{"id":4074,"date":"2026-03-28T10:00:00","date_gmt":"2026-03-28T10:00:00","guid":{"rendered":"https:\/\/microductconnector.com\/blog\/what-is-the-principle-of-the-two-position-three-way-pneumatic-valve\/"},"modified":"2026-09-29T02:20:13","modified_gmt":"2026-09-29T02:20:13","slug":"what-is-the-principle-of-the-two-position-three-way-pneumatic-valve","status":"publish","type":"post","link":"https:\/\/microductconnector.com\/fr\/blog\/what-is-the-principle-of-the-two-position-three-way-pneumatic-valve\/","title":{"rendered":"What Is the Principle of a Two-Position, Three-Way Pneumatic Valve?"},"content":{"rendered":"
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When a controls engineer commissions a small pneumatic actuator, a valve can appear to be the right size and still produce the wrong motion because its three ports were read in the wrong order. The visible fitting may show a supply and working connection, while the exhaust path and the de-energized state remain undocumented. That is why a two-position three-way pneumatic valve<\/strong> should be selected from its schematic, control method and specified port logic rather than from body shape alone. This guide explains the two switching positions, the three-port relationship, normally closed and normally open behavior, and the checks that prevent an unverified assumption from becoming a commissioning fault.<\/p>\n

R\u00e9sum\u00e9 :<\/strong> A two-position, three-way valve has two selectable spool or poppet states and three pneumatic ports, commonly supply (1), work (2) and exhaust (3), although numbering must be confirmed on the actual drawing. In one state, supply is connected to the work port; in the other, the work port is connected to exhaust or another defined port. Whether the valve is normally closed or normally open determines the rest state, and an electrical coil is only one possible actuator. Verify the symbol, port numbers, medium, pressure range and reset method in the current manufacturer documentation before installation.<\/p>\n

Identify the Two Flow States and Three Ports<\/h2>\n

\u201cTwo-position\u201d describes the number of stable or commanded flow configurations, not the number of physical components. A monostable valve normally has one actuated position and a spring-return position; a bistable valve can retain either position after a pulse, depending on its design. \u201cThree-way\u201d describes three flow connections. In a common pneumatic naming scheme, port 1 is supply, port 2 is the actuator or work port, and port 3 is exhaust, but the drawing supplied with the part controls the interpretation.<\/p>\n

\n \"S-VHK2
S-VHK2 pneumatic valve fitting detail. The photograph shows external fitting geometry only; it does not verify an internal 3\/2 circuit or a solenoid actuator.<\/figcaption><\/figure>\n

In the pressure state, the supply path can feed the work port while the exhaust port is blocked. In the return state, the supply may be blocked and the work port may vent through exhaust. Some circuits use the third port for a second inlet or for a different media arrangement. Those alternatives are possible design patterns, not assumptions about a particular S-VHK2 fitting.<\/p>\n

Trace Port Connections on the 3\/2 Valve Symbol<\/h2>\n

A schematic symbol for a 3\/2 valve is normally drawn as two adjacent boxes, one box for each position, with arrows or blocking marks showing the connections in that position. Count the boxes to confirm two positions, then trace the lines from the numbered ports. The symbol tells the reader which passages are open, but it does not by itself establish the valve\u2019s pressure rating, seal material, actuation force or electrical specification.<\/p>\n

For a typical circuit with port 1 as supply, port 2 as work and port 3 as exhaust, the logic can be described conditionally:<\/p>\n