Do you know your wrench time?

Wrench time is the time a maintenance worker spends with tools working on a unit, doing direct diagnostic work or performing safety steps, such as lockout/tagout. It is expressed in minutes a day or as a percentage. A well-run shop might run 49...


Wrench time is the time a maintenance worker spends with tools working on a unit, doing direct diagnostic work or performing safety steps, such as lockout/tagout. It is expressed in minutes a day or as a percentage.

A well-run shop might run 49 percent wrench time, or have 230 minutes of wrench time per day. A new vehicle dealer’s wrench time might even be higher.

To make the topic easier to discuss, we will call wrench time direct time, and time spent on anything else indirect time.

Wrench time is easily measureable by a technique called work sampling. Basically, this is a statistical technique for determining the proportion of time spent by workers in various defined activities.

Work sampling is easy to understand, succinct and can change the productivity for the better. What’s more, this enlightened analysis sums up everything that is wrong with the current maintenance process, business choices and decisions and even management style.

Management Barriers

Most barriers to the effective use of people (high wrench time) are from management. It is fair to say that low wrench time is usually not the result of slack workers, but incompetent management.

Maybe incompetent is too strong, but the business system to maintain vehicles was never intentionally designed. It just grew as an organization lurched from one crisis to the next while patching together a business system in their wake.

If you are interested in better productivity or Lean Maintenance, then you need to be interested in wrench time. If we have an 8-hour (480 minutes) work day, and if our wrench time is 200 minutes, then our indirect time is 280 minutes a day.

If we can eliminate indirect time, workers will get more useful work done. The surprising thing is that workers will not have to exert themselves any harder since they will spend less time spinning their wheels.

Value Added

There is a similar principle in the world of manufacturing called Value-Added Work. Value-Added Work is the work that is actually valuable to the customer and results in a finished product that they want. Customers are only going to want to pay for something they value.

The focus of wrench time is on activity that adds value for your maintenance customer.

Converting some of the pool of indirect time (or not value-added time) to direct time (which is value added) is where many, if not most, of your gains in productivity will come from – at least in the beginning.

Barrier Types

One pitfall to watch out for is that once we find something that works, we want to apply that solution to every problem. When we over-apply any technique we run the risk of creating unintended problems.

There are hard barriers that slow the work, like the physical size or unusual shape of the shop, or the size of the equipment; for example, buying 53-foot van trailers and having a 45-foot shop.

There are also soft barriers (often from policies), like inadequate stocking of parts, insufficient tools and time-consuming procedures.

Generally, the hard barriers can only be solved after extensive study and may require the investment of significant money, like building a new shop.

The soft barriers are frequently easier to fix and give almost instant returns. These might include buying another rolling ladder or an extra oil drain machine.

Look out for procedural barriers, management decisions, shop layouts that require excessive travel, etc. These problems can sometimes be solved in a Saturday of moving things around or investing couple of thousand dollars in improvements.

Two final thoughts: Maintenance workers are in the best position to spot soft barriers. Don’t forget to have some fun fixing the problems.

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