The move came despite representatives of the Unite union and site operator Ineos being locked in talks which could avert the strike set to start on Sunday over the treatment of a union convener. The development looked increasingly like a repeat of a 2008 crisis which disrupted production from several major North Sea fields.
As he arrived for the talks at the Acas conciliation service in Glasgow yesterday, Unite regional secretary Pat Rafferty said he was optimistic a solution could be agreed.
Both sides had said, if the strike did go ahead, it was hoped the flow of fuel from the refinery would not be affected. But Ineos spokesman Richard Longden said: "Individual production units are being progressively taken down and will be brought to a cold status. This is the best way to guarantee the safety of the site during this period of uncertainty.
"We remain hopeful that the union will agree to continue to provide steam to BP to ensure the ongoing operation of the Forties Pipeline System."
The company had previously warned that the threatened strike "could effectively shut much of Scotland".
Ineos UK CEO Gary Haywood added: "Safety is our prime concern and we are already well advanced in the shutdown and we would also like to determine the extent to which the union is willing to help us keep the North Sea pipeline flowing and to keep fuel flowing to the people of Scotland."
The declaration surprised Unite and a spokesman said: "This is a bit of a worry. A cold shutdown means it is unmanned and it takes three or four weeks to restart the thing back up."
The dispute centres on union convener Stephen Deans, who was involved in the row over the selection of a Labour candidate in Falkirk.
A similar strike in 2008 interrupted flows of crude and shut down production at 70 North Sea fields.
BP said it was still in discussions with Ineos and could not comment on potential implications of the shutdown.