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Understanding “Reliability Engineering” vis-à-vis “Resilience Engineering”

The purpose of this write-up is to sensitize the readers about these recent days much discussed engineering topics.


1.0 Reliability Engineering:


Reliability is the probability that a machine will function properly for a specified time. The reliability engineering attempts to increase this probability. The reliability engineering attempts to measure the safety of the structure, stipulate the minimum required safe margin, and propose methods and tools to implement the optimum safety level of a component or systems.


Tactics used to enhance reliability are generally –

o Improving reliability of individual components

o Providing component or system redundancy

o Implementing or improving preventive & predictive maintenance

o Increasing repair capability or speed


Basic units of measure for reliability are Failure Rate and MTBF (Mean Time Between Failure)


2.0 Resilience Engineering:


Resilience is a system's ability to recover from a fault and maintain persistency of service dependability in the face of faults. Resilience engineering, then, starts from accepting the reality that failures happen, and, through engineering, builds a way for the system to continue despite those failures.


Resilience engineering is a subfield of safety science research that focuses on understanding how complex adaptive systems cope when encountering a surprise. The term resilience in this context refers to the capabilities that a system must possess in order to deal effectively with unanticipated events.


For Resilience Engineering, 'failure' is the result of the adaptations necessary to cope with the complexity of the real world, rather than a breakdown or malfunction. The performance of individuals and organizations must continually adjust to current conditions and, because resources and time are finite, such adjustments are always approximate.


This study of Resilience Engineering explores this groundbreaking new development in safety and risk management, where 'success' is based on the ability of organizations, groups and individuals to anticipate the changing shape of risk before failures and harm occur.


3.0 Reliability vis-à-vis Resilience Engineering:


Reliability focuses on the prevention of the event happening in the first place. The focus is on maintaining smooth operation and minimizing the chances of failure. Whereas, resilience focuses on minimizing the consequences of any event and most importantly, enabling the system to bounce back if an event does happen.


Hence, the prime differences can be bulleted as follows:

o Reliability focuses on the prevention of the event happening in the first place. The focus is on maintaining smooth operation and minimizing the chances of failure

o Resilience focuses on minimizing the consequences of any event and most importantly, enabling the system to bounce back if an event does happen. It is about planning for the worst and ensuring that the network can recover quickly


4.0 What does a resilience engineer do?


Differing from ‘reliability engineers’ who focus on keeping systems functioning cost-effectively and safely in their lifespan, ‘resilience engineers’ focus on ensuring systems function correctly before and after changes or disturbances. They collect information and knowledge from the fields of human factors and safety.


The resilience engineering perspective holds that human performance variability has positive effects as well as negative ones, and that safety is increased by amplifying the positive effects of human variability as well as adding controls to mitigate the negative effects.


Bow tie risk analysis looks at both the probability of something happening and the consequences; it is helpful in striking a good balance between resilience and reliability. It is expected that the resilience engineers shall have through in Fault Tree Analysis (FTA) and Event Tree Analysis ETA).


5.0 Fault Tree Analysis (FTA) and Event Tree Analysis ETA):


It is easy to get confused between these two techniques. Indeed, the two are in fact complimentary (and are often used together) but focus on opposite sides of an undesired event.


Often called a BOW-TIE model (because it looks like one) and when complimentary FTAs and ETAs are used, it is called the bow-tie technique.


6.0 Bow-tie Analysis as a tool for Resilience Engineering:

Bow Tie analysis is the combination of both FTA and ETA. It is extremely versatile and achieves success in various applications. It requires multidisciplinary team. It focuses on the visualization of the relationship between undesirable event, its causes, accidental scenarios, the preventive and mitigation measures to limit their consequences. It demonstrates the effectiveness of existing controls. It is structured risk analysis where quantification is not possible or desired. Therefore, it meets the requirement of the resilience engineering.


7.0 Conclusion:


Both Reliability Engineering and Resilience Engineering have lots of advantages.


Greater reliability can have hugely positive effects for your maintenance workforce, by reducing the risk of injury, increasing morale, and providing employees with opportunities to develop professionally.


Resilience engineering provides a new way to control incidents and limit their consequences. Working on resilience might appear costly but if the industry was able to take a longer-term view we could make a long-term impact and enjoy considerable savings.


In general, both of these engineering philosophies can –

o Increased Productivity by improving organizational efficiency

o Reduced Costs

o Enhanced Product Quality

o Improved Customer Satisfaction

o Safety and Risk Mitigation

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