Samson 3730-2 - Determining the Fail-safe Position; Adjusting the Volume Restriction Q

96 EB 8384-2 EN
Operating the positioner
7.1 Determining the fail-safe position
Denethefail-safepositionofthevalve(0%)takingthevalvetypeandtheactuator'sdirec-
tionofactionintoaccount.PositiontheAIRTOOPEN/AIRTOCLOSEslideswitchaccording-
ly:
− AIR TO OPEN setting
Signal pressure opens the valve, e.g. for a fail-close valve
TheAIRTOOPENsettingalwaysappliestodouble-actingactuators.
− AIR TO CLOSE setting
Signal pressure closes the valve, e.g. for a fail-open valve
For checking purposes: after successfully completing initialization, the positioner display
mustread0%whenthevalveisclosedand100%whenthevalveisopen.Ifthisisnotthe
case, change the slide switch position and re-initialize the positioner.
The switch position is prompted prior to an initialization. After an initialization has been
completed, changing the switch position does not have any effect on the operation of the po-
sitioner.
7.2 Adjusting the volume restriction Q
MAX BACK
MIN SIDE
MIN BACK
MAX SIDE
Q
Signal
pressure
Transit time
<1s ≥1s
Connection at the side MIN SIDE MAX SIDE
Connection at the back MIN BACK MAX BACK
* Intermediate settings are not permitted.
Fig.36: Volume restriction Q
The volume restriction Q serves to adapt the air output capacity to the size of the actuator:
− Actuators with a transit time < 1s, e.g. linear actuators with an effective area smaller
than240cm²,requirearestrictedairowrate(MIN).
− Actuators with a transit time ≥ 1sdonotrequiretheairowratetoberestricted(MAX).
Note