Bidirectional sealing ball valves in power applications

摘要

Ball valves have become common place in high pressure steam and water service in power plants. However, it is critical that these ball valves be installed in the correct flow direction. If pressure comes from the downstream side, valve damage could result. There are also examples where valves are installed in the correct flow direction but under certain conditions, pressure is applied from the reverse direction. For vents and drains, this could happen if several valves discharge into a common header such that this header becomes pressurized while one of the valves has no upstream pressure. In addition, when equipment is installed in parallel for redundancy, the inlet and outlet isolation valves could see reverse pressure when closed. This may be applicable for feed water heaters, feed water pumps, control valves or bypass valves. In these cases, a bidirectional sealing valve is necessary.