How to Integrate Control Performance Monitoring and Plant Work Processes
As mentioned in the
June 2009 edition of PaceSetter,
monitoring your assets and understanding the root causes of downtime and
process upsets lets you take the next step towards a condition-based
maintenance program. Condition-based maintenance is one promising approach
for extending the useful life of your plant and your equipment assets as
it enables you to predict upset events in time to prevent them.
Link between control performance monitoring and maintenance
Control performance monitoring belongs to a growing class of condition monitoring
techniques that are fully automated and have the potential to reduce the demands
on the maintenance workforce while simultaneously improving equipment performance
and reliability.
Following are approaches Boise Cascade Company and Abitibi Bowater’s Bridgewater
Division used to integrate control performance monitoring into maintenance work
processes.
Boise Cascade Company
Prior studies across multiple industries have shown that 30% of all controllers are
in manual while only 20% actually reduce variation while in auto. Figure 1 shows the
control usage for one week from four of Boise Cascade’s five pulp and paper mills.
Their situation was not as dire as that described above, but 12% of their loops were
never placed in auto. Figures 2 and 3 show that of the 1,556 controllers
examined, 13% suffered from strong oscillations and 30% appeared to respond to
disturbances either too aggressively or too slowly.
Figure 1: Control Loop Usage
Figure 2: Control Loop Oscillation
Figure 3: Control Loop Response
Determine the economic opportunity
The dollar value of these performance issues was hard to estimate and depended greatly
on the specific controller and process area. Nevertheless, engineers at Boise Cascade
felt that the overall economic opportunity was significant.
Boise Cascade had an opportunity to:
- improve mill performance by focusing maintenance effort on those controllers that needed it most
- improve maintenance productivity by providing an automated alternative to manual inspections
Audit performance issues and causes
Boise Cascade’s first step was to manually audit 32 control loops and document all
performance issues and their causes. Matrikon then collected several weeks of normal
plant operating data and used that data to identify performance issues and diagnose
their root cause. Using software analysis tools, Matrikon automatically identified all
the loops with significant performance issues. Table 1 summarizes the results.
| Performance Metric |
Score |
| Detailed Assessments |
Overall |
100% |
| Diagnostic comments |
74% |
| Automatic Assessment - No User Analysis |
90% |
| Oscillation Detection |
76% |
| Stiction Detection |
% Identified |
83% |
| False Positives |
2 |
Table 1: Agreement Between Automated Performance Assessment and
Manual Audit (Score = % of loops in agreement)
Engineers at Boise Cascade felt that Matrikon’s Control Performance Monitor was
far more reliable than the current practice of inspecting loops on a schedule or
otherwise relying on the operators to detect a problem. After Control Performance
Monitor was installed at all five of Boise Cascade’s pulp and paper mills, the
next step was to determine how to integrate control performance monitoring and
diagnosis technologies into their daily work processes.
Link technology with your maintenance work systems
Boise Cascade first had to identify those people in the mill who
identified, prioritized and executed control loop maintenance work. Ideally,
the maintenance process used by these people would be consistent throughout the
mill and have formal documentation. In their case, they found that the process
was informal and the central players tended to be the Electrical and Instrumentation
(E&I) supervisor and someone from production who played the role of production-maintenance
coordinator. Once the key players and their existing work processes were identified, the
processes could be modified to take advantage of the condition monitoring software.
Follow-up activity would depend on the specific nature of the performance problem and
the root cause. Boise Cascade developed the work flow process shown in Figure 4 based
on the concept of control loop ’Dispositions.’
Figure 4: Boise Cascade’s Control Performance Management Work Flow
The idea was that on a regular frequency, perhaps weekly, the monitoring system identified
poor performing loops and gave them the disposition ’Requires Attention.’ The
production-maintenance coordinator then reviewed the list and assigned it a follow-up disposition.
In this way, they could weed out obvious false positive results and avoid unnecessary work.
Also, no single individual was saddled with sole responsibility for getting value from the
system; it was instead shared among many groups and individuals. They felt very strongly
that this activity should not be a new responsibility piled on top of existing ones but
rather be a new and improved way of performing current duties.
Impact and Conclusions for Boise Cascade
Boise Cascade used this control performance management work flow, or a variation of it, in
four out of five mills and found it difficult to keep usage at an acceptable level across
all areas of the mill. There tended to be islands of activity in areas that were able to
see the value and ‘switch gears’ away from their traditional way of doing business.
In terms of benefit, they quickly saw one of their largest mills eliminate a small number
of scheduled preventative maintenance (PMs) and begin to rely on the automated monitoring
system to trigger an inspection. They also saw a respectable collection of performance
issues that have been identified and fixed thanks to this process, although it was difficult
to assign a return on investment. Nevertheless, Boise Cascade felt that their maintenance
departments took a significant step towards becoming a highly productive, performance
driven organization.
Abitibi Bowater’s Bridgewater Division
Abitibi Bowater also implemented Matrikon’s technology as a key tool to identify issues with
their process control system. In mid-2007, Abitibi Bowater created a control performance
monitoring group consisting of three process engineers, two production supervisors, two
production team leaders and five operators. The control performance monitoring project was
operations driven and improved interdepartmental communication and partnerships.
Abitibi Bowater succeeded with a modified weekly work flow, as shown in Figure 5. Each week,
the control performance monitoring area leads (i.e. two technical assistants and two process
engineers) followed the work flow, using Control Performance Monitor to identify poor
performing loops and working with the appropriate mill personnel to make improvements. Then
every two weeks, the area leads met to discuss their progress.
Figure 5: Abitibi Bowater’s Modified Work Flow
Abitibi Bowater's Key Factors for Long-Term Success
Throughout their three-year journey to implement a control performance improvement
program, Abitibi Bowater's Bridgewater mill started small with progressive implementation
and achieved the following successes:
-
Created awareness and understanding throughout the mill
- The mill manager recognized the value of reducing variability
- Progress, findings and results were publicized internally
- Awareness was increased via regular communication and presentations to all stakeholders and daily, weekly, monthly and quarterly reviews of performance
- Shared responsibility by creating small teams and assigning responsibility to each area lead
-
Involved Operations to lead the effort
- Operations personnel were the ones who benefited most from the efforts
- Maintenance personnel did most of the fixes