Challenge: A CAMERON fully welded ball valve in buried service had been damaged during commissioning from improper cleaning and needed to be replaced. The nearest valves in either direction of the pipeline from the valve were approximately 20 km away. In order to avoid excessive blow off gas, two isolation valves were installed close to the ball valve that needed to be repaired. For additional safety, two inflatable plugs were installed between the isolation valves and the ball valve. To allow access of the lifting crane onsite, additional concrete and gravel was poured to support the crane and underlying pipe. The buried service necessitated that three holes be dug to access the damaged ball valve and the two isolation valves. In order to achieve full isolation, hot tapping of the pipeline was required. The inflatable plugs also required an additional nozzle, which was realized by hot tapping as well. The process to hot tap a pipeline is very involved, and few companies are equipped to handle such a process, therefore the procedure was subcontracted to a company in the area.
Solution: Once all safety measures and support features were in place, the process of removing the damaged ball valve could proceed. The valve was lifted with the crane, the actuator removed, and special portable rotating cutting equipment was used to cut the pipeline on either side of the valve. The process of cutting the pipeline had to be done with care, as every cut would cause the pipe to shift slightly. Additionally, the heat of the sun on the black pipe caused it to expand as the job continued, necessitating more adjustments to the cutting instrument. To finish the process, flame cutting was utilized. Once the pipeline was cut, the valve could be lifted out of the line and a new CAMERON fully welded ball valve, which had been previously delivered by the Cameron team, was installed.
Result: Radiographic examination of the welds between the new valve and the pipeline showed that the process had been successfully carried out by the Cameron installation team. In all, the entire process stopped gas supply for only four days; significantly less than it would have taken had the valve been a split-body design in buried service. The overview and supervision by a Cameron Service Engineer for commissioning and start-up would have helped avoid this problem upon install, but the Cameron team was still able to help the customer get their line up and running with creative problem solving and valve expertise.