Page 16 - Industrial Process Plant Construction Estimating and Man Hour Analysis

Introduction xxxi

6000
Quantity 4000 y = –43817x + 24537 Series1
2000
2
0 R = 1 Linear (Series1)
0.42 0.44 0.46 0.48 0.50 0.52 Linear (Series1)
MH/EA
2
The coefficient of determination, R , is exactly +1 and indicates a positive
fit. All data points lie exactly on the straight line. The relationship between
x and y is such that as x increases, y also increases.

Nonrepetitive one-cycle time study and man-hour analysis
Nonrepetitive time study was used for construction direct craft long-cycle
scopes of work. The time study provides man-hour information for cost estimat-
ing. The study requires continuous timing with an electric timer or video cam-
era. A camcorder with video playback is used, and video tape can be returned to
determine acceptable methods and the time required for the work. Once the time
study is complete, the craft foreman determines the operation or task and cal-
culates the time for the operation or task. The calculation is the net time less any
reductions for task unrelated to the timed task. Normal time is found by
multiplying a selected time for the task or cycle by the rating factor:
T n ¼ T o RF

where
T n ¼normal time, hours
T o ¼observed time, hours
RF¼rating factor, arbitrarily set, number
Example: If the craft worker is fast, then the RF>1.0, say example as 110%.
Task time is 1.8h; then, normal time is (1.8 1.10)¼1.98h.
If the worker is rated 90%, then RF<1 and normal time is (0.90 1.8)¼
1.62h. The rating factor allows the “sample” observation to be adjusted for nor-
mal workers to arrive at a true value. Normal time does not include factors that
affect labor productivity. Allowances for these factors are divided into three
components: personal, fatigue, and delay (PF&D) process of timing the cycle:
Idle time is excluded; craft takes breaks for coffee and rest room; allowance for
personal is 5%. Fatigue is physiological reduction in ability to do work; allow-
ance for fatigue is 5% delays beyond the worker’s ability to prevent; allowance
for delays is 5%. Productivity time in the work day is inversely proportional to
the amount of PF&D allowance; the allowance is expressed as a percent of the
total work day. PF&D allowance is generally in the range of 10%–20%.
Allowance multiplier:
F ə ¼ 100%= 100% PF&D%ð Þ