A pneumatic pilot-operated directional control valve works by using air pressure to shift the spool.
This air pressure is called pilot pressure or control pressure, and it comes from an external air source.
In simple terms, a pneumatic pilot valve is basically a directional control valve without the solenoid pilot section—
it removes the electrical coil and keeps only the main valve body.
Unlike a 4V solenoid valve, which is operated by an electrical signal, a pneumatic pilot valve is controlled entirely by air pressure signals.
This makes it ideal for hazardous, explosive, wet, or high-interference environments where electrical control is not suitable.
AIRTAC pneumatic air-pilot valves: 3A / 4A / 5A / 6A / 6TA series
SMC air-piloted directional valves: SYA / VFA / VZA series
FESTO pilot-air control valves: VUWG / MFH / VL series
OLK Air Pilot Valves Working Principle (3A & 4A Series) (P=Inlet A=B=Outlet,R=S=Exhaust)
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Series |
Model / Type |
Symbol |
Function Description |
Pneumatic fitting |
Action characteristic |
Typical scenarios |
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10-NC (Normally Closed) |
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Pilot ON: P →A Pilot OFF: A →R (Exhaust) |
3A110-M5/ 06: PC -01(G1/8)X2 piece,Silence G1/8 X1 piece 3A210-06/08 : PC -02(G1/4)X2 piece,Silence G1/4 X1 piece 3A310-08/10 : PC -03(G3/8)X2 piece,Silence G3/8 X1 piece 3A410-15 : PC -04(G1/2)X2 piece,Silence G1/2 X1 piece |
Spring Return: NC/NO Switch: Actuates when air signal is present; resets by spring force when signal is removed.
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Controlling Single Acting Cylinders • Air Blow / Cooling Systems:Blow when there is a signal, stop when there is no signal • Safety cut-off circuits (Fail-safe) Immediately shut off the gas circuit if the signal source is lost. |
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10-NO (Normally Open) |
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Pilot ON: A→ R (Exhaust) Pilot OFF: P→ A |
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20 (Double Pilot) |
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Signal 1: Pilot ON: P →A Pilot ON: A→ R (Exhaust) Signal 2: Pilot ON: A→ R (Exhaust) Pilot OFF: P→ A (Air In) |
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Memory/Bistable Memory Function: Valve stays in the last switched position even if the signal is removed. Requires a counter-signal to reset.
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Pneumatic Logic Circuits (Non-electric) • Signal holding systems • Hopper gate control (Open/Hold/Close)
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10 (Single Pilot) |
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Pilot ON: P → B, A → R Pilot OFF: P → A, B → S |
4A110-M5/ 06: PC -01(G1/8)X3 piece,Silence G1/8 X2 piece 4A210-06/08 : PC -02(G1/4)X3 piece,Silence G1/8 X2 piece 4A310-08/10 : PC -03(G3/8)X3 piece,Silence G1/4X2 piece 4A410-15 : PC -04(G1/2)X3 piece,Silence G1/2 X2 piece |
spring Return Standard Directional Control: Cylinder extends with signal; automatically retracts when signal stops. |
Controlling Double Acting Cylinders • Automatic Press Machines:The worker steps on the pneumatic foot valve to give a signal, and the cylinder presses down; Release your foot, the cylinder will automatically rebound • Pneumatic Safety Doors:The door opens when there is a gas signal, and automatically closes when there is no signal. |
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20 (Double Pilot) |
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Signal 1: P → A, B → S Signal2: P → B, A → R |
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Memory/Bistable Pulse Control: Requires only a short air pulse to switch and hold position. Ideal for long-distance signal transmission. |
Long Conveyor Systems • Clamping fixtures requiring Power-off Memory • Flipping mechanism: After the cylinder reaches its end position, it remains in place without dropping even if the signal source is cut off |
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30C (Closed Center) |
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No Signal: All Ports Closed (A/B Blocked) Signal 1: P → A ,B→ S Signal 2: P → B,A→ R |
4A130CEP-M5/ 06: PC -01(G1/8)X3 piece,Silence G1/8 X2 piece 4A230CEP-06/08 : PC -02(G1/4)X3 piece,Silence G1/8 X2 piece 4A330CEP-08/10 : PC -03(G3/8)X3 piece,Silence G1/4X2 piece 4A430CEP-15 : PC -04(G1/2)X3 piece,Silence G1/2 X2 piece |
Stop & Hold The cylinder stops immediately at its current position (acts like a brake). |
Emergency Stops • Vertical Lifting (Preventing drops) • Mid-stroke positioning |
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30E (Exhaust Center) |
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No Signal: A → R, B → S (Exhausting) Signal 1: P → A,B→ S Signal 2: P → B,A→ R |
Free Movement The piston loses pressure and can be moved manually by hand. |
Manual Setup/Debugging:When the machine is stopped, the operator needs to manually move the cylinder to adjust alignment or change molds. • Releasing residual pressure (Safety): • "Floating" applications:follow-up mechanism: Used when the cylinder needs to move freely and follow an external force.
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30P (Pressure Center) |
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No Signal: P → A, B (Pressurized) Signal 1: P → A,B→ S Signal 2: P → B,A→ R |
Equilibrium/Extend Maintains pressure balance (Note: Single-rod cylinders will slowly extend;If it is a dual-rod cylinder, it remains in a force-balanced state.). |
Pressure Balancing Systems • Preventing retraction in specific vertical setups(Less common):When installed vertically with the rod facing downward, the cylinder uses the differential area force to counteract gravity and prevent retraction. |
The 3A / 4A series pilot valve of OLK employs springs with high fatigue life. This is crucial because the three-way valve relies on the spring to return to its neutral position. If the spring breaks, the valve cannot revert to the center, leading to equipment failure. This is one of OLK's quality advantages.Secondly Optimized spool design allows switching at pressures as low as 0.15 MPa.Imported seals + Hard anodized body = 20 million cycles life span.
