

Sliding supports and installation sequence deserve special attention

Monitoring pipe stress while bolting up

Flange leakage

What to do prior to gasket insertion

Spiral wound and kammprofile gaskets

Pipe, hydraulic tubing or flexible connections

Gusseting

Concentric vs eccentric reducers

Vibration problems in piping

What we have learned on piping and gasketing topics

References

5 Rolling Element Bearings 49

Bearing selection overview and windage as a design problem

Radial vs axial (thrust) bearings

Oil levels, multiple bearings, and different bearing orientations

Upgrading and retrofit opportunities

Bearing cages

Bearing preload and clearance effects

Bearing dimensions and mounting tolerances

What we have learned

References

6 Lubricant Application and Cooling Considerations 69

Lubricant level and oil application

Issues with oil rings

Pressure and temperature balance in bearing housings

Cooling not needed on pumps with rolling element bearings

Oil delivery by constant level lubricators

Black oil

Lube application as oil mist (oil fog)

Desiccant breathers and expansion chambers

What we have learned

References

7 Lubricant Types and Key Properties 83

Lubricant viscosities

When and why high film-strength synthetic lubricants are used

Lubricants for oil mist systems

What we have learned

References

8 Bearing Housing Protection and Cost-Justification 91

Non-contacting bearing protector seals

Contacting bearing protector seals

How venting and housing pressurization affect bearing protector seal performance

Cost justification overview

Advanced bearing housing (bearing protector) seal summary

What we have learned

References

9 Mechanical Sealing Options for Long Life 99

Still using packing?

General overview of mechanical seals

All flush plans have advantages and disadvantages

Always obtain the full picture

Seal chamber pumping ring (circulating device) technologies

Lessons to apply to many services

What we have learned

Bibliography

10 Pump Operation 115

Starting centrifugal pumps

Surveillance of pump operation

Centrifugal pump shutdown

What we have learned

11 Impeller Modifications and Pump Maintenance 121

Maintenance essentials

Superior maintenance requires upgrading

Impeller upgrading with inducers

Distance from impeller tips to stationary internal casing components

Impeller trimmings

Impeller wear rings

Vane tip overfiling and underfiling

What we have learned

References

12 Lubrication Management 131

How bad is water contamination?

Avoid solids contamination

Avoid questionable storage and transfer practices

Periodic audits

What we have learned

References

13 Pump Condition Monitoring: Pump Vibration, Rotor Balance, and Effect on Bearing Life 139

Vibration and its effect on bearing life

Monitoring methods differ

Vibration acceptance limits

Causes of excessive vibration

Rotor balancing

What we have learned

References

14 Drivers, Couplings, and Alignment 153

Driver selection

Coupling selection and installation

Installation and removal

Alignment and quality criteria

Consequences of misalignment

Thermal rise and predefinition of growth

What we have learned

References

15 Fits, Dimensions, and Related Misunderstandings 163

Low incremental cost of better pumps

Pump pedestals and bearing housings should not be water-cooled

Summary of bearing-related issues

Constant level lubricators

Bearing housing protector seals (“bearing isolators”)

Motor lubrication summary

Mechanical seal issues

Hydraulic issues

Impeller hydraulics

Mechanical improvement or upgrade options

Process pump repair dimensions

What we have learned

References

16 Failure Statistics and Successful Failure Analysis 183

Mean time between failures and repair cost calculations

Performing your own projected MTBF calculations

Older pumps vs newer pumps

Reliability reviews start before purchase

Structured failure analysis strategies solve problems

The “FRETT” approach to eradicating repeat failures of pumps

What we have learned

References

Index 199

"Seldom has so much practical advice (well-deserving the term “wisdom”) been so readily available in easy-to-read, well-illustrated form.  If you deal with pumps, don’t miss it.”  (Electrical Apparatus, 1 February 2013)