T.D. Williamson (TDW) announced that as the result of a pressure isolation carried out on a major export gas pipeline offshore Malaysia, the pipeline was safely hydro-tested and made ready for commissioning.

The isolation was carried out by TDW on behalf of a major operator on a newly-installed subsea pipeline between the floating production system (FPSO) pipeline end manifold (PLEM) and a key gas complex, located approximately 149 miles (240 km) offshore Terengganu in the South China Sea. The complex features a production platform, riser platform connected by an inter-platform bridge to the production platform, vent bridge and vent boom.

The gas export pipeline designated for isolation stretches 32 miles (53 km) from a primary platform to a PLEM attached to the FPSO. As part of the pre-commissioning project, it was necessary to hydro-test the 16-inch Export Gas Pipeline that stretches from the platform to the FPSO PLEM prior to the dewatering and drying operation, once the pipeline spool and PLEM installation had been completed subsea. TDW was required to use its SmartPlug  isolation tool to create an isolation in the PLEM. The SmartPlug tool was to be used to maintain the pressure rate between the riser and the PLEM while the pipeline was being tested, in order to prevent testing pressures from occurring at the site of the three open ball-valves in the PLEM.

Secure isolation facilitates safe hydro-testing
“Our key objective was to provide an isolation solution whereby the entire line from the platform to the subsea PLEM could be hydro-tested, with the exception of the three open ball-valve sites in the PLEM, which had been tested previously,” said Martin Ullebust, Project Manager for TDW.

With just three months to prepare and execute the operation, TDW drew upon the expertise of engineers and technicians in Malaysia, Australia and Norway. The equipment was air-freighted from Norway to Malaysia.

The TDW team isolated the targeted section by launching its remotely-operated SmartPlug pressure isolation tool from a temporary subsea launcher, moving it seven meters (22 feet) into the pipeline through the main PLEM valve, before setting it. TDW isolated the section of the PLEM while the 16-inch gas export line was hydro-tested to a pressure of 188 bar that was held for 24 hours. Throughout the subsea isolation operation, TDW used its remotely-operated SmartTrack  tracking and monitoring system to enhance control during launching, pigging, setting, pressure monitoring, unsetting and retrieval of the SmartPlug tool.

With the PLEM securely isolated, the operator was able to successfully hydro-test the export gas pipeline, confident that it would complete the critical phase, safely and reliably.