5-6 CHAPTER 5: PNEUMATICS
ALPHA ST320 S2
3.3. Solenoid valve
Directly controlled by the PLC, the solenoid valves activate the cylinders.
By pressing the button A, the cylinders could be activated manually. This button could be kept at the
activation position by pressing it down and turning 90° clockwise. This position could be released by
turning it 90° counter clockwise.
This manoeuvre may prove to be useful during tests or maintenance. When the button is released, the
pneumatic cylinder returns to its resting position (except for pneumatic cylinders activated by double-
effect solenoid valve YV2).
3.4. Air pressure switch SP1
To guarantee the compressed air is supplied to the bar feed system, the
p
ressure switch serves to confirm the pressure is existing.
The pressure switch engages when the pressure is larger than 2 bar and
closes the emergency stop circuit.
When the air pressure drops below 0.5 bar, the switch disengages and
interrupts the emergency stop circuit. An alarm e01 arises.
A
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