Thursday, May 3, 2012

Questions from the Field: Wrench Time Studies

Questions: You had mentioned that we should only conduct a wrench time study on planned work.  What is the reasoning behind this?  If they get pulled off of their scheduled job to work on a“sponsored” job, should we terminate the study for that day?  It seems that we have a lot of sponsored work this week and it is somewhat difficult to stay focused on planed/scheduled work.

Answer: That is correct, planned jobs only.

The purpose of the wrench time study is to see how good the planning system is.  If they are pulled off onto sponsored work, the wrench time will likely drop significantly because troubleshooting, looking for parts, looking for prints, and waiting on production are all part of unplanned work but not a part of wrench time.

Of course this is not to say that you cannot continue the study, but it will represent something very different than if they just stayed on planned work.

So it could be as simple as this:

If they stayed on planned work then the wrench time study is a measure of the quality of the planning process.

If they do not stay on planned work, then the wrench time study is a measure the re-activeness of the organization and how well the crafts are able to accomplish unplanned work.

Both of these are valuable, but they represent two totally different things.

Hope this helps.

Andy Page
Allied Reliability Group


  1. "Wrench time study" (AKA time-and-motion study) should not be used. It should be a "Scheduled Maintenance planning and implementation study" and a "Unscheduled Maintenance planning and implementation study".

    Looking at only what was typically called "Wrench time" from way back when, only gave a narrow perspective and lead to incorrect management changes among other negative effects.In today's hi technology process and manufacturing facilities, a lot of "non-wrench time" is critical to both success and efficiency. To belittle, ignore or downplay those activities required to plan for "wrench-time" and prepare and avoid future unscheduled downtime, was learned a long time ago to be counter productive.

  2. If you want to use wrench time as a measure of planning effectiveness, then it makes sense to measure wrench time for planned jobs only.

    If a metric for overall maintenance efficiency is desired, then wrench time for all work could be used. Then all work orders should be used in calculating wrench time. A low wrench time percentage could be caused by poor planning, or an excessive amount of training, or too much of an administrative burden, or a whole host of potential causes. If the organization is too inefficient, root cause should be determined and corrected.

    I prefer a "jobs completed as planned" metric for measuring the effectiveness of the planning process. Ratio of Planner to Craftsperson is a good measure for the efficiency of the planning process. Percentage of planned work is a good metric for the reactiveness of an organization.

    Just my $0.02.

  3. I have a question in regards to "wrench time" and Back Log. When it comes to scheduled preventive maintenance, it is a no brainer that this work would be consider scheduled work and a time study may be appropriate to establish value added vs non-value added work.

    My question is when it comes to planned recurrance prevention, for example failure anlysis after recovery of the phenomena and for troubled equipment kaizen. These are also assigned maintenance task that are included in the backlog as a planned activity. so, how does this time calculated for planning or scheduling effectivness or how does "wrench time" apply?