Valves Training Manual

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Training manual for industrial valves

Transcript of Valves Training Manual

  • TRAINING MANUAL ON VALVES

    Nuclear Training Centre

    Prepared by : Prashant Puri, STO (M)

    Reviewed by : C.M. Mishra, ENC (MT)

    Approved by : N. NagaichTraining Superintendent, RAPS 1 to 4

    COURSE NO. : SA-M-MP-2.8

    Rev. (1), August, 2002 Next Revision Due : August, 2007

  • PREFACE

    Prashant PuriSenior Training Officer

    This training manual on Valves is intended to be used for basic skill

    training for Scientific Assistant trainees. This manual is prepared with a view

    of imparting training effectively on Function, Construction, Material of parts,

    and testing aspects of the valves to bring the competency in the new entrants

    so that they can do maintenance right at the first attempt. This manual also

    meets training requirement for tradesman trainees.

    I express my sincere thanks to Shri C.M. Mishra, ENC(MT) for his

    guidance and encouragement to complete this task. I am also thankful to Shri

    N.Nagaich, Training Superintendent, RAPS-1 to 4 for his kind cooperation

    and motivation in preparation of this manual.

  • CONTENTS

    S.NO. DESCRIPTION Page No.

    Chapter - 1 General Consideration 1

    1.1 Introduction 1

    1.2 Valve Function 1

    1.3 Valve Selection Factors 1

    1.4 Standards and Specfication 2

    1.5 Abbreviations and Terms 3

    Chapter - 2 Valve Design 9

    2.1 Flow Control Elements 9

    2.2 Movement of Flow Control Element 10

    2.3 Sealing Methods 13

    2.4 Methods of Valve Operation 22

    2.5 Valve Connections 29

    2.6 Installation Techniques 31

    2.7 Drain Connections and Bypass 37

    Chapter - 3 Gate Valve 38

    3.1 General 38

    3.2 Service Recommendations 38

    3.3 Construction of Valve 38

    3.3.1 Solid Wedge 39

    3.3.2 Flexible Wedge 39

    3.3.3 Split Wedge 39

    3.3.4 Double Disc or Parallel Disc 40

    3.3.5 Seats 41

    3.3.6 Stem Assemblies 41

    3.3.7 Stem Seals 41

    3.3.8 Bonnet Construction 42

    3.3.9 Identification of Parts 43

    3.4 Available Materials of Construction 44

    3.5 Installation, Operation and Maintenance 44

  • 3.6 Gate Valve Specifications 45

    Chapter - 4 Globe Valves, Angle Valve, Needle Valves 46

    4.1 General 46

    4.2 Service Recommendations 46

    4.3 Construction of Valve 46

    4.4 Valve Plug Characterization 49

    4.4.1 Linear Flow Characteristic 49

    4.4.2 Equal Percentage Flow Characterstic 49

    4.4.3 Modified Parabolic Flow Characteristic 50

    4.4.4 Quick Opening Flow Characteristic 50

    4.5 Seat 53

    4.6 Stem Assemblies 53

    4.7 Stem Seals 53

    4.8 Bonnet Construction 53

    4.9 Identification of Parts 54

    4.10 Available Materials of Construction 54

    4.11 Installation, Operation and Maintenance 54

    4.12 Glob Valve Specifications 59

    4.13 Y-Type Valve 59

    Chapter - 5 Plug Valve 61

    5.1 General 61

    5.2 Service Recommendations 61

    5.3 Construction of Valve 61

    5.4 Lubrication Plug Valve 64

    5.5 Nonlubricated Plug Valves 66

    5.6 Gland 66

    5.7 Identification of Parts 66

    5.8 Available Materials of Construction 69

    5.9 Installation, Operation and Maintenance 69

    5.10 Plug Valve Specification 71

    Chapter - 6 Ball Valve 72

    6.1 General 72

  • 6.2 Service Recommendations 72

    6.3 Construction of valve 72

    6.4 Identification of Parts 75

    6.5 Available Materials of Construction 75

    6.6 Installation, Operation and Maintenance 76

    6.7 ball Valve Specifications 78

    Chapter - 7 Butterfly Valve 79

    7.1 General 79

    7.2 Service Recommendations 79

    7.3 Construction of Valve 79

    7.4 Identification of Parts 82

    7.5 Types of Butterfly Valve 85

    7.6 Characteristic Curve for Butterfly Valve 90

    7.7 Installation, Operation and Maintenance 93

    7.8 Butterfly Valve Specifications 96

    Chapter - 8 Diaphragm Valves 97

    8.1 General 97

    8.2 Service recommendations 97

    8.3 Construction of Valve 97

    8.4 Identification of Parts 102

    8.5 Installation, Operation and Maintenance 102

    8.6 Diaphragm Valve Specifications 106

    Chapter - 9 Check Valves 107

    9.1 General 107

    9.2 Types of Check Valve 110

    9.2.1 Swing check valves 110

    9.3 Tilting Disc Check Valve 114

    9.4 Lift Check Valves 116

    9.5 Piston Check Valves 120

    9.6 Butterfly Check Valves 120

    9.7 Spring-loaded Check Valves 124

    9.8 Stop Check Valves 126

  • 9.9 Foot Valves 126

    Chapter - 10 Pressure Reliwving Devices 127

    10.1 Purpose 127

    10.2 Definition of terms 127

    10.3 Type and Function of Relief Valves 129

    10.3.1 Relief valves 129

    10.3.2 Safety Valves 132

    10.3.3 Safety Relief Valves 132

