The device is a unique pigging method that employs a crack detection tool that identifies SCC defects and compression sleeves that require repair.

In order to overcome pipeline integrity issues, Agility has split its SCC management program into four phases:

* Planning and Preparation for intelligent pigging; * Intelligent pig run; * Engineering analysis of the results; and, * Repair and restoration.

The ‘pig’ run is a complex four to five day program, requiring a 25-man crew to run the pigging operation. In the lead up to the pig run, Agility established a comprehensive gas supply plan based on simulation studies to assess the impact of disruptions to normal supply as the optimum speed for the pig is one m/s - much slower than normal gas supply.

After confirming that gas supply could be effectively maintained, Agility ensured that the gas supply in the pipeline was optimised before shutting down a section to commence loading of the pig train and water batch. Six batch pigs hold 1-2 km of water in place and these pigs separate the gas from the water, with the intelligent pig positioned between the three batch pigs on either side.

The six batch pigs create a small liquid slug within a gas pipeline system to enable the intelligent pig inside to collect ultrasonic data. During preparation, Agility had to modify the receiver and launcher facilities for the pipeline to allow the loading and unloading of water into the pipeline.

During the launching of the pig train, water was pumped into the pipeline via large, high capacity, high-pressure Halliburton pumps. Due to the desert environment, Agility procured and transported one million litres of water in conjunction with the National Park and Wildlife Services from a dam approximately 30 km from the site. This water was stored in a specially built holding dam 10 to 15 days prior to the survey.

The speed of the pig train was critical in ensuring optimal results and as such, its speed was monitored every kilometre. As the pig train slows down when it goes uphill and speeds up when it goes downhill, pipeline pressure and flows have to be continually adjusted to compensate while managing gas supply to end users. Agility has worked together with gas producer Santos, who has provided excellent support throughout the operation by regulating gas flows to the pipeline.

At the end of the pig run, the water is drained and emptied into a specially excavated and lined dam and all pigs are removed from the pipeline. Any free water left in the pipeline after inspection is removed by running foam and de-watering pigs every four hours. As water in the gas upsets the gas specifications as elevated moisture level in the gas stream causes icing or hydrate formation, Agility has tracked daily gas quality moisture levels by dewpoint analysers installed at Bulla Park, Young and Wilton. Agility also notified potentially affected users prior to the operation as part of its community relations program prior to pigging operations.

After receiving the pigging results, the third phase in the SCC program is initiated to carry out a detailed engineering analysis - to select SCC defects that need to be repaired to maintain integrity of the pipeline at required pipeline pressure.

The fourth phase in the SCC program is the repair and restoration of selected SCC defects.

Sleeve repair programs are akin to running a pipeline construction project. The first crew excavate the defect; the second crew removes the existing pipeline coating and prepares the steel surface for a detailed integrity assessment; and the third crew conducts non-destructive testing and records the features of the defect so that it can assess how accurate the pigging operation has been and also decide if sleeve repairs are required.

When sleeves are needed, a welding crew of seven clamps two large sleeves over the defect on the pipe. The two halves of the sleeve are heated to 300 degrees celsius to expand the steel to weld both halves together while hot. Pipeline pressure and flow is kept low to avoid heating of the carrier pipe. After the sleeve cools, it compresses onto the pipeline and successfully preserves the pipeline’s integrity.

Another crew then recoats and backfills the pipeline after any necessary repairs have been completed. Lastly, the environment is restored and all waste materials are removed from the site and disposed of safely.

Agility’s project management capability in conducting SCC pigging and subsequent repairs is extensive. With the ability to conduct pipeline pigging and to co-ordinate a multi-crew camp in an arid desert environment, Agility is confidently positioned to deliver on future programs.