Sealing success in PNG first

A challenging remote location at high altitude was the destination for STATS Group’s first hot tap and line stopping project in Papua New Guinea.

STATS Group was contracted to provide hot tapping and line stopping services on a redundant 4-inch oil flowline that needed to be recommissioned to bring it back into service.

STATS Group Field Technician Rab Milligan saluted the company’s milestone and success in Papua New Guinea (PNG).

“This was our first project carried out in PNG and the high altitude – at 4200ft – made conditions challenging at times, however the BISEP performed flawlessly,” Milligan said.

A successful completion plug and blind flange installation. Image supplied by STATS Group.

“The project was completed safely and five days ahead of schedule which provided significant savings for the client.”

The BISEP line stopping tool was utilised to provide safe worksite conditions and avoid any discharge to the environment during breaking of containment activities.

For STATS Group Regional Manager for Asia Pacific Gareth Campbell, the project was a real turning point for the company.

“This project is another significant milestone for STATS as we expand our presence to support pipeline operators in PNG and the wider Asia Pacific region,” Campbell said.

The BISEP provided fail-safe, double block and bleed isolation through a single hot tap, increasing safety while also reducing the number of fittings and associated welding and hot tapping activities.

“We are delighted to demonstrate our market leading line stop technology in the PNG market and look forward to future projects as we expand our presence in the region,” Campbell said.

The leak-tight isolation allowed the pipe to be cut and a valve manifold welded into the pressurised flowline to allow a 128bar hydrotest to be conducted prior to reinstatement to confirm that the line could operate safely at its maximum allowable operating pressure.

This is the first project STATS Group has conducted in PNG. Image supplied by STATS Group.

In addition to the provision of the BISEP line stop tool, STATS Group also manufactured and supplied the fitting and completion plug, slab valve and hot tap machine, along with the company’s trained and competent field technicians.

All STATS Group’s supplied equipment was tested and certified prior to mobilisation to site and in line with the project parameters to confirm full functionality.

The worksite was situated next to a road which allowed access for the crane to deliver the equipment to the site location. Once at the worksite the fitting was welded onto the line and tested.

STATS Group then conducted the hot tapping, recovering the coupon and installing the BISEP ready for deployment. To remove the metal cutting chips, the BISEP head was deployed into the line to sweep the line and displace the swarf prior to redeploying the BISEP and hydraulically setting the plugging head.

Setting the BISEP causes the plugging head to contract squeezing the dual seals and causing them to radially expand and contact against the pipe wall. Hydraulic activation allows for high integrity sealing, especially in ageing pipelines which may have internal issues, such as pitting or pipelines with ovality issues.

During the setting process, the pressure within the annulus (space between the primary and secondary seals) rises as the annular space is compressed by the expanding seals.

This pressure was then monitored to prove no pressure loss and provide an initial indication that the seals are isolating, allowing the client to depressurise and drain the line. Once the line was depressurised, the differential pressure across the BISEP plugging head maintains isolation independent of the hydraulic pressure providing a fail-safe isolation.

Once the isolated section of line was drained, the BISEP secondary seal was tested above the pipeline pressure to prove the integrity of the secondary seal.

The seal annulus was then vented to a safe area and locked-in. This allowed the primary seal to be tested and monitored for sealing performance.

Once the secondary and primary seal tests were conducted STATS issued an isolation certificate to confirm leak-tight double block and bleed isolation allowing breaking of containment activities to commence safely.

The BISEP is the only hot tap installed isolation tool in the market that satisfies the design criteria for DNV Type Approval for Pipeline Isolation Plugs.

On completing the successful welding of the flanges and installation of the valve, a hydrostatic test of the 4-inch flowline was conducted at 128bar.

With the client work scope completed, the line pressure was equalised and the BISEP was hydraulically unset and recovered from the line.

STATS Group then redeployed the hot tap machine to install a completion plug marking the end of a successful project.

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This article featured in the March edition of The Australian Pipeliner. 

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