For example, if a feedwater flow control loop oscillates because its set point is oscillating, the problem lies with the drum level controller. The fault analysis should then be applied to the ...

For example, if a pressure-reducing control loop is closely followed in the process by a flow control loop, the two control loops can appear to be fighting each other, causing both loops to oscillate.

Many applications will work with on-off, closed-loop control using an analog sensor measuring temperature, pressure, level, or flow as an input to control a discrete output. The same analog sensors ...

A level controller cascades down to the setpoints of the two reagent flow control loops (A and B) via ratio stations. In the example, the reagent flows have target ratios of 68 percent for “A” and 32 ...

In this example, the flow can be managed by speed adjustment of the pump or position of a valve. The result of the change ordered from the controller is stable and is generally fast and repeatable.

And, in practical terms, it only takes 30 to 45° of parasitic shift for the control loop to begin to exhibit unacceptable behavior. Phase- and gain-margin analyses allow proper analysis and ...