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Someone wrote in this thread, "A large percentage of operations that I work with believe that backlog is bad and their interpretation of backlog is any work past due.  We want backlog.  Ideally 2-3 week's worth of Ready Work for each discipline and 4-6 weeks of Total Backlog.

This statement helps us distinguish between inwardly focused maintenance in contrast to maintenance as integrated logistic support (ILS). The expression of what "we want" is not the same as what "the plant wants." We could expect that the plant wants maintenance work to smoothly flow through the stages of maintenance workflow in the shortest feasible overall maintainability interval. They would want that criteria to decide what we see is an appropriate backlog.

Additionally, ILS would regard backlog as a poor means of control. It is the wagging tail of the dog that should be observed only as the daily difference between new work and a largely constant daily executed workload. Our issue is if the smooth rate of largely first in first out execution, derived for each category of work, matches new work over the long run. In that case, backlog will be net to some baseline of slack in the backlog. Smooth and slack would be derived for work categories rather than overall. But beginning to end the issue is the plant.

ILS

To the point that what the plant wants is the objective, I will describe ILS from 75,000 feet.

Think of a plant as a "system" of equipment that produces goods. Around a primary system of production equipment there is also a system of production support that provides all necessary resources (people, inventory, delivery equipment, and so on) for the operation of the primary system. If the production support is not done optimally the primary system will fall short of what it is capable of.

Now let's extend the idea to include the maintenance of the primary system as needed to be called to serve, remain in service or return to service. In turn, maintenance has a support system to allow it to be able to optimally serve the primary system.

Accordingly, integrated logistic support (ILS) is the lifecycle management and development of maintenance and its support logistics as a system, integrated with the primary system and its logistics as well as integrated with itself.

Within the definition of ILS, we can see that what we want should be what the plant wants, limited only by what is possible with respect to good ILS.

Daniel makes a good point.

However, all of the typical discussion of backlog and its control are actually the RIGHT answer to the WRONG problem.

The right problem is to deliver a smooth weekly flow of each type of work to sustain the plant at its planned performance. What is allowed in backlog should only be necessary as the flywheel by which the maintenance workflow is made cost effective by smooth functioning-erratic flow drives up maintenance cost. The backlog should be a short as possible without losing flywheel effect. To keep at optimally short, protects plant service level because if longer on average than optimal, plant uptime is unnecessarily at risk.

Maybe the root cause of this historic focus on the wrong problem is because we have not yet demanded of ourselves that we learn how to work with data to the depth that smoothed work per week per each category of maintenance work can be derived and, in turn, the range of expected backlog. Therefore, we cling to the discussion of backlog, because we can, rather than tackling one the most basic issues in industrial engineering.

Bruce,

Here is my point of purpose. The role of maintenance is to allow the plant to sustain its strategically decided mission. Let's look at what that means. There is a workload that must be conducted by maintenance to support the plant. Without regard for backlog, the occurring workload over time must be converted to conclusions for the smooth level of work over time and, thus, to be executed per week. When the persistent workload, determined as steady state, is known, the craftforce to serve it can be derived as a steady state. If we don't take the steady state, the reactive state will prove costly to the enterprise ROI. Our purpose is to manage-plan, organize, control and execute-for the smooth outcome rather than manage backlog.

The next part of the point is that weeks in backlog is the tail to the dog of smoothed execution. The objective for backlog is to hold weeks of work in backlog at the minimum that still allows the executed workload to be held at steady state each week. Beyond the cumulative time it would take for each step to the maintenance workstream from recognition to completion the only addition should be the buffer time to assure we will never run short of work as necessary to execute at steady state workload with the craft body designed to conduct it. If the backlog is set by rule of thumb rather than derived and consequently longer than necessary, the plant can experience reduced performance every time the holes in the cheese line up. Or to paraphrase what my kid brother used to say, "The longer work remains in the backlog the more we are giving the ^&#&*'s just one more chance to get at the plant."