Case Study

16" BISEP Line Stopping, Valve Installation, Solar Power Station

Tool - BISEP Line Stopping Tool, SureTap Hot Tap Machine

Location - UAE

Operating Environment - Onshore

Pipeline Medium - Heat Transfer Fluid

Activity - Maintenance

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Isolating a pipeline running at 390°C is hard enough. Doing it at one of the world's largest solar power stations, where the fluid inside doesn't stop being hot just because a shutdown is underway, adds another layer of difficulty.

STATS' First Renewables Deployment: Live Heat Transfer Line Isolation at Solar Power Station

At a solar power station in Abu Dhabi covering around 2.5 square kilometres, STATS deployed its patented BISEP into a 16 inch production line carrying heat transfer fluid during a planned shutdown.

The production line was connected to five large storage tanks and needed to be isolated to allow four valves to be introduced into the system.

One of the World's Largest Solar Power Facilities

The station uses parabolic trough technology to generate electricity: rows of parabola-shaped reflectors concentrate the sun's rays at 30 to 100 times their normal intensity onto heat transfer fluid, which carries that heat to a steam generator. The steam drives a turbine and an electric generator, in much the same way as a conventional fossil-fuel power plant.

Highlights

First time STATS has deployed its hot tapping and line stopping technology in the renewables sector.
BISEP isolated a 16 inch heat transfer fluid line that had operated at 390°C, cooled to 80°C during the shutdown.
Factory Acceptance Test held the BISEP's seals at a constant 90°C for five days before mobilisation to site.
Fail-safe double block and bleed isolation achieved through a single hot tapped intervention, with no additional bleed or vent ports.
BISEP held leak-tight isolation for five days while four valves were installed into the pipeline.

BISEP deployment through mechanical clamp

Five-Day Factory Acceptance Test at 90 Degrees Celsius

During the shutdown, the heat transfer fluid cooled to 80°C from its normal operating temperature of 390°C. To confirm the BISEP's elastomer seals would perform at that temperature, STATS ran a Factory Acceptance Test at its operational base in Abu Dhabi, in a purpose-built test fixture replicating the pipe specification and site temperatures. The BISEP was deployed and hydraulically set in the fixture, with heat transfer fluid held at a constant 90°C for five days, before the equipment was mobilised to the worksite.

A Single Hot Tap Intervention, Fail-Safe Double Block and Bleed

Onsite, a mechanical hot tap fitting and gate valve were installed onto the pipeline at the isolation point and leak tested. STATS' SureTap hot tapping machine cut into the pipework and the pipe coupon was recovered, opening access for the BISEP.

With hot tapping complete, the BISEP, housed in a pressure-competent launcher, was attached to the closed gate valve and leak tested. The launcher pressure was equalised, the gate valve opened, and the BISEP hydraulically deployed into the pipeline. Its dual elastomer seals were then hydraulically set, providing fail-safe double block and bleed isolation without the need for any additional hot tapped bleed or vent ports.

Both the primary and secondary seals were independently tested against full pipeline pressure. The annulus between them was vented to ambient through the BISEP and verified as a zero-energy zone, then closed and monitored to confirm leak-tight isolation.

This project is the first time STATS have utilised their hot tapping and line stopping technology in the renewables sector, this highlights the benefits of the BISEP isolation technology to meet client challenges out with the oil and gas industry. Due to space constraints at the isolation location, the BISEP was the only solution available in the market to meet our client's double block and bleed isolation criteria, as it is deployed through a single hot tapped intervention.

Ajith Pushparajan

Project Engineer

STATS Group

Four Valves Installed, Five Days of Leak-Tight Isolation

Following successful seal testing, an Isolation Certificate was issued confirming the safe, leak-tight isolation of the pipeline. The BISEP then remained in place for five days while all four valves were installed, with its seal annulus monitored throughout and staying leak-tight for the full duration.

This was the first time STATS had used its hot tapping and line stopping technology in the renewables sector, demonstrating what the BISEP can offer clients outside oil and gas. Space constraints at the isolation point meant the BISEP was the only solution on the market able to meet the client's double block and bleed isolation criteria through a single hot tapped intervention.