Maintenance Scheduling

Scheduling means assigning the time to the planned job. In the context of maintenance works, scheduling usually means to set the expected starting times (and ending time also in many cases) for the maintenance functions such as repair or overhauling work. Note that scheduling is not determining how long a job will take. Suppose you estimated that a repair activity of a Milling machine will take eleven hours, this is a measure of the workload. But when you say that the repair work of Milling machine will start say, at 10 a.m. on May 11, you have scheduled it. Scheduling also implies deciding ahead of time and we don't say that you decided to a repair force on a machine only a few minutes before you started the job.

Maintenance scheduling deals with the complaints (for repair) with reference to machine status, the requirements (for improvement) and the availability constraints against achieving planned production on that machine. When you have more than one complaint, you have to schedule them judiciously according to certain rule such as First in First out (FIFO), the job significance in production chain, etc. We shall learn these scheduling aspects in this unit.

The sequencing, scheduling and loading of maintenance jobs often pose a challenge to the plant engineer for the following reasons.

1) The maintenance jobs require the pre-requisite knowledge of the technological and managerial aspects to arrange them the correct order.

2) Sometimes the jobs will be having the fixed order while at other times they will have flexibility. Hence the plant engineer is supposed to know the characteristics of the jobs.

3) The plant engineer should know thoroughly about the probable time of performing each job to find optimal schedule of the jobs so as to minimise the total elapsed time (i.e. the time from the start of the first job to the completion of last job as well as the idle times).

4) The plant engineer should have sound knowledge in judging the parameters for fixing the sequence and schedules of the jobs. Sometimes the sequence is to be found for the jobs on machines or men and in some other times it is men or machine on jobs.

The maintenance schedules are prepared in the following stages.

Sequencing

All the jobs those are to be done in a certain period (a day/week/month, etc.) are written in an order according to predetermined priority rules, i.e. how and when (in which order) to do.

Assignment

The jobs are allocated to the crew so as to complete in lowest possible time, i.e. who to do what.

Work Scheduling

The allocation is assigned with the (starting/ending) time, i.e. when (what time) to do.

Depending on the requirements and needs of the situations the maintenance scheduling may be one or two or three stages shown above, viz. sequencing, assignment and scheduling.