The described situation happens from the inadvertent closure of a block valve or failure of a control valve in the closed position on an outlet line. Typical overpressure application, where this form of protection is required, includes production separators, compressor discharge piping, or pump discharge piping. The safety relief valves are sized to handle 100% of the anticipated upstream flow. If the feed stream is multi-phase, the relief rate is the total inlet flow (gas plus liquids).