What is system availability?

System availability (also known as equipment availability or asset availability) is a metric that measures the probability that a system is not failed or undergoing a repair action when it needs to be used.

There are three qualifications that need to be met for a system to be available:

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    Functioning equipment
    Not out of service for repairs or inspections

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    Functioning under normal conditions
    Operates in an ideal setting at an expected rate

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    Functioning when needed
    Operational at any time production is scheduled

System availability is used to gauge if an asset’s production potential is being maximized, which has a direct impact on the financial health of a business.

Calculating system availability

System availability is calculated by dividing uptime by the total sum of uptime and downtime.

Availability = Uptime ÷ (Uptime + downtime)

Availability equals uptime divided by the sum of uptime plus downtime

For example, let’s say you’re trying to calculate the availability of a critical production asset. That asset ran for 200 hours in a single month. That asset also had two hours of unplanned downtime because of a breakdown, and eight hours of downtime for weekly PMs. That equals 10 hours of total downtime.

Here is how to calculate the availability of that asset:

Availability = 200 ÷ (200 + 10)

Availability = 200 ÷ 210

Availability = 0.952

Availability = 95.2%

World-class availability is considered to be 90% or higher.

How is system availability used?

System availability has a direct impact on the bottom line. When equipment is running as much as possible, it means more products are made and more money is made. In other words, when system availability is high, revenue is also likely to grow.

Because availability is so tied to the financial health of a company, it is commonly used as a key business metric in production-heavy organizations. However, it’s also heavily connected to what several other departments do, including maintenance. Availability is impacted by reliability and maintainability, which are influenced by the processes and tools of the maintenance team. Therefore, availability is used to measure and investigate the effectiveness of these processes and tools, and how they can be improved.

What does system availability mean for maintenance?

Downtime has the biggest impact on availability and is something maintenance has a lot of control over. Downtime can be broken down into planned vs. unplanned and frequency vs. length. Each component can be further broken down until an anomaly is identified. Once issues are pinpointed, they can be addressed and can improve availability.

It’s easy to see which type of downtime (unplanned or planned) is causing an issue with availability.

If unplanned downtime makes up the lion’s share of total downtime, you can start to analyze what is causing this unplanned downtime. It may be due to a lack of preventive maintenance, the age of the machine, or even a severe case of pencil whipping.

If planned downtime seems to be dragging availability downward, you can investigate how your PMs can get more efficient. Are you constantly waiting on parts? Are regular inspections taking longer because there are no checklists or SOPs available? How about the frequency of your PMs — can the asset function properly with fewer routine checkups?

The same logic applies to the frequency and length of downtime. If an asset breaks down a lot, but is fixed quickly, you can focus your efforts on finding why failure is occurring so often, such as too few PMs, age, or a broken PM process. It’s also possible that you may be doing too much preventive maintenance on an asset.

If an asset isn’t down as often, but takes a long time to fix or inspect, it’s time to take a closer look at your maintenance processes. There are dozens of different ways preventive and reactive maintenance can get more efficient. For example, if technicians have to keep walking back and forth from an office to an asset to retrieve paper files, it can cost precious minutes or even hours. If there’s a lack of failure codes, or if they aren’t clear, this can prolong downtime and shrink availability.

Your business and system availability

A big part of your business’s bottom line revolves around system availability. Although asset availability is bigger than maintenance, knowing how your team can influence this maintenance metric is incredibly important to keeping equipment working and production on schedule. Doing a system availability analysis allows you to explore new ways to decrease downtime and make your operation more efficient.

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