8" BISEP, Natural Gas Plant, Malaysia

When a 15-metre section of thin-wall stainless-steel pipework on a live flare line shows damage that cannot be left in service, the options are limited. Shutting down the gas plant is expensive and disruptive. The alternative is an isolation that can be fully verified - one that keeps the pipeline live while creating a proven zero-energy zone safe for cutting, welding, and hot work.

For a major operator at an onshore natural gas plant in Malaysia, STATS provided exactly that.

The 8" stainless-steel flare line at the gas plant had a 15-metre section of damaged, thin-wall piping that needed to be safely cut out and replaced with the line live and pressurised.

Welding new pipework onto a live gas system requires a verified isolation upstream of the work area - not just a mechanical barrier, but one where the integrity of each seal can be independently confirmed before any hot work begins. The monitored annulus between the seals must be proven to be at zero pressure for the full duration of the workscope. For a flare line at an active gas plant, these requirements are non-negotiable.

STATS proposed their patented BISEP - Bi-directional Isolation and Seal Plug - to provide double block and bleed isolation of the flare line through a single hot tap entry point.

The BISEP's dual compression seals are hydraulically activated, expanding radially against the pipe bore to create a leak-tight isolation. The annulus void between the two seals is independently vented and monitored, providing a continuously verifiable zero-energy zone throughout the workscope. Both seals can be independently pressure tested at full pipeline pressure before any pipeline intervention begins - giving the operator documented proof of isolation integrity ahead of any hot work.

A split tee fitting was welded to the 8" flare line at the isolation location. Following pressure testing of the fitting, a STATS slab valve and hot tap machine were attached. The hot tap was conducted, the pipe coupon recovered, and the slab valve closed. The BISEP - housed in its pressure-competent launcher - was fitted to the slab valve, leak tested, and deployed into the pipeline towards the pressure to be isolated.

Once in position, a full seal test regime was carried out: each seal independently tested at full pipeline pressure, the annulus between the seals vented to ambient and confirmed as a zero-energy zone. An Isolation Certificate was issued before any pipeline work began.

The BISEP then remained in the pipeline for 26 hours while the damaged section was cut, removed, and new pipework welded into place. Throughout this period the seal annulus was continuously monitored and remained leak-tight. After a successful reinstatement test of the new pipework, pipeline pressure was equalised and the BISEP recovered into its launcher.

A completion plug was deployed and set into the flange of the split tee fitting. With the plug confirmed and tested, the hot tap machine and slab valve were removed and a blind flange installed. All hot tapping and isolation services were carried out by STATS technicians.

The workscope was completed safely, without incident, and ahead of the planned schedule. The 15-metre section of damaged flare line was removed and replaced with the gas plant remaining live throughout - no shutdown required.