Solenoid Valve Buying Guide: Types, Specs & How to Choose the Right Solenoid Valve A solenoid valve looks simple on the outside — a coil, a body, a port configuration — but getting the specification wrong is one of the most common (and expensive) mistakes in process instrumentation sourcing. This guide covers what a solenoid valve does, the main types you'll choose between, the specifications worth checking before you order, and where certification like ATEX comes into play. Need help specifying or sourcing a solenoid valve for your site? Talk to Our Expert Team What Is a Solenoid Valve & How It Works A solenoid valve is an electromechanically-operated valve controlled by an electric current through a coil. Energising the coil creates a magnetic field that lifts or moves a plunger, opening or closing the valve orifice. Direct-acting solenoid valves move the main orifice directly and work from zero differential pressure; pilot-operated (or "servo-assisted") solenoid valves use the coil to open a small pilot orifice, which then uses line pressure to open the larger main valve — allowing much higher flow capacity from a smaller coil, but requiring a minimum differential pressure to operate. Types & Variants Variant Description Typical Use 2-way (NC) Normally closed, opens on energisation Most common — supply shut-off, dosing 2-way (NO) Normally open, closes on energisation Fail-safe-open applications 3-way Diverts flow between two paths or vents a line Pilot control of actuators, sampling systems Direct-acting No minimum pressure differential required Vacuum or low-pressure applications Pilot-operated Requires minimum differential pressure, higher flow capacity per coil size Higher flow, higher pressure process lines Key Specifications to Check Before ordering, confirm: port size and connection type (NPT, BSP, flanged), orifice diameter (governs flow — Cv/Kv rating), body and seal material compatibility with the process media, coil voltage and enclosure rating (IP65/IP67 for washdown or outdoor areas), pressure differential range the valve is rated for, and response time if the application is fast-cycling. Specification Checklist Item Confirmed? Port size & connection type ☐ Body/seal material vs process media ☐ Coil voltage & enclosure IP rating ☐ Pressure differential range ☐ ATEX/hazardous area certification if required ☐ NC vs NO fail-safe position ☐ Standards & Certifications For installations in hazardous areas — common across oil & gas sites — the solenoid valve's coil and enclosure need the correct ATEX (or IECEx) certification and gas group/temperature class rating for the zone it's installed in. Always confirm the certificate matches your site's classified zone, not just a generic "ATEX-rated" claim on a datasheet. How to Choose the Right One Start from the process media and pressure, not the coil — confirm body/seal compatibility first, then select direct-acting or pilot-operated based on your differential pressure and flow requirement, then confirm the electrical enclosure and any hazardous-area certification your site classification demands. Related Categories Category Description Link Valves Full valve range across solenoid, needle, ball and relief types View Category Pneumatic Equipment Pneumatic actuators and associated components View Category Frequently Asked Questions What is a solenoid valve used for? A solenoid valve provides electrically-controlled on/off (or diverting) flow control for gas, air or liquid lines, commonly used to shut off supply, dose fluid, or pilot larger pneumatic actuators. How do I choose between Emerson ASCO and Anderson Greenwood / Pentair solenoid valves? Emerson ASCO is generally the go-to for solenoid valve ranges themselves, while Anderson Greenwood / Pentair is typically specified for the associated needle, relief and manifold valves in the same process line — the two ranges are often specified together rather than as direct alternatives. What standards apply to solenoid valves (ATEX)? Solenoid valves for hazardous areas need ATEX or IECEx certification matched to the zone classification, gas group and temperature class of the installation. Can ZF Corporation source obsolete or discontinued solenoid valves? Yes — we regularly cross-reference discontinued ASCO solenoid valve part numbers to current equivalents for process line repairs and upgrades. What is the typical lead time for a solenoid valve in the UK? Common port sizes and voltages are typically available from stock; ATEX-certified or less common configurations may carry a short lead time — contact us with the exact specification for a quote. Conclusion Specifying a solenoid valve correctly comes down to media compatibility, the right direct-acting vs pilot-operated choice for your pressure and flow, and the correct electrical/hazardous-area rating. Get those three right and the rest of the specification falls into place. Ready to specify or source a solenoid valve? Talk to Our Expert Team DISCLAIMER: Z…