This is a High Reliability dual poppet Pressure Relief valve used in certain applications that require the ability to test at full pressure between all O-rings. This is a pressure Relief valve that is configured just for that purpose
This is similar to PREVCO's Dual Poppet Pressure Relief Valve (PRV) in that it incorporates dual poppets to provide double sealing redundancy for high reliability applications. However applications that need to be able to meet API16D testable standards this pressure relief valve was designed just for that purpose. There is a separate fitting that bolts onto the top of the unit to hold the second Poppet in the sealed position while pressure is applied between the 2 poppets to insure proper sealing. Another test port is supplied to be able to test between the two interface O-rings where the PRV mounts to the enclosure or device.