American Dryer Corp. AD/ML-310 - Manual (Page 23)

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E. COMPRESSED AIR SUPPLY SYSTEM
The compressed air supply system of the tilting dryer consists of a number of pneumatic pistons located throughout the
dryer. The pistons are actuated by solenoid valves that are under computer control. The pneumatic pistons are used to:
– Tilt the Dryer for Loading and Unloading
– Open and Close the Load and Unload Doors
(for dryer models equipped with automatic doors)
– Operate the Steam Coil Damper (for Steam Heated Models Only)
1. Filter/Regulator/Gauge Assembly
The compressed air supply to the dryer is connected into the 3/8” F.P.T. fitting of the filter/regulator/gauge assembly,
which is located at the bottom rear of the right side of the base.
The filter/regulator/gauge assembly performs three (3) essential functions. The filter removes most solids and
liquid particles from the compressed air stream and traps them in a bowl, where this waste can be readily removed
through the drain valve at the bottom of the bowl.
The filter bowl should be cleaned monthly.
The regulator will remain a nearly constant outlet air pressure so that the dryer’s air pistons will function normally
despite upstream air pressure variations. After the compressed air is connected into the filter/regulator/gauge
assembly, adjust the regulator knob so that the gauge needle reads 80 psi (5.51 bar).
2. Optional Piston Operated Tilting Valves
A 2-way tilt dryer has two (2) of these solenoid valves: one (1) to control the front set of tilting pistons and a second
to control the rear set of tilting pistons. A 1-way tilt dryer has only one (1) solenoid valve.
Each valve has five (5) 3/8” F.P.T. ports and two (2) electric solenoid operators, one (1) on each side of the valve.
To tilt the dryer forward, a 24 volt signal is applied to the rear pistons solenoid connector “L6” and no voltage is
applied to the solenoid connector “L7”. On 2-way tilt dryers, a 24 volt signal is present at the front piston solenoid
connector “L4”, this prevents both front and rear pistons from extending their rods at the same time. The internal
spool in the valve will move and 80 psi (5.51 bar) of air will enter the bottom port of the rear tilting pistons,
extending the rear tilting piston rods and tilting the dryer forward for unloading. The top piston ports are bled into
the atmosphere.
To level the dryer, the voltage signals are reversed. No voltage is applied to the “L6” solenoid, and
24 volts is applied to the “L7” solenoid. The valve spool will now move so that 80 psi (5.51 bar) of air is applied
at the top piston ports, while the bottom piston ports are bled into the atmosphere. The piston rod will now retract
leveling the dryer. On rear tilt dryers, the front tilting piston ports are bled to the atmosphere.
The tilting piston valves are 5-port/3-position valves. If no voltage is applied to both the “L6” and “L7” solenoids,
ALL five (5) valve ports are blocked. This means that, if the dryer is tilting or leveling and the power is shut off, the
pistons will lock in position, holding the dryer in a partially tilted position.
The tilting piston valves are located on the pneumatic plate in the rear of the dryer’s base.