Seals and Sealing Handbook (eBook)

Front cover 1
Seals and Sealing Handbook 4
Copyright page 5
Contents 6
Preface 12
Chapter 1: Introduction 14
1.1 Purpose of this book 14
1.2 What does it cover? 15
1.3 What applications does it cover? 17
1.4 What disciplines are involved? 17
1.5 The future 19
Chapter 2: Static seals 20
2.1 Introduction 20
2.2 O-rings 21
2.2.1 Elastomer O-rings 21
2.2.2 Plastic O-rings 32
2.2.3 Metal O-rings 33
2.3 Alternative elastomer sections 38
2.3.1 Rectangular section rings 39
2.3.2 X section rings 40
2.3.3 T-seals 41
2.3.4 L section seals 43
2.3.5 U-rings 43
2.3.6 Integral backup flange seals 43
2.3.7 Bonded seals 44
2.3.8 Spring seals 47
2.3.9 Hygienic seal arrangements 49
2.3.10 Window seals 52
2.4 Alternative plastic sections 56
2.5 Alternative metal seal designs 58
2.5.1 C-rings 58
2.5.2 Low load C-rings 59
2.5.3 Spring energized metal seals 59
2.5.4 E-rings 60
2.5.5 Sigma seals 61
2.6 Cured in place seals 61
2.6.1 Moulded in place 62
2.6.2 Cured in place 63
2.7 Formed in place seals and gaskets 64
2.7.1 Sealing rigid flanges with anaerobic sealants 65
2.7.2 Sealing flexible flanges 69
2.7.3 Sealant selection 73
2.8 Bolted joints and gaskets 74
2.8.1 Introduction 74
2.8.2 Forces acting in a bolted joint assembly 75
2.8.3 Gasket behaviour 75
2.8.4 Flange types and standards 78
2.8.5 Calculation methods 80
2.8.6 Gasket installation 85
2.8.7 Bolting 86
2.8.8 Gasket types and applications 91
2.8.9 Compact flanges and connectors 105
2.9 Selection of the optimum static seal design and material 110
2.9.1 Temperature 111
2.9.2 Pressure 111
2.9.3 Industry design codes 112
2.9.4 Manufacturing method 113
2.9.5 Sealed fluid 113
2.9.6 Life expectancy 113
2.9.7 Leakage integrity, emissions 114
2.9.8 Manufacturing volume 114
2.9.9 Maintenance and accessibility 115
2.10 References 116
Chapter 3: Rotary seals 118
3.1 Introduction 118
3.2 Lip seals 118
3.2.1 Basic lip seal design 119
3.2.2 Dynamic sealing mechanism 122
3.2.3 PTFE seals 133
3.2.4 PTFE lined elastomer seals 137
3.2.5 Excluders 140
3.2.6 Cassettes 146
3.2.7 V-ring seals 147
3.2.8 Bearing seals 150
3.2.9 Lip seals for pressure 153
3.3 Alternative elastomer and plastic seals 161
3.3.1 O-rings 161
3.3.2 Elastomer fabric seals 162
3.3.3 Elastomer energized plastic seals 163
3.3.4 Spring energized PTFE seals 165
3.3.5 Positive lubrication rotary seals 168
3.4 Mechanical seals 172
3.4.1 Introduction 172
3.4.2 Basic design 173
3.4.3 Method of operation 174
3.4.4 Basic seal types 178
3.4.5 Seal housing design 196
3.4.6 Typical applications and seal arrangements 199
3.5 Compression packing for rotary shafts and valves 232
3.5.1 Introduction 232
3.5.2 Method of operation 234
3.5.3 Packed gland arrangements 235
3.5.4 Fitting and using packing 238
3.5.5 Packing types 241
3.6 Clearance seals 250
3.6.1 Introduction 250
3.6.2 Labyrinth seals 251
3.6.3 Honeycomb and hole slot seals 262
3.6.4 Brush seals 265
3.6.5 Leaf seals 269
3.6.6 Viscoseals 271
3.6.7 Circumferential seals 275
3.6.8 Centrifugal or liquid ring seals 277
3.7 Magnetic fluid seals 281
3.7.1 The particular attributes of a magnetic seal are 281
3.7.2 Ferrofluid types 283
3.7.3 Typical applications 284
3.8 Rotary seal selection 286
3.8.1 Liquid sealing 286
3.8.2 Gas sealing 288
3.9 References 290
Chapter 4: Reciprocating seals 295
4.1 Introduction 295
4.2 Elastomer and plastic seals for hydraulic applications 295
4.2.1 Background 296
4.2.2 Seal stability 298
4.2.3 Sealing mechanism 299
4.2.4 Tandem seal arrangements 312
4.2.5 Rod seal arrangements 317
4.2.6 Piston seal arrangements 317
4.2.7 Excluders 323
4.3 Pneumatic cylinder seals 328
4.3.1 Pneumatic rod seals 329
4.3.2 Excluders 331
