Series RVDT
Thermoplastic [PVC, Polypropylene, PVDF (Kynar) or PTFE] pressure relief valve [ 1/4", 1/2", 3/4", 1", 1 1/2" or 2"] NPT threads, is to be in-line ported with flat PTFE diaphragm, backed by Viton, as the primary seal. Adjusting bolt and lock nut are to be all plastic. Valve is to have Fail-DryŽ Safety Design incorporating a vented chamber between the flat diaphragm and a secondary elastomer diaphragm to protect the spring chamber. [Optional:] Manufacturer shall factory set the pressure relief valve at [between 5 and 100] PSI.

ADD: "With tamper-proof option" after pressure setting, if required.