Millions of tonnes of iron ore shipped from Port Hedland stand to face delays after two more applications for permission to strike were received by the Fair Work Commission on Monday.
The groups that filed before Fair Work Australia were the Australian Institute of Marine and Power Engineers (AIMPE) and the Australian Maritime Officers Union (AMOU). They represent the tugboat engineers and masters, respectively. The groups filed the permissions after Fair Work Australia Commissioner Daniel Cloghan permitted the Maritime Union of Australia (MUA) in March to strike over pay rises and annual leaves.
All three groups have standing work disputes with Teekay Shipping Australia, which runs tugboats for all ships at Port Hedland that use the bulk export port. It is likewise a contractor for BHP Billiton.
Andrew Williamson, AIMPE spokesperson, said the engineers work over 12 hours a day. It seems their concerns border more on reduced work intensity than receiving more pay.
''With the associated extra maintenance we are seeking more time free of duty to redress the fatigue issues,'' Mr Williamson told SMH.
''The protected-action ballot doesn't have to translate into disruption for the port. Yes, it can be the precursor to industrial action, but it might also focus minds in jointly arriving at outcomes outside the envelope and in a timely manner.''
The looming industrial labour strike actions not only threaten to halt the shipping of iron ore through the port, but also disrupt Australia's most lucrative export chain.
In the March quarter of 2014, about 90 million tonnes of iron ore was shipped from Port Hedland, up from 67 million tonnes a year ago, and 56 million tonnes in the same period of 2012.
Australia's Bureau for Resources and Energy Economics forecast iron ore would be worth $78.5 billion to the country this year.
MUA has been seeking clarity on job security, rosters, work hours and pay for its members.
"Bear in mind, this is the biggest port in Australia, the most profitable port in Australia," MUA WA branch secretary Chris Cain earlier said. "My members deserve a decent wage in there for the hours of work that they do and the rosters that they do."
"I don't think the pay is anything out of the ordinary for the north-west."