Pneumatic 5/2 Valve Symbol
Definition: The Pneumatic 5/2 Valve symbol represents a directional control valve with 5 ports and 2 switching positions used in compressed-air circuits to control double-acting pneumatic cylinders, standardised under ISO 1219-1, with terminals P (supply), A (work port 1), B (work port 2), R (exhaust 1), and S (exhaust 2).
Also known as: 5/2 directional control valve, 5-port 2-position valve, double-acting cylinder control valve, 5/2 solenoid valve, pneumatic 5/2 valve, 5-way 2-position valve.
What the Pneumatic 5/2 Valve symbol means
The Pneumatic 5/2 Valve symbol represents a directional control valve with five ports and two discrete switching positions, designed specifically to control the bidirectional movement of double-acting pneumatic cylinders — cylinders that require pressurised air on both the extend and retract sides of the piston. The five ports are: P (compressed-air pressure supply), A (first working port, typically to the cylinder extend/cap end), B (second working port, typically to the cylinder retract/rod end), R (exhaust for port A), and S (exhaust for port B).
In pneumatic circuit diagrams, the 5/2 valve symbol is the most widely used control element in industrial automation, appearing on every circuit that controls a double-acting cylinder such as a linear actuator, air-over-oil intensifier, or rodless cylinder. When the valve is in position 1, P connects to A (cylinder extends) while B exhausts through S; when in position 2, P connects to B (cylinder retracts) while A exhausts through R. The 5/2 valve is actuated by solenoids, pilot air, springs, or manual operators.
How to identify the Pneumatic 5/2 Valve symbol
The 5/2 valve symbol is drawn as two adjacent rectangles (position 1 and position 2) with lines and arrows inside each rectangle showing the five port connection paths for that switching state. Five port labels exit from the bottom and top edges of the two rectangles: P (supply, centre bottom), A and B (work ports, top edge), R and S (exhausts, bottom edges flanking P). An actuator symbol — most commonly two solenoid coil boxes at each end for a double-solenoid 5/2 valve, or one solenoid and a spring for a single-solenoid return variant — is drawn at the ends of the two-rectangle body. The internal arrows in the rectangle show crossed or parallel flow paths to indicate which ports connect in each position.
Function in a circuit
A 5/2 valve controls the direction of air supply to and exhaust from a double-acting cylinder's two air chambers. In position 1: supply (P) feeds port A to the extend side of the cylinder, and port B from the retract side is exhausted to atmosphere through S. The cylinder rod extends. In position 2: supply (P) feeds port B to the retract side, and port A from the extend side is exhausted through R. The cylinder rod retracts. A double-solenoid 5/2 valve is bistable (latching) — it holds its last position when both solenoids are de-energised, providing position memory. A single-solenoid spring-return 5/2 valve returns to one defined position when de-energised.
Standards: IEC vs ANSI
| IEC 60617 | ISO 1219-1:2012 (fluid power systems and components — graphical symbols and circuit diagrams) defines the 5/2 valve symbol as two adjacent position rectangles with five port connections labelled P, A, B, R, S (or ISO 5599-3 port numbers 1, 2, 4, 3, 5 respectively). This is the globally recognised standard for pneumatic circuit documentation. |
|---|---|
| ANSI/IEEE 315 | ANSI/NFPA T3.3.7 R1 uses the same two-rectangle graphical convention as ISO 1219-1 for pneumatic directional control valve symbols. Port labelling conventions match ISO P/A/B/R/S or use port numbers 1/2/4/3/5. Valve reference designator: V or SV. |
| Key difference | ISO 1219-1 and ANSI/NFPA T3.3.7 are functionally and graphically identical for 5/2 valve symbols. Manufacturers such as SMC, Festo, and Parker use ISO 1219-1 port labels on their technical documentation worldwide. The only distinction may be in port number labelling (P/A/B/R/S versus 1/2/4/3/5 per ISO 5599-3 numbering) within the same standard family. |
Terminals / pins
| Pin | Name |
|---|---|
| p | P |
| r | R |
| a | A |
| b | B |
| s | S |
Typical values
Typical 5/2 valve specifications: nominal bore 2.5–16 mm; Cv flow coefficient 0.2–6.0; operating pressure 1.5–10 bar (22–145 psi); solenoid voltage 24 V DC (standard industrial), 12 V DC, 110 V AC, 230 V AC; response time 15–50 ms; temperature range -10°C to +60°C; thread ports G1/8 to G3/8 BSP or 1/8 to 3/8 NPT; lubricated or non-lubricated air.
Where the Pneumatic 5/2 Valve symbol is used
- Control of double-acting pneumatic cylinders for linear motion in pick-and-place robot arms
- Pneumatic rotary actuator (quarter-turn valve actuator) bidirectional control in process plant
- Double-acting pneumatic gripper open/close control on end-of-arm tooling
- Air-cushion piston press and stamping machine bidirectional cylinder control
- Pneumatic slide table and shuttle conveyor bidirectional movement circuits
- Pneumatic transfer system push-pull actuator control in packaging machinery
Example
In an automated assembly machine pneumatic circuit, a double-solenoid 5/2 valve symbol (24 V DC coils, labelled SV1) connects its P port to the supply manifold at 6 bar, port A to the cap end of a 50 mm bore double-acting cylinder, port B to the rod end, and ports R and S to the exhaust manifold. The PLC energises solenoid 1 to extend the cylinder (P to A, B to S) and solenoid 2 to retract it (P to B, A to R) — a circuit appearing on every SMC or Festo pneumatic application drawing for automation equipment.
Key facts
- The Pneumatic 5/2 Valve symbol has two adjacent position rectangles with five ports: P (supply), A (work port 1 / extend), B (work port 2 / retract), R (exhaust for A), and S (exhaust for B).
- 5/2 means: 5 ports, 2 positions — the valve shifts between exactly two discrete flow configurations to extend or retract a double-acting cylinder.
- Standardised in ISO 1219-1:2012; ISO 5599-3 assigns port numbers P=1, A=2, B=4, R=3, S=5. Valve designator: V or SV on pneumatic circuit diagrams.
- A double-solenoid 5/2 valve is bistable (memory): it holds its last position with both solenoids off. A single-solenoid spring-return 5/2 shifts back to a defined rest position when de-energised.
- Port A feeds the cylinder cap (blind) end for extension; port B feeds the rod end for retraction — this convention is standard but can be reversed depending on cylinder mounting orientation.
- 5/2 valves differ from 3/2 valves: a 3/2 valve has only one working port (A) for single-acting cylinders; a 5/2 valve has two working ports (A and B) for double-acting cylinders.
- Typical solenoid operating voltage: 24 V DC for PLC-controlled industrial automation (the global standard); 110 V AC and 230 V AC variants are available for legacy panel installations.
- Mid-position variants (5/3 valves with three positions — pressurised, exhausted, or blocked mid-position) are chosen when the cylinder must be held in mid-stroke under load.
Frequently asked questions
What does the pneumatic 5/2 valve symbol look like?
The 5/2 valve symbol shows two side-by-side rectangles (one per switching position) with lines and arrows inside each rectangle indicating port connection paths. Five port labels exit from the edges: P (supply, bottom centre), A and B (work ports, top), R and S (exhausts, bottom flanks). Actuator symbols — solenoid boxes, springs, or push-buttons — are drawn at the ends of the two-rectangle body.
What does 5/2 mean in a pneumatic valve?
In pneumatic valve nomenclature, '5/2' means the valve has 5 ports and 2 switching positions. The 5 ports are: P (supply), A (work 1), B (work 2), R (exhaust 1), and S (exhaust 2). The valve spool can occupy exactly two positions, each connecting the ports in a different configuration to extend or retract a double-acting cylinder.
What are the five ports of a 5/2 valve?
The five ports are: P (pressure — compressed-air supply), A (work port — typically to the cylinder cap/extend end), B (work port — typically to the cylinder rod/retract end), R (exhaust — for port A's return air to atmosphere), and S (exhaust — for port B's return air). In ISO 5599-3 port numbering: P=1, A=2, B=4, R=3, S=5.
What is the difference between a 5/2 and a 3/2 valve?
A 3/2 valve has 3 ports (P, A, R) and controls single-acting cylinders that have only one air port and a spring return. A 5/2 valve has 5 ports (P, A, B, R, S) and controls double-acting cylinders that need pressurised air on both sides of the piston for both extension and retraction. The 5/2 valve symbol has two working ports (A and B) compared to the 3/2 valve's single working port (A).
What is the difference between single-solenoid and double-solenoid 5/2 valves?
A single-solenoid spring-return 5/2 valve has one solenoid and a spring; when de-energised, the spring returns the valve to a defined rest position (typically P to A). A double-solenoid 5/2 valve has two solenoids, one at each end; it is bistable — it stays in the last energised position when both solenoids are off. Double-solenoid valves are preferred for applications where power loss must not change cylinder position.
What standard defines the 5/2 pneumatic valve symbol?
The 5/2 valve symbol is defined in ISO 1219-1:2012 (Fluid power systems and components — graphical symbols and circuit diagrams). ANSI/NFPA T3.3.7 uses the same graphic conventions. Port numbers follow ISO 5599-3: P=1, A=2, B=4, R=3, S=5. These standards are used internationally in industrial pneumatic system design documentation.
Can a 5/2 valve control a single-acting cylinder?
Technically yes — a 5/2 valve can control a single-acting cylinder by connecting only port A to the cylinder and leaving port B unused (plugged). However, this wastes a work port. The 3/2 valve is the correct and economical choice for single-acting cylinders. A 5/2 valve is specifically designed and selected for double-acting cylinders that require bidirectional air supply.
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