Reliability Engineering Tutorial
Reliability engineering tutorial is designed to guide you through studying and understanding the concepts, rational, language, applications, and tools of reliability engineering. This tutorial serves as a map to show you what and where to look for essential, major material required to know in order to develop and implement a reliability engineering program.
What Is Reliability Engineering and What Purpose(s) Would It Serve?
Reliability engineering is defined as the likelihood of success, in terms of frequency of failures. Some define the reliability as the quality over time. It may not sound like a perfect definition but it has some valuable points to it. When we talk about the quality of the product, we mean its functionality right after it is produced. But when we speak of reliability, we are talking about how long the functionality of the product (as it is promised and planned) is going to last. Therefore, in essence, we are referring to the quality of the product over a limited amount of time. The longer the time the higher the reliability. Let us elaborate this with an example.
Suppose you buy a brand-new bike. If the bike doesn’t work as you have expected, or if the parts break soon after you bought the bike, you would describe the bike has poor quality. But if the bike works great, as you thought it would, for 6 months and then starts showing problems in a way that you have to take it to the shop frequently, you would say the bike is not reliable. Make sense?
In a more technical definition, reliability engineering is defined as the dependability of a product in its life cycle, or the capability of a system (and its components) to function under the given circumstances for a limited amount of time.
Now that we have established the definition of reliability and its relationship to quality, let us move on to the goal of using reliability engineering.
Goals of Reliability Engineering
The most important goal of reliability engineering is to manage and mitigate risks. Reliability engineering intends to:
- Eliminate loss
- Reduce risks
- Manage life cycle asset
In order to reduce the deficiencies, the following steps should be taken into action:
- Spotting the losses of the production and the expensive maintenance assets
- Finding a way to reduce these costs
- Employing root cause analysis techniques to eliminate the losses permanently
- Developing a preventive action plan, based on the applied root cause analysis, to inhibit such defects from happening in future
First you would have to calculate or analyze the risks, and then reduce them. There are several tools and methods to analyze the risks. Some are mathematical and some logical. Below are the most common tools of risk analysis applied in reliability engineering:
- Preliminary hazards analysis (PHA)
- Failure rate and mean time between/to failure (MTBF/MTTF)
- Failure modes and effects analysis (FMEA)
- Criticality Analysis (CA)
- SFMEA – Simplified failure modes and effects analysis
- Design FMEA
- Software FMEA
- Functional FMEA
- Hardware FMEA
- Process FMEA
- Maintainability information (MI)
- Fault tree analysis (FTA)
- Event tree analysis (ETA)
- Reliability Block Diagram (RBD)
- The ‘Bathtub’ Curve
- The Exponential Distribution
- Weibull Distribution
- Minimal Cut Sets
- Markov Analysis
- Monte Carlo
Some of the Main Formula Used in Reliability Engineering Calculations
- R(t) = e -(t/MTBF) where R = reliability, e = 2.718, t= useful life of the unit
- MTBF= T/R ; T = total time; R = number of failures
- MTTF= T/N ; T = total time ; N = Number of units under test.
- Total MTBF time is (Number of units tested X Time on )/Number of failures
Why Reliability Engineering Is Crucial to An Organization?
As stated above, reliability helps the organizations to sustain their quality for a longer time and to cut down the costs of maintenance and warranty claims. Below are some of the key elements that reliability engineering can affect:
- Repair and maintenance costs
- Delays further up supply chain
- Good will
Case Study: The NASA Challenger Accident
Problem: The Challenger space shuttle failed
Causes and Causal Elements:
- The zinc chromate putty repeatedly failed and thus allowed the gas to corrode the main O-rings.
- The wrong material was used in the production of the shuttle O-rings, failed to function properly at low temperatures.
- Elastomers become fragile at low temperatures.
Actions Taken to Fix the Problem:
- The third-O ring was added to enhance the sealing, helped the defected putty that had served as a partial seal
- Substituted the putty with bonded insulation
- Added a capture device to prevent the opening of the joints while the booster inflate under pressure at the ignition time
- Added the third-O ring to seal the joint of the capture device
- Replaced the manufacturing material of the O-rings with nitrile rubber
- Added heating strips around the joints to protect the O-rings from being exposed to the temperatures below 75F
- The size of the gap openings where the O-rings were supposed to seal were reduced 5 times
Would Like to Learn More About Reliability Engineering?
TONEX offers several of diverse hands-on training on reliability engineering designed to answer the needs of various audiences. You can explore through the following list to find out which one would answer your needs the best: