The Series 400 modulating valve, with nonflowing pilot, incorporates an advanced design in pilot operated valves. Under process conditions, both pilot and main valve can be tight to as high as 98 percent of set pressure. The main valve lifts proportionally according to required flow (relief demand), restricting product loss to only the mass required to be relieved to prevent process pressure from exceeding the code allowance.

Well suited for gas and/or liquid services, including dirty and/or wet services. The modulating action is strongly preferred for liquid relief because it minimzes the destructive effects of "liquid hammer".

Available with effective orifice areas of 0.110 to 63.50 in² [0.710 to 409.7 cm²] valve inlet sizes 1" to 10" [25 to 254 mm], set pressure between 15 and 1480 psig [1.03 and 102.0 barg], and continuous service temperatures from -65°F to +600°F [-54°C to +315°C].