Recent girth weld failures in newly constructed pipelines in North America have highlighted the issue of the weld strength undermatching the actual pipe strength. The lowest strength region of a manual girth weld is usually the root pass. This project evaluated using higher strength E8010 shielded metal arc welding (SMAW) electrodes for root pass welding on modern API 5L Grade X70 (L485) line pipe, as part of a solution to increase overall weld strength. The operability, weldability, and productivity of E8010 root pass welding were evaluated by welder operability trials, weldability testing, and welding procedure qualification testing and reviews. Feedback from North American pipeline welders support that E8010 electrodes have satisfactory operability for pipeline open root pass welding. Welding Institute of Canada (WIC) weldability test results support that an E8010 root pass does not significantly increase weld cracking susceptibility when properly used. Furthermore, welding qualification tests and production welding procedures using E8010 electrodes for all weld passes were reviewed and found that productivity is similar to current industry practices using E6010 electrodes for root pass welding. Guidance with recommendations and precautions for using an E8010 root pass was developed. In summary, a higher strength E8010 root pass can be part of an effective solution to address pipeline girth weld strength undermatching.

This article explores technological advancements for detecting pipeline leaks. An ideal leak detection system should not only quickly detect both small and large leaks, but also do so reliably and not trigger false alarms. Operations in gas pipelines can differ quite a bit from those for liquids, so the experience gained in one type of line may not be entirely applicable when changing jobs. Fortunately, computer simulators are increasingly sophisticated, enabling operators to become comfortable handling a variety of situations. In December 2015, the American Petroleum Institute released a set of guidelines (RP 1175), written by a representative group of hazardous liquid pipeline operators, that established a framework for leak detection management. The focus of the guidelines is getting pipeline operators to use a risk-based approach in their leak detection program, with the goal of uncovering leaks quickly and with certainty. The best-case scenario is for leaks to not occur at all, and the industry is making great strides to keep them from happening. The combination of improved technology and risk-based management should enable operators to keep leaks small and contained, and reduce the impact on the environment as much as possible.

The objective of the recently completed Phase 1 of a joint industry project (JIP) at DNV, the results of which are described in this paper, was to determine if welding onto an in-service pipeline that transports a mixture of methane and hydrogen results in an increased risk of hydrogen cracking and, if so, to develop guidance pertaining to measures that can be taken to mitigate the increased risk. The mechanisms and the extent to which steel line pipe can become charged with hydrogen when transporting methane/hydrogen mixtures were reviewed. An experimental program was undertaken to determine the extent to which elevated weld hydrogen levels can result during welding onto pipe pressurized with blends of hydrogen and methane (Task 2a) and from welding onto steel that has been exposed to high pressure blends for an extended period of time (Task 2b). The results of Task 2a showed various increases in weld hydrogen level, depending on the pipe wall thickness, the weld heat input, and the partial pressure of hydrogen. Reactions between the pipe contents, the line pipe steel base material, and surface oxides were also observed. Task 2b resulted in no significant increase in weld hydrogen level as the result of welding onto steel that had been exposed to a high pressure blend for an extended period of time. Additional work is required to determine threshold conditions beyond which increased weld hydrogen levels do not occur and to quantify increases in weld hydrogen levels for a broader range of conditions, including higher and lower partial pressures of hydrogen.

This Milestone Deliverable M02-T04 is draft guidance for the application of higher strength E8010 electrodes for root pass welding. The guidance discusses E8010 root pass weldability, operability, and productivity, and provides recommended applications and precautions for using E8010 electrodes for root pass welding. Subsequent Milestone Deliverable M02-T05 will be final guidance, based upon project team feedback to this draft.

The current preference of regulators in the United States and Canada is to require a delay time prior to nondestructive examination (NDE) of welds for cracking; for both welds made manually during construction of new pipelines and during maintenance activities for existing pipelines. A better approach than imposing a delay time is to prevent cracking, by lowering the bulk hydrogen below a threshold value necessary for cracking to occur. The proactive approach of using post-heating immediately after welding to prevent the weld from cracking in lieu of an inspection delay was explored. An experimental program was carried out to determine the hydrogen diffusion rate in pipe materials, as well as the typical weld hydrogen levels in both a baseline (room temperature) and time and temperature conditions. Experiments were also conducted to measure hydrogen levels in simulated welds in the as-welded condition, after 24 hours at ambient temperature, and after post-heating. The experimental program showed that post-heating newly constructed girth welds made using cellulosic-coated electrodes for approximately 20 minutes at 200 °C (400 °F) and in-service welds made using low-hydrogen electrodes for approximately 20 minutes at 120 °C (250 °F) may be used to mitigate the risk of hydrogen-assisted cold cracking (HACC), thereby justifying immediate inspection. Various heating methods were evaluated to determine how effectively the post-heating time and temperature targets could be achieved for new construction welds and for in-service welds. To aid in the successful implementation of post-heating, guidance material suitable for use by field personnel in the application of post-heating, as well as recommendations for industry standards improvement were developed.