Unite, the trade union, began industrial action over a separate disagreement involving alleged victimisation. But the dispute widened to include workers' terms and conditions. Ineos demanded they accept changes to their contracts, but the union urged members not to accept. Two-thirds of Unite members took that advice. Ineos then announced the petrochemical plant was to close.
What will happen now?
Ineos says the petrochemical plant at Grangemouth is to close while the oil refinery will remain open. PetroChina owns half the refinery that is operated by Ineos.
The steam and power which runs the Forties pipeline delivers a third of the UK's oil output, and BP's Kinneil terminal comes from Grangemouth. A strike at Grangemouth in 2008 shut the Kinneil terminal and that forced 70 North Sea oil platforms to shut down or reduce production.
What is Grangemouth's importance to Scotland?
The refinery supplies 70% of the fuel used at Scotland's filling stations and it also supplies fuel to Northern Ireland and the North of England. So far, these are unaffected as it is scheduled to stay open. But Ineos chief executive Jim Ratcliffe has warned that it, too, may be closed.
There is currently a 20% oversupply of petrol. US refineries pay around $15 a barrel less than UK refineries for crude oil, which has helped US firms to export cheap fuel to the UK.
What will happen if the oil refinery shuts to fuel from the pipeline transferring it from the North Sea?
Nothing, at the moment. The Forties pipeline delivers a third of the UK's oil output, and relies on steam and power from Grangemouth. So far, this has not been interrupted, but if Grangemouth's refinery is forced to close then some alternative will have to be found, with unconfirmed speculation that fuel will be ferried in by tankers to the terminal's jetty or driven
north from south of the Border.
What is going to happen to the workers' pensions?
Nobody has publicly said yet. This will be worked out while the company goes through the compulsory consultation process following liquidation.
What happens next to the plant?
PetroChina has yet to announce a decision whether to restart the refinery.
First Minister Alex Salmond has suggested the Government may try to find a buyer, and UK Energy Secretary Ed Davey has already discussed the issue with Finance Secretary John Swinney.
However, it has been reported by at least one analyst that the plant may struggle to attract a buyer.
The plant is facing intense competition from Asia and the Middle East and Europe has seen a fall in demand for gas.
Ineos recently reduced its asset valuation from £400 million to zero. It believes there is no realistic possibility of a future profit.
Grangemouth could be sold by the liquidator to a company with deep enough pockets to re-equip it.
However, any new buyer could choose to reduce wages or cut pension costs.
Are there any similar recent examples?
Last year the Coryton refinery on the Thames Estuary in Essex closed after its owner, Petroplus, filed for bankruptcy.
It is still attempting to find a buyer, with a Russian energy company thought to be interested. The complex supplied 20% of fuel in London and the South East.
The AA said yesterday that the European commodity trading houses had been predicting the loss of five to six refinery plants over the next two years.