Facts About Maintenance Wrench Time

Keith Mobley; Ricky Smith
Tags: hand tools

Facts About Maintenance Wrench Time

What is Wrench Time?

Wrench time is defined as the actual amount of time a craftsperson spends doing value-added work. A wrench time study, or work sampling study, is aimed at identifying and eliminating or mitigating the time spent on nonvalue-added tasks.

Wrench time does not include:

Wrench Time Facts

Fact #1: World-class wrench time is 55-65%; most companies have a wrench time between 18-30%.

Fact #2: It is not uncommon for the effectiveness of planned and scheduled jobs to be 25% or more than the same job without planning and scheduling (P&S). To see just how critical maintenance effectiveness is, consider the following:

Fact #3: The term “wrench time” refers to a unit of measure for the time maintenance personnel spend doing the actual work for which they are responsible for. It does not include the time a technician spends:

Fact #4: Wrench time is usually expressed as a percentage, and national studies typically put this number between 25-50% for North American Industries.

Fact #5: The goal is to eliminate all delays and nonproductive work so that maintenance personnel can work effectively and efficiently by never having to leave a job once they start, except for regularly-scheduled breaks, mealtimes, and the end of the working day.

Fact #6: P&S is the most effective way to improve an organization’s wrench time. The power in improving wrench time is considerable.

Fact #7: The only way to optimize maintenance wrench time is to have an effective maintenance planning and scheduling process with a highly trained maintenance planner or planner scheduler.

Measuring and Optimizing Wrench Time

One of the most effective ways to measure maintenance wrench time is through a Maintenance Utilization Survey Checklist, which can help an organization identify where technician time is being wasted.

Once you have identified where the waste is occurring, you can begin taking steps to optimize your wrench time. The most effective way to accomplish this is through a formal planning and scheduling process, which requires that roles and responsibilities be well-defined to maximize their effectiveness.

One way to clearly define these roles and responsibilities is by utilizing a RACI responsibility matrix. A RACI responsibility matrix is a “chart designed to ensure clear communication and smooth workflows across all parts of a team by clarifying employee roles and responsibilities for each task, milestone, and decision that takes place throughout a project,” (Forbes). An example of this matrix can be found below.

There are several benefits to a formal planning and scheduling process, including:

Typical maintenance costs versus those experienced by world-class maintenance teams can be expressed as a percentage of the replacement of asset value. According to SMRP, replacement asset value (RAV) is defined as “the monetary value that would be required to replace the production capability of the present assets in the plant. It includes the replacement value of the buildings and the grounds if these assets are maintained by the maintenance expenditures.”

It has been found that typical maintenance costs as a percentage of RAV range from 4.5% to 11.2%, whereas the percentage of RAV for world-class maintenance teams ranges from 2.0% to 3.4%.

There are several ways of improving a team’s RAV, including:


This article is based on the information provided in Rules of Thumb for Maintenance and Reliability Engineers by Ricky Smith and Keith Mobley. To purchase a copy of their book, please visit the Noria Bookstore at store.noria.com.

For questions or additional information related to the material within this article, please contact Ricky Smith at rsmith@worldclassmaintenance.org.