Samson 3730-0 Mounting and operating instructions - Start-Up and Settings
7
Start-up and settings
7.1 Default switch positions
After the positioner has been mounted on
the valve, all switches S1 to S10 must be set
to OFF.
7.2 Fail-safe position
The switch position of switch S1 depends on
the fail-safe position of the valve:
4
AIR TO OPEN · Upon air supply failure,
the valve is completely closed by the
actuator. As the signal pressure in-
creases at the output of the positioner
(OUTPUT 38), the valve opens.
4
AIR TO CLOSE · Upon air supply failure,
the valve is completely opened by the ac-
tuator. As the signal pressure increases
at the output of the positioner, the valve
closes.
To determine the switch position, read the
associated switch position S1 = ON or OFF
from the cover plate at the actuator symbols.
The symbols are read properly when the
symbol shows the actuator on top of the
valve; symbols upside down do not apply.
AIR TO OPEN: Pneumatic connections point
to the right S1 = ON. Pneumatic connections
point to the left S1 = OFF.
AIR TO CLOSE: Pneumatic connections point
to the right S1 = OFF. Pneumatic connec-
tions point to the left S1 = ON.
AIR TO OPEN always applies for dou-
ble-acting actuators. Proceed as described
in section 4.3 to connect the reversing
amplifier.
7.3 Volume restriction Q
The volume restriction Q is used to adapt the
air delivery to the size of the actuator:
4
Actuators with a transit time < 1 s, e.g.
linear actuators with an effective area
smaller than 240 cm², require a re-
stricted air flow rate (MIN).
4
Actuators with a transit time
³
1 s do not
require the air flow rate to be restricted
(MAX).
The position of volume restriction Q also de-
pends on how the signal pressure is routed
at the actuator in SAMSON actuators:
4
The “SIDE“ position applies for actuators
with a loading pressure connection at the
side, e.g. Type 3271-5.
4
The “BACK“ position applies for actua-
tors with a loading pressure connection
at the back, e.g. in Type 3277-5.
The “SIDE”restriction position always applies
for non-SAMSON actuators.
Overview · Position of the volume restriction*
Signal
pressure
Transit
time
< 1 s
³
1 s
Connection at the side
MIN SIDE
MAX SIDE
Connection at the back
MIN BACK
MAX BACK
* Intermediate positions are not permitted.
28
EB 8384-0 EN
Start-up and settings
MAX BACK
MIN SIDE
MIN BACK
MAX SIDE
Q
Fig. 11 · Volume restriction Q
MAX BACK/MIN SIDE setting