The Greek operator Hellenic Petroleum needed T.D. Williamson (TDW) to create a safe working environment for its pipeline maintenance team to carry out repair works on a tower attached to a key gas line at its Aspropyrgos Refinery near Athens, Greece. TDW would provide this by completing a hot tap and STOPPLE plug intervention to isolate the tower for repair works.
The product flowing through the line was fuel gas at 5 barg, containing 5% H2S. The line would have to be cut, plugged and safely isolated without shutting down production. In addition, due to the highly corrosive environment, the entire operation was to be completed in just 48 hours.
With the customised equipment prepared, a standard STOPPLE plug and LOCK-O-RING Plus completion plug, TDW technicians set to work on the intervention. Working in close quarters at the refinery, the team proceeded with extreme precision to safely isolate the line within the 48-hour window. The hot tap proceeded on schedule, and the line was securely plugged in just 40 hours. With the gas line safely isolated, the valve replacement team installed the new valve. Throughout the isolation, pressure in the line was maintained at 5 bar and production continued. The entire operation – including setup, hot tapping, plugging, valve replacement, and setting the completion plug – was completed in nine days.