Everything You Need To Know About Wrench Time

what is wrench time

Wrench time seems to be a controversial topic among maintenance professionals. 

Some believe this metric is too hard to track and that it ignores value-adding activities from its measurements and can lead managers to wrong conclusions. Others state that it is a valuable tool for spotting operational inefficiencies that need to be addressed.  

As with most things in life, the truth lies somewhere in the middle. So we will take a position that wrench time can be a useful metric – if you can measure it properly and analyze it in the right context.  

To enable you to do just that, in the continuation of this article we:

  • define what wrench time is and what it covers
  • present 4 ways to measure wrench time
  • discuss the usual causes of low wrench time and suggest potential solutions
  • give or thoughts on when and if you should consider running wrench time studies

What is wrench time? 

Wrench time (sometimes also referred to as tool time) is a metric that shows how much time maintenance techs spend with a tool in their hand, performing actual maintenance work.  

To understand wrench time, it is really important to understand what it doesn’t measure. Wrench time doesn’t include the time technicians spend on getting the right tools and spare parts, reading the work order, traveling to the location where the job is performed, breaks and idle time, giving instructions, etc., only the time spent performing maintenance work.

Right off the bat, there is your first issue. Many of the activities listed in the last paragraph are essential to performing maintenance work. You can’t complete a Work Order if you do not pick up the right tools and walk to the machine you need to service (unfortunately, teleportation is still not an option :)).

If you plan to measure it, you have to keep in mind that wrench time does exclude many value-adding actions and as such is not a good measure of overall productivity.

wrench time definition
The second problem is that even if you do have high wrench time, that doesn’t necessarily mean your department is doing an excellent job.

Wrench time won’t tell you if workers are performing the job on time (need 4 hours to perform something that should take 3) and if they are actually performing quality work. In other words, you know that some work has been performed, but you do not know how effective it was. This is why some businesses skip measuring wrench time altogether and focus on defining and measuring other maintenance KPIs

4 ways to measure wrench time (worst to best)

Over the years, organizations tried a few different ways to track wrench time, some more successful than others. In the following paragraphs, we will explain four approaches to measuring wrench time, starting with the least accurate one.

1) Self-reporting

Asking technicians to track wrench time on their own comes with two big problems:

  1. they might not be invested enough to track it accurately (or might not even understand what counts as wrench time)
  2. they have an incentive to overreport if they believe this will impact their paycheck or cost them their job
Because of those reasons, it is not rare that self-reporting wrench studies report 70%+ wrench time, while the more realistic numbers suggest that average wrench times are around 30%. This is a big discrepancy and the reason why this method is rarely recommended.

That being said, the self-reporting method is appealing because it requires no additional investment and is the easiest to implement. For those that are considering it, you can make it more accurate by:

  • explaining that the main purpose of this exercise is not to find out who is slacking but to improve the overall performance of the maintenance department
  • using a CMMS like Limble that lets you track time spent on maintenance work directly inside a work order
  • making sure everyone knows what should and shouldn’t be tracked under wrench time  

2) DILO (“Day in life of”)

With a DILO method, you have an observer that is following selected technicians throughout the day to establish a baseline. The problems with the DILO method are twofold:

  • it can happen that this particular day doesn’t represent how an average day at the facility looks like
  • when you know you are being observed/evaluated you will behave/perform better than you usually do (a phenomenon called The Hawthorne Effect)
To reduce the tension between the observer and the technicians, it is important to again drive the point home that the purpose of the wrench time study is not to spy on how hard the technicians work but instead on finding problems that are stopping them from performing more maintenance work.

3) Work sampling

The work sampling approach is where observers visit the plant floor at set intervals, look at the technicians, and mark if they are performing maintenance work or not. The problem with work sampling is that it doesn’t account for people that are not in the line of sight, i.e. technicians that are traveling, that are in the storage room, that went on a short break, and so on.

As with the DILO method, expanding the sample should make the results more accurate (running the study for a couple of weeks instead of a couple of days).

4) Statistical method

The best approach to tracking wrench time is the one that avoids all of the pitfalls we mentioned above. A methodical statistical approach ensures that every technician has an equal chance of being observed and that the observation sample is big enough to represent the actual work being performed over time.

