Brief idea of Loop tuning


#1

What is loop tuning ?
Why we need a Loop tuning

Reduce variabilty,not sending oscillation to downstream.
Manage variablity,sending disturances at the right place.
Reduce interactions,remove oscillations.
Improve quality to increase production.
To do reduce additives consumption,operator interventions.

When we need to do a loop tuning?

A loop that was once functional well,may become unstable or perform poorly under the following conditions.
Changing process conditions
Sticking valves,positioner problems,new configuration.
Plugged lines in pressure or DP transmitter
Fouled heat exchangers
Cavitating pumps

Loop Tuning - Parameter to adjust

F - Filter,small enough to not modify the model (increase dead time)
P - Proportional is the main parameter.
I - Integral slowly remove error remaining after proportional correction.
D- Derivative is used if dead time originates from small time constants.

Types of Tuning

1.Iterative Tuning

Iterative tuning is also known as Trial and error.
Can be very time consuming.Especially for slow loops.
Results in optimal tuning values only for that operating region.
Rarely provides insight into valve problems,non-linearity.

2.Ultimate gain - Zieger Nichols method

3.TOP control tuning rules