3-Way Solenoid Valves
3-way solenoid valves have three ports and switch a common port between two others, which lets them do more than simple on/off: they can divert flow between two lines, fill and then vent a single-acting (spring-return) cylinder or actuator, or select between pressure and exhaust. In process automation the 3/2 configuration is the standard pilot for spring-return pneumatic actuators on ball and butterfly valves — energising the coil pressurises the actuator to drive it one way, and de-energising vents it so the spring returns it to its fail position.
Function is defined by the rest state and porting: normally-closed (pressure blocked, cylinder vented when de-energised), normally-open (pressure connected when de-energised), and universal/distributor types that can be plumbed as NC, NO, or selector. As with all solenoids, construction is direct-acting (coil moves the seal, works from zero differential, ideal for low-pressure piloting and small actuators) or pilot-operated (line differential shifts the main element for higher flow). NAMUR-mount 3/2 valves bolt straight onto the actuator's NAMUR interface, eliminating tubing.
Materials are brass, aluminium or SS316 bodies with NBR, FKM/Viton, EPDM or PTFE seals chosen for media and temperature; instrument-air piloting typically uses aluminium/brass. Ends are threaded NPT/BSP or NAMUR/sub-base. Coils are 24 VDC or 110/230 VAC in IP65/IP67 or ATEX/IECEx Ex d/Ex m enclosures for hazardous areas.
Because actuation is electrical, configuration centres on coil voltage, function (NC/NO/universal), direct-acting vs pilot-operated, NAMUR vs ported mounting, and enclosure/Ex rating rather than mechanical actuators — along with the fail-state the spring-return actuator must reach on power loss. Himalay's MSME partners manufacture 3-way solenoid valves with electrical and leak testing, IP/ATEX-IECEx documentation where specified, material traceability, and PED-CE (EU), SABER (Saudi Arabia), and NACE MR0175 (sour service) coordinated as part of the standard order flow.
