Reliability: The Comprehensive Guide to Asset Management

What Is Reliability?

In previous discussions we defined a reliability culture as the cultural shift required for an organization to fully grasp the full scope of asset reliability. More recently, we distinguished reliability from traditional maintenance, noting that reliability represents a holistic, long‑term approach to managing assets.

But what does reliability actually mean, and why is it crucial to differentiate it from related maintenance concepts?

Fiix Solutions Engineer Stuart Fergusson once described reliability to a former boss as: “What is darkness? It’s the absence of light. Think of reliability the same way—absence of unplanned downtime.”

At its core, reliability is simply the assurance that equipment performs its required function whenever it is needed, without unexpected failures. Another definition often cited is “the probability that a component or system will perform a required function for a given time when used under stated operating conditions.” Both definitions converge on the same idea: a reliable asset operates consistently when called upon.

Reliability vs. Availability

Before we delve deeper, it’s important to clarify that reliability is not the same as availability. According to Weibull.com, availability is “the probability that a system is not failed or undergoing a repair action when it needs to be used.”

The key distinction lies in the timing: a machine can be 100 % reliable yet only 80 % available if 20 % of the time is scheduled downtime for preventive work. Availability incorporates repair time, whereas reliability focuses on preventing failures altogether.

The Evolution of Maintenance and Reliability

Historically, design, operation, technology, and organizational culture have all been recognized as critical to reliability. This broader view explains why the gap between traditional maintenance and modern reliability thinking has widened over time.

The roots of reliability science trace back to the 1960s. Prior to that era, it was assumed that equipment age was the primary failure driver. A seminal study in the aviation sector revealed that only 11 % of failures were attributable to age, forcing a paradigm shift. If 89 % of breakdowns stemmed from other factors, those factors demanded investigation.

Consequently, condition‑based maintenance emerged, linking failures to measurable changes in an asset’s condition rather than its age. This shift required robust root‑cause analysis to pinpoint the true failure origins.

Maintenance

“Fix it when it’s broken.”

Condition‑based maintenance

“If age doesn’t cause machines to break down, we should monitor an asset’s condition.”

Root cause analysis

“What’s the real reason a piece of equipment is failing?”

Reliability‑centered maintenance

“Failure is due to a number of different factors, and many frameworks can contribute to maximizing reliability.”

Reliability‑Centered Maintenance

Condition‑based maintenance added a new dimension to asset management, but it still reacted only to the current condition of a machine. Reliability‑centered maintenance (RCM) expands the scope by making maintenance decisions that maximize overall reliability over time. RCM recognizes that reliability depends on design, culture, technology, and more, and therefore incorporates multiple frameworks tailored to each asset.

RCM is not a replacement for any single maintenance strategy. Instead, it evaluates the most effective approach—time‑based preventive, condition‑based, or run‑to‑fail—based on what truly enhances reliability for that particular asset.

For example, caring for a car with RCM might involve a scheduled oil change (time‑based), tire monitoring (condition‑based), and letting light bulbs run until they fail (run‑to‑fail).

The Bottom Line

Reliability consolidates decades of maintenance insights into a holistic, data‑driven framework. As technology, productivity, and data analytics advance, our asset‑management practices must evolve accordingly. When applied correctly, reliability keeps organizations from “darkness,” ensuring that equipment performs reliably whenever it’s needed.