Urgent repairs to cracked welds at the Gorgon LNG plant will have to be ground out and redone, with every day of delay costing almost $5 million.
Chevron last week pushed back the completion of repairs to cracked welds from early September to sometime in October.
Boiling Cold understands Chevron gave the wrong instructions to the welders working 12-hour shifts to repair eight propane heat exchangers, or kettles, that form part of LNG Train 2.
Welders usually perform critical welds to a set procedure that must conform to the relevant engineering code.
Just as long weeks of repair work on Train 2 neared completion Chevron told welders the procedure it had provided to repair the deeper cracks omitted a final step called post-weld heat treatment.
Geoff Crittenden, chief executive of industry association Weld Australia, said he could not comment directly on the Gorgon repairs without knowing more details.
However, Crittenden said if any weld required post-weld heat treatment but did not receive it, there was a significant risk the weld could crack and fail.
Each welder has to be qualified to perform a welding procedure. The welder follows the procedure under test conditions with the same equipment, materials and position as the job requires. The weld is then subjected to various tests such as X-rays to ensure it is suitable.
Boiling Cold understands the welders working on the Train 2 repairs have flown back to Perth to be qualified on the new corrected procedure.
The delay of between 20 to 50 days to the restart of the 5.2 million tonnes a year LNG Train 2 will cost Chevron and its partners between $100 million to $250 million of lost revenue, assuming similar prices to Woodside.
Delay increases safety concerns
Cracks in the propane kettles on Train 2 were found during a planned maintenance shutdown in May that was planned to finish by July 11.
Unions are concerned about the safety of workers repairing Trains 2 as they are near kettles full of propane on Trains 1 and 3 that have the same design and manufacture as the flawed Train 2 kettles.
The Department of Mines, Industry Regulation and Safety gave Chevron permission to continue operating Trains 1 and 3 under a plan where Train 1 would close for inspection of its kettles in early October and Train 3 would shut down in early January.
Without that permission, all the trains would have had to stop production on August 21, 14 days after regulators first intervened.
The delay to Train 2 repairs from Chevron's incorrect procedure is likely to cause Train 2 to still be under repair when Train 1 is due to be shutdown.
DMIRS director dangerous goods and petroleum safety Steve Emery said the regulator and Chevron are discussing the impact the Train 2 weld repairs may have on the inspection schedule for Trains 1 and 3.
Emery said DMIRS was satisfied with the current level of safety.
Australian Manufacturing Workers' Union state secretary Steve McCartney said the union had no faith in Chevron fixing the cracks or DMIRS making the job safe.
"AMWU understands Chevron attempted to fix the exchangers on Train 2 but failed to undertake the correct welding procedure which has delayed the repairs to Train 2 even further, McCartney said.
"We have been told the procedure failed to include a post-weld heat treatment and that the problem was only discovered near completion of the final repair.
"We can't afford to give Chevron another extension; it needs to be done now to protect the safety of our members."
Chevron's error has been revealed a week before the final phase of a 20 to 30 per cent cull of its Australian workforce begins.
Boiling Cold asked the US major three days ago about the faulty weld procedure and how the public could have faith in its ability to manage hazardous facilities.
Chevron declined to respond.