Non-Surge Aviation Fuel Check Valve - 81AF-8 | Cla-Val
Cla-Val 81AF-8 Non-Surge Aviation Fuel Check Valve
The Cla-Val 81AF-8 is a hydraulically operated check valve designed for aviation fuel distribution lines. It incorporates a controlled opening feature to minimize pressure transients (surge) during operation. The valve is based on the 100-34 Hytrol main valve (reverse flow configuration) and includes two 81-01 pilot valves, a CV flow control for adjustable opening speed, and an X101 position indicator.
Operating Principle
When downstream pressure exceeds upstream pressure, pilot check valves 4A and 4B open, directing higher pressure to the cover chamber of the main valve, causing it to close and prevent reverse flow. When upstream pressure rises above downstream, 4A/4B close, the cover chamber vents to the outlet, and the main valve opens. This sequence ensures reliable check function with controlled response.
Non-Surge Adjustment
The CV flow control regulates the main valve opening speed. Clockwise adjustment reduces opening rate, which is critical in hydrant fueling, loading lines, and pump discharge applications where rapid acceleration of fuel columns can induce hydraulic surge.
Applications
- Aviation fuel distribution networks
- Hydrant fueling systems
- Pump discharge lines
- Installations requiring check function with controlled hydraulic response
- Pump protection points against reverse flow
Installation and Maintenance
Piping must be flushed to remove debris, scale, and foreign matter prior to installation. Block valves upstream and downstream are recommended for isolation during maintenance. Horizontal installation with cover upwards is preferred for inspection, especially for sizes 6" and above. Commissioning requires slow opening of isolation valves and venting air from the cover or via the X101 indicator.
FAQ
Is an external actuator required?
No. Operation is fully hydraulic, utilizing inlet/outlet pressures and the pilot circuit.
What is checked during periodic maintenance?
Cover chamber pressure, tubing restrictions, diaphragm, disc, seat, mechanical deposits, and correct function of the position indicator.
When is this valve selected over a standard check valve?
When check function must be combined with adjustable opening to limit hydraulic shock in fuel lines.
