This larger category of relief valves contains many subcategories. In general, these are valves made to be used as relief devices on large stationary pressurized storage containers with flanged openings. Manifolds utilize an extra valve, which allows for repair or removal of any valve easily. The handwheel carefully closes the gateway to the relief valve being removed, while leaving the rest of the valves to continue to provide proper protection.The “pop-action” setup of a relief valve is what allows for highest protection and minimal product loss, even at relatively excessive pressure. A rubber plug and accompanying chain is provided to protect manifold outlet threads where the relief valve has been removed. The well-constructed relief valve seat disc gives what is called a “bubble-tight” seal. These relief valves are ASME rated for use with both LP-Gas and anhydrous ammonia.