Model PAF450 incorporates a 10” (254mm) reclosing pressure relief valve (PRV) mounted to a center mount 20” (508mm) clamp ring style manhole. It includes a P/V normal vent. The PRV cover also serves as a quick open inspection hatch that incorporates a secondary safety catch. The manhole and clamp ring are certified and marked in accordance with 49CFR178.345-5 with a test pressure of 36 psig.
The PAF450 was legal for installation on US DOT MC306 cargo tanks prior to August 31, 1998. Per 49CFR180.405(h)(2), a properly functioning PAF450 can be repaired and maintained but if the entire assembly needs to be replaced, it must be a PRV that meets the less-than 1 liter surge leakage requirement of 49CFR178.345(b)(3)(ii). Therefore, Model PAF450 is NOT permitted as a replacement on MC306 or DOT406 cargo tanks but can be installed on non-specification tanks or on tanks built and operated in countries where regulations permit.