The Early Years

The early pipeline research and technology development (R&TD) was done under the auspices of the American Gas Association (AGA). According to McClure [1], during 1950 several breaks occurred in a pre-service gas proof test of a 30-inch-diameter natural gas transmission pipeline. These breaks led to propagating failures that ran quite a distance, and involved multiple brittle fractures. Concern for the cause and need to understand this failure process led to work that in 1952 came under the administration of the AGA, which they dubbed AGA Project NG-18. As the propagating fractures occurred in what was to be a natural gas pipeline, the notation ‘NG’ might be thought indicative of Natural Gas. However, the N actually denoted ‘transmission research’, while the G designated the ‘contractor’. The number 18 simply indicated that it was the 18th project being administered by the AGA. This early R&TD was done under the guidance of the ASME B31.8 Research Subcommittee, which in 1957 morphed into the NG-18 Project Supervisory Committee for this Project. In 1957 the Pipeline Research Committee (PRC) of took over administration of the work initiated in 1952 [1], with the PRC being the forerunner to the Pipeline Research Council International PRCI. Details about the PRCI and its mission can be found through the link:

Characteristic Defect Types are Defined

Work on defects as causes of leaks and breaks in pipelines became a part of the NG-18 research in 1953 [2]. The outcomes of that and related work involving line-pipe steel and fracture propagation motivated the first AGA Symposium on Line Pipe Research [2], which was held in 1961. This First LPR Symposium was followed by eight others 1, each of which has considered pipeline defects in some manner.

The First and Second LPR Symposia focused on the steel and its resistance to fracture propagation, whereas the effects of defects were considered in regard to idealized features in machined into strip-samples of pipe steel. Three types of idealized defects were identified then “according to their behavior under internal pressure” [2]. One defect type was termed a ‘plain dent’, a term we still use today in the manner it was defined in 1962. The second was termed a ‘stress concentrator’. This type of defect included features such as vee-notches, weld cracks, and gouges, being distinguished from the first type by a local reduction in the pipe wall thickness, absent a related change in the pipe-wall curvature (i.e., the pipe was dent free). The third type involved combinations of the first two. The defects considered in the Materials and Construction (M&C) Defects Chapter are of the second type, whereas the features considered in the Chapter on Mechanical Damage range from plain dents through stress concentrators, and their combinations.

Defects – a Continuing Focus at the AGA Symposia on Line Pipe Research

The Third through the Sixth LPR Symposia (1965 – 1979) also considered the role of defects. In contrast to the early work, their focus shifted from idealized simple features to address field failures and the specific nature of the defects that caused them, as well as their growth mechanisms.

The Sixth Symposium was the first to recognize the pipeline R&TD then underway in Europe, and the role of the European Pipeline Research Group (EPRG), which has been organized in 1972. Collaborative seminars between those working under the guidance of the PRC of the AGA and those within the EPRG began in 1975. Details concerning the EPRG and its focus can be found through the link:

Collaboration Begins with the European Pipeline Research Group

As much of the early work in Europe reported through the joint seminars was underway at the British Gas Corporation (BG) at their Engineering Research Station (ERS), it is appropriate to make note of the ERS and their role in that collaboration. According to Reference [3], the ERS “came to life … on 2 January 1968” with a view to “initiate research with an emphasis on mechanical engineering, metallurgy, and physics” in regard to “high pressure steel pipelines”. Recognizing the developments then underway Sir Denis Rooke, then BG Chairman, was invited to present an overview of their program at the 6th LPS. He spoke of an on-line (or in-line) inspection tool they were developing to locate defects in their system, which made clear their concern for the potential effects of defects. In noting that this and related work had been underway for eight years at their ERS he indicated that BG had a R&TD program whose scope and depth paralleled that of the work being done under the auspices of the AGA. Details about the ERS and its role in R&TD can be found through the link:

The Collaboration Broadens – The Joint Technical Meetings Begin

The broadened format of the Sixth Symposium continued with the Seventh through the Ninth LPR Symposia (1986 – 1996), with the Ninth being the last due to its redundancy in regard to the PRC-EPRG Seminars. The opening paper at the Seventh Symposium continued the focus on defects as causes of failure. The work on defects at the Eighth Symposium considered pipeline failure mechanisms and characteristics of the resulting effects, whereas the Ninth was considered defect detection, sizing, and assessment. In the years since the transition to the PRC-EPRG Seminar, which since has been renamed the Joint Technical Meeting (JTM), defects of one type or another have remained a focal point at each meeting.


Defects and the related erosion of the designed-in margin of safety have been and remain a source of concern for the pipeline industry. As their causes were understood the work has transitioned to managing defect integrity through detection and sizing, and to methods to quantify their severity. This has been an ongoing topic in each of the JTM and will remain so as the industry works toward the goal of zero incidents [4].


  1. McClure, G. M., “The NG-18 Project: Historical Perspective,” 4th A. G. A. Symposium on Line Pipe Research, Paper D, Dallas, TX, 18 November, 1969, A. G. A. (now PRCI) Cat. L30075.
  2. McClure, G. M., Eiber, R.J., Hahn, G.T., Boulger, F.W., Masubuchi, K., 1st A.G.A. Symposium on Line Pipe Research, Dallas, TX, March, 1961: A.G.A. (now PRCI) Cat. 40/PR (listed later as L00290): more details can be found in Eiber, R. J. and McClure, G. M., “Research on Conditions Affecting Crack Initiation in Line Pipe,” NG-18 Report 4, 11 July, 1960.
  3. Anon., History of the Engineering Research Station, 1964 -1993, Old Flames Website, 12 May, 2009 (
  4. Anon., “Goal is Zero Incidents,”

1 A.G.A. Symposia on Line Pipe Research were held over the period from the 1960s through 1996: 2nd in Columbus OH in 1963, 3rd in Dallas TX in 1965, and thereafter in Houston TX in 1969 (4th), in 1974 (5th), in 1979 (6th), in 1986 (7th), in 1993 (8th), and in 1996 (9th and last).