Equipment Costing
T&S - Chapter 7 Review
CH EN 5253
Terry A. Ring
6/10th scale up/down Factor
• Used for scaling the total capital cost for a
chemical plant of a different size
• Cost2/Cost1 = (Capacity2/Capacity1)0.6
• Accounts for economy-of-scale
Accounting for Inflation
• Cost to purchase = Base Cost*(I/Ibase)
– Base Cost, CB, = Historical price at Io
– I is a Cost Index at present time
• Chemical Engineering, CE, Plant Cost Index
• Marshall and Swift (MS) Equipment Cost Index
• Nelson-Farrar (NF) Refinery Construction Cost
Index
• Engineering News-Record (ENR) Construction
Cost Index
– Cp(I) = Cp(Ibase)*(I/Ibase)
– Cp(Ibase)=FT*Fm*Cbase(Ibase)
FT= Type factor
Fm= Materials factor
Cost Estimate Methods
• Order of Magnitude Estimate
– Method of Hill
• Marshall Swift for I/Ibase
• Six Tenths Rule for Production Capacity
– CTCI-2 (I)=CTCI-1 (Ibase)*(I/Ibase)* (Capacity2/Capacity1)0.6
• Study Estimate (±35%)
– Method of Lang
• CTCI=1.05*fL-TCI ∑ (Ii/Ibase-i) Cp-i
• Lang factors for different types of Plants
– Solids -3.10, Solids&Fluids 3.62, Fluids 4.73
• Sum over all major equipment
• Preliminary Estimate (±20%)
– Method of Guthrie
– Bare module cost, CBM=Cp-base(I/Ibase)[FBM+(FdFpFm-1)]
• d= design factor, p = pressure factor, m =materials factor
• Quote Estimate
Purchase Costs for Equipment
• Size Factor, S, depends on type of
equipment
• Cp(Ibase)= A + b* (S)n
– T & S Method, Ibase= 532.9
• Cp(Ibase)=exp(Ao+A1[lnS]+A2[lnS]2+…)
– Sieder, Seader, Lewin Book
• Ibase = 394 (mid-2000) average
Installation Factors
Materials Factor
Cost obtained on alloy basis
Pressure Vessels
• Storage Tanks
• Distillation Towers
– Tray
– Packed
• Absorber Towers
• Stripping Towers
Pressure Vessels
• Sizing Factor is the weight of steel, W
• Horizontal Vessels, 1,000<W<920,00 lb
CB=exp{8.717-0.2330[ln(W)]+0.4333[ln(W)]2}
• Vertical Vessels, 4,200<W<1,000,00 lb
CB=exp{6.775-0.18255[ln(W)]+0.02297[ln(W)]2}
• Add Platform Costs,
– Horizontal, 3<Di<12 ft
• CPL=1580(Di)0.20294
– Vertical, 3<Di<21 ft
• CPL=258.1(Di)0.7396(L)0.70684
• Weight, W=π(Di+ts)(L+0.8Di)tsρs
• C=FMCB+CPL
• FM= materials factor
– Installation, etc, FBM=4.16 (V), 3.05 (H)
– CBM=FBM*∑CP
Hoop Stress Calc for thickness, ts
• Design Pressure is function of operating pressure, Po
– For Po> 1,000psig use Pd=1.1Po
– For Po< 1,000psig but not for vacuum
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Pd=exp{0.60608+0.91615[ln(Po)]+0.0015655[ln(Po)]2}
Thickness (Hoop Stress Calculation)
ts= PdDi/(2SE-1.2 Pd)
S = max allowable stress for steel is f(T)
E = weld efficiency (fraction)
Minimum wall thickness for given diameters
May add extra thickness for wind stresses, corrosion
Different calculation for vacuum vessels
– Also account for leakage when vacuum vessel is used
Distillation Towers
• Pressure vessel with plates or packing and
additional nozzels and manholes
• Tray Cost
CT=NTFNTFTTFTMCBT
• NT= no. trays
• FNT= 1 for NT>20 otherwise FNT=2.25/(1.0414NT)
• FTT = tray type, 1.0 sieve, 1.87 bubble cap
• FTM= Materials, f(D)
– Carbon Steel FTM=1.0
– 316 SS
FTM=1.401+0.0788 Di
• Installation, etc, FBM=4.16
– CBM=FBM*∑CP
Packed Distillation Column
• Pressure vessel with platforms plus
packing
• Packing Cost basis is volume of packing, VP
• C=VpCPK+CDR
• CPK= is installed cost per unit volume
• Distributors cost, CDR
Absorbers/Strippers
• Pressure Vessel
– plus platforms
– plus packing
• Separate costs for blowers
• Separate costs for motors
– On blowers
– On mixers
– On pumps
Location of Plant Factor
Conclusions
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0.6th rule
Factored Estimate of Major Equipment
Installation Factor
Peripheral equipment, foundations, piping,
etc
• Biggest Mistakes
– No Off Sites - OSBL
• No Electrical Substation
• No Natural Gas Connection, etc.
– Neglecting Major Equipment