Description of Impulse Safety Device
 
1. Use
 The impulse safety device is used for power station boilers or 
 
pressure vessels to prevent the medium pressure from exceeding the 
 
allowable value to ensure their safety valve.
 
2.Characteristics
The impulse safety device works with an impulse safety valve and a main 
 
safety valve. This device has a large discharge ability with convenient 
 
adjustment, double mechanical and electrical protection and user-
 
friendly installation and maintenance.
 
3. Operation Principle
When the medium pressure is lower than the setting pressure, the 
 
impulse safety valve will be enclosed under the spring force, while the 
 
main safety valve will be enclosed under the medium pressure; when the 
 
medium pressure is higher than the setting pressure, the impulse safety 
 
valve will open and steam will enter into the main safety valve's 
 
piston chamber to open the main safety valve and discharge steam to the 
 
outside; when the pressure drops to the reseating value, the impulse 
 
safety valve will be closed to cut off steam going into the safety 
 
valve's piston chamber, and the main safety valve will be closed 
 
automatically as acted by spring and the medium.
 
4. Structure
  1. The impulse safety device is as shown in the figure, mainly 
 
consisting of impulse safety valve, main safety valve, stop valve and 
 
throttle valve.
 
  2. The impulse safety valve is a kind of sping or heavy hammer lever. 
 
The safety device's opening pressure can be adjusted by adjusting the 
 
spring compression or the heavy hammer position on the lever. Also the 
 
impulse safety valve contains an electromagnet to open or close the 
 
valve, with no interference between mechanical and electrical actions.
 
  3. The main safety valve is as shown in the figure. Its steam exhaust 
 
end adopt a flange connection form, and it mainly consists of body, 
 
cushion valve, piston chamber, disc and other parts. The valve adopts 
 
the pressure self tightening and sealed structure. The higher the 
 
medium pressure is, the better the sealability will be. The cushion 
 
valve serves as a buffer in the working process of the main safety 
 
valve to avoid the damage of the sealed surface and the disc.
 
 4. The upper part of the impulse safety valve contains an 
 
electromagnet to open or close. At ordinary times, the close-off 
 
electromagnet may not be electrified, but when the sealed surface of 
 
the valve leaks, it can be electrified continuously to make the valve 
 
sealed; or when the mechanical adjusting reseating pressure is 
 
excessively low, it can be electrified to help the disc return and 
 
procure a higher reseating pressure.
 
5. Installation Instruction
  1. The main safety valve and the impulse safety valve should be 
 
installed together. The distance between the outlet pipe of the impulse 
 
safety valve and the inlet pipe of the main safety valve should be 
 
maintained as relatively long and the distance between the electric 
 
contact pressure meter and the inlet pipe of the main safety valve 
 
should be no less than 5 times of the diameter of the inlet pipe,  of  
 
the  main  safety valve  should  be  no  less  than  5  times of the 
 
diameter of the inlet pipe  for  fear t hat  the  precision  of  the  
 
meter  and  the  impulse  safety  valve  may  be  affected by  the  
 
steam  discharging  process  of the  main  safety   valve.
  2. Before the installation of the main safety valve, the pipeline 
 
shall be cleaned first.
 
  3. The main safety valve and the impulse safety valve must be 
 
positioned vertically. After the installation and the welding of main 
 
safety valve, it shall be under partial heat treatment.
 
  4. The main safety valve shall be fastened upon the framework, which 
 
sustains the counter-reaction force produced in the steam discharging 
 
process of the mains safety valve. The exhaust pipe of the mains safety 
 
valve shall be supported with a special gallow lest the force of its 
 
weight and action would be directly apply to both the main safety valve 
 
and the flange that is connecting them. At the lowest point of the 
 
exhaust pipe, water drainage shall be taken into consideration to avoid 
 
producing water hammer when the main safety valve is discharging steam. 
 
The three loops of filling above the mains safety valve's piston 
 
chamber shall be deeply compressed until the lower surface of the 
 
filling gland touches the upper surface of the piston, and a fine wire 
 
shall be used to fasten the pressure bolt to avoid leakage and refusing 
 
release of the main safety valve.
 
  5. The impulse safety valve and the electromagnets shall be placed 
 
together on a special gallow. The juncture of the upper lever of the 
 
valve and the electromagnets shall be flexible, with no phenomenon of 
 
seizure. The impulse safety valve shall be installed in a place with 
 
little dust, dry air and convenient maintenance and debugging and where 
 
no vibration occurs. Its ambient temperature shall not be higher than 
 
70 Deg C, and its relative humidity not more than 80%.
 
  6. To ensure the agile working of the impulse safety valve, the 
 
distance between the circular arc part of the head of the seat 
 
returning lever and the end of the pressure bar of the valve shall be 
 
adjusted to such a length as the actual travel of the valve plus 1mm 
 
(adjusted by the M10 fastening screw at the top of the cap.)