Why reliability engineering

Participates in the development of criteria for and evaluation of equipment and technical MRO suppliers and technical maintenance service providers. Develops acceptance tests and inspection criteria. Participates in the final check out of new installations. This includes factory and site acceptance testing that will assure adherence to functional specifications.

Professionally and systematically defines, designs, develops, monitors and refines an Asset Maintenance Plan that includes: Value-added preventive maintenance tasks Effective utilization of predictive and other non-destructive testing methodologies designed to identify and isolate inherent reliability problems Provides input to a Risk Management Plan that will anticipate reliability-related, and non-reliability-related risks that could adversely impact plant operation.

Develops engineering solutions to repetitive failures and all other problems that adversely affect plant operations. Creating a product that matches the expectations imposed by the customer permits the product to work as expected. Understanding the conditions allows the design to meet without over designing thus optimizing product cost and customer satisfaction.

Unanticipated failures cost time for customers and for the organization to resolve the failures. Using reliability and availability concepts we can minimize failures and avoid wasting time. Some products require a run-in or burn-in to identify and eliminate early life failures or to refine and optimize system operation. Using reliability engineering techniques we can minimize the time and resource impact of run-in or burn-in operations.

Eliminating or minimizing the time we reduce inventory carrying costs, tooling costs, and energy requirements. At the heart of these lessons is the idea of putting the human first : either when considering the impact of reliability on users, or the developers keeping things afloat.

Success depends on understanding how your users and developers feel and truly empathizing with them when making decisions. SRE gives you the tools to connect these empathetic insights with actionable data. You can also see how Blameless helps empower your SRE practices, join us for a demo! View here. Blameless Homepage. Incident Resolution. Main Blog.

About Us. Schedule Demo. Reliability engineering provides business value A reliable service is more valuable to a customer than one with inconsistent performance.

Reliability engineering empowers development You may think of reliability engineering as an overhead cost to development, an additional layer of work that must be accounted for. SLOs and error budgets SLOs and error budgeting work as a system to ensure downtime, latency, and other indicators of unreliability are kept within acceptable bounds. Incident retrospectives Despite proactive measures, incidents are inevitable.

Automation and consistency SRE principles also accelerate development through their focus on automation and consistency. Get the latest from Blameless Receive news, announcements, and special offers.

One obvious activity already mentioned is quality control, the whole range of functions designed to ensure that delivered products are compliant with the design. For many products, QC is sufficient to ensure high reliability, and we would not expect a match factory or a company mass-producing simple diecastings to employ reliability staff. In such cases the designs are simple and well proven, the environments in which the products will operate are well understood and the very occasional failure has no significant financial or operational effect.

QC, together with craftsmanship, can provide adequate assurance for simple products or when the risks are known to be very low. Risks are low when safety margins can be made very large, as in most structural engineering. Reliability engineering disciplines may justifiably be absent in many types of product development and manufacture. QC disciplines are, however, essential elements of any integrated reliability programme. A formal reliability programme is necessary whenever the risks or costs of failure are not low.

We have already seen how reliability engineering developed as a result of the high costs of unreliability of military equipment, and later in commercial application.

Risks of failure usually increase in proportion to the number of components in a system, so reliability programmes are required for any product whose complexity leads to an appreciable risk. An effective reliability programme should be based on the conventional wisdom of responsibility and authority being vested in one person.

Let us call him or her the Reliability Programme Activities reliability programme manager. The responsibility must relate to a defined objective, which may be a maximum warranty cost figure, an MTBF to be demonstrated or a requirement that failure will not occur. Having an objective and the authority, how does the reliability programme manager set about his or her task, faced as he or she is with a responsibility based on uncertainties? This question will be answered in detail in subsequent chapters, but a brief outline is given below.

The reliability programme must begin at the earliest, conceptual phase of the project. It is at this stage that fundamental decisions are made, which can significantly affect reliability. These are decisions related to the risks involved in the specification design, complexity, producibility, etc. The shorter the development time-scale, the more important is this need, particularly if there will be few opportunities for an iterative approach. The activities appropriate to this phase are an involvement in the assessment of these trade-offs and the generation of reliability objectives.

The reliability staff can perform these functions effectively only if they are competent to contribute to the give-and-take inherent in the trade-off negotiations, which may be conducted between designers, production staff, marketing staff, customer representatives and finance staff.

As development proceeds from initial study to detail design, the reliability risks are controlled by a formal, documented approach to the review of design and to the imposition of design rules relating to components, materials and process selection, de-rating policy, tolerancing, etc. The objectives at this stage are to ensure that known good practices are applied, that deviations are detected and corrected, and that areas of uncertainty are highlighted for further action.

The programme continues through the initial hardware manufacturing and test stages, by planning and executing tests to generate confidence in the design and by collecting, analysing and acting upon test data.