4.3.3 Piston seals 331
4.3.4 Material considerations 333
4.4 Piston rings 334
4.4.1 Introduction 334
4.4.2 Internal combustion engines 334
4.4.3 Compressor piston rings 345
4.4.4 Piston rings for hydraulic cylinders 353
4.5 Compression packing 354
4.5.1 Packing types and application areas for reciprocating duties 355
4.6 Clearance seals 358
4.7 Diaphragms and bellows 360
4.7.1 Flat and dished diaphragms 361
4.7.2 Rolling diaphragms 363
4.7.3 Diaphragm materials 364
4.7.4 Diaphragm applications 366
4.7.5 Polymer bellows 366
4.7.6 Metal bellows 367
4.8 References 370
Chapter 5: Materials 371
5.1 Elastomers 371
5.1.1 Why do we use elastomers? 372
5.1.2 Elastomer material basics 375
5.1.3 Factors to consider when selecting an elastomer 380
5.1.4 Elastomer types and their applications 394
5.2 Plastics 406
5.2.1 Benefits of plastics 407
5.2.2 Potential disadvantages of plastics 408
5.2.3 Mechanical properties of plastics 408
5.2.4 Plastic material types and their applications 410
5.3 Carbon 416
5.3.1 Manufacture of carbon 416
5.3.2 Tribology of carbon 417
5.4 Silicon carbide 418
5.4.1 Reaction bonded 418
5.4.2 Self-sintered silicon carbide 421
5.4.3 Graphite loaded sintered silicon carbide 421
5.5 Tungsten carbide 421
5.6 Silicon nitride 422
5.7 Alumina ceramic 422
5.8 Hard/hard mechanical seal face combinations 423
5.9 Metals 423
5.9.1 Stainless steel 424
5.9.2 Nickel alloys 425
5.9.3 Low thermal expansion alloys 427
5.10 Soft metal overlay 427
5.11 References 428
Chapter 6: Failure guide 430
6.1 Introduction 430
6.2 Static seal failure guide 430
6.2.1 Elastomer seals 430
6.2.2 Plastic seals 436
6.2.3 Metal seals 438
6.2.4 Gaskets 439
6.3 Rotary seal failure 441
6.3.1 Lip seals 441
6.3.2 Other elastomer and plastic seal designs 449
6.3.3 Mechanical seals 450
6.3.4 Dry gas seals 456
6.3.5 Compression packing 458
6.3.6 Clearance seals 459
6.4 Reciprocating seals 460
6.4 1 Polymer reciprocating seals 460
6.5 References 465
Chapter 7: General information 467
7.1 Glossary of sealing terms 467
7.1.1 Elastomer and plastic seals, compression packing 467
7.1.2 Expansion joints and flange gaskets terminology 471
7.1.3 Mechanical seals terminology 476
7.2 Standards 479
7.2.1 General 479
7.2.2 O-rings 480
7.2.3 Hygienic seals 481
7.2.4 Gaskets 482
7.2.5 Rotary shaft lip seals 484
7.2.6 Mechanical seals 484
7.2.7 Compression packing 484
7.2.8 Reciprocating seals 484
7.2.9 Material properties 485
7.2.10 Surface texture measurement 487
7.2.11 Standards organizations 487
7.3 Surface texture measurement 489
7.3.1 Introduction 489
7.3.2 Ra arithmetic mean 490
7.3.3 Root mean square deviation of the profile from the mean line 491
7.3.4 Rt – total height of the profile 493
7.3.5 Rz (ISO) – maximum height of profile 494
7.3.6 History of peak parameters 494
7.3.7 Rsk skewness 495
7.3.8 Material ratio curve 497
7.3.9 Conclusion 498
7.4 Organizations with a direct interest in sealing technology 499
7.4.1 Trade and industry organizations 499
7.4.2 Research organizations 501
Appendix 1: Sealing Technology – BAT guidance notes 503
1 Executive summary 509
2 Preface 514
3 General introduction 517
4 Generic BAT for sealing technologies 522
5 BAT for bolted flange connections 533
6 BAT for rotodynamic equipment 554
7 BAT for reciprocating shafts 570
8 BAT for valves 572
9 Conversion factors 586
10 Further reading 591
11 References 593
Appendix 2: The application of European ATEX legislation to mechanical seals 595
2.1 Ignition Hazard Assessment 605
2.2 Maximum Surface Temperature 608
Index 610
A 610
B 611
C 612
D 614
E 615
F 617
G 618
H 619
I 620
J 620
K 621
L 621
M 622
N 624
O 624
P 625
Q 627
R 628
S 629
T 631
U 632
V 632
W 632
X 633
Y 633
Z 633