Gauging and Inspection of Casing, Tubing, and Line Pipe Threads

Upstream Segment

API RECOMMENDED PRACTICE 5B1 FIFTH EDITION, OCTOBER 1999

REAFFIRMED, AUGUST 2010

SPECIAL NOTES

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UNCONTROLLED COPY--Copyright 1999 American Petroleum Institute

Copyright © 1999 American Petroleum Institute

FOREWORD

This recommended practice is under the jurisdiction of the API Subcommittee on Stan- dardization of Tubular Goods.

No provision of this recommended practice shall be cause for rejection of casing or tubing provided the threads are in accordance with the requirements of the latest edition of API Standard 5B.

This recommended practice is presented as a guide and instructional tool for pipe mill inspectors, third party inspectors, and users interested in developing skills in inspection of threads on oil country tubular goods and line pipe. It includes pictures of numerous gauges and measuring instruments. Every effort has been made to present gauges without regard to the origin of manufacture. Additionally, inclusion of certain gauges should not be construed as an endorsement of the instrument or its manufacture. Similarly, the exclusion of any gauge is not an indication of dissatisfaction with that instrument.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal regulation with which this publication may conflict.

Suggested revisions are invited and should be submitted to the general manager of the Upstream Segment, American Petroleum Institute, 1220 L Street, N.W., Washington,

D.C. 20005.

UNCONTROLLED COPY--Copyright 1999 American Petroleum Institute

iii

Figures

1. Schematic Diagram of an Oil or Gas Well Completed with a Hung Liner 1

2. Typical Pipe Coupling 5

   UNCONTROLLED COPY--Copyright 1999 American Petroleum Institute

3. Line Pipe Thread Configuration 6

   Page

4. Round Thread Casing and Tubing Thread Configuration 6

5. Buttress Thread Configuration for 133/8-in. OD and Smaller Casing 7

6. Buttress Thread Configuration for 16-in. OD and Larger Casing 7

7. Extreme-Line Casing Thread Configuration 7

8. External Thread Inspection Parameters 11

9. Featheredge 12

10. Razor Edge 12

11. Dial-Indicator Type Gauges 13

12. Fixed-Type Gauge 14

13. Gauge Storage Box 14

14. Thread Depth Gauge Setting Standard 15

15. Basic Dimensions of Line Pipe Threads and Casing and

    Tubing Round Threads 16

16. Pin End Thread on Which is Drawn a Longitudinal Line to Facilitate Inspection—Coupling Longitudinal Line is Drawn in Similar Manner 16

17. Picture of Scale Correctly Held for Total Thread Length Determination 17

18. Balanced-Dial Type Gauge for Measuring Thread Height of Internal Threads

    and All External Threads 17

19. Thread Height Gauge for Internal Threads 3-in. OD and Smaller 17

20. Setting Standards for (a) API Round and Vee-Type Threads, (b) Extreme-Line and 16-in. and Larger Buttress Threads, and (c) Vee-Block Setting Standard

    for Contact and Point Verification 18

21. Height Gauge Applied to Setting Standard 18

22. Continuous-Dial Height Gauge Applied to a Vee Block 22

23. Continuous-Dial Type Gauge Applied to a Setting Standard 22

24. External/Internal Thread Height Gauge Applied to a Thread. 22

25. Balanced-Dial Type Gauge Applied to Thread Showing Small Error in

    Thread Height 22

26. Lead Gauges 23

27. Lead Setting Standard with External/Internal Lead Gauge Applied 25

28. External Thread Taper Caliper 25

29. Internal Taper Caliper for 41/2-in. OD and Larger Showing

    Gauge Extensions 25

30. Internal Thread Taper Caliper for Pipe Less Than 41/2-in. OD 26

31. Assembled Internal Taper Gauge for 41/2-in. OD and Larger Pipe 27

32. Flush-Type Ring Gauge 27

33. Insert Style Plug Gauge 28

34. Step-Type Ring Gauge 28

35. Template-Type Ring Gauge 28

36. Standoff of Master Plug and Working Ring Gauges 29

37. Standoff Lines Style Plug Gauge 30

38. Template Style Plug Gauge 30

39. Full-Crested Threads and Triangle Stamp Measurement on a Buttress

    Thread Pin 33

40. Step-Type External/Internal Buttress Thread Height Gauge for 16-in., 185/8-in., and 20-in. Diameter Pipe and Couplings and All Extreme-Line Casing Threads 34

