The History of API OCTG Grades Casner Engineering Services November 6, 2005 The first API specification for pipe was published in 1924.The title was No. 5 - 1924, Specifications for Steel and Iron Pipe for Oil Country Tubular Goods.The specification included line pipe, drill pipe, drive pipe, casing and tubing.Please note that both iron and steel pipe were included. The following Tables tabulate the year that grades were added to or deleted from API OCTG Specifications: CasingAppendix APage 2 TubingAppendix BPage 3 Drill PipeAppendix CPage 4 The tables begin with the grades that were included in the 1924 specification, and continue through the grades which are now included in the ISO 11960.Notes are often included to explain why the grades were added to, or deleted from the specifications. In the years just prior to 1940, the following grade designations were being used for casing and tubing: grade Yield strength, psi Minimum Wrought iron24,000 open hearth iron25,000 A30,000 B35,000 C45,000 D55,000 In 1939, the API Committee on Tubular Goods wanted to add a new grade with a minimum yield strength of 80,000 psi.This would result in 7 grades for a 24,000 through 80,000 pis span of minimum yield strengths.The Committee agreed that there should be a greater difference between the yield strengths of the various grades and agreed to abandon the 6 exiting grade designations for OCTG and to adopt 4 new grades with minimum yield strengths of 25,000, 40,000, 55,000 and 80,000 psi to cover the 25,000 through 80,000 pis span of minimum yield strengths. The Committee also agreed that if the letters A, B, C and D were used with these new grades, the new grades would be confused with existing grades that used these same letters for grades with yield strengths that would not be the same as the yield strengths for the new API OCTG grades.To avoid this confusion, the Committee agreed to adopt the following grade designations for casing and tubing: grade Yield strength, psi Minimum F2525,000 H4040,000 J 5555,000 N8080,000 This combination of alpha and numeric characters was chosen for two reasons.The numeric characters (25, 40, 55 & 80) clearly identify the minimum yield strength of the grades.The letters were chosen to assure clarity.When spoken, 25 might be confused with 55.When spoken, F25 would not be confused with J 55. History Of API OCTG GradesNovember 6, 2005 Casner Engineering Servicespage 2 of 7Appendix A The dates of adoption or deletion of the various grades of OCTG are tabulated in the Appendices on pages 2, 3 and 4. History Of API OCTG GradesNovember 6, 2005 Casner Engineering Servicespage 3of 7Appendix A API Casing Grades Year of Adoption by API All Grades are Steel Except Where Noted grade and manufacturing processyearyield strength Tensile strengthNotes addeddeletedminmin lap welded wrought iron1924194024421 lap welded open hearth iron 1924194025451 lap welded steel1924194025451 seamless low carbon steel 1924192730481 seamless medium carbon steel 1924192735621 seamless high carbon steel1924192745751 seamless grade A steel in 1927, ERW added in 19341927193530482, 3 seamless grade B steel in 1927, ERW added in 19341927194035622, 3 seamless grade C steel in 1927, ERW added in 19341927194045752, 3 seamless grade D steel in 1930, ERW added in 19341930194055954, 5 lap welded F25 wrought iron1940195825406 lap welded F25 open hearth iron1940195825406 lap welded F25 steel1940195825406 seamless and ERW F25 steel1940196225406, 7 seamless and ERW H40 steel1940 40606 seamless and ERW J 55 steel194055756, 8 seamless and ERW N80 steel1940801006 seamless P110 in 1960, ERW added in 199219601101259, 10 seamless C7519631990759511 seamless and ERW K551968559512 seamless and ERW C9519709510513, 14 seamless V15015016015 seamless and ERW L801975809516 seamless C9019849010018, 19 seamless & ERW grade Q12519851251354 seamless L80 9Cr19878095 seamless L80 13Cr19878095 seamless T9519899510520 Seamless & ERW grade M6519986585 History Of API OCTG GradesNovember 6, 2005 Casner Engineering Servicespage 4 of 7 Appendix B API Tubing Grades Year of Adoption by API All Grades are Steel Except Where Noted grade and manufacturing processyearyield strength Tensile strengthNotes addeddeletedminmin lap welded wrought iron1924194024421 lap welded open hearth iron 1924194025451 lap welded steel1924194025451 seamless low carbon steel 1924192730481 seamless medium carbon steel 1924192735621 seamless high carbon steel1924192745751 seamless grade A steel in 1927, ERW added in 19341927193530482, 3 seamless grade B steel in 1927, ERW added in 19341927194035622, 3 seamless grade C steel in 1927, ERW added in 19341927194045752, 3 seamless grade D steel in 1930, ERW added in 19341930194055954, 5 lap welded F25 wrought iron1940195825406 lap welded F25 open hearth iron1940195825406 lap welded F25 steel1940195825406 seamless and ERW F25 steel1940196225406, 7 seamless and ERW H40 steel1940 40606 seamless and ERW J 55 steel194055756 seamless and ERW N80 steel1940801006 seamless P105196019901101259, 10, 21 seamless C7519631990759511 seamless and ERW L801975809516 seamless C9019849010018, 19 seamless L80 9Cr19878095 seamless L80 13Cr19878095 seamless T9519899510520 seamless P110 in 1990, ERW added in 1992199011012510, 21 History Of API OCTG GradesNovember 6, 2005 Casner Engineering ServicesPage 5 of 7 Appendix C API Drill Pipe Grades Year of Adoption by API All Grades Are Steel grade and manufacturing processyearyield strength Tensile strength Notes addeddeletedminmin furnace lap welded open hearth1924194025451 seamless medium carbon 1924192735621 seamless high carbon steel pipe1924192745751 seamless grade B1927194035622, 7 seamless grade C1927195345752, 7 seamless grade D1930198155954, 17 seamless grade E751942751004 seamless grade X951973951054 seamless grade G10519731051154 seamless grade S13519731351454 History Of API OCTG GradesNovember 6, 2005 Casner Engineering ServicesPage 6 of 7 Notes to Appendices A, B & C 1.The first API specification for pipe was published in 1924.The title was No. 5 - 1924, Specifications for Steel and Iron Pipe for Oil Country Tubular Goods.The specification included line pipe, drill pipe, drive pipe, casing and tubing. 