Jul 2016
Gas Transmission
Seam weld identification
Jul 2016
Nov 2017
National Grid Gas Transmission
James Gilliver, box.GT.innovation@nationalgrid.com
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Network Innovation Allowance
Electricity Transmission Networks

The girth weld is relatively easily identified, both on the ILI (inline inspection) data and visually on the exposed pipe. Similarly, the seam weld of submerged arc welded longitudinal (SAWL) or helical (SAWH) pipe is readily identifiable. However for electrical resistance welded (ERW) or high frequency welded (HFW) pipes the seam weld can prove very difficult to locate visually. This is due to the manufacturing technique whereby the flash formed on the outside and inside surface of the bond line is removed to blend smoothly with the adjacent pipe.

Consistent and accurate determination of the seam weld position is important where pipes are being assessed for damage under the P/11 procedure or for proposed pipeline modifications (tapping etc.).

A critical stage of the P/11 assessment process is to determine whether any damage identified during inspection is coincident with the weld or heat affected zone (HAZ). This requires the positive identification of the girth weld and, if it is welded pipe, the seam weld.

Effective weld position determination techniques proposed by this project will have a significant impact on the accurate determination seam weld position leading to improved maintenance and integrity activities.

The aim of this project is to investigate if additional inspection technologies (techniques, tools or guidelines) exist, or can be developed that National Grid engineers or inspectors could implement on site to enable identification of the ERW/HFW bond line and its position around the pipe circumference. 

The deliverable will be guidance document that can be introduced to the National Grid quality management system either as a stand-alone procedure or as part of an existing specification.