Estimating times for maintenance work orders

When helping a maintenance department to go from a reactive to a proactive culture, one of the many elements of the journey is surely the planning of maintenance jobs. Whatever advanced tools you use, your success will also depend on creating the work plan for each job. Regarding the aspect of planning various information is needed but for creating a good weekly schedule the time estimates are crucial.

We all know, realistic job estimates are not only critical to scheduling, but also to coordination, control and the motivation of the technicians.

So, on this journey, you cannot expect that a new planer will already know how to best estimate the time required for the jobs that he/she needs to schedule. At least he/she needs an explanation of existing methods and the journey that he probably will go through. Therefore, detailing the job into major steps is the first instinctive action.

The maintenance department will start in a simple way and refine the approach throughout the implementation according to their maturity.

Methods for estimating required job times in maintenance

Initially, the planer(s) will use pure estimates. Estimates reflect a personal judgment and will depend on each planner’s practical experience.

There are two main problems with estimates:

  1. You may not have consistency between planners,
  2. The estimates will reflect how much they believe the job will take and not how long the job should

The advantage of this method, however, is that it does not take too much effort and therefore the estimates are ok for the beginning.

With time sufficient data becomes available for the planner to use historical averages. Peeks and valleys should be eliminated, and we can calculate the averages. This will depend on complete and accurate data capture and a good feedback loop and therefore good communication between planner and technicians. The issue here is that even if this process step is well set up, we are at the beginning of a journey to maintenance excellence and those averages will not be really the ideal practice. We need to find a way to improve these estimates further.

The next step is to use adjusted historical averages and one way of doing this still is to capture actual times to determine historical averages for a certain period but at the same time through observations establish the efficiency of the crew. Applying the resulting efficiency factor will allow to establish a new estimate of how long the job ought to take in the future. Don’t forget to undertake actions to eliminate the inefficiencies discovered during observations. This is the beginning of creating standards. We should not forget, that carrying out the observations is a cost factor for the maintenance department. The observations must therefore serve as the basis to tell the department what needs to be improved and how each and everyone can contribute. Introducing this change will help to make the department more efficient without bringing haste (muri)  and unsafe behavior into the teams.

The analytical estimates method is another way to proceed in a structured way to determine time estimates and an approach to develop standards for maintenance jobs. In this method, you develop a job sequence that applies to the majority of your jobs or how they normally should be carried out (ideally for shorter jobs you will not take certain steps into account). For each of these steps create a table with three levels of difficulty and determine values for those. For example, one table would have times associated with instruction, preparation and feedback for simple, average and complex jobs. Another would have travel times to different areas for simple average and complex jobs. Another table for allowances and the biggest would be a labor library by equipment. To build this library we do not need additional resources. As maintenance jobs are repetitive we just need to capture new information every time it happens.

There may be other methods and each company can develop its own way. To be successful the most important point is openness and inform all participants of the reason for the introduction of first estimates and then standards. We want equipment up and running so we should make all efforts to give Production a better indication of how long the equipment will be unavailable to them. To give everyone the opportunity to be observant and give their contribution to where the inefficiencies occur, to participate in the improvement to the maintenance function.

As we mention participation, you probably will hear, that each job is different and it is impossible to estimate the duration of every single maintenance job correctly.

This is right, but is it really necessary to be 100% correct ?