An Unplanned Outage, an Unconventional Plan, and a Global Collaboration

When problems strike and normal supply channels are constrained, it can be advantageous to consider alternatives. The Rocksavage plant in the UK found needed parts at a station in Argentina and was able to get its unit back online months earlier than would otherwise have been possible.

Most power plant operators would prefer never to face an unscheduled outage due to a gas turbine failure. But at InterGen’s Rocksavage Power Station, a forced outage in 2022 became an unexpected opportunity for collaboration.

“With the energy industry under the microscope, and with potential supply issues and with the winter months approaching, at first we didn’t really have a clear way forward,” said Rocksavage Engineering Manager Paul Swire.

But the Rocksavage team rallied. They called on Siraj Taj, principal of American company ST Power Services (STP), and other outside expertise and resources. Together, they decided to try, in Taj’s words, “a truly innovative and pragmatic solution that had never been tried before.” As a result, they returned the plant to full operation in half the expected time. Here’s how they did it.

A Series of Unfortunate Events

Rocksavage Power Station is a combined cycle natural gas–fired power plant in England, just southeast of Liverpool. It has a generating capacity of 810 MW, enough to power about 800,000 homes.

At 10:36 p.m. on May 21, 2022, Gas Turbine B (GTB) was nearing the end of its run cycle. A high-temperature alarm went off. Four minutes later, high-temperature alarms sounded further down the turbine. Twelve minutes from the initial alarm, the turbine was shut down.

Plant operators weren’t too concerned, as GTB had been thoroughly inspected four weeks earlier working with STP. It had gotten a clean bill of health and had since gone through nine starts with no problems.

“At first, from an operational perspective, it looked for all the world like a single-indication issue,” Swire said. Two days later, once the turbine had cooled, Swire’s team used a borescope to conduct an internal inspection. They discovered significant damage in the environmental (EV) combustion section that would be difficult to fix without opening the machine.

A more detailed borescope inspection conducted by the original equipment manufacturer (OEM) revealed worse news: the entire bottom half of the EV combustion section would have to be replaced. There was also significant damage across the turbine itself.

The OEM confirmed that it could manufacture a replacement combustor. However, the company was already backlogged from COVID and with existing commitments to long-term service agreement customers. Therefore, the estimated time to provide the new parts was 46 to 48 weeks. In addition to the new part lead time, there were challenges in scheduling resources for the work required for strip-down, replacement, re-assembly, and commissioning.

There was also the risk of finding further significant structural defects once the GT had been stripped and inspected. If additional components were damaged, such as the turbine housing, Swire feared they’d face another long lead time. It was imperative to assess the full extent of the damage.

This, unsurprisingly, “was a very difficult conversation to have with insurers,” Swire said. Rocksavage was keen to avoid having its GT out of service for a year or more. The plant had to be running at full capacity by the winter, when demand would spike. Was there an alternative approach?

Searching the Globe for Solutions

Swire and his team brought in Taj, their trusted consultant, to help them figure out this knotty problem. Taj, who had previously worked for Alstom Power for nearly 24 years, travels the world advising power plant owners and managers on how to optimize their power generation assets.

“There are solutions,” Taj told them. “There’s no one answer to the question. We have to ask the right questions—tough questions, perhaps—then come up with the answers that are probably not industry standard answers, but practical answers.”

InterGen is an independent power company whose plants have high levels of autonomy in operational decisions. Therefore, Swire explained, “there’s a lot of responsibility placed on individual sites and individual managers to make things happen.”

The most important thing for the Rocksavage team to understand, Taj said, was that “you’re not at the mercy of somebody else. You can do things. You just have to reach out to the right people and evaluate your options.”

That’s exactly what they did. Swire first contacted Dutch company Thomassen Energy about the possibility of reverse engineering parts for an EV combustor. But when he shared pictures of the damage (Figure 1), they shook their heads. Certain parts could be manufactured, but they couldn’t make an entirely new one. Swire and Taj then wondered, could they obtain an original combustor?