41. Buttress Thread Runout Gauge 36

42. Buttress Thread Ring Gauge 37

43. Extreme-Line Length Templates 38

44. Extreme-Line Casing Configuration 5-in. through 75/8-in. OD 39

45. Extreme-Line Casing Configuration 85/8 through 103/4-in. OD 40

    UNCONTROLLED COPY--Copyright 1999 American Petroleum Institute

46. Scale Positioned on Extreme-Line Pin for Measuring the Thread Length 41

    Page

47. Extreme-Line Length Measurement Using Templates 41

48. Extreme-Line Thread Height Gauge Setting Standard 42

49. Internal Micrometer Fitted with Flat Contacts for

    Crest-to-Crest Measurement 43

50. Extreme-Line Thread Width Go-No-Go Gauge 43

51. Extreme-Line Thread Ring Gauge with Sliding Seal Gauging Ring 44

52. Extreme-Line Thread Plug Gauge with Sliding Seal Gauging Element 44

53. Go-No-Go Feeler Gauge for Extreme-Line Ring Gauge 44

54. Go-No-Go Feeler Gauge for Extreme-Line Plug Gauge 44

55. Extreme-Line Thread Ring Gauge Installed Hand-Tight and

Seal Ring Advanced 46

57 Extreme-Line Thread Plug Gauge Installed Hand-Tight and

Seal Plug Advanced 46

56 Extreme-Line Thread Ring Gauge Installed Hand-Tight and

Seal Ring Advanced 46

1. Extreme-Line Thread Plug Gauge Installed Hand-Tight and

   Seal Plug Advanced 46

2. Thread Contour Microscope 47

3. Gauging of Tubing Coupling Grooves 48

4. Gauging of Casing Coupling Grooves 48

5. Detail of Alternate Acceptable Contact Tip Configurations 48

Tables

1. Tubing Pin Lc and Box PTL 11

2. Casing Pin Lc and Coupling PTL 11

3. Casing Short Thread Dimensions 19

4. Casing Long Thread Dimensions 19

5. Non-Upset Thread Dimensions 20

6. External Upset Tubing Thread Dimensions 20

7. Thread Height Gauge Recommended Contact Point Dimensions 20

8. Thread Depth for Various Thread Forms 21

9. Recommended Contact Point Dimensions for Lead Gauge 24

10. Recommended Contact Point Dimensions for Taper Calipers 24

11. Casing Long-Thread L1–Short-Thread L1 29

12. Line Pipe Thread Dimensions 31

13. Buttress Thread Casing Dimensions 33

14. Buttress Thread Acceptable Taper 36

15. Extreme-Line Lengths 37

16. Extreme-Line Height Gauge Setting Standard Dimensions 41

17. Extreme-Line Thread Height 41

18. Go-No-Go Feeler Gauge Dimensions for Extreme-Line Ring and

Plug Gauges 45

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vii

Gauging and Inspection of Casing, Tubing, and Line Pipe Threads

1. Introduction

   The ability of line pipe and oil country tubular goods (such as, oil and gas well casing and tubing) to perform properly depends on the physical integrity of the pipe body and con- nections. Threads at each end of the pipe provide a means of joining the pipe segments into a continuous “string” of pipe. There are many thread configurations applied to oil country tubular goods. However, they all have two functions in com- mon: they must resist leakage and tensile failures. This is accomplished by applying threads which are specially designed and accurately machined. Laboratory and prototype testing prior to marketing of the connection verifies the proper design. Accurate machining depends on a repetitive process to simulate tool wear. Excessive tool wear and/or damage after machining reduces the thread’s performance.

   This recommended practice provides guidance and instruc- tion on the correct use of thread inspection techniques and equipment to assure dimensionally accurate connections. The inspector carries a heavy responsibility. This responsibility can be discharged properly only if the inspector is adequately trained. This recommended practice provides the training and insight necessary to perform an adequate inspection of line pipe and oil country tubular goods connections.

   
   

   1. BACKGROUND

      Casing and tubing are two terms which are used to describe oil country tubular goods that become part of a com- pleted oil and gas well.

      When these terms are used in field drilling and production operations, the term “casing” applies to pipe that is used to line the drilled hole to protect the well from formation fluid flow or formation collapse. It is a permanent part of the well in which bottom sections of casing are cemented in place. At times, cement is circulated to the surface. Among the various types of casing are conductor pipe, surface casing, intermedi- ate or protective casing, and production casing (Figure 1). These casing strings extend to the surface. A section of the hole lined with pipe that does not reach the surface is called a liner. Liners may or may not be cemented in place.

      The term “tubing” applies to the innermost pipe in a well. Well fluids are brought to the surface through the tubing. The tubing may be isolated from the casing by a production packer. Tubing is frequently removed from the hole and at times is replaced.

      The terms casing and tubing, when used in a steel mill or in API specifications, are oriented to size and not necessarily to end use. The mills may not know what will be the end use of their pipe. Accordingly, in mill practice and in API specifi- cations, casing generally covers pipe 41/2-in. OD or larger. Tubing generally covers pipe 41/2-in. OD and smaller. This

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      1

      publication uses the terms casing and tubing in the mill/API sense. In most cases, this will also conform to the end use description.

      Each of the pipe connections must be capable of with- standing internal and/or external pressure without leakage. The competence of the design and the accuracy of manufac- ture of the connection provides assurance of the required leak resistance. API connections are among the most accurately machined threads currently mass produced. Each component shape and size is designed and machined to interact with the mating component to form a fluid seal.

