Commissioned in 1986, the Amadeus Gas Pipeline transports gas to Darwin, Katherine and other locations principally to fuel power generation in the Northern Territory. Gas is delivered into the pipeline via the Bonaparte Gas Pipeline as well as from the Amadeus Basin in central Australia.
At 6:15pm on 22 February, APA received a report of gas coming out of the ground approximately 14 km from Palm Valley, which is located approximately 170 km from Alice Springs in the Northern Territory.
A group of local Aboriginal people driving near the site had heard a loud hissing noise, clearly audible over their car’s diesel engine. When they stopped to investigate they found a large crater approximately 2 m wide and deep.Article continues below…
A follow-up visit to the site by Palm Valley colleagues confirmed that it was a gas leak. APA immediately instigated its emergency response procedures and dispatched two technicians from Alice Springs. By 10:30pm that night, the technicians had cordoned off the area to make the site safe.
In the rare event of a gas leak, APA endeavours to implement a repair strategy that causes minimal or no disruption to its customers. After careful consideration, APA decided to prepare for a permanent repair of the leak as an immediate shut-down of the pipeline would have created supply issues for Alice Springs customers.
This required letting the pipeline leak for one more day while Operations Manager Darren Flaus Engineering Manager, Henry Dupal, and their team mobilised the right materials, contractors and resources to make a permanent repair.
Once the emergency had been declared, the whole business moved into ‘emergency management’ mode. There were approximately 25 people directly involved in the response effort, including management personnel, control room operators, engineers, field technicians, contract welders and inspectors.
At approximately 4:00am on 24 February, the first crew of pipeline technicians from APA’s Southern Operations team headed out to the site from the main base in Alice Springs in a fleet of four wheel drive utes, trucks and trailers to commence blowdown and excavation with an excavator and experienced operator.
A second crew departed Alice Springs later that morning comprising engineers, specially-qualified welders and a welding inspector.
The first step was to depressurise the pipeline due to the fact that equipment and welders cannot be brought in until the danger of gas has been removed. Four pipeline technicians conducted blowdowns to empty the pipe of gas at Tylers Pass and Palm Valley (approximately 60 km apart), as the repair location was between these two sites.
The crew was then able to excavate the leak site and inspect the pipeline, a process which took approximately four hours to complete due to the fact that the section of the pipeline where the leak was occurring was located in a remote area of the Northern Territory, and was buried approximately 2 m beneath loose red sand. A scorch mark on the yellow jacket plastic coating at the top of the pipe confirmed APA’s suspicion that a lightning strike had caused the gas leak. Underneath the coating, the crew located the 1 mm diameter hole that was causing the gas leak.
Upon finding the hole, the technicians installed a pinhole repair clamp – a steel clamp strap with a rubber cone that is compressed on the pinhole – which seals the leak. A steel cap sits over this clamp and needs to be welded to the pipe.
According to Mr Flaus, this is a specialised type of welding as it requires gas to be flowing through the pipeline to keep the pipe cooled so the welder doesn’t burn through the pipe. Putting gas back into the pipeline needs to be done within very specific flow-rate and pressure parameters, which is where the engineers’ calculations become very important.
“If the gas flows too slowly, you risk a burn through of the pipeline, which is catastrophic for all onsite,” said Mr Flaus.
“If the gas is flowing too fast, the weld area may cool too quickly, and may cause a flawed or failed weld.”
Not long after the welding had started the team noticed some slight flaring, which suggested that the rubber cone was leaking, and as such welding was stopped. The line pressure was reduced, which meant doing another blowdown and then re-introducing gas back into the pipe again at a much lower pressure, in accordance with the welding procedure flow and pressure conditions.
Three hours later, after another welding attempt, the welding inspector pronounced the weld to be a success. The pipeline was re-pressurised to restore normal flow and the team left the site and returned to Alice Springs almost exactly 24 hours after heading out on the job.
After a mandatory follow-up inspection of the weld the following day, the pipeline was relocated and buried. The operation was officially completed and was deemed a success.
According to Mr Flaus, anyone who has been involved in a similar exercise will know how challenging this process is. When the gas leak was reported APA didn’t know what had caused it or how big it was, which meant the company couldn’t be sure of the repair method.
The logistics, health and safety essentials and personnel management posed the biggest challenge to this response effort. APA needed to mobilise a lot of resources and personnel to a remote location very quickly. The company was bringing people from Darwin, Alice Springs and Tennant Creek, which meant resources had to be backfilled to ensure operations continued. While the entire Southern Operations team was involved in the repair, the company’s Northern Operations team based in Darwin and Katherine provided cover during the event.
In addition, fatigue management was a crucial factor for a response effort such as this one and APA needed to ensure the team was properly rested and fed.
Accurately estimating the repair time and working to this estimated deadline was also very important to consider because, once the repair process started, APA relied on line-pack gas to supply customers.
Mr Flaus said that teamwork and calm competence were the keys to a successful response time and overall effort.
“When you’re under the pump, responding is so much easier when you have highly competent people around you who calmly and quietly step up and do what’s needed, and do it well.
“It’s grace under fire. I felt pretty proud of the people I work with and the way we all handled the situation.”