The TRASAR tuning procedure is comprised of three steps. The three steps are baseline, first step and second step. During each step the pump output % is held at a fixed value over a chosen duration. The TRASAR data is collected after the tuning procedure and fitted to a mathematical model in the
Configurator software. A set of PID values will be computed and can be uploaded to the controller to begin PID control.
For systems configured as intermittent feed systems, the chemical pump will suspend feeding the internal treatment during the feedwater down-time (off-time). This will not interrupt the tuning process.
Tuning Steps
1. Select Edit Fluorometer in the Configurator
2. Select Tune PID Controller in the input configuration screen.
3. On the PID tuning dialog box , select Auto Tune to start the auto tune process. In the Auto Tune PID loop screen, enter the Auto Tune Settings before starting Auto Tune. The Configurator Help Screens provide detailed information on the steps and parameters.
• Ensure that the pump to be controlled has the optimum stroke setting. Click on Calculate
Pump Stroke and enter the required data. It will give the suggested stroke %. The actual feed
rate is shown so that the user can verify by doing a drawdown to confirm the stroke setting.
• Confirm the Setpoint is correct.
• A Baseline Output value should be entered for the baseline step. The user should choose this value such that the TRASAR readings will be between the setpoint and 50% of the setpoint during the baseline duration.
EXAMPLE: If the setpoint is 10 ppm then the Baseline Output should be chosen so that the
TRASAR reading will be between 5 ppm and 10 ppm. So, if the TRASAR pump output is currently set at 50% to maintain 10 ppm. A Baseline Output of 35% would provide a TRASAR reading of approximately 7ppm.
OM0211_________________________________________________________________________
• The Baseline Duration is set to 15 minutes by default and can be changed by the user. The baseline duration should be greater than the system lag time to allow the TRASAR reading
to stabilize.. For intermittent systems, the baseline duration should follow the recommendation,
above as well as exceed the average off-time (down-time) by at least 4 times.
EXAMPLE: If the boiler feed water is off for an average of 5 minutes during an on-off cycle,
then the baseline duration should be at least 20 minutes.
• The Step Output is automatically calculated from the baseline output such that the TRASAR reading goes higher than the setpoint at some point in the tuning process. The setting can be changed if needed.
• The Step Duration is equal to or greater than the baseline duration but can be changed if needed. The first and second step output durations must always equal to each other.
• For intermittent systems, the step duration must follow the above recommendations as well as exceed the off-time (down-time) by at least 4 times
4. After all the tune settings are entered, click on the Start Auto Tune button to begin the tuning process. The analog pump output will automatically change as shown in the plot.
Graphing of the tuning data will be displayed (example)
Note: When the Auto Tune cycle is completed capture the graph by using the “Print Screen” function
and “copy/paste” into a Microsoft XL document. Alternately an editing tool like “Snagit” can be used. The graph can be used to calculate the true system lag time.
5. After all three stages of tuning are complete the Configurator will analyze the data and calculate a set of PID values. Any errors or warnings will be listed on the tuning calculations screen. If any errors appear, the Upload button will be grayed out. Warnings are indicate whether the tune followed all the recommended conditions. Click on Upload and the values will be uploaded to the controller and PID control will initiate. NO REBOOT IS NEEDED.
OM0211
Note: The “I” value will typically be equal to or greater than the system lag time (in seconds). This
should have been measured before tuning (see Section 5.3)
6. If the Configurator is unable to calculate a satisfactory set of values error messages will indicate the cause. .
•
TRASAR reading did not rise when pump speed increased. Check for problems in controlling the pump. Check for air-locked pump.•
Steam load variation was too high during the tuning process. Repeat the tuning when conditions in the boiler are more stable.•
If the variation in the steam load seen during tuning is typical, increase the first step output by 5% and the first step duration by 5 minutes. Then repeat the Auto Tune procedure.Note: “Warning” messages will permit the user to upload these PID values with the
understanding that the values may need some additional manual tuning after monitoring control performance
Note: PID parameters can also be entered manually via the keypad or 3D TRASAR Configurator.
•
For TRASAR tuning, ensure that the change in TRASAR values during the tuning process aregreater than when the pump output is held at a constant output.
Note: See Section 12.5 for additional PID Troubleshooting.