The valve is weight operated to achieve both set opening point and sealing force. With ERL's unique patented compound lever design, we are able to use 8% of the weight required by other makes of weight operated valves for a given set point. This makes testing and servicing of the valve safer and easier.

    Another unique feature of the design is non-linear closure force. This approach provides full set point sealing force with the Seal Plate Assembly closed. When the Seal Plate Assembly opens, the force required to maintain it in the open position decreases dramatically. Increased flow rates at reduced pressure drops, even below set point pressure, are benefits of this design.

    In an overfill condition internal cargo tank, pressure increases instantly. When increasing tank pressure reaches the MSRV Set Point, the Seal Plate Assembly will open to accommodate a flow rate equal to the loading rate to the compartment being protected. Since the valve is totally automatic, the Seal Plate Assembly will close and re-seal vapor tight when loading to the compartment is terminated.

    The operation of this valve is simple. The seal plate seals the valve opening with the closing force required to achieve the proper set point. This force is applied to the seal plate by the clamp arm, which is pulled downward by the operator. The operator is simply a set of levers, which amplify the force of the set point weights. Therefore, the valve will stay sealed at all times, unless pressure builds up in the tank, up to set point. At set point, the upward force applied to the seal plate by the cargo or vapor is great enough to overcome the downward force generated by the set point weights and the valve is allowed to open. Once the valve opens, the liquid can pass through the 12" orifice as long as the tank pressure remains at or above the set point. Once the pressure drops below the set point, the valve re-seals automatically.