Precise Speed Regulation for Pneumatic Drives
The Festo VFOF-LE-BAH-G18-Q4 (part no. 8193269) is a one-way flow control valve engineered to regulate the piston speed of pneumatic drives with high precision. Its exhaust air flow control function with non-return capability allows for fine-tuning of cylinder movement, which is critical in applications requiring controlled acceleration and deceleration. The valve is manually actuated via an internal hexagon adjusting element, enabling simple and repeatable speed settings without special tools. With a standard nominal flow rate of 240 l/min in the flow control direction and up to 220 l/min in the non-return direction, it supports a wide range of actuator sizes and cycle times.
Piloted Check Valve Functionality
A notable feature of this model is the optional piloted check valve function, which is pneumatically actuated through pilot air port 21 (QS-4). When activated, the non-return function can be overridden, allowing free flow in both directions. This is particularly useful for applications that require intermediate stopping or emergency retraction of a cylinder. The pilot pressure range is 2 to 10 bar (29 to 145 psi), and the valve responds with switching times of 6 ms on and 9 ms off, ensuring rapid and reliable response in dynamic systems.
Integration and Mounting Flexibility
The VFOF-LE-BAH-G18-Q4 is designed for screw-in mounting with a G1/8 thread on connection 2 and a QS-4 push-in fitting on connection 1. This configuration simplifies installation into manifolds or directly into cylinder ports. The valve can be rotated 360 degrees, though continuous swiveling is not permissible, offering flexibility in orienting the adjusting screw for accessibility. The nominal tightening torque is 3 Nm with a tolerance of ±20%, and the permissible actuation moment on the adjusting screw is 1 Nm, providing clear guidelines for secure and safe installation.
Durable Construction and Environmental Suitability
Constructed with a PBT housing and cover, brass adjusting screw, and NBR seals, the valve is built to withstand demanding industrial environments. The hollow bolt and sleeve are made of wrought aluminum alloy, and the releasing ring is POM. The product weighs only 29.2 g, minimizing added mass to moving assemblies. It is ATEX certified for use in Zone 2 and Zone 22 explosive atmospheres, and it meets LABS (PWIS) conformity VDMA24364-B1/B2-L, making it suitable for paint and coating applications. The operating pressure range is 2.9 to 145 psi (0.2 to 10 bar), and the ambient and medium temperature range is -10°C to 60°C.
Performance and Efficiency Considerations
For engineers evaluating system efficiency, the VFOF-LE-BAH-G18-Q4 offers standard flow rates of 420 l/min in the flow control direction and up to 460 l/min in the non-return direction at 6 to 0 bar. When the piloted function is actuated, the non-return flow rate adjusts to 150–230 l/min, while unactuated it is 120–220 l/min. This flexibility allows designers to match the valve to specific cylinder speed and force requirements. The valve operates with compressed air per ISO 8573-1:2010 [7:4:4], and oil lubrication is possible if required for downstream components. With a manual exhaust function that is non-detenting, operators can quickly release pressure for maintenance or troubleshooting.