Probability of Fire during Rapid Opening of a Stuck-Close Ball Valve in Gaseous Oxygen System
SourceA ball valve used in oxygen pipelines may get stuck in a closed condition due to prolonged nonuse. Iron particles that are trapped in the gap between the ball and the valve seat bulge as they are converted to iron oxides in contact with oxygen and traces of moisture. Attempts to open a stuck valve quickly during emergency by applying manual torque may lead to an increase of temperature at some locations inside the valve that may well exceed the auto-ignition temperature of particles or nonmetallic parts. It increases the probability of ignition and fire in systems handling oxygen gas. The present work uses finite element analysis software to model a normally closed quarter-turn stuck ball valve that is forced open manually within a very short period of time. Tribology and heat-transfer models have been used to determine the final temperatures reached at the sealing gasket that is subjected to intense friction by the moving ball and trapped particles. Abaqus/Explicit was used to estimate the temperature and determine whether there is a possibility of exceeding auto-ignition temperatures under some conditions. It was found that opening a 150-mm-sized stuck ball valve within 2 s by applying high torque may heat up the seal and the trapped particles to a level that may lead to fire.