Page 241 - Plant design and economics for chemical engineers

212 PLANT DESIGN AND ECONOMICS FOR CHEMICAL ENGINEERS

fL = current labor cost index in new location relative to cost of EL and ML
f,,,, = current material cost index relative to cost of M
f, = cost factor for miscellaneous items
fP = cost factor for piping materials
f, = total cost of field-fabricated vessels (less incremental cost of alloy)
f, = specific material unit cost, e.g., fp = unit cost of pipe
fy = specific material labor unit cost per employee-hour
H, = engineering employee-hours
I = total indirect cost of plant
M = material cost
M; = labor employee-hours for specific material
ML = direct labor cost for equipment installation and material handling
M, = specific material quantity in compatible units
p = total pump plus driver cost (less incremental cost of alloy)
R = ratio of new to original capacity
s. = total income from sales
; = total cost of tower shells (less incremental cost of alloy)
T = total capital investment
V = manufacturing fixed-capital investment
W = working-capital investment
x = exponential power for cost-capacity relationships

PROBLEMS
1. The purchased cost of a shell-and-tube heat exchanger (floating head and carbon-steel
tubes) with 100 ft2 of heating surface was $3000 in 1980. What will be the purchased
cost of a similar heat exchanger with 200 ft2 of heating surface in 1980 if the
purchased-cost-capacity exponent is 0.60 for surface area ranging from 100 to 400
ft2? If the purchased-cost-capacity exponent for this type of exchanger is 0.81 for
surface areas ranging from 400 to 2000 ft2, what will be the purchased cost of a heat
exchanger with 1000 ft2 of heating surface in 1985?
2. Plot the 1985 purchased cost of the shell-and-tube heat exchanger outlined in the
previous problem as a function of the surface area from 100 to 2000 ft2. Note that
the purchased-cost-capacity exponent is not constant over the range of surface area
requested.
3. The purchased and installation costs of some pieces of equipment are given as a
function of weight rather than capacity. An example of this is the installed costs of
large tanks. The 1980 cost for an installed aluminum tank weighing 100,000 lb was
$390,000. For a size range from 200,000 to 1,000,000 lb, the installed cost-weight
exponent for aluminum tanks is 0.93. If an aluminum tank weighing 700,000 lb is
required, what is the present capital investment needed?
4. What weight of installed stainless-steel tank could have been obtained for the same
capital investment as in the previous problem? The 1980 cost for an installed 304
stainless-steel tank weighing 300,000 lb was $670,000. The installed cost-weight
exponent for stainless tanks is 0.88 for a size range from 300,000 to 700,000 lb.
5. The purchased cost of a 1400-gal stainless-steel tank in 1980 was $7500. The tank is
cylindrical with flat top and bottom, and the diameter is 6 ft. If the entire outer