Pump Wisdom E-Book

Heinz P. Bloch

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 259

Veröffentlichungsjahr: 2011

Beschreibung

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.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Dedication

Preface

Chapter 1: Principles of Centrifugal Process Pumps

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

Chapter 2: Pump Selection and Industry Standards

Why Insist on Better Pumps?

ANSI and ISO Versus API Pumps

What We Have Learned

References

Chapter 3: Foundations and Base Plates

Securing Pumps in Place—with One Exception

Why Not to Install Pump Sets in the As-Shipped Condition

Conventional Versus Pre-Filled Base Plate Installations

Epoxy Prefilled 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

Chapter 4: Piping, Stationary Seals, and Gasketing

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 Versus Eccentric Reducers

Vibration Problems in Piping

What We Have Learned on Piping and Gasketing Topics

References

Chapter 5: Rolling Element Bearings

Bearing Selection Overview and Windage as A Design Problem

Radial Versus 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

Chapter 6: Lubricant Application and Cooling Considerations

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

Lubricant Application as Oil Mist (Oil Fog)

Desiccant Breathers and Expansion Chambers

What We Have Learned

References

Chapter 7: Lubricant Types and Key Properties

Lubricant Viscosities

When and Why High Film Strength Synthetic Lubricants are Used

Lubricants for Oil Mist Systems

What We Have Learned

References

Chapter 8: Bearing Housing Protection and Cost Justification

Noncontacting Bearing Protector Seals

Contacting Bearing Protector Seals

How Venting and Housing Pressurization Affect Bearing Protector Seals

Cost Justification Overview

Advanced Bearing Housing (Bearing Protector Seal) Summary

What We Have Learned

References

Chapter 9: Mechanical Sealing Options for Long Life

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 Apply to Many Services

What We Have Learned

Bibliography

Chapter 10: Pump Operation

Starting Centrifugal Pumps

Surveillance of Pump Operation

Centrifugal Pump Shutdown

What We Have Learned

Chapter 11: Impeller Modifications and Pump Maintenance

Maintenance Essentials

Superior Maintenance Requires Upgrading

Impeller Upgrading with Inducers

Distance From Impeller Tip to Stationary Internal Casing Components

Impeller Trimming

Impeller Wear Rings

Vane Tip Overfiling and Underfiling

What We Have Learned

References

Chapter 12: Lubrication Management

How Bad is Water Contamination?

Avoid Solids Contamination

Avoid Questionable Oil Storage and Transfer Practices

Periodic Audits

What We Have Learned

References

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

Vibration and Its Effect on Bearing Life

Monitoring Methods Differ

Vibration Acceptance Limits

Causes of Excessive Vibration

Rotor Balancing

What We Have Learned

References

Chapter 14: Drivers, Couplings, and Alignment

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

Chapter 15: Fits, Dimensions, and Related Misunderstandings

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

Chapter 16: Failure Statistics and Structured Failure Analysis

Mean-Time-Between Failures (MTBF) And Repair Cost Calculations

Performing Your Own Projected MTBF Calculations

Older Pumps Versus 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

Pump Wisdom

Cover based on ideas by Dennis Bowman, PE, Alfred Conhagen, Inc., Houston, Texas. Page layout and formatting by Joy M. Peterson, Asheville, North Carolina.

Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.

Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data:

Bloch, Heinz P., 1933– Pump wisdom: problem solving for operators and specialists/Heinz P. Bloch. p. cm. Includes index. ISBN 978-1-118-04123-9 (hardback) 1. Pumping machinery. I. Title. TJ900.B6483 2011 621.6’9—dc22

2010050397

To Ken and the fellow professionals who appreciate the importance of avoiding pump failures

Preface

Pump users have access to hundreds of books and many thousands of articles dealing with pump subjects. So, one might ask, why do we need this text? I believe we need it because an unacceptably large number of process pumps fail catastrophically every year. An estimated 95% of these are repeat failures, and most of them are costly, dangerous, or both. I wanted to explain some elusive failure causes and clearly map out permanent remedial action. My intent was to steer clear of the usual consultant-conceived generalities and give you tangible, factual, and well-defined information throughout.

