ONLINE LEAK ARREST IN VALVE: A CASE STUDY

摘要

Pipeline integrity is essential for reliable pipeline operations, for preventing expensive downtime and failures resulting in leaking or spilling oil / gas content to the environment. Leaks can cost industries millions of dollars in loss of energy, while increasing emissions, creating safety hazards, and lowering the reliability of operations. Valves and piping systems can fail in a number of ways. Pipelines are widely used for transportation of fluids like oil & natural gas over long distances to the power plants, public supplies and various industries due to safety, efficiency and low cost. High pressure pipelines are generally buried below the ground level for safety, economic and environmental purposes. For smooth and safe operation of pipeline, there are some associated facilities underground as well above ground facilities like Valves, IJ, Fittings, Launcher & Receiver known as pipeline system. To maintain the integrity of the pipeline system, these facilities need periodic maintenance for their effective operability up to their design life. Valves are one the critical component of the pipeline system and failure of it may cause serious hazard and reduce the control over the various parameters like flow & pressure in the pipeline. Shutting down to repair the leak means a loss in associated industry's production leading to revenue loss. Darod - Jafarabad Pipeline (DJPL) is one the Natural Gas Pipeline laid by Gujarat State Petronet Limited (GSPL) to transport natural gas in the coastal region of Saurashtra in Gujarat. DJPL is a 212 KM long pipeline with 10 nos. of SV stations. There was leakage observed from bolted body of Ball Valve installed at Intermediate Pigging Station (IPS) and SV-6 of DJPL and these valves are butt welded and in upstream side which need shutdown of pipeline for maintenance or replacement. Maintenance of valve becomes critical, if there is gas leakage from valve body and the pipeline operation cannot be obstructed due to commitment with downstream customers. In such a situation, Stopple-in is the method to isolate the valve without obstructing / shutting the flow in the pipeline. The valves were in upstream side wherein replacement of valve was done by Stopple-in and Cross plugging method. However, gas leakage was from valve body so that hot work (i.e. pipe cutting) for stopple-in was also a challenge. To arrest the leak from bolted section of valve body, sealant injection methodology was adopted. Before applying this technology on high pressure live pipeline, GSPL insisted to perform the demonstration on prototype arrangement. This prototype was manufactured in the way that it has a manmade leakage point. After sealant injection in the system to arrest the leak, system was kept under high pressure of 55 Bar(g) for 24 hours. During demonstration, system sustained the pressure without any failure at leakage point. After successful demonstration, said methodology applied on leakage valve installed on high pressure line without any shutdown to arrest the leak.