The impulse safety  device is the main safety valve,  with auxil-iary  valve support contained. This  device has characteristics as  large discharge ability,  convenient adjustment,  dual mechanical  and electric protection and few workload in installation and maint-enance.
         This device is used for inlet  and outlet pipe of reheater to avoid mediun pressure exceeding the allowable value to ensure the reheater shall  run safely.
        1.The impulse safety device  is as shown in the  figure, mainly consisted of impulse safety valve,  the main safety valve, stop valve  and throttle valve.  Impulse safety valve  is a kind of  spring safety   valve. It is mainly consisted   of  body , bonnet, disc and other parts.The impulse safety valve can  be adjusted by using the spring to regulate the pressure.
          The impulse safety  valve contains an electromagnet  to open and another to close  the valve. The actions  of the mechanism and the electric   appliance are separate and will not  affect each other .
          2.The main safety valve is as shown in the figure.  With astructure of single exhaust and both ends of flange connection, it is  mainly consisted of body, bonnet, piston chamber,  disc, stem and  other parts.
          3.Both the sealed surfaces of  disc and seat of  the impulse  safety valve are made of hard alloy of cobalt by overlaying welding Both the seat and the disc of the main safety valve  are made of   hard alloy of  cobalt by plasma spray welding.
         4.The upper part of  the impulse safety valve  contains an elec-tromagnet to open and another to close off.   At  ordinary times, the close-off electromagnet  may not be electrified, but when the sealed surface of the valve leaks or when the mechanical  addition adjusting   reseating pressure is excessively low,   it can be electrified by closing  electromagnet to make valve sealed or  help the valve clack return and procure a higher seat reseating pressure.
         5.The impulse safety valve only leaves the factory after  it has passed the seal  and sensitivity tests,  proved to be qualified.
         When the medium pressure inside the reheater exceeding the allowable value, the impulse safety valve opens firstly; the steam enters into the piston chamber of the main safety valve, forcing the main safety valve to open; the reheater bengins discharging steam;after the excess pressure has  been released, the  impulse safety   valve closes, stopping the steam entering  into the piston chamber of  the main safety valve; the main safety valve automatically colses at the reactions of the spring and medium.