Emerson Rosemount OCX 8800 Reference Manual page 178

Foundation Fieldbus
Figure 7-21:
Solution
If the flow is controlled, steam pressure variations will be compensated before they
significantly affect the heat exchanger temperature. The output from the master
temperature loop is used as the setpoint for the slave steam flow loop. the BKCAL_IN and
BKCAL_OUT connections on the PID blocks are used to prevent controller windup on the
master loop when the slave loop is in Manual or Automatic mode or it has reached an
output constraint.
168
PID function block cascade control example
Figure 7-22 illustrates the correct function block configuration.
OCX 8800