Pipeline Integrity Management Under Geohazard Conditions (PIMG)
Chapter 26 HIGH STRAIN WELD SOLUTIONS FOR GEOHAZARD ACTIVE ENVIRONMENT
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The Sabah Sarawak Gas Pipeline (SSGP) is a 512 km x 36” O.D. Grade X 70 onshore natural gas pipeline that was completed in 2013 to transport 750 MMscfd of gas from the Sabah Offshore Gas Terminal (SOGT) to the Malaysia Liquified Natural Gas (MLNG) Complex at Bintulu, Sarawak, Malaysia. SSGP traverses through many different types of terrains. Two pipe parted incidents in June 2014 and January 2018 resulted in PETRONAS re-evaluating its pipeline repair and maintenance practices for pipeline constructed in geohazard active environment.
The pipe parted incidents triggered a reassessment of the weldment robustness against the geohazard active environment along the whole SSGP pipeline route. One of the issues needed to address in SSGP failure incidents was on the weld strength under-matching phenomena. Managing the active geohazard impact to the pipeline to minimum effect as practically possible was a daunting task and will be a never ending maintenance activity at SSGP. On top of that, a number of actions were also undertaken for strengthening the girth welds. Thus, in order to manage, reduce the risk and dampen the geohazard’s effect on the weld, a new welding procedure has been designed, tested at full scale and qualified. The aim is to have a weld with improved & higher strain capacity that can ‘match’ the pipe base metal strain capacity. The new girth welding procedure is also intended to be used for any SSGP weld repair and maintenance purposes.
This paper presents PETRONAS experiences, challenges and new solutions developed to mitigate the inferiority of the strain capacity of the weld (mainly due to weldment strength under-matching) compared to the higher pipe strain capacity.
Summary of the immediate cause of the parted incident at SSGP at the geohazard active areas, the strain capacity and the weld strength under-matching situation of the original weld from pipeline construction, the new improved design of the weld, the new improved welding procedure, qualification via full scale bend test, the challenges faced during welding of the repaired section and the precautions of welding done under temperature-fluctuation-affected pipeline which impacting the expansion and contraction of the pipeline.
This paper presents aspects of weld strain capacity improvement - designed, tested and implemented for geohazard active environment. The new improved weld design and procedure have been deployed ever since it was qualified, for any weld repair and maintenance for this SSGP Pipeline.
This paper presents PETRONAS updated practice in improvement weld strain capacity to increase the robustness of the weld and the pipeline in against the geohazard active environment of SSGP pipeline. The additional work done and improvement performed demonstrates: 1) Options for improving weld strain capacity 2) Full scale test for validating and qualifying the new weld design and welding procedure.