Maintenance Work Measurement

Abstract

The effectiveness of maintenance operations management can be substantially improved if goals to evaluate and improve the performance of such operations are established and implemented. An essential and necessary prerequisite for evaluating productivity and performance of maintenance is the availability of job standards. The purpose of this chapter is to present techniques for developing jobs time standards. The techniques presented include: work measurement techniques, work sampling, pre-determined motion time systems, standard data, and estimation. A number of examples are provided to demonstrate the concepts.

Exercises

• 1. A maintenance job has been studied for 20 observations. The mean actual time is 5.8 min, and the standard deviation of the time is estimated to be 2.0 min. How many additional observations should be taken for 95 % confidence that the mean actual time has been determined within 15 %?

• 2. An analyst has observed a maintenance job long enough to become familiar with it and has divided it into four elements. The element time for the first five cycles is shown in the following table along with the performance rating for each element.

  Element no.	Cycle no. 1	Cycle no. 2	Cycle no. 3	Cycle no. 4	Cycle no. 5	Performance rating (%)
  1	1.5	1.6	1.5	1.6	1.7	100
  2	2.5	2.3	2.3	2.4	2.3	90
  3	1.8	3.0	1.8	1.8	1.9	95
  4	1.3	1.1	1.4	1.2	1.3	115

  • a. Compute an estimated basic time for the job on the basis of the available data.

  • b. On the basis of available data, what sample size should be taken? Estimate the time for element no. 1 within 5 % of the true mean time with 95 % confidence.

• 3. The analyst in problem 2 performed a work sampling study in the raw task and recorded observations as appear below in the categories of activities. What allowances should be made for unavoidable delays?

  Activity category	Observed frequency
  Normal work activity	112
  Avoidable delays	17
  Unavoidable delays	16