Sonic nozzle (available as an option)
Excessively high air velocity (e.g. due to low inlet pressure) may cause the desiccant to "float" in the
vessels. The desiccant beads scrape against each other, creating additional dust. High-speed flow occurs
when a compressor starts against an empty air net or when working at a discharge air pressure that is too
low. A high volume of compressed air output can result in a pressure drop, which in turn increases the
speed.
Therefore, it is recommended to protect the drying medium against excessive volumetric flow through the
desiccant by installing a sonic nozzle.
Refer to the instruction delivered with the sonic nozzle to install and adjust it.
2.2 Operation
The construction of the air dryer is simple, reliable and easy to service. The dryer has two towers,
containing the adsorbing material or desiccant. The desiccant is a very porous grain material which can
adsorb large amounts of water vapor.
The operation cycle of the dryer is repetitive and is controlled by the Purelogic™ controller and a PDP
(Pressure Dew Point) sensor (when installed and activated).
The compressed air entering the dryer is led to one of the towers by means of the inlet valves (IV), which
are controlled by a pneumatic actuator (PA). As the air flows upwards through the tower, the desiccant
adsorbs the water vapor and the compressed air is dried. The dry air leaves the dryer via the outlet,
connected to the top of the tower.
While the desiccant in the first 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: a
small portion of the dried air passes a nozzle (N), expands to atmospheric pressure and flows downwards
through the other tower, regenerating the desiccant. The regenerating air is released via the corresponding
exhaust valve (PV) and the silencer (S).
The regeneration time is regulated by a programmed half cycle time. Solenoid valves, controlled by the
controller, energize the pneumatic valves that determine the function of the towers. In case a PDP sensor is
installed and activated, a second small portion of the dried air flows via the control air valve (100), a small
air filter (101) and the pressure regulator (PR - only used on 232 psi versions) to the PDP sensor.
The PDP sensor constantly measures the pressure dew point of the air leaving the drying tower. As long as
the PDP temperature is below the set point (-40 °F or -100 °F), the drying tower will keep on drying, until
the PDP temperature exceeds the set point. On that moment the regenerated tower will start drying the
compressed air and the other tower will start regenerating. As long as the PDP temperature is below the set
point, regeneration of the non-drying tower is stopped after the pre-set time interval of the timer has
elapsed. As a result, reduction of purge air is achieved.
Flow diagram
The figure below shows the pneumatic diagram of the dryer.
Instruction book
10 2920 1891 00
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