Yokogawa YVP20S - Manual (Page 169)

17-8
<Toc> <Ind> <17. FAILSAFE HANDLING>
IM 21B04C50-01E
Step7 This step requires privilege level 3, 4, 8 or 9.
Open the Configuration dialog. Select the Position tab. The position limit changes
made in Step 5 will prevent failsafe action from occurring and will disable FOA and
Position High Limit. Unless there is an important control consideration, do not
change these values.
Click Clear Latch.
Click yes to the switch to OOS to Release Failsafe. Then return to Manual operation state
to resume manual operation of the valve. Then follow plant procedure to return to
automatic control. The Deviation Error Failsafe configuration can later be restored by
resetting the T2 parameter in Configuration>Position.
Figure 17.10 Clear Latched
Figure17.11 Change Mode to OOS Warning
WARNING
Setting the T2 Parameter, to cause failsafe after a sustained position error, can cause
unwanted process shutdowns. The T2 setting should be used cautiously. Care must be
taken to avoid interaction with other configuration parameters, particularly High and Low
Position limits.
17.5.2 If the failsafe is caused by internal diagnostics
If an A/D Converter Failure or Position Sensor Failure of the XD_Errors occurs, the A/D
converter or displacement sensor may be malfunctioning. Take appropriate action, such as
placing a service call.