Life renewal of 15 t needle valve

During the 2014 routine refurbishment of a 60-year-old 60′′ diameter scour needle valve at SSE's Quoich Dam in the North West Highlands of Scotland, it was found that the inlet casing had deteriorated beyond repair and required replacing. The valve inlet casing was severely corroded, deeply pitted and the internal stay vanes were found to be cracked. This was considered to be due to over excessive vibration during partial openings of the valve over an extended period of time. Different options were researched to provide a life renewal for the 15 t valve, most involving the installation of a new replacement. The solution adopted was to recast the 5 t inlet casing using a UK foundry and machine workshop and all remaining salvageable parts of the valve being suitably refurbished. This paper describes how a change of material properties and minor alterations to the internal geometry of the inlet casing provided a cost-effective solution and increased the life expectancy of the needle valve.