Definition, Goals, And Techniques in Reliability Engineering

Jan 25

How do you assess the quality of the goods you purchase?

In a plant, traditional quality control will entail completing prescribed inspections and testing. If the product meets all of the standards, it is considered ready to use. However, you cannot claim to have purchased a good product if you had to go through the warranty process two or more times before the warranty term expires.

Reliability and dependability are two words that come to mind while thinking about reliability. By adding the dimension of time to the quality equation, engineering helps us measure product quality. To put it another way, we no longer care if a thing will perform its intended purpose at the time of purchase. Rather, we aim to ensure that the product performs as expected under typical settings for as long as feasible.

Not only does reliability engineering assist firms in producing more reliable goods, but it also instructs maintenance teams on how to maintain them in order to maximize MTBF (mean time between failures) and asset lifespan.

If you want to learn more, we'll go through the following topics in the next section of this article:

the idea of trustworthiness
the fundamentals of reliability engineering
the fundamentals of reliability evaluation and how reliability engineers may help enhance equipment dependability

What is the definition of dependability?

The capacity of a component or system to satisfy specified performance requirements over a period of time, assuming typical operating circumstances, is referred to as reliability.

To put it another way, if two systems run under the same conditions, the one that lasts longer and has fewer serious problems is the more dependable.

Because no one can foretell the future or promise that a product will not break after X hours of usage, measuring dependability involves a certain amount of risk, which is represented as likelihood. We may use reliability calculations to predict the likelihood that a system will perform well after x hours or days of operation, among other things. Naturally, every system's dependability will be great at first and then drop with time.

The terms "reliability" and "durability," as well as "quality" and "availability," are frequently used interchangeably. Although the ideas are similar, they should not be confused. Here's a quick rundown of each.

Durability vs. reliability

When faced with the obstacles of typical operation over the course of its intended lifespan, durability may be described as a physical product's capacity to stay functioning without requiring excessive maintenance or repair (definition stolen from Tim Cooper).

The major distinction between dependability and durability is that the former is concerned with how long a product can endure despite the failures it encounters, whilst the latter is concerned with reducing the total number and frequency of such breakdowns.

Furthermore, the durability component is utilized to represent a physical feature, whereas reliability may be used to virtual systems as well.

Durability can be measured in hours of usage, operating cycles, or years of life, depending on the product and its field of application.

Quality vs. dependability

Quality is a difficult notion to describe. Examining the elements that influence product quality is one typical approach to define it. This leads to the notion of eight quality dimensions.

This is a simple method to distinguish between dependability and quality since we can think of reliability (and durability, if you look closely) as one degree of quality.

If we consider reliability on its own, another approach to think about their connection is to state that a dependable system is one that maintains its quality over time.

Availability vs. reliability

The proportion of time that a system is available (totally operational) to do what it was meant to do is called availability.

In IT, the term is frequently used to define the availability of cloud infrastructure. The greatest availability systems are in the 99.99 percent level (which indicates that a service/system is only available for 52 minutes out of every year; sometimes merely for routine maintenance).

Reliability and maintainability have an influence on availability. More dependable systems will have fewer failures, resulting in increased availability. Similarly, the sooner you complete scheduled maintenance, the less downtime you'll have, resulting in higher availability.

What is the definition of reliability engineering?

The systematic use of best engineering principles and procedures to develop more dependable goods in a cost-effective way is referred to as reliability engineering. The technique of reliability engineering may be used throughout the product lifetime, from design to production through operation and maintenance.

However, the primary benefit of reliability engineering is the early discovery of potential reliability concerns. We can drastically reduce future expenses if we discover a dependability issue early in the product lifecycle, such as during the design stage (i.e. by eliminating the need for a significant product redesign after it is already in the market). The graph below illustrates this concept.

The following are the objectives of reliability engineering:

To avoid specific failure modes and minimize the likelihood and frequency of failures by applying technical knowledge and procedures.
Identifying and correcting the reasons of failures that occur despite best attempts to avoid them.
To figure out how to cope with failures that do happen if the causes haven't been addressed.
Methods for predicting the anticipated dependability of new designs and assessing reliability data should be used.

If you look closely at the list, you'll see that the objectives are organized in a way that corresponds to the natural progression of the use of various dependability approaches. If some of the failures can be avoided with simple design modifications, it's pointless to try to implement redundancies for all of them. To put it another way, the actions outlined above should be performed in the sequence listed above to guarantee that dependability practices are implemented in a cost-effective manner.

The fundamentals of reliability evaluation

The ultimate purpose of reliability testing is to have a solid collection of qualitative and quantitative proof that our component/system will not provide an unacceptable degree of risk when used. It's an important aspect of the reliability engineering process.

