Predicting the future

Carter Holt Harvey's Whakatane mill in New Zealand has adopted a predictive maintenance system from Rockwell Automation to pinpoint and avoid potential problems, which can occur during production. But has it really worked?

Located in New Zealand's Bay of Plenty region, the Carter Holt Harvey (CHH) Whakatane mill manufactures a range of clay coated boards, boxboard, and industrial grade plaster linerboard. The unit produces over 85,000 tonnes/yr. As the primary plantation forest owner in New Zealand, CHH exports products to 15 countries, mainly in the Pacific Rim, making it one of the largest forest and building product manufacturers in the Southern Hemisphere. The company's activities include plantation forestry, sawmilling, the manufacture and merchandising of wood products and building materials, as well as pulp, paper, paperboard and tissue manufacturing. On top of that, the outfit is involved in paper and industrial products distribution and the production of a range of building materials.

With a geographically dispersed customer base placing orders months in advance, on-time delivery, consistent quality and reliable production schedules are critical to the Whakatane mill's success. Downtime can not only prove costly, but can also result in paper grade changes that fail to meet customer quality requirements. In the past, breakdowns have cost the Whakatane mill about $100,000 in lost time and materials, with a history of trouble due to dryer bearings (a critical element in keeping the line running consistently).

To gain better control over the site's mechanical failures, the Whakatane mill implemented an integrated condition-based monitoring system from Rockwell Automation in the mid-1990s. The Emonitor Odyssey machinery information system includes both condition-based software, and the related data acquisition hardware, in addition to ongoing technical support. Odyssey integrates vibration, speed, process and other condition data into a common database, providing operators with a complete picture of the health of their plant machinery. Capable of consolidating critical machinery information from a variety of monitoring technologies, the Microsoft Windows-based software system can be used with portable data collectors or permanently installed surveillance or continuous monitoring systems.

According to Colin Gracie, reliability engineer at the mill, "We needed to get a better handle on the condition of our critical equipment components so that we could resolve the mechanical failures that, if not corrected, could lead to major unplanned shutdowns. Since implementing the system, we haven't lost a single dryer bearing."

Backbone philosophy

Condition-based monitoring has always been the backbone philosophy for the maintenance effort at Whakatane and the original monitoring system had served the mill well for years. But when that system became outdated, a new program was required to keep up with business requirements. "The previous system was limited in both the number and frequency of test points and restricted to hard copy historical data, a situation that made trending and long-range analysis difficult, if not impossible. Today, trending of condition-based information to identify problems and root cause is critically important in order to improve the efficiency of the maintenance process," says Gracie.

The redefined condition-based maintenance vision included computerized data collection, storage and reporting capabilities across a much broader range of the critical production equipment. This package allowed the mill to cover more equipment, more frequently with fewer workers.

Rockwell Automation provides a solution to maintenance and downtime problems

After researching the alternatives in the marketplace, Whakatane mill selected an integrated solution from Rockwell Automation - Entek - that included both condition-based software and the related hardware. According to Gracie, "We chose this software, because we believe the heart of any great condition monitoring program is the database. This software is developed in a true Windows environment, and it has the ability to adapt to our requirements. The other important points were the software's multi-instrument capability and the ongoing technical support available in New Zealand."

Condition-based maintenance results

Since installation of the Odyssey solution in April 1996, dryer bearings loss has been virtually eliminated. The CHH maintenance department has recorded a 60% reduction in unplanned downtime, resulting in savings of $230,000/yr. The predictive maintenance program has allowed the mill to increase the number of machine test points by 150% making the entire manufacturing process more reliable. Moreover, the increased confidence in the system has allowed the company to reduce its maintenance, repair and operations (MRO) inventory by $55,000.

Predictive maintenance and improved planning has also allowed the mill to progressively reduce unscheduled downtime. The system indicates potential equipment faults, allowing the maintenance team to plan repairs into scheduled shutdowns. For example, a planned dryer bearing change may take 6-8 hr, while an unplanned emergency change could take up to 12 hr and result in wasted or ruined products. The 30-50% time saving is substantial, especially in terms of cost/hr of lost production.

Maintenance supervisors rely heavily on Odyssey's condition-based monitoring information to plan ongoing plant maintenance and cut back unscheduled downtime and related costs. The trending of condition-based information to identify problems and root cause is critically important in improving the efficiency of a predictive maintenance program. With the help of an integrated condition-monitoring solution, the production and maintenance teams at Whakatane mill work collaboratively to collect and analyze the data - keeping the facility operating at peak production.

According to Gracie, "Using the old system, if something went into alarm, we would need to go back out to the site to retest and analyze the problem in order to define a corrective course of action. Using the new equipment, if something goes into alarm, information is automatically fed into a database. With this information, we can quickly, and with confidence, identify the fault and take the proper corrective action."

Target exceeded

To date, the condition-based maintenance results have been maintained and continuously improved since the program was implemented. Some aspects of the program, such as the reduction in inventory, continue to be ongoing processes. External audits are conducted on a regular basis to maintain the high level of maintenance. When the original maintenance downtime target of 15 hr was achieved, the downtime target was lowered once again. All performance targets have been met and in some cases, exceeded. For example, the mill has achieved and maintained an operational equipment efficiency (OEE) of 97.5% for several years.

According to Gracie, "This predictive maintenance system was the right decision for the Whakatane mill, as it combined support and software and adapted to the mill's requirements as our needs changed. The system adapted with us as we moved into a multi-user networked environment and began using more data collectors and multi-site support." Finally, the success of the predictive maintenance system has allowed the maintenance department to greatly expand its reliability department, as this group has come to utilize the growing amount of maintenance information available. Ultimately, this has allowed the Whakatane mill to focus on reducing the number of planned maintenance tasks than have been traditionally undertaken.