If you are executing Preventive Maintenance on equipment that continues to break down or your maintenance cost continues to increase I recommend you read this article on the 10% Rule of Preventive Maintenance. This short explanation of the 10% Rule of PM may be what you need to take that next step in the journey to optimizing reliability or just reducing equipment failures.

“The 10% Rule of Preventive Maintenance is simple and it works”

Here is how the 10% Rule of Preventive Maintenance works. The 10% Rules of PM stated that if a PM is executed within 10% of a time frequency then it is considered compliant with the standard. An example would be a monthly PM must be completed within 1-1/2 days on each side of the due date in order to be in compliant (I recommend you use 30 days as an average for a monthly PM calculation). The reason for applying this rule is it reduces the variation of PM Execution time frequency. In maintenance we must identify and reduce variation in the maintenance process and this is a great example where it should be applied.

In the example below a 30 day PM is executed in June near the end of the month (too many problems at the beginning of the June so PMs had to be pushed  back) at the beginning of July the same PM is executed  (things were going well at the beginning of the month so one must complete your PMs because we know bad days are coming), in August the PM is executed on the 28 of the month (because of too many problems at the beginning of the month). This 30 day PM is actually a 28 day PM, a 3 day PM, and a 58 day PM. See the problem?  This problem is worst when a company uses a maintenance software or EAM (Enterprise Asset Management) software that kicks out all PMs for the month on the 1st and you think we have 30 days to complete the PMs.  The crew or planner are told to make sure these PMs are completed sometime within the month so they can meet 100% PM Compliance. Can you see the problem now? In many organizations the focus is on PM Compliance rather than stopping equipment failures.

PM Rule

The 10% rule of Preventive Maintenance was first created by a Maintenance professional by the name ofDon Nyman. Don was one the greatest maintenance and reliability professional I ever had the honor to know and work with.  I have been applying and teaching the 10% Rule of Preventive Maintenance all over the world and have seen the results and they are amazing.

Below are some basic a few basic principles which must be followed when applying the 10% Rule of PM:

Principle #1:  Management must be totally committed and believe in this process.

Principle #2: Insure your PM Procedures are repeatable with instructions, steps, specifications, etc.

Principle #3:  It is acceptable to have low PM Compliance when you first begin this journey however what is not acceptable is for the PM Compliance not to improve.

Principle #4: When measuring PM Compliance using the 10% Rule be sure and track total maintenance cost, mean time between failure of critical assets, emergency vs pm labor hours to insure management sees the results of this process.

PM Effectiveness (2)

Principle #5: Begin application of this process to your organization’s most critical assets or take one area or one equipment type. Do not attempt to apply this to all your assets overnight.

Principle #6:  As failures are reduced expand this process throughout your organization. Be sure before you move to the next area, asset, etc. that repeat-ability of the 10% Rule PM has demonstrated success over 6-12 month period.

Develop and apply your own principles as you gain knowledge and experience using this process.

Many companies will never apply the 10% Rule of PM because of many reasons and that is ok, what is not ok is to say it does not work. Alcoa Mt Holly outside of Charleston, SC, USA has been applying this rule to 100% of their assets for many years and have shown tremendous success as a result. In the chart below you will see their Maintenance Cost is 2.0% as a Replacement of Asset Value (international standard for evaluating maintenance cost – 2.0% is world class) and their PM compliance is 85.77%. This is a large aluminum smelter with a carbon plant and cast house in case you wanted to know how large this plant is. You can Google “Alcoa Mt Holly” if you wish to learn more about their plant or see a picture of the site.


The challenge today is for you to determine if this journey is worth taking.  If you are not applying the 10% Rule of PM and have a high PM compliance but equipment continues to fail then the 10% Rule of PM is for you. Be sure you develop a well thought out plan before you execute.

If you have comments or questions please post them on this blog or send me an email at

NOTE:   I need participants in a research study I am conducting on the “10% Rule of PM”.

I need all levels of maintenance organizations who:

  • are not using the 10% Rule of Preventive Maintenance at any level
  • are currently using the 10% Rules of Preventive Maintenance at any level (with good or bad results)
  • are interested in implementing the 10% Rules of PM in a specific area of your operation
  • are willing to share results from the study (your name or company does not have to be used), I would like for you to volunteer the use of your name, title, and company however it is not required, confidentiality will be provided (you have my personnel guarantee on it)
  • all business types are preferred, Oil and Gas, Food and Beverage, Mining, Facilities, Government, etc. The study will break out the data by business type along with combined data of all business types.
  • if you are interested in assisting me with this study please let me know. It would be a great educational experience for you and me as well.

What metric do you use for PM Compliance?


7 Responses to 10% Rule of Preventive Maintenance

  1. Raman Autar says:

    Hello Ricky, we looked at Alcoa in ealry 2000 when we were emabarking on our Maintenance Best Practice journey so I am familar with their achievements. So. tell me, why was Alumax so good in certain aspects like managing backlog, PM Compliance, etc and still not doing well in producing results? Is it that they were doing the things right but not doing the right things?

    • 9rsmith_9 says:


      I cannot vouch for 2000. In 1998 John Day retired and Alcoa bought Alumax so a lot of changes were going on in maintenance and at the plant during the time you visited the plant. 13 years later however I can tell you right now they are awesome. I spent 3 days in the plant with all levels of maintenance and engineering and can validate that out of over 200 maintenance organizations I have seen they are #1.

      Thanks for your input my friend.


  2. Bjarni Ellert Ísleifsson says:

    Hi Ricky,

    Great post as always, thank you for sharing. PM Compliance is important as well as the Schedule Compliance, the 10% rule focuses on the Schedule compliance and sets the quantitative rule around the execution of PM activities.

    We also need to be constantly critical of what PM´s we are doing and if failures continue look at why that is, we might be executing the wrong Maintenance activities if we have constantly the same failures.

    Keep up the good work my friend, hope to see you soon.

    Best regards, Bjarni

  3. cheloiniguez says:

    For all the trouble it could save you, employ effective preventive maintenance in your facility.

  4. Ted Martland says:

    Overtime/Straight Time in ’97 = 1 at Alumax. If this is not a percent, it is certainly clear why Maintenance Spending /RAV is almost double that of Alcoa in 2012 (100 hours/100 hours =1). I would have to assume that Raman is correct from the information provided.

  5. Kevin says:

    Have to be careful with some statistics when it comes to compliance etc. Sometimes the focus is to meet the KPI at any cost – and I have known of work orders/PM routines being issued and closed (without any work being done!!) to make the stats look good.

    • Ricky Smith says:


      You are correct, some companies do not use data correctly thus they never know where they are. It is known that any metric which shows the “real story” is what one needs on this journey to optimizing asset health and thus reduction of failures and I know the 10% Rule of PM, if applied correctly brings awesome results.


      Ricky Smith CMRP

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