API-RP-576

4.7.1 General
A balanced safety-relief valve is a direct spring-loaded pressure-relief valve that
incorporates a bellows or other means for minimizing the effect of backpressure on the
operational characteristics of the valve. Whether it is pressure tight on its downstream
side depends on its design. See Figure 5 and Figure 6.
4.7.2 Applications
Balanced safety-relief valves are normally used in refinery and petrochemical process
industries that handle flammable, hot, or toxic material, where high backpressures are
present at the valve discharge. This typically occurs where material from the valve is
routed to a collection system. They are used:
• in gas, vapor, steam, air, or liquid services;
• in corrosive service to isolate the spring and the bonnet cavity of the valve from process
material;
• when the discharge from the valves is piped to remote locations.
Fion Zhnag/ Charlie Chong