Automatic drain valves are used to automatically discharge condensate from low points in piping, oil-water separators, air tanks, and the bottoms of various filters. They can be installed in locations where manual draining is inconvenient—such as high places, low-lying areas, or cramped spaces—thereby preventing re-contamination of the compressed air by condensate that might otherwise remain due to forgotten manual draining.
Electronic vs. Mechanical Automatic Drain Valves
Automatic drain valves come in electronic and mechanical (physical) types. Electronic drain valves operate via a solenoid valve; the timing and frequency of the automatic discharge cycle can be adjusted using the settings on the unit.
Mechanical drain valves operate based on the buoyancy of an internal float. As the liquid level inside the unit rises, the float rises, automatically opening the valve.
Electronic Automatic Drain Valves
Electronic automatic drain valves utilize a solid-state electronic timer (analog circuit) paired with a solenoid valve to achieve the timed, automatic discharge of condensate from compressed air systems. They are widely used with components such as filters, separators, dryers, air storage tanks, and drip legs. Both the discharge duration and the interval between discharges can be adjusted to meet specific requirements.
Working Principle:
Inside the automatic drain valve, there is an air-filled chamber (acting much like a balloon). In the absence of water, air pressure forces this chamber to seal the drain outlet.
As water accumulates within the unit and reaches a certain level, buoyancy overcomes the air pressure, causing the chamber to float upward and open the drain outlet. Water is then expelled by the air pressure; as the water level drops, buoyancy decreases, allowing the chamber to descend and reseal the drain outlet.