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AUSTRALIAN WELDING | SEPTEMBER 2016
Improving Welding Operations
At Longford Gas Plant While undertaking preheat and post-weld heat treating work for the Longford Gas Conditioning Plant, Wood Group PSN saved $1 million in contracting fees, nearly 150 working hours, and delivered improved safety outcomes, thanks to the Miller Pro Heat 35 Induction Heating system and the training and support from Welding Industries of Australia (WIA).
The Task In April 2014, Wood Group PSN won a contract to provide brownfield engineering, procurement and construction service support at the Longford Gas Conditioning Plant Project for Esso Australia. Part of Wood Group PSN’s responsibilities was to establish a pair of 1,200m long pipes to bring raw gas from the offshore facilities to the gas conditioning plant. The company’s engineers laid down two 600 nominal bore pipes with 32mm wall thickness. One pipe would carry untreated, raw gas to the plant, while treated gas would flow through the other. The pipe sections would be welded together using a combination of gas
Image Courtesy of ExxonMobil Australia.
metal arc welding and flux-cored arc welding. But each of the 76 welds would require preheating and postweld heat treatments, to ensure the metallurgical integrity of the pipes would not be compromised by the temperature fluctuations caused by the welding work. According to David Barry, Construction Welding Superintendent at Wood Group PSN, strict statutory codes and scientific tests govern this type of welding work. “Before we start welding, we go through all manner of welding procedure qualifications, proving all the equipment, welding methodology, proving we’ve got enough preheat so it doesn’t cool too quickly, proving that our postweld heat treatment is correct and the results we achieve meet the requirements,” he said.
Bringing It In-House Normally, preheat and post-weld heat treatments are considered complex specialist tasks, requiring a third party contractor with resistance-type heating equipment. But there are both risks and costs involved in bringing in third party contractors on site.“Contractors sometimes aren’t familiar with the requirements, haven’t received the proper training, or have no experience working in a major hazard facility,” David said. Having to work around their schedules also added to the cost, and made it difficult to manage other parts of projects. When the team learned about the Miller Pro Heat 35 Induction Heating system from WIA, they knew that it would enable them to bring the preheating and post-weld heat treatment work in-house and still deliver the same results, but in a faster, more cost-effective and safer way. WIA helped smooth the way by providing comprehensive training and support. “The training process started when WIA first introduced us to the equipment. We worked very closely with them programming the machines, and setting up the hardware on the pipes,” David said. “As we drew closer to commencing production welding, WIA came down for a few days to work with the engineers who would be doing the work, and ran them through some formal training.”