2
1
1
4
3
2
5
6
July 2020
Installation, Operation and Maintenance Manual
MAN 575 Rev. 4
14
Operation and Use
Section 3: Operation and Use
ON-OFF service: four way control valve
The diagram shows the simplest On-Off control. The gas supply pressure is applied to one
side of the cylinder and exhausted from the opposite side. When the control valve (2) is
actuated the connections of supply and exhaust to the cylinder chambers are reversed.
The control valve can have many types of actuating devices (solenoid, manual control,
pneumatic pilot, spring, etc.). The spring return control valves allow "fail safe" operation.
Figure 9
ON-OFF service: Air Fail Safe System
This system allows "fail safe" operation when the pressure in the gas supply line drops below
a set value. The diagram shows the actuator (1 ) in the "fail safe" condition. When the gas
supply pressure drops below the pressure switch (5) set point, the pneumatic supply to the
solenoid valve (6) pilot is exhausted and the actuator moves to the "fail safe" position by
using the gas stored in the tank (4). The tank is connected to the gas supply through the
check valve (3).
Figure 10
Manual
control
Pnematic pilot
control
Dual solenoid
control
pressurized air
atmospheric pressure air
Solenoid control
pressurized air
pressurized air (low pressure)
atmospheric pressure air
