Seals and Sealing Handbook, Sixth Edition

648 Pages·2014·27.734 MB·English

by  Robert K. Flitney

SIXTH EDITION
SEALS AND SEALING
HANDBOOK
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SIXTH EDITION
SEALS AND SEALING
HANDBOOK
ROBERT FLITNEY
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Butterworth-Heinemann is an imprint of Elsevier
Butterworth-Heinemann is an imprint of Elsevier
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The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK
Third edition 1990
Fourth edition 1995
Fifth edition 2007
Sixth edition 2014
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A catalogue record for this book is available from the British Library
Library of Congress Cataloging-in-Publication Data
A catalog record for this book is available from the Library of Congress
ISBN: 978-0-08-099416-1
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Printed and bound in United States of America
14 15 16 17 18 10 9 8 7 6 5 4 3 2 1
CONTENTS
Foreword ix
Preface xi
Acknowledgements xiii
1. Introduction 1
1.1 Purpose of This Book 1
1.2 What Does it Cover? 2
1.3 What Applications Does It Cover? 4
1.4 What Disciplines Are Involved? 4
1.5 The Future 6
2. Static Seals 7
2.1 Introduction 7
2.2 O-Rings 8
2.3 Alternative Elastomer Sections 25
2.4 Alternative Plastic Sections 44
2.5 Alternative Metal Seal Designs 46
2.6 Cured-in-Place Seals 49
2.7 FIP Seals and Gaskets 51
2.8 Bolted Joints and Gaskets 61
2.9 Selection of the Optimum Static Seal Design and Material 96
References 102
3. Rotary Seals 105
3.1 Introduction 105
3.2 Lip Seals 105
3.3 Alternative Elastomer and Plastic Seals 150
3.4 Mechanical Seals 162
3.5 Compression Packing for Rotary Shafts and Valves 224
3.6 Clearance Seals 243
3.7 Magnetic-Fluid Seals 276
3.8 Rotary Seal Selection 281
References 284
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vi Contents
4. Reciprocating Seals 289
4.1 Introduction 289
4.2 Elastomer and Plastic Seals for Hydraulic Applications 289
4.3 Pneumatic Cylinder Seals 324
4.4 Piston Rings 331
4.5 Compression Packing 351
4.6 Clearance Seals 355
4.7 Diaphragms and Bellows 357
References 367
5. Materials 369
5.1 Elastomers 369
5.2 Plastics 408
5.3 Carbon 418
5.4 Silicon Carbide 422
5.5 Tungsten Carbide 424
5.6 Silicon Nitride 424
5.7 Alumina Ceramic 424
5.8 Diamond-Coated Faces 425
5.9 Hard/Hard Mechanical-Seal-Face Combinations 428
5.10 Metals 429
5.11 Soft Metal Overlay 433
References 434
6. Failure Guide 437
6.1 Introduction 437
6.2 Static Seal Failure 437
6.3 Rotary Seal Failure 448
6.4 Reciprocating Seals 467
References 473
7. General Information 475
7.1 Glossary of Sealing Terms 475
7.2 Standards 487
7.3 2D Surface-Texture Measurement 499
7.4 3D Surface-Texture Measurement 509
7.5 Organizations with a Direct Interest in Sealing Technology 510
Contents vii
Appendix 1: Sealing Technology – BAT Guidance Notes 515
1 Executive Summary 521
2 Preface 525
3 General Introduction 528
4 Generic BAT for Sealing Technologies 532
5 BAT for Bolted Flange Connections 543
6 BAT for Rotodynamic Equipment 563
7 BAT for Reciprocating Shafts 579
8 BAT for Valves 580
9 Conversion Factors 594
10 Further Reading 600
11 References 601
Appendix 2: ESA Position Statement on ATEX Directive 94/9/EC
and Its Applicability to Mechanical Seals
A Definition and Requirements for Mechanical Seals Classified as Machinery Elements 603
B Definition and Requirements for Mechanical Seals Classified as ATEX Components 604
C Auxiliary Support Systems 605
D Repairs, Overhaul and Maintenance of Equipment 606
Appendix – A Terms & Definitions 608
Index 611
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FOREWORD
Since you are consulting this book, you are probably in the process of selecting or
replacing a seal for a particular application. This can be a difficult task, since of all the
different kinds of machine elements, the seal exhibits the greatest variety. There are
many different types and classes of seals, e.g. static and dynamic, rotary and recipro-
cating, packing, mechanical (or face) seals, and lip seals. The sizes of seals range from
millimetre scale (for micro-bearings) to metre scale (for canal locks). The prices range
from a few dollars for an O-ring to hundreds of thousands of dollars for nuclear reactor
coolant-pump seals.
This large variety results from the very wide range of seal applications, e.g. in actu-
ators, pumps, motors, mixers and bearings, as well as from the particular industry in
which the seal is used, e.g. automotive, aerospace, construction, agriculture, hydraulics
and pneumatics.
If you make a poor choice in selecting your seal, the result can be failure, usually in
the form of excessive leakage but sometimes in other forms such as excessive heat gen-
eration. When a machine breaks down, the odds are pretty high that it is the seal that
has failed. The cost of failure can be much higher than just the price of the seal, since it
would include removal and installation costs, costs associated with downtime and pos-
sibly costs associated with liability. Even if a seal does not radically fail, a poorly chosen
seal can result in unnecessarily high energy costs, lower efficiency, unfavourable system
performance (e.g. of hydraulic systems) and environmental pollution.
The various demands on a fluid seal are quite stringent, and some are contradic-
tory. The leakage must be low or effectively zero, but a contradictory demand is low
friction and low wear rate. Further, the seal material must be compatible with the
sealed fluid, and the design must allow the seal to function properly over the range of
required operating conditions, e.g. pressures and temperatures.
To satisfy these demands, seals have evolved into effective machine elements. While
they may appear deceptively simple compared to other machine elements, their opera-
tion is actually quite complex. Mechanical seals are precision devices, which must be
carefully engineered to function properly. Polymeric lip seals, both rotary and recipro-
cating, rely on micro-scale surface characteristics to operate successfully and therefore
require careful and precise material formulation and processing.
In the approximately 40 years that I have been involved with fluid seals, I have seen
the design of mechanical seals progress from a purely empirical process with a lot of
‘black magic’ to a sophisticated design process, making use of complex computational
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