Minimising Downtime During Multiple Valves Change Outs on Critical Gas Export Pipelines

To enable the safe replacement of five valves whose passing rates exceeded allowable limits, PETRONAS Carigali Sdn Bhd (PCSB) in 2017 used a three-module high pressure isolation tool (HPIT) to isolate one 24-inch and two 32-inch critical gas export pipelines at ANDR-A in the Angsi field in offshore Peninsular Malaysia. The SmartPlug® tool provided a double block and monitor (DBM) isolation without requiring depressurization or bleeding down the entire pipeline, which avoided prolonged shutdown. Because the three pipelines shared a common header at the ANDR-A topside, they required simultaneous isolation. Although HPIT had been deployed on main gas export pipelines several times before in Malaysia, this was the first time three isolations were required to be executed at the same time on the same platform during a single shutdown campaign. This Case Study describes the steps taken from planning, site visit and engineering to the safe and successful execution of the isolations.