A Scottish oil rig yard yesterday won a major North Sea contract worth #35m.

The Barmac facility at Ardersier, near Inverness, will build three new modules weighing 1700 tonnes, which will be installed next year as part of an upgrading programme being carried out by American-owned oil company Chevron on its Alba field.

Work will start in September on the contract, with the steel modules being sailed out in a year's time for installation on the field 135 miles north east of Aberdeen.

This is the fourth multi-million pound contract which has been won in recent months by American-owned Barmac, which operates Ardersier and the recently upgraded yard at Nigg, on the shores of the Cromarty Firth.

It brings the current order book to over #200m and the deals will ensure that the workforce increases from its present 850 to over 2000.

The Alba contract will, at its peak, provide direct employment for 140 people.

The fabrication company, a joint venture between offshore engineers Brown and Root and J. Ray MacDermott, is to build a removable 32,000 tonne platform for French oil company Elf's adjacent Elgin and Franklin oil and gas fields, which are being developed jointly.

Yesterday James Gray, union leader at BARMAC, welcomed the Alba deal.

He said: ''The company has secured this deal in addition to being awarded the two biggest North Sea contracts of the year.

''This proves that the yards are very competitive and it justifies Barmac's decision to spend several millions of pounds upgrading its drydock facilities at Nigg, where a lot of the work will be done.''

qThe Lewis Offshore yard in Stornoway has landed another contract which will keep the majority of local workers employed until spring 1998.

The contract, from Bluewater Engineering, is worth around #3m, and comes as the largest contract won by the yard since it reopened in 1990 is drawing to its conclusion.

The contract also gives Lewis Offshore a share in an all-Scottish project for the Ross field in the Moray Firth, for which Lewis Offshore will build parts.

The new contract is expected to start in September. It will employ up to 200 men and will mean that most local workers will have security until February 1998.