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- Title
Welding on in-service gas pipelines using low-yield electrodes.
- Authors
Schipaanboord, Wim N.; Marquering, Jan; Koppens, Bart G.; Spiekhout, Jan
- Abstract
THIS ARTICLE DISCUSSES the technical background to being able to weld safely on gas pipelines, particularly older pipelines with a higher carbon equivalent. Making connections in gas pipelines that may not be taken out of service (and, typically, operating at 130 bar and with a flow rate of 10 m/s) requires special techniques. Hot tapping is often applied; split tees to enable this technique are welded to pipelines that are - and remain -completely operational.The split tees are placed on the pipeline and then welded together using longitudinal welds to make one tee piece; after inspection, circumferential welds are made to create the connection between the tee piece and the pipeline. This same welding technique is also used to repair damage to pipelines. This can be in the form of a buttering-up repair as part of a pipeline-rehabilitation programme, or installing repair sleeves. Installing repair sleeves can also be a follow-up to an in-line inspection that has established that there is damage to the pipeline, or to an activity that has been reported as doing damage as a result of external interference (such as excavation, trenchiess techniques for installation of cables or other pipelines, and ploughing). NV Nederlandse Gasunie has conducted research since 1978 by, among others, TNO (Netherlands Organization for Applied Scientific Research) in order to obtain a sound basis for a reliable and safe way to weld onto gas pipelines. This article incorporates over 30 years' operational experience with welding on gas pipelines, and addresses regulations, critical aspects of welding on operational gas pipelines, and the control of these critical aspects. The metallurgical backgrounds are also discussed.
- Subjects
PIPELINE welding; NATURAL gas pipelines; WELDED joints; TAPS &; dies; METALLURGY
- Publication
Journal of Pipeline Engineering, 2013, Vol 12, Issue 1, p29
- ISSN
1753-2116
- Publication type
Article