Page 283 - Industrial Process Plant Construction Estimating and Man Hour Analysis
P. 283
262 Industrial process plant construction estimating and man-hour analysis
12.9.3 Application of the range method for equipment
12.9.3.1 Illustration: SCR—Exhaust stack silencer
Data for input (Table 12.9.1):
TABLE 12.9.1 Calculation of expected cost and variance for the installation
of exhaust stack silencer probability that the cost will exceed $26,400
L $ M $ H $
4652 4786 4912
4626 4682 4828
4592 4723 5232
6372 5652 5942
6002 6123 6180
Element L $ M $ H $ E(Cr), $ Var (Cr), $
Support brackets 4652 4786 4912 4784.69 1877.8
Baffles 4626 4682 4828 4696.91 1133.4
Wall bracket 4592 4723 5232 4785.91 11377.8
Baffle guide 6372 5652 5942 5820.24 5136.1
Perforated liner 6002 6123 6180 6112.24 880.1
$26,200 $20,405
PR mean cost > ECrÞ ¼ 0:5 PZðÞ
½
ð
Z ¼ UL ECrÞ= var CrÞ½
ð
½
ð
where Z ¼ value of the standard normal distribution, Appendix A
UL ¼ upper limit of cost, arbitrarily selected
Data for input:
UL ¼ $26,400
E(Cr) ¼ $26,200
Var (Cr) ¼ $20,405
Z ¼ 1.40
P(Z); Appendix A; 1.40 ¼ 0.4192
then, P(Cost > $26,400) ¼ 8.08%
