A 36” general service water valve had failed in the open position. Unable to close the valve, plant maintenance could not service a failed pump. Additionally, the failed valve was in a very tight valve pit with only a few feet from a 54” common header to the inboard flange of the valve. This space would not allow for use of our more robust pivot head linestop head so folding head was the only option. The GSW line was operating at 110psi and ambient temperature.
RJ Stacey worked with the client to find an appropriate fitting and tooling design to allow a folding head linestop to be performed safely in the restricted space available. Once an appropriate fitting was approved and welded to the pipe, our overbore linestop valve was installed and a 36×24 hot tap completed. Next, the folding head linestop machine was attached to the linestop valve and indexed into the pipeline. Once residual downstream pressure was bled off, the failed 36” valve was removed and replaced, by maintenance contractor. The final step of the project was to set a completion plug and recover our linestopping valve. Upon completion of the project the only thing left attached to the pipeline is the welded 36×24 fitting with a completion plug inside the nozzle and a blind flange cap for safety.
The linestop allowed for temporary isolation of the 36” pump isolation valve. Once this was completed the client could service the 36” pump without a plant-wide water outage of the 54” common header. The operation saved the plant from a total outage which would have been required to regain service of the 36” pump otherwise.