# Three-port, two-position valve

> Source: https://rodlesspneumatic.com/resource-center/pneumatic-glossary/3-2-valve/
> Language: en-US
> Category: Valves & circuits

## Definition

Three-port, two-position valve: Directional valve with three ports and two switching states. Common for single-acting actuators and on/off air functions. Read the applicable product data and technical standard before treating a catalog value as interchangeable.

## Key facts

- **Term:** 3/2 valve
- **Full form:** Three-port, two-position valve
- **Selection effect:** Common for single-acting actuators and on/off air functions.

## 3/2 valve: definition and engineering context

Three-port, two-position valve. Directional valve with three ports and two switching states.

The term belongs to the valves & circuits context. Its exact limits can depend on the cited standard, catalog convention, unit system, reference state, and component configuration.

## Why 3/2 valve affects pneumatic selection

Common for single-acting actuators and on/off air functions.

- 5/2 valve: Common for double-acting cylinders.
- 5/3 valve: Specify closed, pressure, or exhaust center; center function changes actuator behavior.
- NC: Confirm which ports the catalog calls normally closed.
- NO: Use when the required fail-state needs flow.

## How to evaluate 3/2 valve in a catalog or replacement project

Read the value together with its unit, test basis, operating pressure, temperature, circuit state, and manufacturer definition.

For replacement work, compare the complete datasheet and drawing. A matching abbreviation or nominal size does not by itself prove functional or dimensional interchangeability.

- Five-port, two-position valve: Directional valve with pressure, two working, and two exhaust ports.
- Five-port, three-position valve: Directional valve with a defined center state.
- Normally closed: Flow path is closed in the defined normal or de-energized condition.
- Normally open: Flow path is open in the defined normal or de-energized condition.

## What to verify before selection

- Common for single-acting actuators and on/off air functions.
- Common for double-acting cylinders.
- Specify closed, pressure, or exhaust center; center function changes actuator behavior.
- Confirm which ports the catalog calls normally closed.

## Common mistakes

- Treating 3/2 valve as a universal definition without checking the manufacturer or standard context
- Mixing gauge and absolute values, incompatible units, or different reference conditions in one comparison
- Selecting a component from the term or nominal value alone without checking the complete operating point and drawing

## Frequently asked questions

### What does 3/2 valve mean in pneumatics?

Three-port, two-position valve. Directional valve with three ports and two switching states.

### Why does 3/2 valve matter when selecting a component?

Common for single-acting actuators and on/off air functions.

### Can 3/2 valve values be compared directly between catalogs?

Only after the unit, reference condition, test method, operating point, and manufacturer definition have been reconciled.

## Technical references

- [ISO 5598:2020](https://www.iso.org/standard/67985.html): Provides the international fluid-power vocabulary used to interpret pneumatic terminology.
- [ISO 1219-1:2012](https://www.iso.org/standard/60184.html): Defines graphical symbols and circuit-documentation principles for fluid-power systems.