In this context, risk is defined as the product of the likelihood of failure (how often a failure will occur) and the severity of the failure (what is the fallout of the failure; can include safety risk, potential secondary damage, cost of spare parts and labor, production losses, etc.).

Failure mechanisms and failure modes must be understood

Drawing the line between cause and failure is not always straightforward. There would be no need for reliability engineers or failure analysis if this were not the case.

Complex systems must be "broken down" into components in order to fully comprehend failure modes and mechanisms and effectively address them. This allows you to examine them on an individual level as well as in relation to one another.

In addition to what has already been said, the way the system interacts with its user and the environment is another factor to consider, since both abuse and bad working circumstances can affect product reliability.

Reliability engineering activities and approaches that are commonly employed

There are a range of strategies and activities that may be applied as part of our reliability engineering efforts, depending on how complicated the system is and the sort of system we're looking at:

Analysis of the underlying causes (RCA)
Maintenance with a focus on reliability (RCM)
FMEA and FMECA
FMEA for Design and FMEA for Process
Failure's physics (PoF)
Self-assessment built-in
Analysis of the reliability blocks
Analyzing field data
Analyze the fault tree
Getting rid of a single point of failure (SPOF)
Analyzing human mistake
Analyze the operational risks
Examining maintenance records to determine failure rates and gather data on failures
Various data gathering tests that assess how well a system or component performs under stress...

Using all of these methods, we may identify weak places in our system and determine the likelihood that these flaws will result in problems. We must deal with them by corrective action if the perceived danger is significant enough. Design adjustments (e.g., increasing redundancy), detection control, maintenance instructions, and user training are all common options.

Quantifying trustworthiness

As stated at the introduction to this post, dependability is frequently a game of luck (probability). Because you'll be working with percentages and statistical data to define risk, it's critical that everyone on the team is on the same page and agrees on the acceptable risk levels they're aiming for.

As a result, it's critical to use accurate terminology when outlining issues and suggesting remedies. Furthermore, some reliability experts advise focusing on solutions rather than failure possibilities due to insufficient statistical data and other uncertainties.

How can reliability engineers make their facility's equipment more reliable?

There are a number of ways that reliability engineers may aid in the improvement and optimization of maintenance operations at their site, resulting in greater equipment dependability. We'll go through a couple of them here.

Assisting in the development and design of spare components

The wear and tear that comes with regular use has no bounds. To keep running well, most assets will need to be outfitted with spare components on a regular basis.

Instead of regularly reloading their spare parts inventory, companies with the necessary resources may choose to employ CNC machines or 3-D printing to make their own components. Furthermore, they may have an ancient equipment with no longer available replacement parts or be dealing with a serious malfunction that necessitates a bespoke part.

In these cases, reliability engineers can collaborate with the maintenance team to develop, test, and manufacture high-quality replacement components that will increase the asset's reliability.

Identifying and comprehending failure reasons is something that reliability engineers should excel at. As a result, they may be charged with doing root cause analysis (RCA). They can look at OEM manuals, maintenance procedures, equipment maintenance records, and other data to figure out why certain machines are failing and make recommendations on how to remove and/or minimize each of the failure causes.

Using RCM procedures is one method to address probable causes.

Ensuring that maintenance efforts are directed towards the proper failure modes

This is a continuation of the preceding point. Since the previous point focused on identifying what you aren't doing (which failure types you aren't addressing), let's now look at what you could be doing incorrectly.

Most businesses will find themselves in a scenario where they are doing routine maintenance on an asset yet it continues to fail. While there are a variety of causes for this, one of them is that maintenance professionals are performing incorrectly, such as failing to address the proper failure modes. Referring to RCA analysis can be quite useful in this situation.

Similarly, reliability engineers can examine how various maintenance techniques are carried out and how they might be improved on a regular basis. They can see if the maintenance crew is following outdated procedures and doing preventive maintenance chores that add value and address the appropriate issues. In a solid CMMS system, all of them should be easily accessible.

Check out our guide to learn more about CMMS. What is a computerized maintenance management system (CMMS) and how does it work?

Finally, reliability engineers may assist in the selection of appropriate condition monitoring sensors and equipment for advanced maintenance techniques such as Condition-based maintenance and predictive maintenance.

Final thoughts

Efforts to improve reliability engineering yield severe results. Regardless of the size of your firm, dependability approaches may be adopted with the correct information.

We hope that enterprises will continue to invest in dependability in the future since it benefits everyone involved. Production firms gain from higher-quality goods, maintenance teams benefit from easier maintenance, and users benefit from fewer performance concerns during the product's lifetime. It's a win-win-win situation for everyone.