1. Damage to the high-pressure blades caused by the molten environmental (EV) combustor material. Courtesy: InterGen

The particular Alstom GT26 model used by Rocksavage was one of only a handful still in use worldwide. Swire and Taj began following a global trail of breadcrumbs as they searched for parts. Swire reached out to Thomassen, which suggested he speak with SS&A Power Group in Switzerland, where an engineer connected him with the Dock Sud power plant in Buenos Aires, Argentina. Swire sent the borescope images to Dock Sud. Dock Sud sent back photos of the exact components Rocksavage needed.

“That was a major breakthrough,” Swire said, but it was only the beginning. The parts had been in storage for years, and in use at Dock Sud before that. Were they in good condition? Would they fit? Would they function?

Taj and Swire were aware they were taking a risk. As far as Taj knew, no other power plant had ever attempted to repair a gas turbine using original secondhand parts.

It was a pragmatic decision. With their combined expertise, they knew they could adjust, modify, and repair the parts while ensuring the best standards, clearances, and tolerances. “We are confident that some things will be right, but we will deal with the problems as they come,” Taj told the Rocksavage team.

Parts planning was only one piece of the puzzle; resource planning and scheduling was the other. The people they needed to assist with the work were busy with scheduled outages (many of them deferred because of COVID). The OEM also played a crucial role, as it possessed the knowledge and history of the Dock Sud components and the resources that would be required. The Rocksavage team faced a long list of what-ifs—and a ticking clock.

The Team Leaps into Action

The first order of business was inspecting the spare parts at Dock Sud. Independent engineers from SS&A and the OEM flew to Buenos Aires along with Chris Bailey, maintenance and reliability manager for Rocksavage. The team examined the parts and on first inspection found no significant mechanical defects. Most importantly, the components were compatible with the Rocksavage GTs. The plan was a go.

Meanwhile, Rocksavage sought to obtain a different part from the OEM’s main GT store: the plant’s old EV rear wall, which had been stored there. Swire flew to Switzerland to inspect it, and the part was brought to the UK after assessment and refurbishment. Other parts were made by third-party manufacturers, machine shops, and the OEM.

On July 21, a GT24 crew from the U.S., led by Swiss engineers, arrived at Rocksavage to strip and inspect the gas turbine (Figure 2). As they completed their work in late August, Swire hoped to keep them in England to assist with rebuilding the GT. “The worst thing you want to do,” he said, “is have everyone leave site with one of your gas turbines in bits and no real sight on when you’re going to rebuild it.”

2. Rotor removal underway as part of the strip and inspect phase. Courtesy: InterGen

Of course, that’s exactly what happened. The team had already committed to returning to the U.S. to work on a planned outage, so they had left by the time the parts arrived from Argentina on Oct. 4. A UK-based crew was found, and the work of rebuilding began.

“Every day was a raft of on-the-hoof decisions and ad hoc engineering,” Swire said. As winter neared, the team pulled together to get the job done efficiently. The reassembly was completed Nov. 25. With excitement and trepidation, they powered up the turbine. GTB was back in action—six months ahead of even the most optimistic original schedule.

Swire’s advice to any plant manager in a similar situation: Don’t go it alone. “Reach out to other independent power service providers, and owners and operators of similar plants and equipment,” he said. “Engineers always want to assist and love a challenge!” That’s exactly what Taj does in his consulting work. “We thrive on being the pragmatic solution provider,” he said.

The benefits of their approach included improved quality, lower costs, and significant time savings. They demonstrated that Rocksavage was a reliable and profitable asset, thus increasing the chance of future investment in the plant, including hydrogen fuel upgrades. Rocksavage returned to full generation capacity just in time to deliver vital energy to the people of the UK—helping to keep the lights on during the depths of winter.

1-Lower-half-EV-Combustor-with-the-blow-back-damage-evident 2-RCA-Inspections-with-the-GT-Rotor-removed 3-used-ev-rear-wall-hood-cover 4-used-ev-lower-hood-rear-wall-assembly-including-burners 5-used-ev-combustor-front-segment 6-used-ev-outer-liner-carrier 7-used-ev-inner-liner-carrier 8-newly-rebuilt-EV-CC-Rebuild-Unit 10-Ready-to-roll-Rebuild-completed
Paul Swire and Siraj Taj with the newly rebuilt EV & SEV combustor for pre-assembly measurements and alignment. Courtesy: ST Power Services

Melissa Barber ([email protected]) is a freelance writer.

SHARE this article