Solenoid valves are among the most widely used devices for automatically controlling the flow of liquids and gases in industrial systems. This guide covers the main types of solenoid valves, what distinguishes each one, and how to choose the right type for your application.
Types of Solenoid Valves
Direct Acting Solenoid Valve
In a direct acting solenoid valve, the plunger is connected directly to the sealing mechanism. Energizing the coil pulls the plunger up and opens the valve immediately; de-energizing it lets the plunger return and shut the valve. There’s no dependency on line pressure, which makes direct acting valves reliable at low or zero pressure and gives them fast response times. See Aira’s direct acting solenoid valves.
Pilot Operated (Indirect Acting) Solenoid Valve
Pilot operated solenoid valves use the pressure of the media itself to help open and close the valve, working through a pressurized diaphragm. A small pilot orifice needs a minimum pressure differential (typically around 0.5 kg) to function. When the coil energizes, the pilot orifice opens, releasing pressure above the diaphragm and allowing the main valve to open. This design is electricity-efficient but generally slower to respond than a direct acting valve, and it requires a minimum operating pressure to function correctly. See Aira’s pilot operated piston type and pilot operated diaphragm type solenoid valves.
Semi-Lift Diaphragm Solenoid Valve
A semi-lift diaphragm design combines direct and pilot operated principles. The diaphragm is lifted by both the plunger and the pressure differential together, rather than relying on either alone. This allows the valve to operate reliably across a wider range of pressures, including at pressures too low for a purely pilot operated design to function.
Pulse Type Solenoid Valve
Pulse type solenoid valves are a specialized category used to fire short, high-force bursts of compressed air — most commonly for cleaning dust collector filter bags by dislodging accumulated particulate. They’re built for rapid, repeated cycling rather than continuous flow control. See Aira’s pulse type solenoid valves.
General Purpose Solenoid Valve
General purpose solenoid valves are designed for standard industrial media — water, air, and other non-aggressive fluids — without the specialized body materials or sealing needed for corrosive chemicals, high temperatures, or hygienic processing. They’re typically the most economical option when application conditions are straightforward. See Aira’s low pressure solenoid valves for general-duty applications.
Two-Way and Three-Way Solenoid Valves
Solenoid valves are also classified by port count. A two-way solenoid valve has one inlet and one outlet port and is the most common configuration, used simply to start or stop flow. A three-way solenoid valve has one inlet and two outlet ports (or two inlets and one outlet), allowing it to direct flow along one of two paths or combine two flow sources — commonly used for diverting or mixing duty.
Normally Open (NO) vs. Normally Closed (NC)
Solenoid valves are also categorized by their default (de-energized) state: a Normally Open (NO) valve stays open until power closes it, while a Normally Closed (NC) valve — the more common configuration — stays closed until power opens it. This distinction matters for fail-safe design: an NC valve fails shut on power loss, while an NO valve fails open. For a full breakdown of when to use each, see our dedicated guide on NO vs. NC solenoid valves.
Solenoid Valve Voltage Options
Solenoid coils are available in standard voltage options to match different electrical systems: common DC options include 12V DC and 24V DC, typically used in control and automation panels, while common AC options include 110V AC and 220V/230V AC, matched to regional mains supply. Confirming the correct voltage and coil type upfront avoids compatibility issues during installation.
How to Choose the Right Solenoid Valve
Selecting the correct solenoid valve for an application comes down to a few key checks:
- Media compatibility. Confirm what the valve will control — solenoid valves are generally suited to liquids, air, and steam, but are not designed for media carrying solid particles, which can jam the orifice or damage the seat.
- Body material. Match the body material to the media and environment. Plastic-bodied valves suit corrosive or chemical media within their temperature limits; metal-bodied valves (brass, stainless steel) suit higher temperatures and more demanding mechanical duty. An application like controlling ink flow, for example, needs a body and seal material specifically compatible with that fluid’s chemistry.
- Normally Open vs. Normally Closed. Choose based on what state the system should default to if power is lost — see the NO vs. NC guide linked above.
- Voltage. Confirm the required coil voltage matches your control system (see voltage options above).
- Certifications and standards. For hazardous or regulated environments, confirm the valve carries the relevant certification for your application — such as ATEX or CE for explosion-proof and general safety compliance in the region you’re installing in.
Aira Euro Automation manufactures direct acting, pilot operated, pulse type, and general purpose solenoid valves for industrial process applications. Get a quote, explore the full solenoid valve range, or read our related guides on solenoid valve mechanism, NO vs. NC solenoid valves, and solenoid valve troubleshooting.
