This dashboard shows that almost 61% of the control loops have Default Tuning, consequently, they have NEVER been tuned.
These two dashboards immediately show optimization opportunities
These two dashboards immediately show optimization opportunities
The onsite discovery phase is the next step in the journey, where our experts take the results of the LTI and do a deeper dive into your process. Your LTI dashboard will outline the key focus areas for immediate improvements and provides a guideline for the onsite Discovery Phase.
Process data will be collected, analyzed and compiled in a comprehensive report that will detail recommendations for improvement and, where possible, the potential ROI for each recommendation.
Process data will be collected, analyzed and compiled in a comprehensive report that will detail recommendations for improvement and, where possible, the potential ROI for each recommendation.
A series of recommendations will come out of the Discovery stage.
These recommendations will cover:
- Process modifications
- Control Strategy modifications
- Instrumentation Repair/Replacement
- Loop tuning
Example
The first step during the Discovery Stage is to examine and walk down the process equipment. In this example, a pH controller was analyzed. The caustic addition was done at the outlet of a tank in Building #1. Building #1 required Intrinsically Safe instrumentation whereas Building #2 did not. Consequently, the pH was measured in Building #2.
The lengthy piping distance between caustic addition and the pH sensor introduced 150 seconds of process time delay. This long delay made controlling the pH very difficult, resulting in having the operator putting the controller in Manual mode.
This lack of control caused quality issues
The lengthy piping distance between caustic addition and the pH sensor introduced 150 seconds of process time delay. This long delay made controlling the pH very difficult, resulting in having the operator putting the controller in Manual mode.
This lack of control caused quality issues
It was recommended that the process design by modified by installing a slipstream along with a pH sensor that was Intrinsically Safe.
This reduced the process time delay, making the pH controllable.
This reduced the process time delay, making the pH controllable.
Example: Boiler Feedwater Pump
In the Discovery Stage, the data showed that the flow curve tapered off as the valve opened. The process sensitivity decreased to a point where the flow controller was too sluggish at the upper end.
This was confirmed by observing the discharge pressure versus the feedwater flow.
The primary recommendation was to replace the worn-out pump. However, the lead delivery time for this mammoth pump was over 52 weeks.
The primary recommendation was to replace the worn-out pump. However, the lead delivery time for this mammoth pump was over 52 weeks.
The interim solution was to install a characterizer between the output of the PID block and the valve.
The end result was a linearized flow curve. This would ensure that the controller tuning response was the same throughout the full range of the PID output.
Example
In the Discovery Stage, the data showed that this chemical injection control valve had 10% backlash or hysteresis.
This translated into a control imprecision of 70 GPM or 32% when compared to a flow controller setpoint of 215 GPM.
This valve imprecision caused significant product quality problem and overdosage.
This translated into a control imprecision of 70 GPM or 32% when compared to a flow controller setpoint of 215 GPM.
This valve imprecision caused significant product quality problem and overdosage.
Example: Loop Tuning
Following the ‘Recommendations’ path, control loops will benefit will be optimized. Typically, this is done using the EnTech Toolkit. This toolkit will collect, analyze and calculate and manage the tuning parameters.
In this example, the level controller was tuned improperly. This caused the inflow to oscillate and destabilized upstream control loops.
The level controller tuning was then calculated properly retuned to prevent level and flow oscillations.
In this example, the level controller was tuned improperly. This caused the inflow to oscillate and destabilized upstream control loops.
The level controller tuning was then calculated properly retuned to prevent level and flow oscillations.
-(1).png "Degradation of control loop performance can be slow and insidious. Once a control related problem has been detected and identified, it has been occurring for a long time.")
Degradation of control loop performance can be slow and insidious. Once a control related problem has been detected and identified, it has been occurring for a long time.
This phase will monitor your control assets on a periodic basis and track their performance. Top Quartile performers use this predictive monitoring program to ensure maximum performance from their control loops.
Automatic Control Loop Performance Monitoring
For our DeltaV customers, an additional monitoring step can be incorporated by applying a continuous loop performance package called DeltaV Insight. This program will continuously monitor certain dynamic aspects of selected control loops. It will provide several metrics including the following:
- Percentage of time the control loop is not in its normal mode
- Variability
- High process oscillations
- Tuning