Requirements for safety valves in steam generators

     1. For steam generator boilers with a rated evaporation capacity greater than 0.5 t/h, at least two safety valves (excluding economizer safety valves) shall be installed. For those with a rated evaporation capacity less than or equal to 0.5 t/h, at least one safety valve shall be installed. For hot water boilers with a rated heat output greater than 0.35 MW (30×10⁴ kcal/h), at least two safety valves shall be installed. For those with a rated heat output less than or equal to 0.35 MW (30×10⁴ kcal/h), at least one safety valve shall be installed.

          Safety valves must be installed at the outlets of separable economizers and steam superheaters.

          Boilers with a rated steam pressure less than 0.1 MPa shall use dead-weight safety valves or water-sealed safety devices.

    2. Safety valves shall be installed vertically and, whenever possible, at the highest position of the drum or header. No steam extraction pipes or valves shall be installed between the safety valve and the drum or between the safety valve and the header.

    3. The total discharge capacity of the safety valves must exceed the maximum continuous evaporation capacity of the boiler. Moreover, after all safety valves on the drum and superheater are opened, the steam pressure in the drum shall not exceed 1.1 times the design pressure.

         The discharge capacity of the superheater safety valve shall ensure sufficient cooling of the superheater under that discharge capacity to prevent burnout.

   4. Safety valves must be equipped with the following devices:

  ⑴. Spring-type safety valves shall have a lifting lever and a device to prevent unauthorized adjustment of the set screw.

  ⑵. Lever-type safety valves shall have a device to prevent the weight from moving on its own and a guide frame to restrict the lever from overtravel.

  ⑶. Dead-weight safety valves shall have a device to prevent the weights from flying off.