The setting philosophy and safety function of emergency block valves in modernized large scale refinery and chemical plants is presented.

The safety protection systems include slam shut system,control system for liquid level of low-temperature gasholder,linkage system for outlet gas temperature of air-heated vaporizer,gas temperature control system after water bath heater and so on.

Engineers have to think highly first on the cause and effect analysis while designing on safe protection of manufacture equipments,with full consideration of all the factors resulting in potential accidents,taking reasonable measures on shut down and off-work,trying all means to avoid frequent on and off works of the devices and narrow the influence area resulted from the emergency shutdown.

Aiming at avoiding high risks at sour gas fields,a reasonable emergency shutdown scheme should be worked out to timely introduce safety protection system in case of emergencies.