Preheater protection valves

In the event of a defective tube system these valves are designed to stop the feed of high pressure feedwater and to bypass it around a heater or a group of heaters in shortest time. Protection is achieved in the system by installing a  quick closing changeover valve in front of and a quick closing check valve behind the heaters in the pipework. The motive power is the feedwater pressure, so that the system is failsafe if either electric or pneumatic supplies fail.