2-Way Solenoid Valve: Working Principle, Types, and Sizing
2-Way Solenoid Valve: Working Principle, Types, and Sizing
A 2-way solenoid valve is the simplest member of the directional solenoid valve family: it has one inlet and one outlet and opens or closes a single flow path on an electrical signal. Carroland manufactures a full range of 2-way solenoid valves for air, water, and neutral gases, built to widely used ISO interface dimensions, and has supplied automation lines since 1992 as an ISO 9001-certified, Foxconn-approved pneumatic components supplier.
How a 2-Way Solenoid Valve Works
When the coil is energised, the magnetic field lifts the plunger and opens (or releases) the orifice so media can pass. When the coil is de-energised, a spring returns the plunger to its rest position and the port closes. The entire action is electrically actuated, which makes the valve ideal for automated on/off control without manual intervention.
Normally Closed vs Normally Open
A normally closed (NC) valve blocks flow until power is applied; this is the default for safety because a power loss stops the flow. A normally open (NO) valve lets flow pass until power is applied and is chosen only when the process must keep running during a power failure. Most automation lines standardise on NC valves.
Direct-Acting vs Pilot-Operated
A direct-acting solenoid valve uses coil force to open the orifice directly, so it works from zero bar and suits small flow rates. A pilot-operated valve uses line pressure to assist opening, enabling larger flow with a smaller coil, but it requires a minimum pressure differential to function. The right choice depends on available pressure and the required flow.
Key Selection Parameters
- Port size – typically 1/8″ to 1″ for compact automation duty.
- Pressure range – confirm the valve covers both supply and back-pressure.
- Media compatibility – NBR, EPDM, and FKM seal options cover air, water, and many neutral liquids.
- Coil voltage – 12 V DC, 24 V DC, 110 V AC, or 220 V AC with surge suppression and an IP65 enclosure.
- Response time – direct-acting designs switch in milliseconds.
Typical Applications
2-way solenoid valves appear in water treatment, compressed air lines, medical devices, packaging machinery, irrigation, and fuel lines where an approved seal set is specified. For a complete walkthrough of media, pressure, and voltage trade-offs, see our solenoid valve selection guide.
Why Source from Carroland
Carroland builds 2-way solenoid valves on ISO-standard body dimensions with consistent port geometry, so they drop into existing manifolds and panels. As an ISO 9001-certified and Foxconn-approved supplier with in-house tooling since 1992, we support OEM volumes, custom voltages, and documented dimensional reports. Related options include the water solenoid valve line for liquid duty.
Frequently Asked Questions
What is the difference between a 2-way and a 3-way solenoid valve?
A 2-way solenoid valve has one inlet and one outlet and simply opens or closes a single flow path. A 3-way valve adds a third port to divert flow between two paths, which is useful for actuator control. For a straightforward on/off shutoff, a 2-way valve is the correct and lower-cost choice.
Can a 2-way solenoid valve handle both compressed air and liquid?
Yes, provided the wetted materials and seals are compatible with the media. Carroland offers NBR, EPDM, and FKM seal options and a brass or stainless body so the same valve family covers air, water, and many neutral liquids. Always confirm media compatibility before commissioning.
What coil voltages are available?
Standard coils cover 12 V DC, 24 V DC, 110 V AC, and 220 V AC, with integrated surge suppression and an IP65 rated enclosure. Other voltages can be configured for OEM volumes.
When should I choose normally closed instead of normally open?
Normally closed (NC) is the default for safety: power loss closes the valve and stops flow. Choose normally open (NO) only when the process must keep flowing during a power failure. Most automation lines use NC valves.
What is the typical service life?
Direct-acting 2-way valves typically deliver 10 to 50 million cycles depending on pressure, duty cycle, and media cleanliness. Proper filtration of the supply and correct voltage extend service life significantly.