Pareto Power in Maintenance


Some of the most important activities in Maintenance require a very large commitment of time and effort. Examples include naming all stock items and all equipment, setting up PM programmes and developing spare parts lists.

Some of these activities can be greatly simplified while achieving most of the benefits if you know where the greatest opportunities lie. The right place to start can be identified by carrying out a “Pareto analysis”.

Typically, improvements based on such a Pareto analysis are expected to achieve 80% of the benefits when 20% of the work is done. Good information records will identify the 20% that will provide the greatest benefits.

In maintenance, the “Pareto effect” is often much stronger that 80/20. Here are a few examples.

  1. Spare parts lists

The most important spare parts lists are for those items of equipment on which corrective maintenance or routine parts replacements are most frequently carried out.

In one plant where a project to establish new spare parts lists was being started an analysis of work order records showed that 60% of all corrective maintenance was carried out on less than 3% of all equipment. Starting with this 3% would obviously provide a much faster return on the cost of developing this critical information than working through the entire plant from end to end. In fact, once the 3% of spare parts lists was completed by maintenance experts, it would then be reasonable to use a process, such as the “automatic” spare parts list function available in many maintenance computer systems to gradually develop the lists for the other 97%. (NOTE – “Automatic” spare parts lists generation usually results in many errors, unless it is carefully managed by area maintenance experts. See “Spare Parts Lists“).

  1. Preventive maintenance inspection programmes

In a large pulp mill, a study of 3 years of excellent, equipment-level downtime records showed that, of over 12,000 items of plant, 87 items (much less than 1%) caused 80% of all unscheduled maintenance downtime. The establishment of a PM programme for these 87 items reduced the unscheduled downtime by over 50% within 18 months.

This is an excellent example of the value of good maintenance/operating information. In this case, all downtime that resulted in less-than-target production on each shift was recorded and the equipment that caused each loss was identified. This is, arguably, the best measure of maintenance because it not only provides a measurement of Maintenance’s “product” (reliability), it also provides this information in a form that lends itself to a Pareto analysis that can be used directly to improve performance. For more on this see “Measuring reliability“.

  1. Maintenance costs

Where equipment maintenance costs are important (and they may not be – see “Why measure maintenance costs?“), then a Pareto analysis of long- and short-term costs for all equipment items, showing the highest-cost items only provides a much more useful report than a simple monthly report on the cost of all equipment.

Where there is a lack of data, a substitute for a Pareto analysis is to interview experienced operators and tradespeople and their supervisors to identify, for example, the equipment which is repaired most frequently.



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© Veleda Services Ltd

Don Armstrong, President