During production, QC activities ensure that the proven design is repeated, and further testing may be applied to eliminate weak items and to maintain confidence. The data collection, analysis and action process con- tinues through the production and in-use phases. Throughout the product life cycle, therefore, the reliability is assessed, first by initial predictions based upon past experience in order to determine feasibility and to set objectives, then by refining the predictions as detail design proceeds and subsequently by recording performance during the test, production and in-use phases.

This performance is fed back to generate corrective action, and to provide data and guidelines for future products. The activities are described fully in subsequent chapters. Obviously the reliability programme activities described can be expensive. However, despite its intuitive appeal and frequent presentation in textbooks and teaching on quality and reliability, this picture is misleading. Closer thought easily uncovers the error in the picture.

In other words, all effort on an effective reliability programme represents an investment, usually with a large payback over a short period. The only problem is that it is not easy to quantify the effects of given reliability programme activities, such as a certain amount of testing, on achieved reliability. However, experience shows clearly that the more realistic picture is as shown in Fig.

It was W. Deming Reference 9 who first explained this relationship in his teaching on production quality. The truth has been clearly demonstrated by the success of the companies that have wholeheartedly adopted this teaching.

Achieving reliable designs and products requires a totally integrated approach, including design, training, test, production, as well as the reliability programme activities. In such an approach it is difficult to separately identify and cost those activities that are specifically devoted to reliability, as opposed to say performance or cost. The integrated engineering approach places high requirements for judgement and engineering knowledge on project managers and team members.

Reliability specialists must play their parts as members of the team. Intrinsically reliable components , which are those that have high margins between their strength and the stresses that could cause failure, and which do not wear out within their practicable lifetimes.

Such items include nearly all electronic components if properly applied , nearly all mechanical non-moving components, and all correct software. Intrinsically unreliable components, which are those with low design margins or which wear out, such as badly applied components, light bulbs, turbine blades, parts that move in contact with others, like gears, bearings and power drive belts, etc.

Systems which include many components and interfaces, like cars, dishwashers, aircraft, etc, so that there are many possibilities for failures to occur, particularly across interfaces e. It is the task of design engineers to ensure that all components are correctly applied, that margins are adequate particularly in relation to the possible extreme values of strength and stress, which are often variable , that wearout failure modes are prevented during the expected life by safe life design, maintenance, etc.

Therefore we must submit the design to analyses and tests in order to show not only that it works, but also to show up the features that might lead to failures. When we find out what these are we must redesign and re-test, until the final design is considered to meet the criterion. Then the product has to be manufactured. In principle, every one should be identi- cal and correctly made.

Of course this is not achievable, because of the inherent variability of all manufacturing processes, whether performed by humans or by machines. It is the task of the manufacturing people to understand and control variation, and to implement inspections and tests that will identify non-conforming product. For many engineering products the quality of operation and maintenance also influence reliability.

Failures are caused primarily by people designers, suppliers, assemblers, users, maintainers. Therefore the achievement of reliability is essentially a management task, to ensure that the right people, skills, teams and other resources are applied to prevent the creation of failures.

Reliability and quality are not separate specialist functions that can effectively ensure the prevention of failures. They are the results of effective working by all involved. There is no fundamental limit to the extent to which failures can be prevented.

We can design and build for ever-increasing reliability. Deming explained how, in the context of manufacturing quality, there is no point at which further improvement leads to higher costs. This is, of course, even more powerfully true when considered over the whole product life cycle, so that efforts to ensure that designs are intrinsically reliable, by good design and effective development testing, generate even higher pay-offs than improvements in production quality.

The creation of reliable products is, therefore, primarily a management task. Guidance on reliability programme management and costs is covered in Chapter British Standards Institution, London. Quality and Reliability Engineering International. Wiley published quarterly. IEEE Trans. IEEE published quarterly. Deming, Out of the Crisis. Drucker, The Practice of Management. Heinemann Define a failure rate, and b hazard rate. Explain their application to the reliability of components and repairable systems.

Explain how this theory relates to the behaviour of the component hazard function. What are the main objectives of a reliability engineering team working on an engineering development project? Describe the important skills and experience that should be available within the team. Briefly list the most common basic causes of failures of engineering products.

It is sometimes claimed that increasing quality and reliability beyond levels that have been achieved in the past is likely to be uneconomic, due to the costs of the actions that would be necessary. Present the argument against this belief. Illustrate it with an example from your own experience.

This results in the usual engineering definition of reliability as: The probability that an item will perform a required function without failure under stated conditions for a stated period of time. Reliability can also be expressed as the number of failures over a period. The objectives of reliability engineering, in the order of priority, are: 1. Why teach Reliability Engineering? Why do Engineering items fail? The main reasons why failures occur are: 1.

Probabilistic Reliability The concept of reliability as a probability means that any attempt to quantify it must involve the use of statistical methods.