BP on Friday began preparations to shut down its key North Sea Forties pipeline system, which supplies nearly half of the UK’s North Sea oil, ahead of the strike planned this weekend at the Grangemouth oil refinery, near Edinburgh.

Grangemouth supplies power and steam to the nearby Kinneil plant, which processes crude oil from the Forties pipeline system. The power plant is due to shut on Saturday before the strike by 1,200 refinery workers over pensions starts on Sunday.