Pressure Relief Device

■  The Relevant Codes
     1. API 526, Flanged Steel Pressure-Relief Valves
     2. API RP 520, Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries
     3. API RP 521, Guide for Pressure-Relieving and Depressuring Systems
     4. ASME BPV, Section VIII, Divion 1, Nonmandatory Appendix M
     5. ASME B 31.1, Power Piping, Nonmandatory Appendix II

■  Definition of Pressure Relief Device
     A pressure relief device is actuated by inlet static pressure and designed to fully open
     during an emergency or abnormal conditions to prevent a rise of internal fluid pressure
     in excess of a specified value.
     The device also may be designed to prevent excessive internal vacuum.

■  Type of Pressure Relief Device
     1. Relief valve
         A spring-loaded pressure relief valve actuated by the static pressure upstream of the vlave.
         The valve opens normally in proportion to the pressure increase over the opening pressure.
         A relief valve is used primarily with incompressible fluids.
     2. Safety valve
         A spring-loaded pressure relief valve actuated by the static pressure upstream of the valve
         and characterized by rapid or pop action.
         A safety valve is normally used with compressible fluids.
     3. Safety relief valve
         A spring-loaded pressure relief valve that may be used as either a safety or relief vlave
         defending on the application
     4. Balanced pressure relief valve
        A spring-loaded pressure relief valve that incorporates a means for minimizing the effect of
        back pressure on the performance characteristics
     5. Rupture disk device
        A nonreclosing differential pressure relief device actuated by inlet static pressure and desinged to
        fuction by bursting the pressure-conntaining rupture disk.

■  Open Discharge Installation
     An installation where the fluid is discharged directly to the atmosphere or to a vent pipe that is
     uncoupled from the safety valve.

Where, L ≤ 4 * Do, M ≤ 6 * Do