Your Reliability Engineering Professional Development Site
All models are wrong, some are useful. ~ George E. P. Box
If you know me, you know I do not like MTBF. Trying to predict MTBF, which I consider a worthless metric, is folly.
So, why the article on predicting MTBF?
Predicting MTBF or creating an estimate is often requested by your customer or organization. You are being specifically asked for MTBF for a new product.
You have to come up with something.
Focus on failure elimination, otherwise equipment failures never stop because they are forever being introduced and perpetuated by poor procedures and practices, poor quality control and poor business management systems.
Knowing defects cause future equipment failures, production downtime, unnecessary costs and lost profits, it is necessary to put defect elimination strategies into place to purposely stop defects occurring and to remove the defects that are already present.
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“Any decision is better than No Decision” goes the Law of Decision making. However, sitting on the fence, humming and hawing, chewing the cud, weighing every option, exploring every avenue and leaving no stone unturned can, and often does, eventually amount to, at the end of the day, and in its cold light, without beating about the bush, or wasting any more time…indecision.
Indecision, at least for those affected, leads to a number of things including frustration, demotivation, and anger. These feelings are not felt by those who dwell in indecision as they are blissfully unaware and are ignorantly oblivious as to the adverse effects of their procrastination. They are also incognizant as to their responsibility for wasting everybody’s precious time as well as being bewilderingly ignorant that a definitive decision to do nothing may allow for some productive work elsewhere. But they would rather keep people on tenterhooks and in a state of limbo and avoid any gainful and concurrent activity. Productivity for them is of no consequence…people can always catch up later…or can they?!
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In our first two videos we discussed alarms and event rates. Today we will be discussing rework. What is rework? How can we identify rework? George has it covered. Check it out this latest video and if you have any questions feel free to leave a comment!
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We are happy to release this video on Lognormal Distribution which is a popular distribution to model failures of non-repairable items. In this video, Hemant Urdhwareshe has explained basic concepts of lognormal distribution and its application examples. Hemant also explains its mathematical relationships to calculate MTTF, standard deviation and other parameters In addition, in the video, Hemant has illustrated how to use Minitab and Excel to visualise Lognormal Distribution. Hemant is a Fellow of ASQ and is ASQ CRE, CMBB, CSSBB, CQE and CMQ/OE. We are sure that viewers will find it useful.
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Leaders often initiate change. They are expected to develop a vision for their organization (what we want to become) and create a mission (how we are going to get there). This implies that leaders are dissatisfied with the current state and are motivated to work towards a better future.
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How heavy should you be? Perhaps this is a sensitive question. The average weight of a human is about 65.2 kg or 143.7 lbs. So if your weight is above this figure, are you ‘too heavy’? Conversely, if you are below this figure, are you ‘too light’? Being over and underweight can bring a whole raft of health consequences.
Hopefully you would agree with me in saying that the ‘average’ human weight is not a good benchmark to use if you want to get healthier. Or at least it is not the only benchmark you should think about.
But unfortunately … many manufacturers use approaches that are embarrassingly close to this ridiculous approach to continual improvement.
Failure Modes and Effect Analysis (FMEA) is an excellent foundation for Reliability Programs. It is also a stepping stone to build Reliability, Availability, and Maintainability (RAM) models. Here lies the “beauty” of doing Reliability and Maintenance analysis. Whereby information from one analysis can help enhance another analysis.
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The 8D (Eight Disciplines) method is a problem-solving methodology designed to find the root cause of a problem, devise a short-term fix, and implement a long-term solution to prevent recurring problems. It was first introduced in Ford’s 1987 Team-Oriented Problem Solving manual and has since become a widely used problem-solving method, also known as Global 8D. The 8D process consists of eight disciplines, each focusing on specific aspects of problem-solving
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Recently received a request for my opinion concerning the calculation of system availability using the classic formula
$$ \displaystyle \large A=\frac{MTBF}{MTBF+MTTR}$$
The work is to create a set of goals for various suppliers and contractors to achieve. The calculation values derive from vendor data sheets and available information concerning MTBF and MTTR. The project is in the design phase; thus, they do not have working systems available to measure actual availability.
How would you go about improving on this approach? [Read more…]
Plant and equipment failures are business process failures. Plant stoppages and breakdowns result from failure-causing practices built into business processes and from leaving the right reliability practices out of them. Processes may superficially look okay because they have documentation, charts and records, but if you suffer a steady stream of failures, problems, and rework, then your processes contain unforeseen ‘traps’ into which your people and equipment regularly fall. Failure was not intended when your processes were chosen and designed, but failure is what happens when they are used.
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In the previous articles in this series, we discussed the role that agile digital delivery capabilities plays in your company’s competitiveness and why rapid delivery is so important. In this article, we will look at the many reasons that Agile adoptions frequently fail to deliver what companies expect and suggest some things that you should do to address them.
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In this video, Hemant Urdhwareshe explains how to estimate tolerance interval at given confidence level and specified percentage of distribution. The purpose of tolerance intervals is to assure that the tolerance limits specified during design are achievable during production! Often, the designers specify tolerance limits that are not demonstrated and create lot of rework and/or rejection during production phase. This can increase cost of poor quality (COPQ) and result in redesign of the product and/or revising specifications after the product is released for production. Changes made after product launch can be expensive
I am adding a small correction: at 7:01 minute, please read the tolerance interval as 152 to 308, (and not 358 as shown in the footer).
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Air, sea, space, land, or underground? Commercial, government, or military? Reliability Centered Maintenance has something for everyone!
Absolutely. In fact, in Stanley Nowlan and Howard Heap’s book on RCM, they state:
The content of scheduled-maintenance programs developed by experienced practitioners of MSG-2 techniques may be quite similar to the programs resulting from RCM analysis, but the RCM approach is more rigorous, and there should be much more confidence in its outcome. The RCM technique can also be learned more quickly and is more readily applicable to complex equipment other than transport aircraft.
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In most industries we ideally want the lowest-cost maintenance strategy, one that balances risk of unplanned vs planned maintenance costs to a lifetime minimum.
This is what we’ve calculated in a previous article HERE, and this article/exercise is a follow-on from this.
The downside of using this method is that it may select a maintenance interval where the inherent reliability of the component at changeout time is less than is required for operational reasons, or that we’re not getting the best “increase in reliability vs marginal cost” value. [Read more…]
