Page 29 - Industrial Process Plant Construction Estimating and Man Hour Analysis

Introduction xliii

TABLE 11 Straight time and overtime additional MHs—cont’d

Range of impact Use
Other factors Minor Average Severe ST OT
Ripple 8% 20% 30%
Season/ 10% 20% 30%
weather
Availability of
skilled labor
Ratio of name
calls to open
calls
Plant permit
requirements
Safety
10% 5%

Work sampling and man hour analysis

Work sampling is a statistical technique for determining the proportion of time
spent by craft crews performing manual construction task. In a work sampling
study, a large number of observations are made of workers over an extended
period of time. The observations must be taken at random times during the
period of study. Work sampling is the application of statistical sampling
techniques to the study of construction labor activities, measurement of labor
efficiency, and productivity information.
Application of work sampling and man-hour analysis
Model:
ðÞ
Hs ¼ N i Htð Þ RFÞ 1+ PF&DÞ=N
ð
ð
where
Hs¼standard man-hours per task
N i ¼observation of event i
Ht¼total man-hours worked during sample study
RF¼rating factor
PF&D¼personal, fatigue, and delay allowance
N¼number of random observations during sample study