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Not just another weld

Published by , Editorial Assistant
World Pipelines,

The challenges of in-service welding (ISW) operations on a high-pressure, high-flow, large diameter gas pipeline are outlined by Frede Maxwell, Brian Anderson, Paul Gonzales, Darren Sutherland, Bie Cornell and Dave Albertson, WeldFit.

Not just another weld

In preparation for the planned expansion of a natural gas pipeline, a major US-based pipeline and terminal company sought a contractor for in-service welding (ISW) operations. The request was a challenging one, not just because the operator was seeking to keep product moving through the system without interruption but also because of the high-flow, high-pressure, and large-diameter characteristics of the pipeline in question. Despite these complexities, WeldFit succeeded in meeting the operator’s needs while remaining on schedule and maintaining high safety standards.

WeldFit was first approached by the company, which owns and operates pipelines and terminals for crude oil and natural gas, in the spring of 2022. The company was preparing to carry out an expansion project that would boost the throughput capacity of one of its natural gas transportation systems to more than 2.5 billion ft3/d, an increase of more than 500 million ft3/d. To support this expansion, the company was seeking a contractor to carry out 13 welding jobs at nine sites along the target pipeline.

More specifically, the pipeline owner/operator was looking for a contractor that could develop ISW procedures specifically for its expansion project, which entailed installations of line stop and hot tap fittings at multiple locations. The job required bespoke, specialised services because of the need to keep natural gas flowing through this complex system at an operating pressure of 1440 psi and flowrate of 42 ft/sec. without any interruptions (Figure 2).

In light of these requirements, WeldFit was a good match, not just as an experienced provider of hot tap and line stop services but also because it offers ISW – a specialised operation that allows fittings to be welded to a live pipeline without any compromise in flow rates or the integrity of the weld – as part of its turnkey line intervention services.

To this end, WeldFit began working with the company to develop ISW procedures for the expansion project which covered a section of buried 42 in. pipeline that is more than 400 miles long. Four of these jobs were to be carried out at four separate locations, each including the installation of two 42 in. x 42 in. x 2.250 in. line stop fittings. Another four jobs were to be carried out at four separate locations, each including the installation of one 42 in. x 36 in. x 2.250 in. hot tap fitting. The final job was to be carried out at a single location and involved the installation of one 42 in. x 30 in. x 2.250 in. hot tap fitting (Figure 1).

The preparations

These jobs had to be planned carefully, as the complexity of the operating environment at each site was certain to make ISW a challenge.

On the one hand, the pipeline company set strict standards for the chemical composition of the materials used. Its gas transportation system was composed of high yield carbon steel pipe, and WeldFit had to manufacture fittings that complied with these standards.

On the other hand…

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