REGISTER NOW! August 1, 2022. FREE 1–Hour Virtual Uptime Elements Introduction

Availability is part of the Reliability Strategy Development toolbox

What is availability?

Availability is a tool for measuring the percent of time an item or system is in a state of readiness where it is operable and can be committed to use when call upon. Availability ceases because of a downing event which causes the item/system to become unavailable to initiate a mission when called upon. In the simplest view the metric is availability = uptime/(uptime + downtime). For many other definitions see MIL-HDBK-338, section 5.

Why use availability?

The measure is important for knowing the commitment of time for performing the mission and it usually only involves the use of arithmetic.

When to use availability?

Often the measurement tool is based on past experiences and the complement of the measurement tool addresses unavailability to perform the task.

Where to use availability?

In design of a system it is a calculated value and in operation of a system it is a performance index that is often easy to use and provides and index that is understandable to the average person. Today there is a great tendency to "Enronize" availability metrics by using uptime metrics that presents data in the best light (an issue of data integrity) to maximize managerial bonuses by excusing (deducting) downtime from the calculations to put lipstick on the pig. Use the KISS principle. Think of availability in terms of the investor's typical year of 8760 hours. The no-excuse annual metric in hours is availability = uptime/8760. Suddenly you'll find a metric of great interest to investors that can be bench marked as a financial issue, and thus motivate the management team to solve real issues of importance to the business. Please note, you can have high availability but many failures and thus low reliability as availability ≠ reliability. Likewise, you can have high availability but little output so team the metric with effectiveness to get the complete story.

These definitions are written by H. Paul Barringer

Return to Reliability Tools

Paul Barringer

Paul Barringer, is a reliability, manufacturing, and engineering consultant. His worldwide consulting practice involves, reliability consulting, and training with a variety of discrete and continuous process manufacturing companies and service industries.

He has more than fifty years of engineering and manufacturing experience in design, production, quality, maintenance, and reliability of technical products. His experience includes both technical and bottom-line aspects of operating a business with an understanding of how reliable products and processes contribute to financial business success.

Upcoming Events

August 9 - August 11 2022

MaximoWorld 2022

View all Events
banner
80% of Reliabilityweb.com newsletter subscribers report finding something used to improve their jobs on a regular basis.
Subscribers get exclusive content. Just released...MRO Best Practices Special Report - a $399 value!
DOWNLOAD NOW
Reliability Leader Fluid Cleanliness Pledge

Fluid Cleanliness is a Reliability Achievement Strategy as well as an asset life extension strategy

MaximoWorld 2022 Conference Austin Texas

Connect with leading maintenance professionals, reliability leaders and asset managers from the world's best-run companies who are driving digital reinvention.

“Steel-ing” Reliability in Alabama

A joint venture between two of the world’s largest steel companies inspired innovative approaches to maintenance reliability that incorporate the tools, technology and techniques of today. This article takes you on their journey.

Three Things You Need to Know About Capital Project Prioritization

“Why do you think these two projects rank so much higher in this method than the first method?” the facilitator asked the director of reliability.

What Is Industrial Maintenance as a Service?

Industrial maintenance as a service (#imaas) transfers the digital and/or manual management of maintenance and industrial operations from machine users to machine manufacturers (OEMs), while improving it considerably.

Three Things You Need to Know About Criticality Analysis

When it comes to criticality analysis, there are three key factors must be emphasized.

Turning the Oil Tanker

This article highlights the hidden trap of performance management systems.

Optimizing Value From Physical Assets

There are ever-increasing opportunities to create new and sustainable value in asset-intensive organizations through enhanced use of technology.

Conducting Asset Criticality Assessment for Better Maintenance Strategy and Techniques

Conducting an asset criticality assessment (ACA) is the first step in maintaining the assets properly. This article addresses the best maintenance strategy for assets by using ACA techniques.

Harmonizing PMs

Maintenance reliability is, of course, an essential part of any successful business that wants to remain successful. It includes the three PMs: predictive, preventive and proactive maintenance.