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Breaking new ground on Cortez pipeline project

Published by
World Pipelines,

Pipeline engineering specialist STATS Group has completed the world’s first leak-tight double block and bleed isolation of a high pressure CO2 pipeline system.

The project, on behalf of Kinder Morgan, was part of a pipeline intervention and isolation operation on a high pressure 30 in. CO2 pipeline extending over 500 miles from southwestern Colorado to Denver City in the US and operating at 2140 psi.

The purpose of this project, which took place as part of a larger initiative to convert a non-piggable pipeline into a piggable pipeline, was to install full bore inline valves and retrofit pigging launchers and receivers into the pipeline system. The installation of a 24 in. bypass pipeline around the isolated section allowed continuous production and avoided system downtime during maintenance activities.

STATS Group is a pioneer of fail-safe double block and bleed isolation of pipelines using its patented BISEP™ technology. The BISEP provides leak-tight isolation, dramatically increases safety over traditional line-stop technology and doesn’t require any additional hot tap vents or bleed ports. The BISEP contains dual energised seals and the annulus zero-energy zone proves and monitors the seal integrity before and during intervention work.

All equipment used on the project was designed, manufactured, assembled and tested at STATS Group’s facility in Houston, Texas.

While the pipeline operated under normal conditions, the site contractor excavated the pipeline and welded on split tee fittings, based on qualified and approved in-service welding procedures. Two 30 in. fittings provided access for the BISEPs, enabling mid-line isolation, and two additional 24 in. fittings allowed production to continue around the isolated section through a bypass line.

High pressure slab valves, supplied by STATS were installed on each fitting and STATS technicians subsequently leak-tested and hot tapped the pipeline at each location, successfully breaking containment and retrieving the pipeline coupons.

The 24 in. bypass line was then installed, purged and leak-tested allowing the slab valves to be opened and flow to pass into the bypass line. The BISEPs were then installed onto the 30 in. fittings and the upstream BISEP was deployed into the flowing pipeline.

The downstream BISEP was then deployed and set in the pipeline creating a mid-line isolation and diverting the flow through the 24 in. bypass line. The section of pipeline between the BISEPs was then vented in a controlled manner to a safe location allowing the BISEP seals to be tested and verified.

Both primary and secondary seals were pressure tested with full pipeline pressure in the correct direction and the annulus between the seals was vented to ambient. After secondary and primary seal tests the isolation certificate was issued. The BISEP annulus provides a zero-energy zone between the seals, which is monitored for the duration of the isolation.

Steve Rawlinson, STATS Group vice president Americas, said: “Hot tapping and isolating liquid and gas pipelines has a long and successful track record globally, however this is the first time the isolation of high pressure CO2 pipelines has been attempted due to a number of challenges which we successfully overcome.

“With the maintenance work successfully completed and the isolation no longer required, pressure was equalised between the BISEPs and the tools were hydraulically unset and recovered into the launchers and the slab valves closed.

“To date, STATS have carried out isolations at four sites along the CO2 pipeline operating at around 2000 psi and have completed in excess of 160 days of individual BISEP isolation, whilst avoiding system downtime during critical maintenance activities. Throughout the isolations there has been no degradation of the seals or leaks past the primary barrier, allowing the critical launcher and receiver upgrades to occur safely and without any uncontrolled release of pipeline product.

“The BISEP isolation capabilities has once again proven to offer compelling advantages over traditional line-stop technology for achieving provable, testable and monitorable double block and bleed pipeline isolation.”

Edited from source by Stephanie Roker

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