      Inspecting the threaded ends of pipe determines if the manu- factured product is in compliance with the design specification. Oil country tubular goods and line pipe are inspected at the manufacturer’s facility prior to shipment. Additionally, the pipe may be inspected at the pipe yard, job site, and/or drilling rig.

      
      

      Figure 1—Schematic Diagram of an Oil or Gas Well Completed with a Hung Liner

      2 API RECOMMENDED PRACTICE 5B1

      
      

      
      

      The manufacturer’s inspection is not normally an inspec- tion of each individual connection. Rather, it is normally an inspection of a statistically designed sample based on manu- facturer’s experience. The field inspection generally is an inspection of each threaded end. The scope of the field inspection varies based on the owner’s desires and the inher- ent constraints of field inspection.

      Corrosion resistance and sealing ability of connections are improved by plating the threads, usually in the coupling or box, with zinc, tin, or metallic phosphate. The plating pro- duces a beneficial effect; however, it generally interferes with the precision of gauging of these threads because it’s difficult to plate threads uniformly. This is particularly true of zinc and tin, which are electroplated. The portion of the thread closest to the anode receives the greatest thickness of plated metal. Some manufacturers may prefer to apply the coating to the pipe (pin end) member, particularly on special or premium- type connections. In all cases, coatings are applied for the purposes of (a) antigalling during makeup, (b) anticorrosion while in storage, or (c) as an aid to sealing (in threads) for leak resistance.

      Gauging of threads by manufacturers is performed prior to coating. Field gauging of coated threads may be less accurate than gauging at the manufacturer’s facility. Discretion should be used, therefore, in interpreting the results of field gauging of coated threads. Additionally, manufacturer gauging is per- formed prior to assembly of the pipe components. Accord- ingly, gauging of assembled (made-up) threaded components can result in the components not conforming with the specifi- cation values because of makeup distortion.

      Off-specification components of coated, but unmade-up components can be recognized by field gauging. If a dispute arises, however, the coating shall be removed and the compo- nent regauged.

      The manufacturers make a conscious effort to eliminate off-specification tubular goods within the financial and statis- tical constraints of the manufacturer. Users, particularly at critical wells or pipelines, desire an inspection at the drilling rig or field site to eliminate any thread damage which occurred during shipment, or any off-specification threads which may not have been found at the manufacturer’s facility.

      It is important to locate and eliminate damaged or off-spec- ification pipe. Rejecting “good” pipe, however, results in a financial burden being imposed on the manufacturer and/or operator. Thus, inspection shall be performed with care and reason.

      
      

   2. SCOPE

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      Information contained in this recommended practice is intended for use of pipe manufacturer inspectors, quality con- trol personnel, field inspectors, threading unit operators, and users and purchasers of oil country tubular goods and line pipe.

      This publication was prepared under the auspices of the API Subcommittee of Tubular Goods and the Resource Group on Threading and Gauging. As such, the scope is lim- ited to inspection of API casing, tubing, and line pipe connec- tions. However, the basic techniques of gauge usage apply to any threads for which the thread element specifications are known. Specifically, this recommended practice was written to supplement and augment the latest editions of API Specifi- cations 5CT and 5L, which mandate physical and mechanical properties of casing, tubing, and line pipe. Additionally, this recommended practice is designed to be used with the latest edition of API Specification 5B, Specification for Threading, Gauging, and Thread Inspection of Casing, Tubing, and Line Pipe Threads. It does not duplicate the massive dimensional tables contained in the latest edition of API Spec 5B. Instead, it provides instruction in inspection techniques appropriate to comparing the dimension of the product with specified dimensions and tolerances for that product. Accordingly, the primer can be used for the inspection of API thread elements without direct reference to the latest edition of Spec 5B. In all cases, the latest edition of Spec 5B takes precedence if a dis- pute arises between parties.

      This publication uses photographs to demonstrate the proper use of representative gauges normally used by thread inspectors. Gauges presented are limited to those appropriate to both mill and field use. Thus, nonportable instruments such as comparators and contour readers are not included. How- ever, there is no intent to limit the use of such instruments or methods by inspectors.

      
      

2. References

   This specification includes by reference, either in total or in part, the following:

   API

   Spec 5B Specification for Threading, Gauging, and Thread Inspection of Casing, Tubing, and Line Pipe Threads

   Spec 5CT Specification for Casing and Tubing

   Spec 5L Specification for Line Pipe

   RP 5A5 Recommended Practice for Field Inspec- tion of New Casing, Tubing, and Plain End Drill Pipe

   
   

   1. REQUIREMENTS

      Requirements of other standards included by reference in this specification are essential to the safety and interchange ability of the equipment produced.

      
      

   2. EQUIVALENT STANDARDS

Other nationally or internally recognized standards shall be submitted to and approved by API for inclusion in this speci- fication prior to their use as equivalent standards.