01671H (DCN6051) 5-1
5.1 Overview
Refer to Figure 5-1, Figure 5-2, and Figure 5-3 for the following:
The M701 dries and scrubs ambient air to produce zero air.
The compressor draws air in from the rear panel bulkhead union and inlet filter. At the
compressor outlet, the air is under pressure and hot from the compression. The relative
humidity is high as a result of the high pressure.
The air is conducted through the cooling coil where heat is removed by transfer to the
cooling fan air. With the pressure still high but the temperature reduced to ambient, the
relative humidity is at its highest. At this point, the air is usually supersaturated.
From the coil, the wet air passes through a coalescing filter where the excess water is
separated and settles in the bottom of the filter. The controller periodically opens the
solenoid drain valve allowing the water to be expelled through a rear panel bulkhead
union (drain).
The partially dried air passes a pressure relief valve, set to open at 90 psig., and enters
the Regenerative Dryer which removes essentially all the remaining water and a portion
of the other contaminants. The pressure relief valve may open occasionally and can be
loud but this is a normal part of the operation of the M701.
The dry air then passes through a check-valve to the storage tank. A pressure switch
turns off the compressor when the pressure in the tank reaches a set high value, and
turns the compressor on when the pressure reaches a set low value. Thus, when air
demand is low, the compressor is turned off and the tank fulfills the demand. The
pressure in the tank varies from approximately 35 psig to approximately 80 psig
depending on the demand. As the air leaves the tank, its pressure is controlled to 30
psig by an air pressure regulator mounted on the front panel. This maintains a constant
pressure at the calibrator inlet and is displayed by the pressure gauge on the M701 front
panel. (Some specials with restricted output are set to 50 psig.)
For a final clean-up, the dry, regulated air enters the specific scrubbers:
First, the optional Hydrocarbon scrubber where Hydrocarbons and CO are catalytically
converted to CO2 and water. Then, the NO scrubber where NO is oxidized to NO2, then,
the activated charcoal scrubber where the NO2 is absorbed. Then the optional CO
scrubber, where CO is catalytically oxidized to CO2, Finally, the clean dry air passes
through a fine particulate filter and leaves the M701 through the rear panel bulkhead
union (Zero Air Out).