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  • Integral Relief Valve / 10″ Fill
  • Less than 1 Liter Leakage
  • Increased Flow Rate
  • Secondary Safety Hatch
  1. Pressure Relief Valve setting 3.63 psig
  2. Rated Pressure Actuated Emergency Venting: 494,084 cu. ft. free air per hour @ 6.25 psig
  3. Rated Liquid Flow Capacity 1335 gpm @ 5.0 psig

PAF manholes with integral latch style surge suppression relief valves are designed for use on DOT406 and replacement on MC306 specification cargo tanks. Manholes are certified and marked in accordance with 49CFR178.345-5 with a test pressure of 36 psig. Manhole covers are 6 gauge stainless and are secured to the tank weld collar with a clamp ring and bold 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 6496ALB 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 self-latching model substitute L742 for L716 in assembly number.


Cover Plate Relief Valve Clamping Ring, Bolt, Washer, Strongback & Latch Clamping Ring Nut Normal Vent Weight Part #
Steel Zinc Plt. Alum. Steel Zinc Plt. Brass Alum. 24.2 PPVL726BXB
Stnls 304 Alum. Stnls 304 Stnls 304 Alum. 24.7 PPVL716CXB
Stnls 316 Alum. Stnls 304 Stnls 304 Alum. 24.7 PPVL716DXB

NOTES: Manhole assemblies, as listed above, have Buna-N gaskets (suffix "B").
For variation in gasketing change the last letter of assembly number as follows.

Suffix "V" indicates Viton collar gasket & Viton 10" fill gasket

Suffix "W" indicates White Hypalon collar gasket & white Hypalon 10" fill gasket

Suffix "T" indicates Teflon envelope collar gasket & Tef-Sil 10" fill o-ring

Manhole collars are available in aluminum steel and stainless steel. Please see parts page for correct numbers.
When welding collars to tank, care should be exercised to insure collar remains flat and round.


For the black lid only, Part #7509ALBN