What
The Roy Hill Iron Ore Project in the Pilbara Region of Western Australia required construction of a new rail line to transport the ore from the Roy Hill mine near Newman to new port facilities at Port Hedland. To meet the new port facilities civil design requirements, the rail line needed to be constructed well below the current ground level, which required all surrounding infrastructure, including a section of APA Group’s Pilbara Energy Pipeline (PEPL) on the Pilbara Pipeline System, to be lowered.
The PEPL is a 219 km, 457.2 mm diameter, high-pressure gas transmission pipeline. It connects gas sources in the Carnarvon Basin with power stations located at Karratha and Port Hedland, as well as mining operations in the Pilbara region located on the Port Hedland to Telfer Gas Pipeline.
Barrie Sturgeon from APA’s Infrastructure Development team was the Program Manager for the relocation project.
“The original PEPL pipeline was constructed in 1995,” said Mr Sturgeon.
“With the new rail line planned to transverse the PEPL at a location approximately 20 km south-west of Port Hedland, an 800 m section of the pipeline needed to be lowered 8 m. This sounds straightforward, except that the pipeline was required to stay live during construction as downstream customers needed an uninterrupted gas supply, adding the complexities of working with a live pipeline,” he said.
When
The project commenced with the front-end engineering and design phase in late-2011 and the project developed into detailed engineering, approvals and procurement phases during 2012. Timing was critical as the construction phase had to be carried out during the Pilbara region dry season to avoid the increased risk of cyclonic weather impacting such a large civil and excavation project. Failure to do so would have delayed the project by six months or resulted in increased project risk if construction was pushed into the wet season.
The other schedule driver was to have the site available to allow the Roy Hill engineering, procurement and construction contractor to commence on their planned start dates for the rail corridor works. APA commenced the construction phase in July 2013.
How
The pipeline installation involved the construction of a new pipeline section and bypass lines in order for the mainline to remain live during the process. This method involved multiple hot tapping and stopple train (stoppling) processes, which added a level of complexity and risk.
The three main phases of works onsite each presented a certain level of complexity: ground preparation, pipe stringing and lowering, and installation and commissioning.
Ground preparation
The excavated area needed to include enough space to allow fabrication works of the new pipe string. Construction works commenced with the excavation of approximately 84,000 cubic metres of earth (equivalent to 45 Olympic-sized swimming pools) that was stockpiled to the side of the excavation. Project teams needed enough space for the works to be carried out while also allowing enough clearance to the adjacent operating pipeline. A clearing area of approximately 100 m wide by 1.4 km long was used, with the bypass pipeline located 12 m across from the adjacent live pipeline.
Pipe stringing and lowering
Once civil works were completed, the pipe was strung along the excavated trench with bends fabricated using cold field bending machinery. Once the fabrication of the pipe string was completed, including the installation of branch fittings, the pipe was then lowered and hydrotested to ensure pressure retaining integrity of the new pipeline section.
Installation and commissioning
Hot tapping into the operating pipeline allowed for the bypass lines and the new pipe string to be purged and commissioned. With the new line in operation, double stopple trains were installed to cut the flow to the original pipeline and divert it into the new pipeline. This allowed for the original line to be cut so tie-in spools could be installed.
APA Manager Support Services (Transmission) Craig Connor, who led the operations support team that managed the installation processes, said “These are complex and high risk processes and it was great to use APA’s in-house skills and expertise to provide technical support for the project.”
Upon completion of the tie-in installation and welding, the pipeline was returned to operation. The redundant line was then removed from the ground and all open excavations were backfilled and the site restored to the original condition ready for Roy Hill to proceed with the construction works on their rail corridor.
The PEPL Relocation Project was completed in 10 months in December 2013, just prior to the wet season commencing in January 2014.
Who
The project was managed by APA Group, utilising its Infrastructure Development team, with project engineering and management support from Enscope. The APA Transmission Operations team managed the hot tap and stopple processes with TD Williamson. Monadelphous KT completed the main civil and pipeline scope. At construction peak, approximately 45 people were involved in the project, both in construction and management. With the site only a short drive to Port Hedland, the team was accommodated
in town.
When delivering a project of this scale, a critical component is communicating with key stakeholders to ensure each group’s specific objectives and timings are well co-ordinated. Project teams generally focus on the delivery objective, which in this case was the relocation of the new section of pipeline, while the operations teams are responsible for maintaining asset integrity and ongoing operations. To align the independent objectives, the project and operations teams worked closely together to understand various stakeholder requirements during the planning phase, including the rail line construction project schedule, the complexities of working next to a live pipeline, and importantly, the downstream customer requirements.
Challenges
Every large-scale civil project has its challenges and this one, undertaken in the vast Pilbara region with the added complexity of constructing next to a live gas pipeline, was no exception.
“Ensuring zero harm to any project personnel, particularly during rising temperatures of 30-40 degrees Celsius onsite, whilst ensuring continual supply to customers, as well as the sheer civil scope of the project and doing all this within the restricted timeframe of the dry season, made for a very challenging and rewarding project,” said Mr Sturgeon.
“I am very pleased with the project outcomes of a project delivered to scope, within the timeframes and allocated budget, and, most importantly, without any significant incident or injury to personnel.”
JARGON BUSTER
Cold field bending is widely used for bends with a large radius and a small bending angle in gas pipelines. Cold bends are made from straight pipes using a cold-forming process with a bending machine in the field.
Hydro testing is used to determine and verify pipeline integrity. The test involves filling the pipe system with a liquid, usually water, which may be dyed to aid in visual leak detection, and pressurisation of the vessel to the specified test pressure.
Hot tapping is the precise process of drilling a hole in an “˜in-service’ or live piping system without spilling its contents or interrupting its flow. It is a means by which access is made to the inside of an operational pipeline, using either a drill or a circular cutter.
Stoppling is a plugging system which is designed to stop flow through a line while equipment installation, maintenance work or repairs are being made. A plugging head is inserted into the line through a fitting and flow is stopped and/or redirected through bypass piping.
