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Heating Systems - Safety Valves Size vs. Boiler Power

Safety valves with boilers ranging 275 to 1500 kW.

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Fired pressure vessels shall be fitted with safety relieving devices with sufficient capacity to relieve all vapor that may be generated in the vessels during normal operation. The safety relieving devices shall be fitted with proper controls to ensure safe operation.

Boiler rating
Minimum clear bore
of safety valves and vents
275 1 x 20
350 1 x 25
440 1 x 32
530 1 x 40
880 2 x 40
1500 80 to 150

Note! Check domestic regulations - Safety Valve Standards

  • 1 kW = 3412 Btu/h
  • 1 inch = 25.4 mm

Safety valves should be removed at least once each year for inspection and cleaning of any deposits that might affect their operation.

To eliminate the necessity of shutting the system down for the inspection, a three-way stop valve may be installed under 2 safety valves, each with the required relieving capacity, installed so that both safety valves cannot be closed off from the vaporizer at the same time. Alternatively may 2 or more separate safety valves be installed with individual shutoff valves, in which case the shutoff valve stems is mechanically interconnected in a manner that allow full required flow capacity at all times.

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