How to select an SMC solenoid valve
Port count. Use a 5-port valve to control a double-acting cylinder, since it pressurizes one side while exhausting the other. Use a 3-port valve for single-acting cylinders, pilot supply, vacuum switching, or simple on and off flow. Use a 2-port valve for on and off fluid or air control without directional switching.
Pilot operated or direct operated. Pilot-operated valves in the SY, SYJ, JSY and VQ families need a minimum supply pressure, typically 0.15 MPa, to shift the spool. Direct operated valves operate from 0 MPa and are required for vacuum, very low pressure, and circuits where pressure may be absent at startup.
Body size and flow. In the SY series, body size tracks directly to Cv and port size. SY3000 with M5 ports and Cv near 0.25 to 0.5 suits cylinders under 25mm bore. SY5000 with 1/8 inch ports and Cv near 0.5 to 1.0 suits 25mm to 63mm. SY7000 with 1/4 inch ports and Cv near 1.0 to 2.0 suits 63mm and above or high-speed work. Undersizing slows cylinder actuation. Oversizing wastes panel space and increases air consumption on exhaust.
Single or double solenoid. A single solenoid valve has one coil and a return spring, so it reverts to a known default position when de-energized. A double solenoid valve holds its last commanded position with both coils off. Double solenoid is required where the actuator must hold position through an E-stop or power loss rather than defaulting to retracted or extended.
Electrical. 24VDC is the most common voltage in automated machinery. SMC valves are also built in 12VDC, 100VAC and 200VAC. Voltage and connector type, whether DIN connector, lead wire, M8 or M12, are set by the part number suffix. Confirm voltage before ordering, since coils are generally not field-interchangeable on assembled valves.
Body ported or base mounted. Body ported valves take tubing directly at the valve. Base mounted valves sit on a sub-base or manifold rail that carries the port connections. For three or more valves, a manifold base cuts piping labor, panel space and wiring time, and allows valve replacement without breaking tubing on plug-in types.
Material options. SMC publishes option prefixes on many valve and manifold part numbers. The 20- and 21- prefixes indicate copper, fluorine and silicon-free construction for semiconductor, display and paint applications. The 10- and 25A- prefixes cover other material and specification variants. These are filterable attributes rather than separate categories, so a copper-free VV5Q21 manifold sits alongside the standard version.
Frequently asked questions
What kind of solenoid valve do I need for a double-acting cylinder?
A double-acting cylinder needs a 5-port solenoid valve, sometimes called a 4-way valve. It sends air to one cylinder port while exhausting the other, then reverses on the opposite signal. A 3-port valve cannot do this because it has only one output port. In the SMC lineup, the SY3000, SY5000 and SY7000 series cover most double-acting cylinder applications, with body size selected to match cylinder bore.
What is the difference between SMC SY3000, SY5000 and SY7000?
They are the same 5-port valve family in three body sizes. SY3000 has M5 port threads and suits cylinder bores under 25mm. SY5000 has 1/8 inch ports and suits 25mm to 63mm. SY7000 has 1/4 inch ports and suits 63mm and larger or high-speed applications. All three are pilot-operated, available body ported and base mounted, and compatible with SS5Y manifold bases in the matching size.
What is a direct operated solenoid valve?
A direct operated solenoid valve uses the magnetic force of the energized coil to open or close the seat with no pilot air required. It operates from 0 MPa, including full vacuum. Pilot-operated valves such as the SY and SYJ series need a minimum supply pressure, typically 0.15 MPa, to move the spool. If a circuit can sit at zero pressure or works under vacuum, specify a direct operated valve.
When should I use a valve manifold instead of individual valves?
Three or more valves in the same area of a machine is the usual threshold. A manifold shares supply and exhaust across all stations, so piping drops from several runs to one, and wiring consolidates into a single D-sub, ribbon cable or fieldbus node rather than a cable per valve. Plug-in manifolds add the ability to swap a valve without disconnecting tubing, which shortens changeout during production.
What is the difference between a body ported and base mounted SMC valve?
A body ported valve has supply, output and exhaust ports on the valve body, so tubing connects directly to the valve. A base mounted valve sits on a separate sub-base or manifold rail that carries the port connections. Base mounted valves can share a common manifold, and on plug-in types the valve can be removed without disturbing tubing.
What is the difference between single solenoid and double solenoid valves?
A single solenoid valve has one coil and a return spring. When de-energized, the spring returns the spool to its default position. A double solenoid valve has two coils and no return spring, so the spool holds its last commanded position when both coils are off. Double solenoid is specified where the actuator must maintain position through an E-stop or power loss instead of defaulting to a fixed state.
Are SMC SY series valves interchangeable with other brands?
SY series valves are not dimensionally interchangeable with other manufacturers on standard manifold bases, since the SY manifold interface is SMC-specific. SMC's ISO series, meaning VQ7-6, VQ7-8, VS7, VSS8 and VSR8, conforms to ISO 15407 and ISO 15408 and is interchangeable with compliant valves from other manufacturers on the same ISO manifold station. For cross-referencing a non-ISO SMC valve to a replacement, use the SMC discontinued part cross-reference tool or contact Automation Distribution at 1-888-600-3080.
What voltage do SMC solenoid valves use?
SMC solenoid valves are built in 24VDC, 12VDC, 100VAC and 200VAC. 24VDC is the most common in industrial automation. Operating voltage is encoded in the part number suffix, often as a single digit, though the coding varies by series. Verify the voltage code for the specific series before ordering, since coils are generally not field-interchangeable between voltage ratings on assembled valves.
What does the 20- or 21- prefix on an SMC part number mean?
A leading 20- or 21- indicates copper, fluorine and silicon-free construction, specified for semiconductor fabrication, flat panel display manufacturing and paint or coating lines where trace contamination causes defects. The base part number and its performance specifications are otherwise unchanged, so 21-VV5Q21-03C6FS0-D is the copper-free version of the standard VV5Q21 manifold.
My SMC valve is discontinued. How do I find a replacement?
Use the SMC discontinued part cross-reference tool to look up a current equivalent by part number. Many legacy SY series valves cross to current SY or JSY equivalents with the same manifold footprint, though pilot pressure, response time and flow can differ between generations. Confirm the crossover specifications against the original before committing to a design change.
Need help specifying a valve or manifold?
Automation Distribution is an authorized SMC Corporation of America distributor. For manifold configuration, valve sizing against cylinder bore and cycle time, fieldbus interface selection, or cross-referencing a discontinued part number, call 1-888-600-3080 or contact our technical team.
