Quick release valve: dumping air at the cylinder or brake-chamber port for a faster return stroke
Quick release (quick exhaust) valves · screwed into a cylinder or brake-chamber port so the air dumps locally instead of travelling back through the control valve
A quick release valve, called a quick exhaust valve in industrial pneumatics, is a three-port valve fitted directly at the port of a cylinder or air chamber. While the supply line is pressurised the valve passes air to the cylinder and holds its exhaust port shut; when the control valve vents the supply line, the pressure difference flips the valve and the cylinder's air leaves through the quick release valve's own exhaust, without flowing back through the hose and the control valve. The result is a faster return stroke or brake release. It does not protect against overpressure.
Quick exhaust valves for pneumatic cylinders and quick release valves for air-brake chambers, with or without silencers. Spring-loaded and pilot-operated pressure relief and safety valves that open on overpressure are covered on the Pressure relief valve page; waterworks air release valves for pipelines are a separate product.
CNFX editorial research · Sources checked October 12, 2026 · 3 sources
Exhaust flow from 2 to 3 rises from 660 to 6,480 l/min across G1/8 to G1/2
Festo publishes two flows for each size of its SE quick exhaust valve: supply 1 → 2 into the cylinder, and exhaust 2 → 3 out of it. The exhaust path is the larger of the two in three of the four sizes. [1]
All values above are Festo's standard nominal flow rates for the SE-…-B and SEU series. [1] The exception is G3/8, where 2 → 3 (2,760 l/min) is slightly below 1 → 2 (2,880 l/min). [1]
Editorial calculation: fitting the silencer costs exhaust flow — at G1/2 the SEU's 4,020 l/min is about 38% less than the SE's 6,480 l/min, at G1/8 the 550 l/min is about 17% less. Festo gives the SEU a noise level of 85 dB(A). [1]
Both series work from 0.5 to 10 bar with filtered compressed air, lubricated or unlubricated, at −20 to +75 °C, with die-cast zinc (G1/8, G1/4) or die-cast aluminium (G3/8, G1/2) housings and nitrile rubber seals. [1] SMC's AQ quick exhaust valve uses an aluminium die-cast body, a zinc die-cast cover and an NBR valve; its -H type changes NBR to FKM and its -L type changes NBR to CR. [2]
Port (Festo SE / SEU)
Nominal size
Flow 1 → 2
Flow 2 → 3, SE
Flow 2 → 3, SEU with silencer
G1/8
5 mm
300 l/min
660 l/min
550 l/min
G1/4
7 mm
960 l/min
1,200 l/min
1,100 l/min
G3/8
11 mm
2,880 l/min
2,760 l/min
2,280 l/min
G1/2
15 mm
4,560 l/min
6,480 l/min
4,020 l/min
02
Mount it at the cylinder port and drive it from a valve that can exhaust
Festo states that the valve must be connected directly to the cylinder port to get the full quick exhaust effect. [1] SMC's operation manual for the AQ series adds the circuit conditions under which the valve works or fails. [2]
The switching valve upstream must be a 3, 4 or 5 port valve with an exhaust port, and the quick exhaust valve fails to operate if the pressure at its IN port falls more slowly than at its OUT port. [2] SMC lists three causes of noise from incomplete exhaust or vibration: residual or back pressure on the IN side, an IN–OUT pressure difference below the minimum operating pressure, and IN-side piping or a solenoid valve with a smaller effective area than the quick exhaust valve. [2]
SMC also warns that the valve cannot be used where zero leakage is required, because some leakage is allowed in its specification, and that air must not be exhausted from the EXH port while air is supplied to the IN port. [2] Its own exclusions list brake circuits, press clutches, emergency shut-off and safety equipment among uses outside standard specifications. [2]
Give the supplier the cylinder bore and stroke, the port thread, the supply valve and its flow, the working pressure range, whether a silencer is needed, and the seal material for the air quality and temperature.
03
Air-brake quick release valves: one supply, two delivery ports, within 1 psi
Truck and trailer air-brake systems use the same principle in a dedicated valve. Bendix describes its QR-1 and older QRV quick release valves as speeding up the exhaust of air from the brake chambers, mounted close to the chambers they serve, with one supply port, two delivery ports and one exhaust port. [3]
In standard form the valve delivers within 1 psi of control pressure to the chambers; versions with a greater differential or zero hysteresis are available for special applications, and QR-1 valves can take noise-reducing foam crosses or silencers. The QR-1 uses a diaphragm without a spring in its standard configuration, while the QRV and differential QR-1 versions use a spring and spring seat. [3]
Bendix's minimum inspection interval for the QR-1 is every 12 months or 3,600 operating hours, whichever comes first. In its leakage test, with a brake application held, a 1-inch soap bubble in 3 seconds is permitted at the exhaust port and no leakage is permitted between body and cover. [3]
04
Data for a quick release valve enquiry
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Use: [pneumatic cylinder return stroke; air-brake chamber]
Port: [thread size; number of delivery ports]
Flow: [exhaust flow 2 → 3 or effective area; supply valve flow]
Pressure: [working range; differential or hysteresis needed]
Exhaust: [open; silencer; noise limit]
Seals and body: [NBR, FKM, CR; zinc, aluminium]
Testing: [leakage allowed at exhaust]
1 company lists this product among what they make. Company figures are quoted from each
company's own website; every card states where the relationship came from.
Zhejiang VOB Technology Co., Ltd.
Manufacturing site to be confirmed for the order
Lists quick release valves (for example FA2025, FA2027, FA2039A, FA2141A, FA2142A) among truck air-brake parts such as brake chambers, relay valves and foot brake valves.
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
Is a quick release valve the same as a pressure relief valve?
No. It opens its exhaust when the supply pressure upstream falls, so a cylinder or brake chamber empties faster; it does not open on overpressure. [1][3]
Where should a quick exhaust valve be fitted?
Directly at the cylinder port; Festo states this is needed for the full quick exhaust effect, and Bendix mounts brake quick release valves close to the chambers they serve. [1][3]
Why might a quick exhaust valve not work?
SMC lists a switching valve without an exhaust port, IN pressure falling more slowly than OUT, back pressure on the IN side, or IN-side piping smaller in effective area than the quick exhaust valve. [2]
Sources and what still needs a direct check
Sources checked 2026-10-12. Flow, pressure and materials come from Festo's SE/SEU quick exhaust valve datasheet; circuit conditions and materials from SMC's AQ series operation manual; air-brake data from Bendix's QRV and QR-1 service data sheet SD-03-901.
