Equipment Costing T&S - Chapter 7 Review CH EN 5253 Terry A. Ring

6/10 th scale up/down Factor Used for scaling the total capital cost for a chemical plant of a different size Cost 2 /Cost 1 = (Capacity 2 /Capacity 1 ) 0.6 Accounts for economy-of-scale

Accounting for Inflation Cost to purchase = Base Cost*(I/I base ) –Base Cost, C B, = Historical price at I o –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 –C p (I) = C p (I base )*(I/I base ) –C p (I base )=F T *F m *C base (I base ) F T = Type factor F m = Materials factor

Cost Estimate Methods Order of Magnitude Estimate –Method of Hill Marshall Swift for I/Ibase Six Tenths Rule for Production Capacity –C TCI-2 (I)=C TCI-1 (I base )*(I/I base )* (Capacity 2 /Capacity 1 ) 0.6 Study Estimate (±35%) –Method of Lang C TCI =1.05*f L-TCI ∑ (I i /I base-i ) C p-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, C BM =C p-base (I/I base )[F BM +(F d F p F m -1)] d= design factor, p = pressure factor, m =materials factor Quote Estimate

Purchase Costs for Equipment Size Factor, S, depends on type of equipment C p (I base )= A + b* (S) n –T & S Method, I base = C p (I base )=exp(A o +A 1 [lnS]+A 2 [lnS] 2 +…) –Sieder, Seader, Lewin Book I base = 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 C B =exp{ [ln(W)] [ln(W)] 2 } Vertical Vessels, 4,200<W<1,000,00 lb C B =exp{ [ln(W)] [ln(W)] 2 } Add Platform Costs, –Horizontal, 3<D i <12 ft C PL =1580(D i ) –Vertical, 3<D i <21 ft C PL =258.1(D i ) (L) Weight, W=π(D i +t s )(L+0.8D i )t s ρ s C=F M C B +C PL F M = materials factor –Installation, etc, F BM =4.16 (V), 3.05 (H) –C BM =F BM *∑C P

Hoop Stress Calc for thickness, t s Design Pressure is function of operating pressure, P o –For P o > 1,000psig use P d =1.1P o –For P o < 1,000psig but not for vacuum P d =exp{ [ln(P o )] [ln(P o )] 2 } Thickness (Hoop Stress Calculation) t s = P d D i /(2SE-1.2 P d ) 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 C T =N T F NT F TT F TM C BT N T = no. trays F NT = 1 for N T >20 otherwise F NT =2.25/( N T ) F TT = tray type, 1.0 sieve, 1.87 bubble cap F TM = Materials, f(D) –Carbon Steel F TM =1.0 –316 SS F TM = D i Installation, etc, F BM =4.16 –C BM =F BM *∑C P

Packed Distillation Column Pressure vessel with platforms plus packing Packing Cost basis is volume of packing, V P C=V p C PK +C DR C PK = is installed cost per unit volume Distributors cost, C DR

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 0.6 th 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