WHY

APA identified that moving the Young to Lithgow compressor package to Marsden would allow for the Moomba to Sydney mainline to be pressure decoupled from the Marsden to Tamworth pipeline. This lateral includes the Central West Pipeline, which stretches from Marsden to Dubbo, and the Central Ranges Pipeline, which continues from Dubbo to Tamworth.

“The compressor package relocated to Marsden has a 400 kW capacity which is ideally suited for the pressure and flow requirements on the Marsden to Tamworth pipeline,” said APA Project Manager Jeff Emmett.

Decoupling would allow additional Moomba to Sydney mainline storage capacity and line-pack to be available for peaking and storage services on the Central West Pipeline, accommodating any further gas demand in the Marsden to Tamworth pipeline.

Furthermore, the removal of the compressor at Young has opened the way for installation of a larger compressor.

“With the increased demand coming from the Young to Wagga and Young to Lithgow pipelines, the original compressor did not have the capacity to adequately service both of these pipelines,” said Mr Emmett. “A new, larger 1 MW unit, which will serve both lateral pipelines, is currently being installed at Young to replace the original compressor unit.”

WHAT

The main scope of works involved relocating the existing 400 kW YL compressor package from Young and installing it 130 km further up the Moomba to Sydney pipeline at Marsden. The scope also included the design, construction and commissioning of a whole new compressor station at Marsden.

Works included:
• Upgrading the existing Marsden odorant plant;
• Upgrading the existing Marsden site and infrastructure to accommodate the compressor package and associated facilities;
• Design and installation of a backup, gas-powered generator set;
• Installing additional buildings and structures including a new site office, a garage, a shelter over the odorant plant, two water tanks and pumps to supply water to the site;
• Modifying the existing site control hut to accommodate the installation of the new automated station control system to allow local and remote control of the compressor package and odorant plant;
• Design and installation of additional valves and pipework; and
• Upgrading the electrical supply from the local electricity supplier Country Energy to meet the increased loads at the site by installing a higher rated transformer and larger cabling.

The size of the existing site – which is raised approximately 1 m above the surrounding area as it is prone to flooding – needed to be extended to accommodate the new facilities. This involved the installation of 825 cubic metres of fill and compaction.

WHEN

The project was approved in October 2009, with design commencing in November 2009 and reaching completion in March 2010. Construction began in March 2010 and the initial run of the compressor took place on 31 May 2010. Construction was completed by June 2010 and the site was fully commissioned on 3 August 2010.

WHO

APA employees undertook the detailed design, procurement and execution of the compressor relocation from Young to Marsden, as well as providing the mechanical and welding installation. Electrical installation was performed by RIC Electrical, based in Wagga Wagge, while civil and structural work was contracted to Donnelly Mining and Civil Contracting, which is based in Dubbo.

APA used a number of local suppliers for the project from the closest town, West Wyalong, which is 35 km from the site. Suppliers included the local hardware shop, automotive parts shops, metal fabrication shops, cement supplier, gravel and fill supplier, and flooring shop (for the control building vinyl supply and installation). Donnelly Mining and Civil Contracting also made use of local suppliers.

Overall, 28 APA employees, 76 contractors and a number of consultants – for the design, construction and commissioning phases – were engaged to work on the project.

HOW

The project was managed by the APA Major Projects group based in Fyshwick, Australian Capital Territory. Design and engineering was undertaken by the APA Asset Management and Engineering (AM&E) group also based in Fyshwick, ACT, using knowledge from previous compressor projects. APA electrical and mechanical engineers provided the design for their respective disciplines. The final civil design and sign off was completed by a civil contract engineering company based in the ACT.

As the site was within an existing operational site, the following precautions were taken during the construction and commissioning phases:
• The APA ‘Permit To Work’ system was used for all onsite work; this system includes a job hazard analysis process for all works being undertaken;
• A ‘Hot Work’ permit with continuous gas monitoring was used for all works onsite;
• Site pre-start meetings were held each morning to discuss the day’s activities and to discuss any safety issues relating to the work;
• All persons working onsite were required to complete a site induction;
• All contractors worked under the APA ‘Permit to Work’ system and were supervised by experienced APA personnel;
• A construction safety plan was developed in conjunction with the principal contractors.

APA obtained necessary regulatory approvals from the NSW Department of Industry and Investment. To facilitate the approval process, APA developed a Review of Environmental Factors (REF), Preliminary Hazard Analysis, Final Hazard Analysis and Construction Safety Plan. All requirements identified in these documents were implemented during design and construction.

The REF considered the local landowner impact, and APA also held consultations with the Bland Shire Council to address necessary council requirements relating to the project.

The commissioning phase of the project included:
• Calibration and testing of all electrical instrumentation, such as pressure transmitters, temperature transmitters, etc;
• Calibration and setup of all mechanical devices, such as regulators, valves, etc;
• Point-to-point testing between the field devices and the new station control system;
• Purging, pressurising and leak testing of the new station pipe work;
• Confirmation that the new onsite control system was displaying the correct information for the site;
• Confirmation that the emergency shutdown was working;
• Confirmation that the compressor controls were working;
• Running the compressor package in various modes to confirm correct operation;
• Confirmation that the SCADA screens in the Young Control Room were correct and that the compressor package could be remotely started and stopped correctly;
• Confirmation that the new odorant plant would dose at the correct rate and could be controlled remotely from the SCADA; and,
• Confirmation that the backup generator set would automatically start in the event of a power outage and take the site load.

CHALLENGES

The delicate nature of the relocation presented a number of challenges, such as de-integrating the compressor at Young so that the infrastructure at Young still worked correctly once the compressor was removed. Safely isolating the compressor package at Young – mechanically and electrically – to allow the compressor to be removed while still utilising some of the existing pipework and cabling was not only tricky, but required detailed engineering to maintain gas supply for the Young to Lithgow pipeline.

Foresight was important in tackling some challenges. “The surrounding area around the Marsden site becomes very boggy with rain,” said Mr Emmett. “The access road to the site was improved early on in the project to allow all-weather access. As it happened, heavy rain did occur during the construction phase and at one point, the raised area of the site and the access road were the only areas not submerged underwater.”

Hot-tapping works were required to allow the station pipe work to be vented down while still maintaining gas supply to the town of West Wyalong. APA personnel performed the hot-tap with the APA welders completing the initial welding for hot-tap fittings. Careful planning – including consultation with network operator Jemena – and a number of precautions were used to ensure that any challenges were met head-on.

Prior to the operation, the planned procedure for the hot-tap was documented and carefully reviewed by experienced personnel with hot tapping experience. A complete job hazard analysis was also completed to determine all hazards and what control measures would be required to mitigate these hazards. During the operation, APA ensured that suitably trained and experienced personnel were available to perform the hot-tap, and made a spare hot-tap drill available onsite to ensure there was no downtime in the event of a drill breaking.