MRO Magazine

A Credible Priority System Allows Scheduling to Succeed

May 27, 2019 | By Doc Palmer

Photo Credit: Getty Images.

A credible work order priority system is vital for effective scheduling. The scheduling function is the critical agreement between operations and maintenance about what the maintenance group should do and when. The priority system allows for properly creating schedules with the right work. It should offer enough but not too many choices, or not be too complex.
Not only is the quantity of choices an issue, but so is the description of choices in terms of time limits or descriptions. Some plants also have criteria in their priority systems that don’t belong. Proper consideration of these issues helps for proper scheduling.
Organizations are better at specializing than co-ordinating. The expression “things fall in the cracks” is an example of co-ordination problems between specialized groups. A schedule with its priority system is a critical coordination device between operations and maintenance.
What new work must start immediately? What other new work is too urgent to wait until next week? If it can wait beyond this week, how long can it wait? The priority system addresses these questions. The maintenance group must try to follow the current schedule of work, but know when it should break the schedule. In addition, the schedule for next week must consider all the work in the backlog that is ready to go, but cannot possibly place all the work in the single week.
A credible priority system helps properly sort work. Without the schedule and a credible priority system, an operations group simply expects maintenance to come when called for reactive maintenance. Such an expectation leads to less proactive maintenance and generally less productivity. Maintenance should be able to productively keep after proactive maintenance and only break the schedule when appropriate. “Appropriateness” is embodied in the priority system, the established coordination contract between operations and maintenance.
A credible priority system should have over three levels. Many proactive maintenance tasks originate from the maintenance group; a proper scheduling process encourages operations to initiate more non-urgent work requests. How should operations describe the relative urgency of such new work? A plant usually distinguishes between emergencies (that must be started now) and other urgent work (that cannot wait until next week); this leaves work that can wait beyond the week.
A plant could simply have three priorities: Emergency, Urgent and Routine. However, a goal to have less than 20 per cent of emergency and urgent work would mean that 80 per cent of the work would have only a single level. A single level consisting of 80 per cent of the whole backlog is insufficient to help guide scheduling. An additional priority describing what can wait beyond next week would help.
A minimum of four levels is required for a credible priority system. Five levels are even better such as Emergency (Now) and Urgent (Complete this week, Within two weeks, Within one month and Longer than one month). A credible priority system needs enough levels to spread out all the work adequately.
On the other hand, having too many levels or being too complex also causes problems. Going beyond five levels adds difficulty to operations making a quick judgment and describing how long the work can wait. There is some logic in having more than five levels, simply to encourage more people to pick a level four or five, but at a certain point too many levels are simply “gaming” the system and it loses credibility.
Extremely complex systems also hinder operations in stating how long the work can wait. An example could be systems that multiply different factors together such as using work type times, equipment criticality. Plus an arbitrary “fudge factor.”
The description of the levels is another matter. Should the levels set time deadlines or use descriptive adjectives for each level? The problem with setting deadlines is that if there is too much work, maintenance cannot meet the deadlines. It is also difficult for operations to set deadlines for maintenance work outside of the current week.
The advantage of descriptive adjectives is that no matter the amount of work that exists, it could be sorted in order of relative importance. However, the problem using adjectives is never having enough descriptions to describe enough situations.
In addition, operations desire to know how long to expect for a response. A system that has deadlines, but also a limited number of qualifying descriptions is very practical in practice. The word “routine” is a good description to distinguish it from emergency and urgent work, but is overly broad. Plants that use routine and have only three levels might consider expanding routine to routine high, routine normal, and routine low. That would improve a three level system to five levels without alarming everyone.
Some plants think they have five levels, but only have three levels in reality. Consider safety, emergency, urgent, routine and outage. Safety is more of a priority type than an actual priority. For example, an immediate life-threatening situation should be an emergency whereas a blemish on a handrail should be a routine matter, although both are safety related.
Consider having a separate field for tracking safety-, environmental-, reliability- and efficiency-related work apart from the priority system itself. Similarly, outage is more of a unit condition than an actual priority.
Scheduling programs need a credible priority system to allow proper selections of work agreeable to both operations and maintenance. Five simple levels seem to be practical in having enough priorities without becoming confusing. Credible priority systems usually contain time deadlines, but having some wording describing the level is also helpful. In addition, avoid items in the system that do not necessarily dictate relative urgency of response.
Remember that the point of the priority system is to help operations and maintenance quickly and easily communicate the relative urgency of the particular need for the work.
TIP: A priority system should allow easy and quick judgment to describe the relative urgency of the response for the work.
Doc Palmer, PE, MBA, CMRP, is the author of McGraw-Hill’s Maintenance Planning and Scheduling Handbook. As managing partner of Richard Palmer and Associates, he helps companies worldwide with planning and scheduling success. For more information, including a schedule of current public workshops, visit, or e-mail Doc at


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