8.7　Auxiliary Systems of Boilers

8.7.1　The continuous blowdown and intermittent blowdown system of drum boilers shall comply with the following requirements:

1　The drum type boilers should adopt one-stage continuous blowdown flash system and the bypass for switching from the continuous blowdown system to intermittent blowdown flash tank shall be in place.

2　Each boiler should be provided with one blowdown flash system.

3　The intermittent blowdown flash tank shall have a capacity sufficient to accommodate the requirement for emergency water drainage of boilers.In cases where the calculated emergency water drainage of boilers is excessive,appropriate measures to limit the drainage flow should be consulted with the boiler manufacturer.

4　For drum type boilers with sub-critical parameters,continuous blowdown system may be eliminated if the conditions permit.

5　The intermittent blowdown flash tanks should be equipped with water-steam separator mounted on the steam exhaust piping.

8.7.2　The atmospheric steam exhaust of boilers shall comply with the following requirements:

1　The noises generated as a result of atmospheric steam exhaust of boilers shall comply with the environmental protection stipulations.

2　Silencers shall be installed on the atmospheric steam exhaust pipes of boilers and the steam exhaust pipes of pressure control valves.

3　Silencers shall be equipped on the drum safety valves and superheater safety valves with the lowest popping pressure,and on steam exhaust pipes of reheater safety valves of units with intermediatepressure cylinder start-up.Silencers should be provided on the steam exhaust pipes of other safety valves.