    10.3.4 Pilot-Operated Relief Valves 133

    10.3.5 Rupture Discs 134

    10.4 Safety and Relief Valve Design Features 136

    10.4.1 Bodies 136

    10.4.2 Nozzles 138

    10.4.3 Nozzle Orifice Size 139

    10.4.4 Springs 140

    10.4.5 Trim and other Parts 141

    10.4.6 Seating 141

    10.4.7 Tightness 143

    10.4.8 Common Causes of Leakage 143

    10.4.9 Bellow Seals 146

    10.4.10 Blowdown Rings 148

    10.4.11 Bonnets and Yokes 148

    10.4.12 Lifting Mechanism 151

    Chapter - 11 Application of Valves 154

    11.1 Recommended Valve Services 154

    11.2 Applications & Relative Merits of Valves 156

    Chapter - 12 Valve Maintenance and Storage 158

    12.1 Safety 158

    12.2 Routine Maintenance 158

    12.3 Valve Outside Leaks

    12.3.1 Joints and Flangs 159

    12.3.2 Gland Packing 159

  • 12.4 Maintenance of Valve Seats and Discs 159

    12.4.1 Lapping of Valve Discs 160

    12.4.2 Seat Lapping Plate 161

    12.4.3 Lapping of Wedge (Gate Valve) 161

    12.4.4 Machining of Disc 163

    12.4.5 Tips on Lapping Procedure 163

    12.5 Recommended Lapping Compounds for Lapping 164

    Valve Seats

    12.6 Over Hauling Safety Valves 164

    12.6.1 General 164

    12.6.2 Safety Valve Floating 165

    12.7 Overhauling a Wedge Gate Valve 167

    12.7.1 Dismanting 167

    12.7.2 Inspection 168

    12.7.3 Lapping of Valve Wedge 168

    12.7.4 Lapping of Body Seat 169

    12.7.5 Sealing Rings 171

    12.7.6 Reassembly 171

    12.8 Storage 172

    12.9 Handling 173

    12.10 Installation 173

    Chapter - 13 Valve Inspection and Testing 175

    13.1 Scope 175

    13.1.1 Inspection 175

    13.1.2 Pressure Test 176

    13.2 Integrity Testing in Safety Valves 178

    13.2.1 Purpose 178

    13.2.2 General 178

    13.2.3 Hydraulic Test 178

    13.2.4 Pneumatic Test 179

    13.2.5 Adjustment of safety valve cold differential test pressure 181

    13.3 Hydrodtstic Testing of Steel Valves 181

  • 13.3.1 Scope 181

    13.3.2 Specific Test Requirement 181

    13.3.3 Test Pressure 182

    13.3.4 Gate Valve 182

    13.3.5 Globe and Angle Valves 183

    13.3.6 Check Valve 183

    Chapter - 14 Valve Trouble Shooting 187

    14.1 For Gate and Globe Valves 187

    14.1.1 Problem : Seat Passing 187

    14.1.2 Problem : Leakage Through Body Bonnet Joint 187

    14.1.3 Problem : Leakage through gland packing 188

    14.1.4 Problem : Operational difficulty 188

    14.2 For Butterfly Valve 189

    14.2.1 Problem : Disc Does Not Seat Within Liner Because 189

    14.2.2 Problem : Shaft Leakage Due to Non Sealing of 189

    O Ring

    14.2.3 Problem : Valve Shaft Does Not Turn 190

    14.2.4 Problem : Valve shaft but the valve does not 190

    control fluid

    14.2.5 Problem : Excessive play in the linkage 190

    14.2.6 Problem : Actuator fails to maintain stable position 191

    when requirements are constant

    14.3 For Safety Valves 191

    14.3.1 Problem : Leaking of Safety valve 191

    14.3.2 Problem : Incorrect popping pressure 192

    14.3.3 Problem : Incorrect Blowdown 192

    14.3.4 Problem : Spindle Bending 192

    14.3.5 Problem : Hang-up 192

    14.3.6 Problem : Valve Simmering 193

    14.4 For Plug Valve 193

    14.4.1 Problem : Passing (Internal Leakage) 193

    14.4.2 Problem : Leakage 193

  • 240

    14.4.3 Problem : Leakage through Gland packing 194

    14.4.4 Problem : Hard Operation 194

    14.5 For Ball Valve 194

    14.5.1 Problem : Passing Internal Leakage 194

    14.5.2 Problem : Leakage Through Body Bonnet Joint 195

    14.5.3 Problem : Leakage Through Gland Packing / O Ring 195

    14.5.4 Problem : Hard operation 195

    14.6 For Diaphragm Valve 196

    14.6.1 Problem : Passing (Internal Leakage) 196

    14.6.2 Problem : Leakage through Body Bonnet Joint 196

    14.7 For Check Valve 196

    14.7.1 Problem : Stuck Closed 196

    14.7.1 Problem : Stuck Closed 196

    14.7.2 Problem : Passing of the Valve 196

    14.7.3 Problem : Leakage Through Body Cover Joint 197

    Check-List for Wedge Disc Gate Valve Practice 198

    Check-List for Butterfly Valve Practice 202

    Check-List for Diaphragm Valve Practice 206

    Check-List for Relief Valve Practice 210

    Check-List for Globe Valve Practive 215

    Check-List for Wedge Disc Gate Valve Practice 219

    Check-List for Tapper Plug Valve Practice 227

  • 1CHAPTER - 1

    GENERAL CONSIDERATION

    1.1 INTRODUCTION

    Valve is an equipment used as one of the critical organ of the process circuit ofnuclear industry. Proper working of valves ensure better availability of unit, safety ofthe plant, equipment, processes and men. Passing or leaking of the fluid in valveslead to reduction in efficiency and consumption of excess costly fluids, resulting inhigher production cost.

    1.2 VALVE FUNCTIONS

    Valves are used in piping systems and on processing vessels or tanks