Doc Palmer, the author of McGraw-Hill’s Maintenance Planning and Scheduling Handbook, gives a great example of how could this be implemented in practice in his discussion on wrench time over at Plant Services blog:

“Most plants can, over the course of about a month, conduct a reasonable study that might be representative of the ongoing plant using a single day each week for observations. For example, the observer could use Monday the first week, Tuesday the second week, etc., through Friday the fifth week. Going down through names on a set roster and making two observations each half-hour over the course of eight-hour days would provide 160 observations and margin of error of plus or minus 7%. Thus, a plant at 35% wrench time would know if it is between 28% and 42% and probably not at 55% (or 80%). A plant that improved to 50% wrench time would know if it is between 43% and 57% and probably not a typical plant at 35%.”

Usual causes of low wrench time and potential solutions

Let’s presume you have accurately measured wrench time and you are not satisfied with the results. Below are the common causes of low wrench time, accompanied by proposed solutions.

1) Poor maintenance planning and scheduling

Low wrench time can often be tracked down to poor maintenance planning and scheduling:

  • spare parts and tools not being available
  • poor communication that results in people not knowing where to go next, which tools they need so they have to go back for something, that there was a change in task priority, etc. – all of this results in excessive travel time
  • the job place/machine not being ready (a technician has to wait for a cleaning crew to finish their job, for a safety manager to perform a lockout tagout procedure and similar)
The easiest way to eliminate the above issues is with a mobile CMMS. It simply is not feasible to expect someone to create a perfect schedule if he has to track everything in a spreadsheet. 

Additionally, CMMS enables you to create Work Orders that list tools and parts a technician will need as well as the location of the asset, easy drag-n-drop maintenance calendar for faster scheduling, reports for tracking and measuring maintenance work, alerts when the number of spare parts in stock is low, push notifications about task priority changes, and much more.

2) Too much reactive maintenance

Reactive maintenance is its own story. On one hand, you might think that if you are only servicing equipment when it breaks down, the volume of maintenance work is lower than if you do parts replacements, oil changes, inspections, and other proactive maintenance activities. On the other hand,  technicians could have their whole days filled out putting out fires across the plant floor.

The real problem with reactive maintenance in the context of wrench time is those secondary issues that come with it – lack of spare parts, technicians getting interrupted in the middle of their job with calls about new issues, not being sure where to go next, and general lack of organization that slows technicians down at every step.

The best way to deal with that is to transition to preventive maintenance or condition based maintenance and look for a good CMMS that can support such transition.

3) Waiting on spare parts and tools

It is only natural that an organization has a limited number of tools and spare parts. If technicians often have to wait for a certain tool to become available to perform their task or if they have to walk to the storeroom only to realizes that there is no spare parts available, that is a wasted time that could have been better spent elsewhere.

This issue can be tackled by implementing best practices for managing spare parts inventory and ensuring that maintenance managers/planners schedule the work in a way that takes the number of available tools into consideration.

(When) should you run a wrench time study?

To decide if you should run it or not, you need to be able to weigh the positives against the negatives of a wrench time study

If you decide it is worth it and that it can point you to major problems plaguing your maintenance department, that is perfectly fine. Just be aware of its deficiencies and what the numbers are really telling you.

Oftentimes, low wrench time will just let you know that your technicians’ time is not properly utilized. You will have to dive into additional analysis and common causes we explained above to find what is stopping your technicians from spending more time on hands-on maintenance actions.

Do or do not, there is no try

If you do decide to run a wrench time analysis, you would be smart to remember those wise words from master Yoda. If you want to learn anything useful from this exercise, you have to be sure that your measurements are as accurate as possible. In other words, do it right or do not do it at all.

If your wrench time numbers are low, CMMS can help you spot workflow inefficiencies and eliminate the causes of low wrench time. If your numbers are high, mobile CMMS can still help your technicians be even more productive through faster communication channels, preventive maintenance checklists, and instant access to maintenance history. If you do not want to measure wrench time, CMMS offers plenty of reports to track how your maintenance team is performing. It covers all of your bases. 

For those interested in finding out more, leave a comment below or send us an email.

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