Teekay Shipping is seeking a court injunction to stop its engineers from striking at Port Hedland in a move that would hold up some of the $100 million in daily iron ore exports.
Teekay claims the proposed industrial action is unlawful and wants the Federal Court to halt the four-hour strikes that would bring the port to a standstill on Saturday, Monday and Wednesday morning.
It claims a protected order that is required to render strikes lawful expires tomorrow.
The process to get another order would take several weeks.
But the Australian Institute of Marine and Power Engineers claims it does not expire until Saturday, and that subsequent stoppages are lawful because the first one falls in the order period.
AIMPE senior national organiser Andrew Williamson said the dispute was over excessive overtime, with many workers suffering fatigue and one worker falling asleep at the wheel.
Mr Williamson said the union was demanding Teekay employ an extra six tugboat crews. He said the workers were also seeking an extra 3.5 per cent a year in the next pay deal, on top of their $225,000 base salary.
"Let's be clear about one thing - our members don't want this overtime," he said.
"We have had an example of one of our members doing an 18-hour shift this year, and one person . . . fell asleep at the wheel. Thankfully, he did not get hurt but this has got to stop."
Teekay Shipping claims shifts lasting longer than 12 hours were an exception.
It said pay demands for a four-year pay deal were worth 9.5 per cent more money once extra entitlements were included.
A statement said the engineers were already well remunerated with entitlements, such as about $1560 a week in mortgage or rent assistance and 13 per cent superannuation contributions, taking annual packages between $280,000 and $390,000.
BHP Billiton said it believed the proposed strike was unlawful and it would pursue all options to stop it.
"Any industrial action has the potential to cost our business and the local and national economy millions of dollars," it said.
It is understood Fortescue Metals Group and the State Gov-ernment are also considering intervening to stop the strikes.