Weir Engineering Services (WES) has partnered with a UK based power station as part of a project to convert their plant from a coal-fired to a biomass-fired power station which will allow the plant to supply the National Grid with up to 390 Megawatts of low-carbon electricity.

The project included the extensive overhaul of 11 butterfly valves and gearboxes in a variety of conditions, having been repaired by several different companies over a number of years. Some of the valves had been left untouched since their installation around 40 years ago (when the plant generated electricity from coal).

The quality standards requested by the customer required an extensive report of the differences found, detailing defective, worn or damaged components, along with the proposed repair strategy.

After the process of stripping down, cleaning and inspecting, (including non-destructive testing), the team noted that most of the coating was worn and in some cases had peeled off completely. Actuator mountings on the gearboxes and gearbox housing had also suffered severe corrosion and would require considerable work to repair.

Each of the valves had their own specific issues and therefore required a custom solution to cater for the variety of dimensions for each of the disc and shaft seals.

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The WES team measured each body and disc to calculate the required seal dimensions. The bearing trunnion housing of the valves had been machined out over the years and replaced with different solutions, again all solutions were custom. The shafts had also suffered from wear due to the ingress of debris from failed shaft seals.

The team machined them back and re-sprayed metal surfaces to recover the required design dimensions. Additionally, the customer agreed to a standard size to repair, or removed the helicoils of the valve body flange holes, which had been fitted in different sizes and locations on valve flanges.

In addition to the 11 butterfly valves and gearboxes, the team completed and restored a variety of equipment including: 42 turbine valves, three lid assemblies, three in-situ seat replacements, 48 onsite overhauls of valves, seven condensate extraction pumps, seven booster pumps, two CW pumps; and one start and standby feed pump.

Throughout this three month process the team ensured each of the customer's needs were met and delivered in line with the high quality standards expected. This resulted in the power station having fully overhauled valves fitted for a further 10 years of power generation.

WES was delighted to be supporting their customer by delivering such a crucial service to their processes. This power plant is important, not only to WES as a customer, but the UK as a whole, as it sources sustainable renewable fuel such as wood pellets - which deliver greenhouse gas savings to bring electricity to the UK.

The customer was continually impressed by the flexibility and innovation shown by the WES team. Each time the outlook of the project changed, the team continued to adapt to support them as it was required.

Although this project is complete, the team continues to work with their customer to identify methods of improving their processes and supporting them in meeting the plant's objectives of supplying 390 Megawatts of low-carbon electricity to the National Grid.

At the conclusion of the project, Brian Fairley, Supervisor at Weir, commented: "We're proud to have met the challenges posed by the project and delivered for our customer." And James White, Contract Engineer, explained: "The differences found in the valves made the spares identification and manufacturing a serious challenge. However, we've delivered a very successful result for our customer and were delighted to do so."