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Optimize your Preventive Maintenance

by Christer Idhammar

Preventive maintenance (PM) is often set up in a very inefficient way in many mills. It is typical to see that the PM program is work order driven instead of route driven. Many PM tasks are still done while equipment is down because this was how it was set up, and no one has ever questioned whether this is still needed, or guard design prohibits on-the-run inspections, etc.

Because the system is work order driven, the execution of PM tasks is often very ineffective. For example, a PM system that was recently analyzed revealed that inspection of six limit switches on a sludge press took one hour for an electrician every week. This was because the PM system was work order driven and issued one work order per inspection, and the inspection included travel time. A good inspection of six limit switches on the run in a route-driven system should not take more than five minutes, and it could be integrated with mechanical inspections of the sludge press or done by an operator.

Of course, all big system suppliers will tell you that their system can handle PM routes very efficiently, but that is very seldom true. The route must be set up in a work order combining many tasks, which is better than in the above example but is still very inefficient for many reasons.

It is also very common that separate PM systems are set up for mechanical, electrical, instrumentation, and lubrication inspections without any integration of PM tasks. Obviously, this will result in much unnecessary duplication of work. On top of this, it is common to add operator inspections without removing the inspections now done by operators for PM tasks included in existing mechanical, electrical, and instrumentation inspections.

WHAT YOU CAN DO? You must use a system that will allow you to compile all PM activities under each equipment number and print and/or electronically display route-based PM activities.

When you have done this, it will be easy to decide what PM tasks you are going to keep, change, or eliminate. To truly optimize your total PM, you will benefit greatly from professional training in smart look-, listen-, smell-, and touch-type inspections; inspection frequencies; and methodology to decide whether a PM task is valid or not, since it is sometimes more cost effective to operate until breakdown and prepare a corrective action when the breakdown occurs.

When prioritizing "what" and "when" to perform a PM task, I propose the following guidelines:

  1. Do it while equipment is in normal operation.
  2. If this is not possible, do it when equipment is shut down.

If you follow this guide, more than 90% of all PM tasks can be done on the run, thus freeing up valuable hours during a shutdown.

To determine who should perform a PM task, the following prioritization is suggested:

  1. Operator
  2. Maintenance area craftsperson
  3. In-house maintenance specialist in, for example, vibration analysis
  4. Outside expert in, for example, thermovision or X-ray.

Following this principle will eliminate duplicate and unnecessary PM tasks. Total PM hours can be reduced by 50 to 70%, and at the same time, you will improve your PM.

When deciding how to do a PM task, you can easily overcomplicate it with an elaborate analysis. A better way of deciding is to use available standard documents describing what to do and why you do it. Using these standards can reduce the PM enhancement/implementation and training time by 30 to 70%.

Graph 1 describes the expected results, which have been similarly documented in many mills. With an elaborate analysis, you will not reach an optimum of PM costs. Results are quickly generated from organizing and doing the basics correctly, without complicated analyses.