For permitted non-DOT applications. Do not use this assembly as a replacement on MC306 or DOT406 cargo tanks. Weld collar sold separately.
The Betts FVA9720BXB PAF450 20-inch manway assembly combines a clamp-ring manhole cover with a 10-inch reclosing pressure-relief valve and a pressure/vacuum normal vent. The relief cover also opens for inspection, allowing access through the smaller central hatch without removing the complete manhole assembly.
This configuration has zinc-plated steel for the manhole cover, strongback, and latch, aluminum relief-cover and vent components, and nitrile (Buna-N) seals. Select it by the existing manway size, tank application, and compatibility of the seals with the contents. It is the standard-latch assembly; a self-latching mechanism is an optional configuration.
Inspection access and pressure relief in one assembly
The secondary safety catch provides an intermediate catch for the inspection cover. The included normal vent serves the tank's routine pressure/vacuum venting needs, while the larger valve provides reclosing pressure relief. Neither feature replaces checking the tank's required relief capacity and permitted equipment specification.
| Feature |
Benefit |
| Central inspection hatch |
Access the tank through the relief cover without removing the full clamp-ring assembly. |
| Secondary safety catch |
Provides a second catch position when opening the inspection cover. |
| Reclosing relief valve |
Returns toward its closed position after a pressure-relief event. |
| Replaceable seals and components |
Allows worn parts to be serviced using compatible genuine Betts replacements. |
Technical specifications
| Specification |
Detail |
| Manufacturer part number |
FVA9720BXB |
| Model and nominal manway size |
PAF450; 20 inches |
| Relief valve size |
10 inches |
| Cover, strongback, and latch |
Zinc-plated steel |
| Relief cover and normal vent |
Aluminum |
| Seal selection |
Nitrile (Buna-N) |
| Minimum relief set pressure |
3.0 psig |
| Rated air relief capacity |
375,000 SCFH at 5 psig |
| Rated water relief capacity |
1,434 gpm at 5 psig |
| Manhole and clamp-ring test pressure |
36 psig; this is a test value, not a tank operating-pressure rating |
Assembly and installation components
| Component |
Selection |
| Included assembly |
Manhole cover with relief-valve mechanism, normal vent, seals, and clamp-ring hardware. |
| Weld collar |
Excluded; select separately to match the tank shell material and manway dimensions. |
| Self-latch conversion |
Optional 6807SL-KIT1; not included in this standard-latch model. |
| Additional inbreathing vent |
The FVA configuration does not include the separate vent supplied with the FSA-prefix version. |
Before ordering
Have the installer inspect the existing collar and clamp-ring arrangement. A distorted, corroded, or damaged sealing surface can prevent proper seating. Use a collar that stays flat and round after welding, and verify that the gasket is compatible with the carried product.
| Check |
Requirement |
| Tank specification |
Confirm this non-DOT assembly is permitted for the application; it is not a replacement assembly for MC306 or DOT406 tanks. |
| Fit and seals |
Confirm 20-inch nominal size, collar condition, seal compatibility, and required relief performance. |
| Installation |
Follow Betts EB-01-08 for seating the clamp ring and final fastener torque; a visible gap must remain between ring ends. |
| Clamp integrity |
Inspect to EB-08-25; remove from service any ring with damaged welds, distorted clips, or contacting ends. |
| Service safety |
Safely relieve residual tank pressure and address fall, pinch, and cargo-related hazards before work. |
| California warning |
Chromium (hexavalent compounds) exposure can cause cancer and reproductive harm. See P65Warnings.ca.gov. |
Need help confirming the correct assembly? Contact UnitedBuilt through online chat, email parts@unitedbuilt.com, or call 602-253-7750 with your tank specification, manway size, and existing assembly number.
