The outer shell and weather cover prevent the possibility of snow and ice buildup at the discharge nozzle. Should precipitations enter the focusing nozzle when the weather cover is open, it will simply drain to the outside of the valve through a group of drain holes at the base of the focusing nozzle.

The pressure sides of both valves achieve a minimum discharge velocity of 40 meters per second even at the lowest flow rates. This number is obtained due to the fine finish of the inner cone, smooth air flow path provided in the nozzle orifice and the accurately controlled weight operated opening mechanism. A damper is provided to prevent valve oscillations or chatter on both the pressure and vacuum sides of both P-V Valves.

Both ERL Superac 6" High Velocity weight operated P-V Valves operates automatically on both the High Velocity pressure side and the vacuum side of each valve. All of the operating mechanisms are located outside of the vapor exhaust stream. This is critically important since it eliminates valve sticking due to contaminant build up between shafts and bushings. The Superac design uses sealed stainless steel bearings at all pivot points, which greatly improves valve set point accuracy. This design creates a valve, which is repeatable to 3% of set opening point and has a total pressure increase of less than 10% from initial opening to the full open flow rate exceeding 18,000 barrels per hour on the pressure side. The weather cover can be either closed or open during operation. With this cover closed, the pressure side of the valve exhausts through a radial 30 x 30 mesh stainless steel flame screen. The portion of the cover over the vertical discharge section of the valve is hinged so that it may be opened to allow the high velocity flow to travel straight up in order to effectively get the vapors out of the deck working environment.

The focusing nozzle that directs this flow upward is similar in construction to a high velocity hose nozzle in that it incorporates both an inner cone and an outer focusing shell. This construction results in superior performance.