Rockwell Automation 1771-QDC, D17716.5.87(Passport) CLAMP AND EJECT MODE - Manual (Page 197)

Tune Your Machine
Chapter 10
10-24
Pressure Alarm Setpoints
The QDC monitors process pressures and compare them against two
different types of high pressure alarm setpoints. Pressures are compared to
absolute pressure alarm setpoints (configured in the MCC - refer to
chapter 4) on a continuous basis and without regard to current machine
mode or operational cycle. Pressures are compared to profile pressure
alarm setpoints (configured in the respective configuration blocks - refer to
chapter 7) only during the execution of the subject profile. In general:
Use absolute pressure alarms to detect dangerously high pressure
conditions. We recommend these alarm setpoints be set well above
normal operating levels while still below levels that could result in
machinery damage or danger to personnel. Program your PLC ladder
logic to stop the QDC module and place the machine in a safe condition
if one of these alarms is triggered
Use profile pressure alarms to detect abnormally high pressure
conditions. We recommend these alarm setpoints be set only marginally
above the highest pressure expected during any acceptable iteration of
the subject profile while still low enough to be indicative of process
problems. Program your PLC ladder logic to interrupt the process or
signal the machine operator to determine corrective action if one of
these alarms is triggered
Profile Watchdog Timer Presets
Set your Profile Watchdog Timer presets after your machine is running
repeatable quality parts. Set them only marginally longer than the
repetitive duration of the subject profile. Expiration of these timers can
then be used as an early alert to operators that a process problem may be
developing.
Watchdog time-outs may also be used in your PLC ladder logic to
automatically initiate a corrective action. For example, your PLC could
monitor the Low Pressure Close profile watchdog and initiate a re-open,
re-eject, and close re-try if it times-out during profile execution.