2The grade names seamless low carbon steel pipe, seamless medium carbon steel pipe and seamless high carbon steel pipe were changed to grades A, B, and C respectively in 1927. 3.Grades A, B and C were only manufactured by the seamless process until the ERW manufacturing process was added to Spec 5A in 1934. 4.This grade was adopted to meet the need for a general service grade for deeper wells. 5Grade D was only manufactured by the seamless process until the ERW manufacturing process was added to Spec 5A in 1934. 6.A new series of grades and grade names were adopted for casing and tubing in 1940.The new grade names were a combination of a letter and the minimum yield strength of the grade in ksi.It was not intended that the letter would have any significance in itself, but would give phonetic clarity to the grade name.For example 25 and 55 could be confused when talking, but F25 and J 55 would not. 7.This grade was deleted since the difference in the cost between this grade and the cost of the next higher grade was so small that it cost more to stock this extra grade than was saved by stocking two grades.Buying the higher grade saved money, and the higher grade had higher performance properties. 8.In 1940 when J 55 grade was adopted to replace grade D casing and tubing, a 75 ksi minimum tensile was adopted instead of the 95 ksi applicable to grade D so J 55 could be furnished by either the seamless or ERW process. 9In 1960 when P grade casing and tubing were being considered, the user members wanted the highest yield strength available.On that basis, it was concluded that P grade casing should have a minimum yield strength of 110 ksi.Since it was very difficult to achieve 110 ksi yield in the small heavy wall tubing because it cooled so slowly, it was concluded that this new normalized and tempered tubing grade could only have a minimum yield strength of 105 ksi. 10.Lone Star Steel asked, and API added the ERW process for P110 in 1992 11.In the late 1950s, and before Q&T products were available, Gulf Oil (now part of Chevron) wanted a high strength tubing grade with a maximum hardness of 22 HRC for sour service.This hardness limit required that the minimum tensile strength be 95 ksi, or 5 ksi lower than N80.Because of the natural yield/tensile ratio of normalized or normalized ant tempered products, this hardness limit required that the minimum yield strength be no higher than 75 ksi.This product was called modified N80 at the time, and was given the name C75 when adopted by API. History Of API OCTG GradesNovember 6, 2005 Casner Engineering ServicesPage 7 of 7 12.In 1968, Gulf Oil (now part of Chevron) reported that the actual tensile strength of seamless J 55 casing almost always exceeded 95 ksi, the minimum tensile strength of grade D drill pipe which like J 55 casing has a minimum yield strength of 55 ksi.Gulf Oil recommended that the minimum tensile strength of J 55 be increased to 95 ksi to take advantage of the higher joint strengths for round thread and buttress thread casing that would result. Since a 95 ksi minimum tensile would be difficult to achieve with ERW, API agreed to adopt a new grade, instead of raising the minimum tensile strength of J 55.Since tubing joint strengths are based on the yield load of the connection rather than the parting load, the calculated joint strength of tubing would not be increased by increasing the minimum tensile strength.As a consequence, the user members only asked that grade K55 be adopted as a casing grade. 13.Phillips Petroleum wanted a casing grade higher than C75 to use in mild sour service environments. C95 be adopted to meet this requirement.Many user member opposed adoption of this grade because it was not suitable for a severe sour service environment. 14.In 1970, the user members wanted to use the letter C in the name of the new 95 ksi restricted yield strength grade to show that it was a sour service grade like C75.They insisted on the name C95. The advantage of clarity of the name with a combination of letters and numbers in the grade name was lost. 15.The adoption of grade V150 casing was considered by API under agenda item 2015, but was dropped from the agenda in 1974. 16.The user members preferred the microstructure of Q&T pipe to N&T pipe for sour service, and as soon as manufacturers were able to furnish Q&T pipe with upsets to a 15 ksi range, the User members asked that a new sour service grade pipe be adopted.Since the natural yield/tensile ratio of Q&T pipe is higher than N&T pipe, the user members wanted to raise the minimum yield strength of the new sour service grade from 75 ksi to 80 ksi to increase the performance properties, and grade L80 was born. 17Grade E75 drill pipe with tool joints only costs about 10 percent more than grade D55 drill pipe with tool joints but can drill approximately 5,000 feet deeper.As a consequence, grade D drill pipe was not cost effective and the drilling contractors had stopped buying grade D drill pip.This grade was deleted. 18.Grade C90 was adopted to meet the requirements for a grade which was suitable for severe sour service and stronger than grade L80. 19.In 1984, the user members wanted to use the letter C in the name of the new 90 ksi restricted yield strength grade to show that it was a sour service grade, like C75.They insisted on the name C90. Again, the advantage of clarity was lost 20.Grade T95 was adopted to meet the requirements for a grade which was suitable for severe sour service and stronger than C90. 21.In 1992, the user members of API asked that the physical properties of P105 tubing be increased to be the same as P110 casing to increase the performance properties of P grade tubing.P105 grade tubing was replaced with P110 tubing and P105 grade tubing was deleted from Spec 5CT.