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Articles: Reliability Engineering

The Effects of Maintenance on Reliability

Publisher’s Note:  I will caution you that a) Bill Brinkley comes from the commercial Aviation industry where reliability is not optional and b) he pulls no punches when speaking to industrial maintenance professionals.  I an interested in hearing what you can take away from this paper that was presented at IMC-2007.  You can email me your comments or you can post them here.

In an airline environment, maintenance is king. An aircraft receives about 17 man-hours of maintenance for every flight hour. That may seem excessive - unless you are the one riding in that aircraft. So - the question is, do aircraft really break all that often and do they need that much maintenance? Are they that unreliable? The answer, of course, is no.

Aircraft are designed to be reliable, so why perform all that maintenance? Over ninety percent of the maintenance performed on an aircraft is preventive or servicing in nature. Preventive maintenance is done to maximize availability of the aircraft for operational service and minimize the number of failures occurring at inconvenient times or places.

The Failure Dilemma!

How do I move towards Proaction when I work in such a Reactive environment?

Maintenance Strategies

Break Down Maintenance
The fix controls you, you do not control the fix. The basic strategy is totally reactive. When things break, we fix them!

Preventive Maintenance
This is a time-based maintenance strategy. On a predetermined periodic basis, equipment is taken off-line, opened up, and inspected. Based on the visual inspection, necessary repairs are made (if any) and the equipment is put back on-line. Some preventive maintenance is necessary. For example, various state laws require that annual boiler inspections be conducted. While this is a well-intended strategy, it can be very expensive as typically 95% of the time everything was OK.

The Principles Driving Safety & Reliability: A Look at the History of DuPont

During my 27 years with DuPont, the safety culture was apparent. It was a part of everyone's job every day. As a result of a benchmarking study in the late 1980's and creation of a System Dynamics model to explain the benchmark results, it became clear that safety and reliability operate on the same principles. Both are significantly affected by defects and both require a commitment from everyone in the organization for improvements to be achieved.

The Ups and Downs of Reliability Engineering and CMMS Implementation at Lone Star Steel

Creating a structured reliability engineering department in a facility that has never had one is challenging enough. If you simultaneously implement a new computerized maintenance management software (CMMS) program, the hurdles get higher. The key to success is to have the right management support, good communication and a clear vision of what the future should be. This paper will discuss some of the triumphs and pitfalls that we have encountered on our unending journey through a complex culture change.

Tools for Improving Maintenance strategies and failure analysis processes

A tool is anything used as a means of accomplishing a task or purpose. The purpose of this research is to review the tools available that could be used as a means to improve maintenance strategies and failure analysis processes. The tools reviewed basically fall into one of two categories, these being "Prediction" or "Problem solving". The predictive and problem solving tools reviewed are generic tools that are not specifically aligned to any software package or vendor. In many cases software has been developed to fit these tools or in some cases a generic tool or process has developed from a software package.

Tools to Focus on Plant Reliability

The focus of maintenance has changed from repairing equipment to keeping it running for longer between breakdowns. This requires more consideration of how to get longer running life between repairs, i.e. higher reliability, on a machine. To accomplish this a number of ‘tools' have been invented and developed to allow maintainers to pinpoint problems and fix them. In this article three of the most effective ‘tools' will be introduced. Root cause analysis, Weibull analysis and lifecycle simulation can be used to help organizations achieve proactive approaches to maintenance or adopt a "reliability based approach" to maintenance.

Total Productive Maintenance

Total productive maintenance (TPM) is a corporate-wide effort involving all employees to fully use equipment to the maximum limit employing an equipment-oriented management concept to reduce failures and increase utilization of equipment and processes in a productive manner. TPM programs are teamwork programs and require a corporate culture of teamwork devoid of us vs. them issues. All employees are expected to accept ownership of the equipment and processes to do many small things all the time to insure high levels of availability by eliminating failures in the early stages with low cost actions. The employees approach the process equipment as owners rather than renters.

Understanding & Comparing Risk

By Brian Y. Webster

In the Oct/Nov11 edition of Uptime (Risk & Criticality), a concept of risk was introduced that utilized a Euclidean distance of probability and consequence, mathematically written as

Risk2 = Probability2 + Consequence2

The author claimed that "this [method] provides for accurate comparison of relative risk."¹ The purpose of this article is to explain the conflict between traditional risk calculation methods and distance methods, as well as the potential poor business decision that could result from using distance methods. For the purpose of this article, the Euclidean distance for assessing risk as described in the original article will be called the "positional risk."

Utilizing Advanced Statistical Reliability Methods to Improve Overall Asset Performance

By Mark Latino

Event data analysis can be a very useful in understanding how and when assets fail. It can also provide insight to help plant personnel understand what action to take and when to take it. In other words, it helps in the process of building a strategy for asset performance management.

Weibayes Estimates

If you've got one piece of failure data and nothing else, you're a poor person without much hope. I've you've got one piece of failure data and a Weibull database, you're a rich person with a map on the back of an envelope and a compass by your side to get you out of the abysmal swamp of ignorance and misunderstanding.

Weibull Analysis

Weibull analysis is the tool of choice for most reliability engineers when they consider what to do with age-to-failure data. It uses the Weibull distribution which says mathematically that reliability, R(t) = e^{-(t/h)^b} where t is time, h is a scale factor know as the characteristic life (most of the Weibull distributions have tailed data and lack an easy way to describe central tendency as the mode≠median≠mean, however, regardless of the b-values, which is a shape factor, and all of the cumulative distribution function values pass through the h value at 63.2% which thus entitles it to be know as the single point characteristic life).

Weibull Database

The smartest way to maintain a reliability database is in Weibull format and Weibull databases are available. Seldom do you see Weibull databases from vendors because they jealously protect their data for proprietary reasons-they life/die financially from the Weibull database information.

What is guaranteed Maintainability?

It might seem trivial, but the best way to improve reliability is to choose equipment that doesn't breakdown! At the very least, choose designs that when they do fail they are easy, inexpensive and quick to fix. With the right choices in the beginning, maintenance departments can guarantee maintainability. The field of guaranteed maintainability was coined by Atlanta based consultant, Ed Feldman.

What’s the FRACAS?

Failure Elimination Made Simple

by Ricky Smith, CPMM, CMRP and Bill Keeter, CMRP

How good is your organization at identifying failures?  Of course you see failures when they occur, but can you identify when recurring failures are creating serious equipment reliability issues?  Most companies begin applying RCA or RCFA to “high value failures”.  While this is not wrong, I prefer to either not see the failure in the first place, or at the least, to reduce the failures to a controllable level.

Which Reliability Tool should I use?

Publisher's note: When a person has a hammer - everything looks like a nail. Once a maintenance engineer learns techniques like Reliability Centered Maintenance (RCM) or Weibull analysis, it seems like they apply the technique to every potential area of failure they can find - whether RCM or Weibull analysis can add value or not. Reliability tools must be used in the proper context to create the best result and the more tools we understand the better we can apply them.

We asked our favorite reliability guru, Mr. H. Paul Barringer to help us understand what reliability tools are available to us as maintenance professionals, when we can and should use them and what results we can expect if we apply them correctly.   - Terrence O'Hanlon, CMRP, Publisher

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