Pressure Relief Valve setting 3.0 psig
Rated Pressure Actuated Emergency Venting:
250,000 cu. ft. free air per hour @ 5.0 psig
Rated Liquid Flow Capacity 1012 GPM @ 5.0 psig

PDF manholes with integral latch-style surge suppression relief valves are designed for use as replacements for PAF9000 model manhole assemblies on MC306 tanks. Manholes are certified and marked by 49CFR178.345-5 with a test pressure of 36 psig. Manhole covers are 7 gage steel or stainless and are secured to the tank weld collar with a clamp ring and bolt which can be easily removed to provide access into the tank.

The integral 10” relief valve provides emergency pressure relief and meets the 1-liter surge leakage limit imposed by 49CFR178.345-10(b)(3)(ii). The relief valve also serves as a 10” latch style fill which can be easily opened to provide access for filling the tank or for inspection. Relief valves contain an adjustment feature to allow for fine-tuning of set pressure in the field. Other standard features include a heavy-duty clamp ring, secondary safety latch, and model 6238ALB pressure-vacuum vent mounted in the 10” relief valve cover.

Manholes are available with a self-latching feature that allows the 10” relief valve/fill cover to drop and securely latch upon movement of the tank if the cover is inadvertently left open. For the self-latching model substitute R442 for R416 in the assembly number.