The Model 7149 high-pressure dew point monitor and alarm system is designed to provide a simple, reliable method of measuring the dew point (moisture content) of high-pressure (up to 5000 psig) dry air systems. It is a variation of the system incorporated in our high pressure desiccant air dehydrators. Here, it is used as a stand-alone device, downstream of an air dehydrator whose built-in monitor/alarm system is unreliable or no longer supported by the original manufacturer, or in conjunction with an inter stage membrane dehydrator (IMD) not containing its own dew point monitor. The fi rst installation with an IMD is on USS MAHAN, DDG 72. Fittings furnished as standard allow easy installation at the end of the HPAC discharge hose.
Measurement is made by a highly sensitive aluminum oxide sensor, which is bathed by a continuous stream of
air. Its impedance varies with the air’s moisture content, and is read by the humidity alarm controller . The operator may adjust the controller to achieve the desired alarm point. The dew point meter on the front of the control panel displays the current outlet air dew point. A sample valve compatible with a MIL-I-24144 high-pressure frost point indicator is provided.
If at any time the outlet air moisture content exceeds the controller’s set point, the controller activates the humidity alarm. This alarm includes the fl ashing red humidity alarm lamp , the audible alarm(buzzer), and the humidity alarm remote connection . The buzzer can be disabled by the audible alarm switch . The humidity alarm remote connection is a relay closure (closed on alarm) with a 6800-ohm resistor in parallel. The remote
signal is ICAS-compatible.