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Reliability is at every organization’s bottom line. All tasks, programs, or strategies involved in asset management and maintenance aim to achieve reliability. Understanding and measuring it is critical for organizations to achieve optimum reliability and enjoy its benefits.

Definition of Reliability

Reliability is the ability of a machine, equipment, or asset to function without failure or breakdown, thus completing its intended tasks or purposes. In maintenance management, it is critical because it is a reflection of asset performance, productivity, efficiency, and optimum use of resources.  

Organizations measure the reliability of an asset at a specific period and under a set of operating conditions. There are several methods to compute reliability values depending on the varying situations. What is common in all these methods, however, is that they all consider the historical data on asset failures. Failures that happened in the past give valuable insight into an asset’s reliability.

Tools for Calculating Reliability

There are three essential tools when calculating asset reliability:

1. Failure Modes and Effects Analysis (FMEA)

Failure Modes and Effects Analysis is an analytical process where you identify all the ways an asset can fail and their related causes and effects. In this process, you also rank these failures according to their Risk Priority Number (RPN). The RPN is a rating system that considers a failure’s severity, and likelihood of occurrence and detection.

2. Fault Tree Analysis (FTA)

Fault Tree Analysis involves the logical assessment of the possible causes and probability of occurrence of asset failure. First, you identify the asset failure and then, work backward to identify the physical, human, or latent factors that led to the failure. FTA is also helpful in showing how assets behave through single or multiple failures. 

3. Reliability-Block Diagram (RBD)

Reliability-Block Diagram is a complementary tool to the Fault Tree Analysis. RBD is where you detail the step-by-step process of each failure that led to the main failure. It is a visual representation of areas with poor reliability or areas where improvements can be made to reduce the severity and likelihood of failure. 

Other Essential Metrics for Reliability

Aside from the analytical processes above, below are other metrics that are also useful when evaluating asset reliability:

Mean Time Between Failures (MTBF)

It is the average time an asset is in operation measured from one failure to the next. MTBF shows how long assets can be used before they are expected to fail. The higher the MBTF, the higher the asset reliability.

Mean Time to Repair (MTTR)

Mean Time to Repair is the average time spent to repair a failure and restore the asset to full operating conditions. MTTR indicates an organization’s ability to resolve failures when they occur. Low MTTR means assets are repaired faster, and thus have high reliability.

Failure Rate (FR)

Failure Rate is the number of failures recorded over a period. FR indicates failure probability. The lower the FR the less likely that a failure will occur, and therefore, the higher the reliability.


Availability is the total amount of time that an asset is available. This is calculated by dividing the total operating time by the sum of operating and downtime (including planned and unplanned). High availability means high reliability.

Real-Time Condition Data

Real-Time Condition Data includes the results of tests and other inspection methods that help monitor the real-time condition of assets. Examples of these methods include oil analysis, vibration analysis, ultrasonic test, and infrared thermography. Effective and regular monitoring helps provide information for detecting and preventing failures before they occur. These real-time data improve reliability by driving predictive maintenance.

How to Achieve Optimum Reliability

There are multiple and complex concepts involved in reliability. With powerful analytical software like Redlist, collecting, organizing, and analyzing failure data is more accurate and less time-consuming. First, Redlist replaces error-prone manual checklists, allowing maintenance team members to collect accurate and digitized records. Next, Redlist stores these records in a secure yet accessible database. Finally, Redlist is equipped with analytical tools that process the data and provide real-time results for fast and results-based decisions. Redlist can help you make reliability a simple and achievable bottom line for your organization. Schedule your free demo with our experts today!

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