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Reliability – What does it mean?

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Reliability – What does it mean?

  • Posted by: Art Durnan
  • Category: Maintenance Improvement

In September I was invited to sit on a panel at a meeting of the Global Mining Standards and Guidelines Group (GMSG) on the subject of reliability. I was lucky enough to sit with an esteemed group of experts who had many years of mining, asset management and reliability experience.

The Global Mining Standards and Guidelines Group facilitates global mining collaboration on solutions to common industry problems, needs and technology through standards, guidelines and best practices. GMSG operates on the five principles of inclusivity, collaboration, innovation, optimisation and technology.” You can find their web site here:  http://www.globalminingstandards.org/.

Likewise, many of the panel members and attendees were my friends and it was great catching up. The panel started off by answering several questions.

  • What does reliability mean to you? How do you explain your mandate to others?
  • What are some of the key things you have done in your organization to be successful?
  • What defines success? How do you know you’re meeting your mandate?
  • How do you measure it?

Since we got the questions in advance I had some time to think about how I would answer but it also did give me time to reflect historically on how we established reliability as a job title in mining. It was in about 1995 that I first received the title of Director of Reliability for a major mining operation. I did have some understanding of what manufacturing reliability meant from my time working in Aerospace and Defense as I had a close friend who was a failure analyst in semi-conductor manufacturing. He would receive a failed circuit board, test it and write a failure report. The group kept statistics on failed components and used the data to improve quality. My friend, as I came to learn, was doing classic Reliability Engineering.  Actually in my role as Director of Reliability, I supervised engineers doing predictive maintenance tasks and got involved in some root cause analysis work that often extended to Failure Modes and Effect Analysis.

We began to train in Reliability Centered Maintenance and that was the program of the time being widely promoted by the likes of John Moubary (RIP) and others.  I moved on from that job with a new appreciation for what could be done with shifting to on condition maintenance. The next time I actually encountered the title again was as a corporate Manager of Maintenance and Reliability with in fact a staff that had the title of Reliability Engineer although they widely differed in skills. As time went on the title became more common until almost every mine had someone who was called a Reliability Engineer.

Here is how I answered the first question:

“Reliability is the probability that an asset (component) will complete a mission under a stated set of conditions.”

This is but one definition of reliability and there are many, but this one works well for me in the mining and processing context. The example I often give is that a haul truck needs to be able to complete its scheduled production hours at the intended capacity hauled. So it is really a measure of mission success. One measure that gives some insight to machine reliability is Mean Time Between Failure defined as Operating Time/Number of failures. It gives an answer that is average time to failure and is a window into the reliability of the machine. In my experience MTBF for mining haulage could be reported as low as 24 hours or as high as 120 or higher. But just think about it and MTBF of 24 hours means that every truck on average is down every day for something. The question I always asked “Is that acceptable?” If we were running an airline would you fly with us? Growth in Mean Time Between Failures as a metric implies an improvement in machine reliability. In mining, attempts have been made to use the Overall Equipment Effectiveness metric and for mobile equipment it has application but is a bit hard to us as a comparative indicator with mine planning altering haul routes etc.

The second question was easier for me to answer. Reliability cannot be achieved in the vacuum of an effective maintenance program alone, but requires a total organizational focus, of course, from the way equipment is designed, procured, operated, maintained, improved etc.  We learned in mining in the last decade that if equipment is operated within its design limits it breaks less. I say this today as a joke, but this was a major breakthrough in thinking as was typical of the time that equipment was operated overloaded and under maintained. Seldom then and even today do we realize the inherent reliability of equipment.  An operator focus on reliability is essential to any successful program. Likewise, maintenance as a function must be about removing defects if reliability is to grow. Changing the same parts that are failing prematurely will not likely improve the reliability of the equipment and, in fact, may decrease due to improper repair practices.

There is one part of the equation that also needs to be considered and that is productivity. A highly reliable fleet can in fact cost too much to operate. The fact that a business needs to produce at a cost that is less than what the marketing people can sell the product for is still the first guiding principal. Margin remains king during constrained market conditions as we are experiencing now.

In a past life and fairly recently I was accused by accountants of providing a too high availability on the haulage fleet. That the reliability programs did not consider the cost and we were over maintaining. These comments came from people who never had the challenge of maintaining equipment and got somewhat lost in a failed analysis.  As I always said at the end of any project, the auditors will show up to bayonet the wounded.

The fact was that the enterprise had over capitalized during the boom and in chasing incremental production ended up with excess capacity. This showed up as standby time and that is counted in the availability calculation. Because of that utilization remained low. You have to operate the equipment to generate revenue. There was one thing true, however, in all of this and that is we had a history of over maintaining because our strategy was set by purchasing agreements that mandated time based change outs. Useful parts were being thrown away early.

At XRT we have a lot of experience in improving the Reliability of equipment, practical advice for organizations that are trying to improve and proven use of technology to get there. If we can help let us know.

We’ve had a radiant fall in Wyoming,  but it snowed last week on the valley floor. Winter is not quite officially here yet, but surely coming. The Wyoming Cowboys are winning most of their games, a welcome change from years past.

Good luck with your reliability programs and take a look at the GMSG site. The group will be doing some work on Reliability so stay tuned.

Regards Art

Author: Art Durnan
With over 45 years of industry experience primarily in Asset Management, Art is an pioneer in Asset Management. Previously Art held positions in project management, engineering design, and process engineering in hydrometallurgical and pyrometallurgical processes.

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