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Machine Design

Hydraulic-over-air relay valves

Hydraulic-over-air relay valves are designed to convert hydraulic-modulated input pressure to a proportional output air pressure. The valves are suited for on and off-highway applications, including controlling an air-braked trailer with a hydraulically braked towing vehicle that has an air power source.

A hydraulic vehicle component, such as a master cylinder or hydraulic control valve, delivers a given hydraulic input pressure, which sends a pilot signal to the relay valve to modulate air-brake pressure on the other end.

Three different hydraulic-over-air relay valve designs are available: single, dual, and tandem.The valves accommodate 150-psi maximum air pressure and 2,000-psi maximum hydraulic pressure. The adjustable valves can operate from a 3:1 to 21:1 hydraulic-to-air-pressure ratio, at temperatures to 250°F.

Mico Inc., 1911 Lee Blvd., North Mankato, MN 56003, (507) 625-6426,

© 2011 Penton Media, Inc.

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