Two companies have been fined $140,000 following the death of two men in an explosion in Broome.
Oilfields Transport Services and Baker Hughes were fined over the accident, which occurred four years ago.
Baker Hughes was fined $80,000 and Oilfields Transport $60,000.
The workers died in December 2008 when a tanker they were standing next to ruptured and exploded while they were emptying it of barite power.
Barite power is widely used in the oilfields industry as a weighting agent for drilling fluid.
The workers initially collected two tanker loads of barite power from a Baker Hughes depot for transfer to a supply vessel at the Broome wharf.
The powder could not be transferred to the vessel because it contained too much moisture, causing it to clog inside the tanker.
After this the men returned to the depot to empty the tankers.
One tanker was successfully unloaded, and in a statement WorkSafe said a number of de-pressurisations had caused the second tanker to rupture.
"On a number of occasions, the tanker was de-pressurised while the inside was manually scraped down, then re-pressurised to remove the powder," it said.
"On the final occasion the tanker exploded […]"
In a statement WorkSafe said the tanker was "not maintained in a safe working condition" and had not been inspected by WorkSafe or other regulators in "many years".
“Safety procedures and adequate training had also been neglected, in all probability contributing to the loss of life that occurred that day," it said.
“But the real tragedy is that there were safe systems of work available to both employers that could have prevented these deaths.”