Five valves were found to be seized by the main contractor during a refurbishment project on a service reservoir. Two valves were scours, two were the reservoir outlets and one was a line valve, all apart from the line valve were 6 meters deep and situated in the reservoir tanks.
Replacement of the valves would have incurred lengthy planning to ensure safe isolation along with possible intervention of mechanical line stops. The size and weight of the valves prevented removal without a review of the reservoir roof condition, loading and access restrictions.
HydroV valve release equipment was used for an initial period of 80 minutes. During this operation, the frequency was measured at the valve itself to determine any losses. The valve became free and was cycled using a standard tee bar arrangement. The spindle extensions were removed from the remaining valves to maintain efficiencies and the following release times achieved:
Three spindle extensions were deemed not fit for purpose. These were replaced completely with new wall brace supports.