Check & Relief ValvesA valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically valves fittings, but are usually discussed as a separate category. V66 Catalog 2D / 3D Spec. Working Pressure : 6,000 psig Cracking Pressure : 220 to 6,000 psig -18 to 400℉ (-28 to 204℃) Stainless Steel with FKM seals DK-Lok 1/4 to 1/2 in. OD Pipe thread 1/4 to 1/2 in.Brief Description Install the valve between the pump outlet as close as possible, and any shut-off device in the discharge line. The preferable mounting position is vertical with the adjusting cap at the top. By-passes the system fluid to porevent instrument or sensitive gauge in the system from excess pressure. When the inlet pressure overcomes the set spring pressure on th poppet, the poppet lifts off the valve seat,allowing flow to pbypass and thereby balance the system pressure.