Betts PAF manhole with integral 406-98 Surge Suppression Pressure Relief Valve is the proven leader for cargo tank longevity, protection and safety.

The 406-98 incorporates a 10” (254mm) reclosing pressure relief valve (PRV) that satisfies primary pressure relief for specification US DOT406 and TC406 cargo tanks.  The PRV meets the dynamic pressure surge requirements of 49CFR§178.345-10(b)(3)(ii) with less than one-liter leakage as tested per TTMA RP No. 81.  The PRV cover also serves as a quick-open inspection hatch that incorporates a secondary safety catch. PPVL models include a 6496 P/V normal vent.

The offset 20” (508 mm) clamp ring style manhole has provisions for mounting a bolted style vapor recovery valve and liquid level sensor. Manhole and clamp ring are certified and marked in accordance with 49CFR178.345-5 with a test pressure of 36 psig.

PAF 406-98 is also available in a self-latch model by designating part number L863 in place of L820. On self-latch models, a stop bracket holds the PRV at a 91° position; if the cover is inadvertently left open, movement of the tank will cause PRV cover to drop and catch to a semi-closed position.

PAF 406-98 PRV must not exceed a maximum temperature of 212°F (100°C).  Stainless versions of the PRV are available using prefix “PPSS”.  For replacement on MC306 cargo tanks, see Betts’ line of PAF306 surge manholes.