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Butterfly Valve Overhaul & Coating

Mechanical overhaul and coating of rotary strainer including the casting in of the seal lands.

ANALYSIS

Client : British Energy Generation Ltd

Location: Dungeness B Power Station
Work undertaken: Mechanical overhaul, glass flake coating, rebuild & pressure test

BP Strainer

Part of the work undertaken by the RPM Group during the 2003 outage at Dungeness B Power Station was the overhaul of four 72" nominal bore Butterfly valves. The valves had been removed during an earlier outage but had not been overhauled. This was the situation with barely eight weeks to go before the valves would be required for the 2003 outage. A preliminary inspection on site showed that at least three of the valves had previously been fitted with stainless steel trim and as such would probably not require the major expense or, more importantly, the lengthy lead time required to manufacture new trim. With this in mind RPM were able to confidently predict that they could strip down the valves into their component form and refurbish them, including coating repairs and the manufacture of any spares.

As expected the three stainless trimmed valves only required replacement shaft bearings and thrust discs which were manufactured from a self lubricating composite material suitable for seawater duty. The valve bodies and blades were grit blasted to remove and any loose / damaged coating and areas of localised damage filled An overall top coat of glass flake filled coating was then applied.

BP Strainer

The fourth valve had bronze trim which was in a poor condition having suffered from erosion corrosion. For cost considerations, it was decided not to go ahead with the manufacture of replacement stainless trim at this juncture. Instead the best of the valves being replaced, which had by now been removed at the start of the outage was sent up to Kellington for partial strip down and coating repairs, with particular reference to the erosion damage to the blade rim. The four valves were rebuilt, fitted with new EPDM rubber seals and hydraulically pressure tested before being delivered back to site. Whilst the short time frame prevented some preferred modifications from being carried out, such as changing over to countersunk socket screws rather than studs and bolts on the seal clamp ring, the valves were back on site on schedule. To achieve this refurbishment RPM utilised a combination of in house facilities and specialist subcontractor services, the very foundation on which the RPM service is built.

Why RPM

  • In-house or on-site application
  • Steel or concrete substrates
  • Fast response by skilled, committed experts

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