As any close review of what has been offered in the past will uncover, many texts were written primarily to benefit one particular job function, ranging from pump operators to pump designers. Some books contain a hidden bias, or they appeal to a very narrow spectrum of readers; others are perhaps influenced by a particular pump manufacturer’s agenda. Give this text a chance; you’ll see that it is different. I gave it the title Pump Wisdom because wisdom is defined as applied knowledge. If you concur with this very meaningful definition you will be ready for a serious challenge. That challenge is to practice wisdom by acting on the knowledge this text conveys.

Although I had written or co-authored other books and dozens of articles on pump reliability improvement, some important material is too widely dispersed to be readily accessible. Moreover, some important material has never been published before. I therefore set out to assemble, rework, condense, and explain the most valuable points in a text aimed at wide distribution. It was to become a text with, I hope, permanence and “staying power.” To thus satisfy the scope and intent of this book, I endeavored to keep theoretical explanations to a reasonable minimum and to limit the narrative to 200 pages. Putting it another way, I wanted to squeeze into these 200 pages material and topics that will greatly enhance both pump safety and reliability. All that is needed is the reader’s solid determination to pay close attention and to follow up diligently.

Please realize that in years past, many pump manufacturers have primarily concentrated their design and improvement focus on the hydraulic end. Indeed, over time and in the decades since 1960, much advancement has been made in the metallurgical and power-efficiency-related performance of the hydraulic assembly. All the while, the mechanical assembly or drive end of process pumps was being treated with relative indifference. In essence, there was an imbalance between the attention given to pump hydraulics and pump mechanical issues.

Recognizing indifference as costly, this text tries to rectify some of these imbalances. My narrative and illustrations are intended to do justice to both the hydraulic assembly and the mechanical assembly of process pumps. That said, the book briefly lays out how pumps function and quickly moves to guidelines and details that must be considered by reliablity-focused readers. A number of risky omissions or shortcuts by pump designers, manufacturers, and users also are described.

I also want the reader to know that the real spark for this book came from AESSEAL, a worldwide manufacturer of sealing products. I have come to appreciate them as an entity guided by quality principles, with a workforce that pursues excellence at every level of the organization. Of the many business entities I have worked with over the past five decades, they represent the one closest to my own ideal. They practice what a reliability-focused company should be doing; I consider them an example of how a business should conduct itself. I also want to acknowledge them for rapidly providing artwork assistance whenever I asked.

Please take from me a good measure of encouragement: Make good use of this book. Read it and apply it. Today, and hopefully years from now, remember to consult this material. Doing so will acquaint you with pump failure avoidance and the more elusive aspects of preserving pump-related assets. And so, although you undoubtedly have more problems than you deserve, please keep in mind that you also deserve access to more solutions than you previously knew about or currently apply. Sound solutions are available, and they are here, right at your fingertips. Use them wisely; they will be cost-effective. The solutions you can discern from this text will have a positive effect on pump safety performance and asset preservation. They have worked at best-of-class companies and cannot possibly disappoint you.

Heinz P. Bloch, P.E.Winter 2010/Spring 2011

Chapter 1

Principles of Centrifugal Process Pumps

Pumps, of course, are simple machines that lift, transfer, or otherwise move fluid from one place to another. They are usually configured to use the rotational (kinetic) energy from an impeller to impart motion to a fluid. The impeller is located on a shaft; together, shaft and impeller(s) make up the rotor. This rotor is surrounded by a casing; located in this casing (or pump case) are one or more stationary passageways that direct the fluid to a discharge nozzle. Impeller and casing are the main components of the ; the region or envelope containing bearings and seals is called the mechanical assembly or power end ().