The Relief Valve is actuated by the system pres sure on the inlet side of the valve. Valve loading is provided by a spring. The adjustment is done by removing the cap and rotating the screw clockwise or counter-clockwise. Spring load balances against the opening force of the up stream (or re lief) pressure. Valve will open at the slightest increase in pressure above the spring set point, and will close when the excess pressure has been relieved.
The higher the system pressure is above the relief set point pressure, the more flow the valve will pass. It is therefore typical to specify the maximum capacity of a back pressure relief valve at 10% and 20% over set pressure.
Pressure Adjustments
To adjust set pressure of valve, remove top cap, loosen lock nut and adjust pressure by rotating adjustment screw. Rotating the screw clockwise increases the compression on the spring thereby increasing the set pressure. Rotating the screw counterclockwise lowers the set pressure. Tighten the lock nut and replace top cap and gasket.