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Operation principle
The operation cycle of the dryer is repetitive and is controlled by a factory-set timer,
programmed in the controller.
While the desiccant in one tower dries the compressed air, the desiccant in the second
tower is being regenerated. Regeneration of the desiccant is achieved by means of purge
air from the drying tower.
The compressed air entering the dryer is led to one of the towers by means of the inlet
selector valve. The position of the selector valve depends on the condition (activated or
not) of the solenoid valves. While the air flows upwards through the tower, the desiccant
adsorbs the water vapour and the compressed air is dried.
The dried air leaves the dryer via the outlet selector valve.
A small portion of the dried air passes a nozzle (8 for PD3, 7 for PD1), expands to
atmospheric pressure and flows downwards through the other tower, regenerating (drying)
the desiccant.
The regeneration air is released via the solenoid valve and the silencer of the regenerating
tower. The solenoid valves are controlled by the controller.
After a pre-set period, the function of the towers is reversed. The fully regenerated tower
will now dry the air, while the desiccant in the other tower will be regenerated.
By default, the regeneration timer will restart from the beginning of the cycle in case of a
power failure during operation.
Purge control
The dryer is equipped with a dew point sensor, extending the drying time and saving
compressed air. The regeneration time remains timer controlled.
Operation principle:
The sensor constantly measures the atmospheric dew point of the air leaving the drying tower.
While the dew point is measured below the purge saver set point the dryer will continue to supply dry air,
but the purging of the regenerating tower will be de-active. Once the dew point rises above the set point
the purge cycling function will become active.
Summary of Contents for dMED 025
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