Editing Piper Alpha (section)

==Upgrades and production modes==

In 1978, major works were carried out to enable the platform to meet British government gas-conservation requirements, and to avoid waste from the [[Routine flaring|flaring of excess gas]].{{sfnp|The Hon Lord Cullen|1990|loc=vol. 1, p. 14}} A gas conservation module (GCM) was added, built on top of module B. After this work, Piper Alpha operated in what was known as "phase-2 mode", i.e., using the GCM facility. In phase-2 mode, the GCM would treat the gas obtained in the crude oil separation process, separate [[Natural-gas condensate|condensate]] (or natural gas liquids, NGL) from it, reinject the condensate in the oil export pipeline to Flotta, and compress the gas for export to the pipeline to MCP-01. From the end of 1980 until July 1988, phase-2 mode was its normal operating state.{{sfnp|The Hon Lord Cullen|1990|loc=vol. 1, p. 15}}

In the late 1980s, major construction, maintenance, and upgrade works were planned by Occidental, and by July 1988, the rig was already well into major revamp, with six projects identified, including the change-out of the GCM unit. This meant that the rig was returned to its initial "phase-1 mode", i.e., operating without the GCM unit, only three days before the accident.{{sfnp|Lord Caplan|1997|loc=vol. 1, section 3.2}} Despite the complex and demanding work schedule, Occidental made the decision to continue operating the platform in phase-1 mode throughout this period and not to shut it down, as had been originally planned. The planning and controls that were put in place were thought to be adequate.{{sfnp|Lord Caplan|1997|loc=vol. 1, section 3.1}} At the time of the accident, Piper weighed around 34,000&nbsp;tonnes.{{sfnp|McGinty|2009|p=52}} It continued to export oil at just under {{convert|125000|oilbbl|m3}} per day (or 10% of the entire production of the UK sector of the North Sea, which made it the world’s single largest oil producer)<ref name=":18" /><ref name=":1" /> and to export Tartan gas at some {{convert|33|e6ft3|m3|abbr=out|lk=off}} per day at [[Standard temperature and pressure|standard conditions]] during this period.