Indirectly actuated servo/pressure assisted solenoid valves are suitable to control high flows with a low power consumption. The valves consist of a main membrane (or piston) and a piloting system: typically a 2-way solenoid valve kit.

All the indirectly actuated valves are subject to the principle of the servo drive: they use the energy of the fluid input to open and close the valve seal (diaphragm). As a consequence, to operate properly, they require a minimum pressure differential between the inlet and outlet.

Valve closed
When the solenoid coil is not powered, the mobile plunger keeps the pilot hole closed. The pressure coming from the inlet and passing through the filling hole is pressurizes the upper part of the main membrane. Acting on a larger surface, the pressure exerts the necessary force to keep the valve closed.

Valve Open
When the coil is powered, the magnetic field produced can lift the movable core, opening the pilot hole. The pressure present above the membrane (piston) is thus gradually discharged towards the outlet of the valve. At this point when the force exerted by the fluid pressure on the lower surface of the membrane, is greater than the force exerted by the same on the top of the membrane, the seal, (diaphragm) is lifted up, and the valve opens.

Valve closed again
After switching off of the coil, the mobile plunger returns to the rest position closing the pilot hole.
Through the filling hole, the pressure rises in the upper par of the membrane to the inlet value. This grows the closing force of the membrane and moving the membrane back to the closed “rest” position.

Our most popular servo/pressure assisted solenoid valves are listed below.

Brass bodied solenoid valves

107 Series 2/2 Normally Closed - 207 Series 2/2 Normally Open - 117 Series 2/2 Bistable (latching)

Connections: 1/4", 3/8”, 1/2", 3/4", 1”, 1 ¼”, 1 ½”, 2”, 2 ½”, 3”
Threads: ISO G or NPT (on demand)
Voltages available: 12VDC; 24VDC; 24VAC; 48VAC; 120VAC; 230VAC (Others on demand)
Body material: Brass
Armature Material: AISI 303
Springs: AISI 302
Membrane material: EPDM, NBR, FPM and WRAS EPDM

AISI 316 Stainless Steel bodied solenoid valves

177 Series 2/2 Normally Closed - 277 Series 2/2 Normally Open 

Connections: 3/8”, 1/2", 3/4", 1”
Threads: ISO G o NPT (on demand)
Voltages available: 12VDC; 24VDC; 24VAC; 48VAC; 120VAC; 230VAC (others on demand)
Body material: AISI 316
Armature Material: AISI 303
Springs: AISI 302
Membrane material: EPDM, NBR, FPM and WRAS EPDM

N.B. The WRAS EPDM seal/diaphragm is a special order item. As such a 4 - 5 week lead is advised.