A zero relief device is required when rupture discs are connected in series with safety valves and consists of a pressure gauge, relief valve, tee, and receiver. Used between the safety valve and the rupture disc, or in other confined spaces where backpressure is to be removed.
According to API 520, ASME VIII, ISO 4126, GB567, GB38599, a relief valve and pressure gauge must be installed between the rupture disc and the safety valve to ensure proper rupture.
