Equipment Costing
Chapter 22 (p558-597)
CH EN 4253
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 Ibase
– 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)
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
– CTCI= ∑ CBM_i
• Quote Estimate
Purchase Costs for Equipment
• Size Factor, S, depends on type of
equipment
• Cp(Ibase)=A*(S)b
• Cp(Ibase)=exp(Ao+A1[lnS]+A2[lnS]2+…)
• Your book gives 2006 base costs
• Ibase = 500 (2006) average
Pumps & Electric Motors
• Pump Types (Centrifugal, Gear, Plunger)
– Centrifugal Pump
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Size factor, S=Q(Head)0.5
Base Cost, CB=exp(9.2951- 0.6019[ln(S)] +0.0519[ln(S)]2)
Cp=FTFMatCB
Fm materials factor see Table 22.21
FT pump type factor see Table 22.20
Other types of pumps have different CB formulas
– Electric Motor to drive pump
• Size Factor=Power consumption, PC=PT/ηp/ηM=PB/ηM=QHρ/(33,000ηpηM)
• Q= flow rate, H = head, ρ = density
• Efficiencies (pump and motor) are a function of flow rate and break
horsepower (power without any losses), respectively
• CB=exp{5.4866+0.013141[ln(PC)]+0.053255 [ln(PC)]2 +0.028628 [ln(PC)]30.0035549[ln(PC)]4}
• Cp=FTCB
• FT= motor types factor see Table 22.22
• ηM=~90%
– Installation, etc, FBM=3.3
– CBM=FBM*∑CP
Fans
• Fan
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Sizing factor is the volumetric flow rate, Q
Different CB formula for different types of fans
CP=FHFM CB
FH Head factor see Table 22.24
FM material of construction factor
• Fiberglass
• Stainless steel
• Nickel Alloy
1.8
2.5
5.0
• Motor size by PC=QHt(in. water)/(6,350 ηFηM)
• ηM =~90%, FBM = 2.15
• CBM=FBM*∑CP
Blowers
• Sizing factor is the power consumption, PC
• Centrifugal (turbo) Blower
CB=exp{6.6547+0.7900[ln(Pc)]}
• CP=Fm-fansCB
• Motor
– Motor size by PC=QHt(in. water)/(6,350 ηFηM)
– ηM =90% , FBM = 2.15
• CBM=FBM*∑CP
Compressors
• Compressor types
– Centrifugal, CB=exp{7.2223+0.80[ln(PC)]}
– Reciprocating, CB=exp{7.6084+0.80[ln(PC)]}
– Screw, CB=exp{7.7661+0.7243[ln(PC)]}
• Size factor is the power consumed, PC=PB/ηC
• CP=FDriveFMatCB
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FDrive =1 (electric motor), 1.15 (steam), 1.25 (gas turbine)
FMat = 1.0 Carbon steel, 2.5 SS, 5.0 Nickel Alloy
CBM=FBM*∑CP
FBM = 2.15
Heat Exchangers
• Types of Heat exchangers
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Floating, CB=exp{11.667-0.8709[ln(A)]+0.09005[ln(A)]2}
Fixed Head, CB=exp{11.0545-0.9228[ln(A)]+0.09861[ln(A)]2}
U-tube, CB=exp{11.147-0.9186[ln(A)]+0.09790[ln(A)]2}
Kettle, CB=exp{11.967-0.8709[ln(A)]+0.09005[ln(A)]2}
Thermosiphon, CB=
Double pipe, CB=exp{7.1248-0.16[ln(A)]}
• Size Factor is HX area, A
• CP=FpFMatFLCB
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Pressure Factor, Fp= 0.9803+0.018(P(psig)/100)+0.0017(P(psig)/100)2
– Not for double pipe
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Materials Factor, Fmat=a+(A/100)b, a & b from Table 22.25
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a≥1.0 note error in first row of Table 22.5
Tube Length Factor FL= 1.25 for 8 ft, 1.0 for 20 ft. on a sliding scale
CBM = FBM*CP, FBM=3.17 (S&T), 1.80 (DP), 2.17 (Fin/Fan)
Fired Heaters
• Size Factor is the heat duty, Q
• CB=exp{0.08505+0.766[ln(Q)]}
• CP=FPFMatCB
• FP=0.986-0.0035(P(psig)\500)+0.0175(P/500)2
• Fmat=1.4 Cr-Mo alloy steel, 1.7 for
stainless steel
• CBM = FBM*CP, FBM=2.19
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 see Table 22.26
– 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 nozzles 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 and
packing
• Separate costs for blowers
• Separate costs for motors
Other process equipment
• Different sizing factors
• Different basis cost equations
• Same methods used for cost calculation
Other Process Equipment
• Various Size Factors
• Table 22.32