 When I began my career in the paper industry, maintenance time was viewed essentially as a mill cost which should be minimized. After all, the time spent in making repairs reduced the output from the paper machines, and the same jobs often were repeated over and over, due to incorrect procedures or the use of makeshift materials. In fact, some mill superintendents refused to shut down the machines unless absolutely forced to do so by equipment failures.
The prevailing attitude was to run as many hours of the day as possible, since restarting after shutdowns was not always an easy endeavor. Eventually more technically oriented personnel were integrated into the mill management positions, and maintenance began to be viewed differently. Gradually, it was realized that planning and completing required maintenance could result in increased productivity, due to significant reduction in overall machine down time.
After the thinking evolved to viewing maintenance as a potential benefit, attention became focused on equipment history, leading to the making of lists of anticipated repair needs in the event of either a scheduled or non-scheduled outage. But basing repairs simply on operating history proved to be inadequate, due to the dynamic nature of paper machine operation. In addition, the complexity of machine processes increased, as larger and faster paper machines were installed in the mills.
In spite of the limitations of the earlier repair lists, there was a positive result which grew from the practice: the concept of maintenance planning. Planning meetings including both operating and maintenance key personnel began to be conducted regularly. Some of the elements of the meetings included:
• Deciding if the critical areas of the machine had been adequately inspected.
• Clearly establishing the key contact personnel for communication control during the shutdown. One of the important persons identified was the Maintenance Planner/Coordinator.
• Differentiation of the work to be done during a planned versus an emergency outage, and the individual manpower required by the crafts.
• Identifying what work could be done "on the fly". (This is an often overlooked area of opportunity.)
• Deciding on whether an extended shutdown was needed or whether sufficient work could be accomplished using a series of "mini-shutdowns".
• Separating the tasks between in-house or outside contracted personnel, if applicable.
• Arranging for support as needed from major suppliers or the paper machine OEM.
• Establishing the critical path of maintenance work in order to keep tabs on the progress of the work compared to expectations.
• In post-shutdown meetings, critiquing the work done and whether the time allotted was reasonably met. If not, deciding what could be done differently during a future shutdown.
• Making certain that all safety aspects of each job were reviewed, and that lock-out procedures were understood.
In my experience, it was more efficient to use the "mini-shutdown" method rather than longer outages, unless a major repair dictated otherwise. We elected at the time to rotate between two shorter monthly cycles-one of about 8 hours, the other about 14. These were usually coordinated with critical machine clothing changes. Needless to say, the planned time targets were not always achieved. For example, some critical repair need might have been discovered during the shutdown which could not be delayed until the next outage. And, at specific times of the year longer outages might be required, as established in a union contract.
There are many other components of maintenance that are important to mills. These are being used in today's paper mills to provide improvements in both predictive and preventive maintenance. Two of the important areas are as follows:
1. Maintenance training: Totally accepting on-the-job training as adequate for key skilled maintenance personnel will likely result in less than desired performance. Many of the OEM's and repair centers conduct training courses in the correct procedures to use on specific equipment, such as bearings, pumps, rolls, motors, etc. Giving at least the skilled maintenance team leaders these opportunities is worth the cost of involvement. It is also very useful to make sure the Maintenance Planner is exposed to industry accepted maintenance planning procedures.
2. Specialized training: Deciding on the need for specialized training for mill maintenance personnel or electing to have these services performed by outside specialists is an important management decision. Here are a few items which fall into this classification:
a.) Vibration analysis: Being able to measure and interpret vibration data is a valuable asset, but equipment is costly and the amount of training required is significant.
b.) Oil particulate and corrosion analysis: Mills may not have the laboratory facilities to do this work.
c.) Alignment: While some mills have the ability to perform alignments, my preference would be to have this type work done by outside experts.
d.) Temperature monitoring and infra-red photography: These can be done by well trained mill personnel, and will provide valuable information for trouble-shooting.
e) Machine clothing and roll cover analyses: Mills should insist that suppliers provide these services using worn samples. Much can be learned concerning retention of original properties, contamination, and wear patterns.
f.) Roll balancing: It is critical that all rolls be balanced to strict tolerances after each period of operation. The roll cover supplier, OEM, or roll repair facility used is normally better equipped to do this work.
Most of the critical functions on today's paper machines are continuously monitored with instrument measurements retained in computer data bases. This information should be analyzed and used in the mill's predictive maintenance process. Often, variations begin to approach statistical control limits before equipment related failures actually occur. Staying "ahead of the curve" will not only help prevent unscheduled outages, but also more carefully and completely identify the future work to be scheduled.
Robert Moore is a retired chemical engineer, and is an experienced technical and fictional writer. His past work experience spanned the chemical, paper and equipment manufacturing industries, including holding management positions at Voith Paper, Scapa plc, and The Mead Paper Corporation. |
