RELIABILITY - WHAT DOES THAT MEAN

WHAT IS RELIABILITY?

When we ask the question, what Reliability means, what sort of ideas come to mind? You may say - a product is reliable when it lasts for a long time. This is the concept of Durability. Another will say - a product is reliable when it does exactly what I expect it to do. This is the concept of Quality. A third may say - a product is reliable when it is ready to perform its function whenever needed. This is the concept of Availability.

Reliability is a concept that should include all those expectations listed. Quantify Reliability is more difficult. This is because reliability can not be confused with quality. Reliability is something broader. The concept is linked to failures in the time domain. Both the number of failures and when they take place are difficult to predict due to the inherent uncertainties to these variables. Uncertainties that lead to the modern definition of reliability as a statistical variable.

Technical Definition of Reliability:

"The probability of a product work the way it was designed within specific conditions and for a certain period of time without fail."

"The probability that an item will perform a required function without failure under stated conditions for a stated period of time."

“The ability of an apparatus, machine, or system to consistently perform its intended or required function or mission, on demand and without degradation or failure.”

Therefore, satisfactory performance of a product, equipment or system, takes place under the three conditions below:

1. Function

2. Time

3. Operational and environmental conditions

This probability is also known as Probability of Survival.

Because this is a statistical variable, the reliability deals with probability distributions associated with the characteristics of failures assigned to the product, whether it be a discrete component or a set of components that make up a more complex device or system.

In general, we can say that reliability is the Probability of Success. The opposite of Reliability is the Probability of Failure. All of this taking into account the specific environmental conditions or, Operational Context.