Inspection of Pressure-relieving Devices

API RECOMMENDED PRACTICE 576 FOURTH EDITION, APRIL 2017

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Copyright © 2017 American Petroleum Institute

Foreword

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms and Definitions 2

4. Pressure-relieving Devices 4

   1. General 4

   2. Pressure-relief Valve 4

   3. Direct-acting Pressure-relief Valve 6

   4. Pilot-operated Pressure-relief Valves 10

   5. Rupture Disk Device 11

   6. Pin-actuated Devices 22

5. Causes of Improper Performance 23

   1. Corrosion 23

   2. Damaged Seating Surfaces 27

   3. Failed Springs 28

   4. Improper Setting and Adjustment 30

   5. Plugging and Fouling 30

   6. Galling 34

   7. Misapplication of Materials 34

   8. Improper Location, History, or Identification 34

   9. Improper Handling 34

   10. Improper Differential Between Operating and Set Pressures 37

   11. Improper Inlet/Outlet Piping Test Procedures 37

6. Inspection and Testing 37

   1. Reasons for Inspection and Testing 37

   2. Shop Inspection/Overhaul 38

   3. Inspection, Testing, Maintenance, and Setting of Direct-acting Spring-loaded Valves on Equipment. . 48

   4. Inspection, Testing, Maintenance, and Setting of Direct Spring-operated Safety Valves Used

      on Fired Pressure Vessels 50

   5. Inspection, Testing, Maintenance, and Setting of Pilot-operated Pressure-relief Valves 51

   6. Inspection, Testing, Maintenance, and Setting of Weight-loaded Pressure and/or Vacuum Vents

      on Tanks 52

7. Inspection and Replacement of Rupture Disk Devices 53

   1. Rupture Disk Removal and Replacement 53

   2. Examples of Rupture Disk Failure Modes 53

   3. Rupture Disk Holder 57

   4. Inspection and Replacement of Rupture Disks 57

8. Pressure-relief Valve Visual On-stream Inspection 57

   1. General 57

   2. Post-relief Event 58

9. Inspection Frequency 58

   1. General 58

   2. Frequency of Shop Inspection/Overhaul 59

   3. Time of Inspection 60

   4. Inspection and Servicing Deferral 61

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      Page

10. Records and Reports 61

    1. General 61

    2. The Need to Keep Records 62

    3. Responsibilities 62

    4. Sample Record and Report System 63

Annex A (informative) Pressure-relief Valve Testing 64

Annex B (informative) Sample Record and Report Forms 67

Bibliography 73

Figures

1. Pressure-/Vacuum-relief Valve 6

2. Weight-loaded Emergency Vent 7

3. Open Bonnet, Direct-acting Spring-loaded Pressure-relief Valve 8

4. Closed Bonnet, Direct-acting Spring-loaded Relief Valve 9

5. Balanced Bellows Direct-acting Spring-loaded Pressure-relief Valve 10

6. Unbalanced Piston Main Valve, Pilot-operated Pressure-relief Valve 12

7. Diaphragm Main Valve, Pilot-operated Pressure-relief Valve 13

8. Diaphragm Main Valve, Pilot-operated Pressure- and Vacuum-relief Valve 14

9. Forward-acting Conventional Rupture Disk 14

10. Forward-acting Scored Rupture Disk 15

11. Reverse-acting Knife Blade Rupture Disk 16

12. Reverse-acting Scored Rupture Disk 17

13. Graphite Rupture Disk 18

14. Rupture Disk in Union Holder 19

15. Rupture Disk in Screw-type Holder 19

16. Rupture Disk with Insert-type Holder 19

17. Insert-type Holder Installation 19

18. Conventional Domed Rupture Disk 20

19. Piston-type Pin-actuated Device 22

20. Butterfly-type Pin-actuated Device 23

21. Acid Corrosion in Carbon Steel Bonnet Caused by Leaking Seating Surfaces 24

22. Chloride Corrosion on 18Cr-8Ni Steel Nozzle (with Machined Seating Surface) 24

23. Sulfide Corrosion on Carbon Steel Disc from Crude Oil Distillation Unit 25

24. Chloride Attack on 18Cr-8Ni Steel Disc 25

25. Pit-type Corrosion on 18Cr-18Ni Steel Bellows 25

26. Alloy 400 Rupture Disks Corroded in Sour Gas Service 26

27. Body and Bonnet Coated with Epoxy for Corrosion Protection 26

28. Seating Surface of Disc Deformed by Chattering 27

29. Seating Surface of Disc Damaged by Frequent Operation of Valve Too Close to

    Operating Pressure 28

30. Spring Failure Due to Corrosion 29

31. Spring Failure Due to Stress Corrosion 29

32. Inlet Nozzle Plugged with Coke and Catalyst After Nine Months in Reactor Vapor Line 32

33. Outlet Valve Plugged with Deposits from Other Valves in Common Discharge Header 32

34. Moving Parts of Valve Fouled with Iron Sulfide (FeS2) 33

35. Disc Frozen in Guide Because of Buildup of Products of Corrosion in Sour Oil Vapor Service 33

36. Improper Storage of Valves 35

37. Example of Improper Storage of Valves 35

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    Contents

    Page

38. Identification Tag for Pressure-relieving Device 39

39a Identification Tag for Pressure-relieving Device (pre-2013) 39

39b Identification Tag for Pressure-relieving Device (mandatory Jan. 1, 2013) 39

40a Identification Tag for Pressure-relieving Device (pre-2013) 40

40b Identification Tag for Pressure-relieving Device (mandatory Jan. 1, 2013) 40

1. Block Valves on Pressure-relief Valve Inlet and Outlet Sealed Open 42

2. Sulfur Deposits in Body of Valve 43

3. Safety Valve and Relief Valve Leak Detector 49

4. Operating Ratio Exceeded, Then Subjected to Vacuum 53

5. Operating Ratio Exceeded—Tabs Are Stretched 54

6. Disk Subjected to Corrosion 54

7. Dent Caused by Water Freezing in Discharge Line 55

8. Rupture Disk Holder Subjected to Excessive Corrosion 55

9. Rupture Disk Holder Subjected to Corrosion 56

10. Rupture Disk Holder Corrosion Due to Leakage 56

11. Rupture Disk Holder Subjected to Overtorque 57

A.1 Typical Safety Valve and Relief Valve Test Block Using Air as a Test 66

1. Sample Form for Recording Pressure-relieving Device Specifications 68

2. Sample Historical Record 69

3. Sample Inspection and Repair Work Order Form 70

4. Sample Testing Report 71

5. Sample In-service Report 72

Inspection of Pressure-relieving Devices

1. Scope

   
   

   This recommended practice (RP) describes the inspection and repair practices for self-actuated pressure-relieving devices commonly used in the oil/gas and petrochemical industries. As a guide to the inspection and repair of these devices in the user’s plant, it is intended to ensure their proper performance. This publication covers self-actuated devices such as direct-acting spring-loaded valves, pilot-operated pressure-relief valves, rupture disks, pin-actuated devices, and weight-loaded pressure vacuum vents.

   
   

   The recommendations in this publication are not intended to supersede requirements established by regulatory bodies. This publication excludes tank weak seams and/or sections or tank thief hatches, explosion doors, fusible plugs, control valves, pressure-regulating devices, integral rotating equipment components, other devices that either depend on an external source of power for operation or are manually operated, or devices not designed to be inspected or recertified. Inspections and tests made at manufacturers’ plants, which are usually covered by codes or purchase specifications, are not covered by this publication.

   
   

   This publication does not cover training requirements for personnel involved in the inspection and repair of pressure-relieving devices. Those seeking these requirements should see API 510 and API 570, which give the requirements for a quality control system and specify that the repair organization maintain and document a training program ensuring that personnel are qualified.

   
   

2. Normative References

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

API 510, Pressure Vessel Inspection Code: In-service Inspection, Rating, Repair, and Alteration API Standard 520 (all parts), Sizing, Selection, and Installation of Pressure-relieving Devices API Standard 521, Pressure-relieving and Depressuring Systems

API Standard 526, Flanged Steel Pressure-relief Valves

API Standard 527, Seat Tightness of Pressure Relief Valves

API 570, Piping Inspection Code: In-service Inspection, Rating, Repair, and Alteration of Piping Systems

API Recommended Practice 580, Risk-Based Inspection

API Standard 620, Design and Construction of Large, Welded, Low-pressure Storage Tanks

API Standard 2000, Venting Atmospheric and Low-pressure Storage Tanks

ASME Boiler and Pressure Vessel Code (BPVC) 1, Section VIII: Rules for Construction of Pressure Vessels; Division 1: Pressure Vessels

ASME PTC 25, Pressure Relief Devices

NB-18 2, Pressure Relief Device Certification

1 ASME International, 2 Park Avenue, New York, New York 10016-5990.

2 The National Board of Boiler and Pressure Vessel Inspectors, 1055 Crupper Avenue, Columbus, Ohio 43229, www.nationalboard.org.

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