Installation Guidance for Boiler Safety Relief Valves

by Newgram

Considerations when sizing of relief valves for boiler system

    • 2 or more safety relief valves should be provided on boiler/s with heating surface greater than 50 m2 (500 ft2); otherwise comply with local regulation or adhered to international guideline/standard whichever more stringent.
    • Safety relief valves should be sized to operate up to >6% of the maximum allowable working pressure for high pressure boiler.
    • Isolation valve should not be installed on the relief valves.

Example: Maximum working pressure of the boiler system with heating surface of 60 m2 is 120 barg.

Safety relief valve to operate would be 120 barg + (6% x 120) barg = 127barg.

The second safety relief valve to operate should be set at the maximum working pressure of 120 barg.

Boiler system integrated super heaters

    • Safety relief valves for the boiler should be designed to provide relieving capacity of up to 75% of the relieving capacity (in kg/hr) of the boiler system.
    • Safety relief valves for the super heaters should be designed to provide relieving capacity of up to 25% of the relieving capacity (in kg/hr) of the boiler system.

Independently fired super heaters

The relieving capacity for the safety valves should be based on 2.7 Kg/0.1m2 of heating surface.


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