Maintenance can be broken down into three groups: running repairs; repetitive jobs; and non-repetitive jobs. Running repairs are the quick- fix jobs that crop up on any given day, unknown the day before. They are completed within about five working days. Repetitive and non-repetitive jobs can be scheduled one to 12 weeks ahead of time.
The only part of the load that is steady is repetitive work. Non- repetitive work, which generally has a lower priority than running repairs, will fluctuate as the running repairs fluctuate.
Not only must a balance of work and crew be planned, the plan must include the best use of available resources. Greater productivity will be achieved while equipment becomes more available and maintenance costs come down.
The relative urgency of all activities, including the urgent and unpredictable, must be known in order to select those to be done next so that the best use is made of the available labor. Without parts, of course, nothing can be scheduled.
The backlog is the planned, non- repetitive work. If equilibrium in the workforce is to be maintained, then non-repetitive work, running repairs, absenteeism and overtime must also be in equilibrium. The size of the backlog has to be identified, kept stable or gradually reduced. To reduce the backlog, or keep it stable, it is essential to complete sufficient scheduled work continuously. When work on running repairs displaces scheduled work, the backlog goes up.
More than anything else, the accuracy of the backlog depends on the adherence to preventive maintenance. This is illustrated in the accompanying diagram.
* Phase 1 — The backlog is stable. The amount of major overhauls, the construction jobs, and the like, that are being performed vary with the incidence of running repairs. But this work is equivalent in manhours to new non-repetitive work that has been identified, planned and is ready for scheduling. There is only a small predictable variation in the workflow of preventive routines because care was taken to keep it as even as possible when the hours for each new routine were distributed.
* Phase 2 — The backlog starts to increase. Preventive maintenance is the principal source of uncovering problems before they become serious enough to cause equipment failure. If inspections, lubrication or servicing are missed, and this trend continues as shown, unnecessary breakdowns occur. An increase in unscheduled repairs and emergencies displace the scheduled work and the backlog starts going up. If it rises slowly, no immediate action is necessary.
* Phase 3 — The rate of increase in the backlog becomes very evident and persistent, and most of the jobs in it are moving to higher priority. The first response is to schedule overtime. Hiring new personnel, even if they are readily available, rarely provides immediate relief. There is always a delay while they get to know the work.
* Phase 4 — The backlog peaks. The cause of the problem is corrected with the restoration of the repetitive routines. Overtime handles the highest priority work in the backlog, which, if left undone, would develop into a cont inuous series of quick-fix repairs. The backlog starts to decline.
* Phase 5 — Overtime is stopped and then is applied again because the backlog still contains too many priority-1 jobs. Further consideration of new workers is unnecessary because the amount of non-repetitive work being done on regular hours is increasing.
* Phase 6 — The proportion of scheduled work increases when some of the running repairs are displaced by preventive routines. The productivity of these routines is better, and this helps to reduce the backlog. The backlog gradually returns to its original level.
* Phase 7 — As the backlog falls, there is time to decide how much surge it should provide, when this level will be reached, and the action necessary to keep it there.
There is no set correct level of backlog. Like any instrument of management, the finer it is tuned, the greater the contribution it makes to the continued success of the enterprise. Keith Bowley is a Toronto-based maintenance consultant.
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