ATI Q46H/85 PAA System Part 8 – PID Controller Details
56
O&M Manual
Rev F (8/17)
of operation, and become highly exponential at the extreme ranges of the measuring scale. In
addition, if a chemical process is not symmetrical, that means it responds differentially to the
addition and subtraction of chemical. It is important in these applications to study steady-state
impact as well as step-change impact to process changes. In other words, once the process has
apparently been tuned under normal operating conditions, the user should attempt to force a
dramatic change to the input to study how the output reacts. If this is difficult to do with the actual
process input (the recommended method), the user can place the control in manual at an
extreme control point such as 5% or 95%, and release it in manual. The recovery should not be
overly oscillatory. If so, the loop needs to be de-tuned to deal with that condition (reduce P
and/or I.)
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