Implementing the project was relatively inexpensive, costing slightly more than CDN$46 000. Yet, it resulted in savings of about $28 000 during just one planned outage. More importantly, the project demonstrated that over the long-term, this technology would improve control valve reliability and reduce field device maintenance costs throughout the mill. In fact, timely and effective troubleshooting using this technology actually prevented an unscheduled shutdown of the mill's finishing line.
The valves selected were those typically removed during annual shutdown periods and sent out for evaluation, repair, and/or replacement. Because the performance of these valves is critical to the efficient operation of the mill, it was considered necessary to physically check them each year, even though the process was costly and frequently revealed nothing wrong.
The Asset Management Solutions (AMS) software offered a means of eliminating this practice by continuously monitoring the operation of those valves and reporting on their condition without removing them. The software's performance in the mill during the pilot project was so favourable, its use was continued. It now tracks some 75 valves. It could eventually be networked to all 540 control valves throughout the mill as well as other intelligent field devices, providing operating and maintenance benefits.
As a concept, asset management ensures the timely maintenance of field devices so they can deliver maximum performance and service life at minimal cost. Saving time and avoiding expensive equipment failures are key benefits of asset management programs.
The AMS software, developed by Fisher-Rosemount, allows mill personnel to look directly into smart field instruments in a way not possible previously. It communicates with any HART or FOUNDATION Fieldbus device on a control network, capturing information generated by those smart devices. Massive amounts of field-based data are integrated into a single database, organized, processed and presented for use by engineers and technicians.
Time is saved by:
Streamlining routine maintenance tasks such as loop checkout and tuning, as well as instrument configuration and calibration;
Troubleshooting field devices by examining their condition from the safety and convenience of the maintenance shop;
Making ongoing maintenance more efficient than ever before through predictive maintenance;
Documenting maintenance activities automatically, thus eliminating time-consuming manual record keeping.
Installation and evaluation
Initiating the pilot project in the Grande Prairie mill was relatively easy. The AMS software, installed in a file server located remotely in a computer room, is networked by means of RS232/485 converters through Elcon multi-plexer boards in termination cabinets and out to the selected control valves. The control platform is a Honeywell TDC 3000. The HART communications protocol enables AMS to pick the desired information off the DCS without interrupting or degrading the I/O signals. Installation costs are limited because no additional field wiring to the selected valves is needed.
The smart control valves chosen for this project are located throughout the site: power plant, utilities, chemical recovery, and the pulping and finishing units. They were picked because of their importance to the process or because they had been troublesome in the past. Typically, these particular valves were removed annually and sent out for FlowScan examination and repair if necessary. Eliminating that procedure during the May 2000 shutdown saved the company more than $26 000.
Other benefits were even more significant. For example, fast troubleshooting by technicians using AMS actually prevented an unscheduled finishing line shutdown after the system drew attention to the lack of pressure control on a critically important 170-lb steam valve on the Flakt dryer. Since the valve was not operating properly, plans were made to replace it, requiring the finishing line to shut down for a minimum of three hours. However, the detailed picture of the valve's performance provided by AMS of what was actually happening at the valve enabled the mill to pinpoint the root cause of the problem -- sticking at a certain point in its stroke. With this knowledge, the control system operators were able to work around the problem until the valve could be replaced about a week later during a planned outage - preventing a costly unplanned shutdown.
AMS allows a faster and improved diagnosis of that problem with AMS. AMS also brings current data on the condition of every one of the networked valves back to the file server where maintenance or control personnel have access to the information at any time. When designated operating parameters are exceeded by one of the field devices, a "device alert" calls attention to the condition, which might possibly lead to operating problems. Technical personnel are then able to evaluate the situation and determine how long that piece of equipment can be expected to operate effectively. Depending on their prediction and the importance of the equipment to mill operations, a "repair now or wait" decision can then be made. Of course, corrective measures are taken immediately if necessary, but every effort is taken to prevent an unexpected shutdown. Predictive maintenance concentrates on keeping essential equipment operating while less critical equipment receives an appropriate amount of attention.
The pilot project tested and evaluated only the ability of AMS to monitor the condition of a select few control valves and prevent unnecessary maintenance while avoiding severe problems. However, it is also capable of providing key employees with information they need without having to go out and look for it. The software is tied in to the business LAN as a means of delivering information to people who need it, even in another mill in another country. The remote tie-in capability includes a protected Weyerhaeuser "Intranet link" to the mill's valve supplier, enabling AMS application and valve troubleshooting support as requested.
The mill will be developing a customized alarming and reporting capability, sending e-mail messages to appropriate persons to give them early warning that certain valves should be examined. These are the initial steps in establishing a predictive maintenance program.
Previously, these critical control valves were not actively monitored, and valve maintenance was performed during planned maintenance shutdowns or upon failure. The process of moving from a conventional maintenance system to predictive begins when software-monitoring tools are effectively used to minimize or eliminate re-work and labor-intensive preventive maintenance checks.
The next step is the application of automatic, enhanced reports to initiate action on specific equipment, thus eliminating the need for unnecessary preventative maintenance checks. Therefore, only periodic checks are necessary to validate system performance.
The described systematic procedure relies heavily on the skills of the Information Technology Department. Its skills are necessary to automatically sort, short-list, and present "relevant information" to the right people.
The two-fold purpose in applying AMS to the reliability of Grande Prairie's pulp production processes are:
Effective application of maintenance resources during plant operations: Use "condition based monitoring-maintenance tools" to prevent catastrophic failur es. (See previously described example of 170-lb steam valve.)
Improve the efficiency of valve re-building activities normally scheduled during maintenance shutdowns. The mill accomplishes this by using historical data as decision criteria in determining which valves need to be re-built.
The pilot project showed that shop personnel would accept AMS. The local Fisher-Rosemount representatives from Spartan Controls Ltd. in Grande Prairie were helpful in training personnel, answering questions and showing them how online monitoring and valve diagnosis can make their lives easier.
While the system is not yet fully utilized by all instrument technicians, the mill is planning ongoing training coupled with "hands-on" time to completely integrate appropriate people into AMS.
The mill is looking forward to moving the AMS from a pilot project to a full-fledged mill resource, adding many more control valves and possibly other field devices to the existing system. P&PC
Ben Klimach and Rick Sirockman are with Weyerhaeuser, Grande Prairie, AB.