Ultrathin-walled heat recovery boiler passes 305 start-stop cycles in offshore power trial

A compact heat recovery boiler built with unusually thin-walled pipes has completed a demonstration test without a single leak, according to researchers at SINTEF and the technology company Techouse. The boiler was started and stopped 305 times to mimic roughly 30 years of offshore service, and vibrations stayed within safe limits. The result suggests that steam bottoming cycles, long confined to larger installations, could be fitted to cramped platforms that still depend on gas turbines.

Why platform space matters

About 250 gas turbines operate on Norwegian offshore platforms, supplying electricity and mechanical power for equipment such as export compressors. Some have been replaced by power from the mainland, but that option depends on grid availability and distance from shore. The remaining turbines release large quantities of heat and CO2 through their exhaust.

On land, gas-fired plants routinely capture this exhaust heat, raise steam and drive a second turbine in a bottoming cycle, which yields considerably more electricity from the same fuel. Offshore, the equipment has generally been too large and heavy. A few older, larger platforms installed such systems about 25 years ago, but those still running gas turbines have little spare deck area.

Designing for size and durability

An offshore heat exchanger must be compact and light, yet efficient and able to tolerate sharp swings in temperature and pressure. Each design choice, from pipe selection to flow paths and geometry, affects the others. The SINTEF team developed a computational tool, FlexHX, to simulate and optimise configurations before anything is built. The wider development effort has taken 15 years.

Meeting the size target required pipes thinner than standard dimensions and packed more densely with fins, the small ribs that enlarge the surface available for heat transfer. SINTEF researcher Ruben Mocholi Montanes said the team had no operating experience with such thin walls. The concerns were increased vibration, which can wear equipment, and thermal fatigue from repeated start-ups and shutdowns. Earlier simulations had flagged possible weak points, but these needed checking in real operation.

The demonstration plant at Stord

The demonstration facility at Stord recovers heat from a 5 MW gas turbine, about 20% of the capacity of a typical offshore unit. Its boiler matches the length and height of those used with offshore turbines but is only 20% to 25% as wide, so the design can be scaled up. Techouse chief technology officer Pål Kloster reported a pipe wall thickness of 1.65 mm, with welded fins 0.5 to 0.75 mm thick.

The plant was more heavily instrumented than normal, with data logged every second and high-speed filming used to look for vibration. Water and steam chemistry, including conductivity, pH and oxygen levels, was controlled and monitored. Assuming about 10 start-stop cycles a year, the team ran more than 300 cycles to represent 30 years. They recorded no leaks after 305 cycles, and the system coped well with the temperature changes.

According to the developers, a boiler of this type would be about 50% lighter and need roughly 15% less space than a conventional design.

Limitations and next steps

The full analysis of the raw data has not yet been completed, and the tests used a boiler at partial width and about one fifth of typical turbine capacity. Mocholi Montanes said the results already give strong grounds for confidence in the thin-walled pipes. The researchers see applications on older platforms with little room to alter the existing layout. The source does not describe a schedule for a full-scale offshore installation, so that step, along with any wider performance data on fuel savings and emissions, remains to be reported.

Source: Ultrathin pipes solve space constraints on platforms (Tech Xplore, 12 November 2026).

Image: AI-generated illustration.