UPDATE 2-Strike closes major British oil pipeline

(Adds emergency fuel imports paragraphs 10-12)

By Jeremy Lovell

LONDON, April 27 (Reuters) - A pipeline carrying nearly half of Britain's oil was closed on Sunday as a strike over pensions began at the neighbouring Grangemouth refinery in Scotland, operator BP (BP.L: Quote, Profile, Research) said.

The refinery, owned by international chemical company Ineos, produces a tenth of Britain's petrol and diesel but also supplies vital steam to BP's Kinneil plant that starts to process the crude oil coming ashore from 70 North Sea fields.

Unions rejected pleas to operate the steam plant at the level necessary to keep Kinneil functioning during the two-day stoppage which began at 0600 BST (0500 GMT).

The company said that assuming it got power back as soon as the strike ended and Forties fields resumed production rapidly, the pipeline could be back in operation within 24 hours but might take a few more days to get back to full flow.

The strike is the first to close a British refinery in more than 70 years.

The Forties pipeline carries an average of 700,000 barrels per day (bpd), close to half the 1.5 million barrels the country produces daily. One fifth of Britain's gas supply also relies on the Forties system.

The Forties oil alone is worth 50 million pounds ($100 million) a day and the pipeline's closure will make a significant dent in already stretched government coffers which take half of the revenues in tax.