The Basics of Planned and Deferred Maintenance

Fred Schenkelberg
May 1, 2018 · 4 min read

The Basics of Planned and Deferred Maintenance

We can plan to do more than we are capable of accomplishing. The remaining items, if they warranty accomplishing become deferred. They roll over to the next’s day’s list of actions to take.

Of course, in practice, the process to plan, execute, and defer maintenance activities is a bit more complex than described above. The ability to maintain equipment in working order along with minimizing downtime and costs is in large part the balance between resources available to conduct maintenance and the increased risk of system failure due to deferred maintenance.

The Role of Planning Maintenance

When I purchased my car it came with an owners manual. It included a maintenance schedule. Change oil every 5,000 miles, rotate tires, etc. The equipment manufacturer created a suggested maintenance plan based on their experience with customers of their vehicles.

Your equipment likely included a plan for maintenance as well, yet depending on how you use the equipment the suggested maintenance activities may or may not serve to minimize downtime or costs. The combination of the manufactures suggestions and your experience forms the basis for the type and frequency of maintenance activities.

The planning may include inspections, opportunistic replacements (when the panel is open replace the valve, for example), measurements, durations, cycles, hours of operation, or similar inputs. Equipment may experience failures or otherwise require maintenance attention to restore full operation. These tasks may require immediate attention or may be planned tasks in the near future. A first step is often to simply list all of the expected alignments, adjustments, replacements, and repairs, necessary to keep the equipment operational for its expected operating duration. Then regularly update the list with the additional tasks based on day to day operation and notices equipment failures or degraded operation. This can become a long list.

A common next step is to prioritize the various tasks based on the cost of downtime, or similar measure. The idea is to focus resources on the tasks that avert the most dangerous or expensive failures. Other factors may include the cost of the task, the duration of downtime for repair, the lead time for parts, etc.

The role of planning maintenance is to identify and execute the maintenance tasks that optimize the availability of the equipment and minimize disruption and costs to the organization. Understanding what needs to be done and when permits the stocking of parts and materials just as needed thus reducing stocking and storage costs. Proper planning also permits the scheduling of training, necessary equipment, and talent to execute the tasks efficiently. It also permits the ability to balance the workforce and schedule to accommodate the necessary maintenance.

The Role of Deferred Maintenance

When planning for equipment maintenance we consider the effect of equipment failure or poor operation. When we do not have sufficient resources to execute the planned maintenance as expected those tasks become a backlog, or deferred till a later time.

Tasks become deferred when they still need to be accomplished yet we are waiting for parts, properly trained technician, or necessary tools. The maintenance task is not occurring when it should minimize the chance of failure, thus deferred. The task may include a new date when it will be accomplished, yet in the time between when it should have been done and when accomplished the chance of failure is higher than desired.

The role of deferred maintenance is to accommodate the balance between resources, costs, and equipment availability. It is rare that we have sufficient resources exactly when necessary thus the deferred maintenance list provides a buffer while keeping the priorities for necessary maintenance activities intact.

If the deferred maintenance list becomes too large it is a reflection that there is an unacceptable degradation in the ability to operate the equipment as desired. The chance of failure, and the unplanned downtime goes up.

This goes back to the balance between the cost of downtime versus the cost of maintenance. The deferred maintenance list is an indicator that you have the balance about right or not. Understanding the reasons for deferred tasks permits improvement in the appropriate area of your program, such as training, spares and tool stocking, etc.


There are many different ways to approach your maintenance program, yet it will include a set of maintenance tasks that you can anticipate, prepare to accomplish, and schedule. The accomplishment of tasks at the right time keeps your equipment operating well. Delaying, deferring, tasks increases the risk of equipment failure. Keeping track of and analyzing the items on the deferred maintenance list enables you to improve your program.

The balance between planning and deferring maintenance tasks is a function of the resources available and the expectations of equipment availability.

Originally published at Accendo Reliability.

Fred Schenkelberg

Written by

Reliability Engineering and Management Consultant focused on improving product reliability and increasing equipment availability.

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