# What optimisation delivers in practice.

> What controller optimisation delivers in practice: case studies with before and after figures, calculated from the trend data from before and after the optimisation.

Running is not the same as controlling well. A controller that is not optimally tuned costs wear, alarms, manual intervention and margin to the trip limit every day, even when nobody seems bothered by it. Below you can see how big that difference was, calculated from the trend data from before and after.

## [Drum level control, from drum level to feedwater pump](/en/results/drum-level-control)

A drum level, a feedwater valve and pumps moving up and down in the same rhythm. Now within a band half as wide, with 62% less valve movement.

- **−49%** Level variation: The drum level moves within a band half as wide around the setpoint.
- **−95%** Large level deviations: More than 10% of the trip band from setpoint: from 8.4% to 0.4% of the time.
- **−62%** Valve movement: Each bar is one hour of feedwater valve movement. The same work, with far less travel.
- **−87%** Fluctuation of valve differential pressure: The pumps now hold the pressure across the feedwater valve steady, instead of swinging along with the valve.
- **−50%** Flow variation: The feedwater flow runs twice as evenly.
- **−76%** Tracking error of the flow control: The flow control follows the master's demand much more accurately.

## [NOₓ trim controller, SCR ammonia dosing](/en/results/nox-trim-controller)

A controller that corrected more than 40 times per hour and consistently came out too high. Now closer to the setpoint, with half as much correcting.

- **−49%** Spread around setpoint: The band within which the NOₓ value stays 95% of the time has become a lot narrower, especially at the top.
- **−71%** Time well above setpoint: More than 20% above setpoint: from 11.7% to 3.4% of the time.
- **−49%** Controller output movement: Each bar is one hour of controller movement. The same work, with half as much correcting.
- **−1.5%** Mean deviation from setpoint: Was +5.7%: the controller consistently came out too high, now practically on setpoint.
- **−23%** Direction changes: The controller output changes direction less often: from 40.4 to 31.1 times per hour.
- **−14%** Ammonia slip: Less unused ammonia downstream of the catalyst.

## Do you know what your controllers are quietly costing you?

The only way to know what there is to gain is to look at your data. We do that in the free PID Performance Scan, and it starts with a no-obligation introduction.

[Schedule an introduction](/en/contact)

[More about the free scan](/en/services/performance-scan)