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Engineering Practice Cost Engineering: Equipment Purchase Costs

A methodolody and examples for estimating equipment costs are presente me to use their cost database as one of the key informa­ tion sources. Ratioing for different capacities and size exponents. ngineers have the responsibility to create proj­ When the cost of equipment, processes, or plants having ects having attractive returns on investment andthe same design features is plotted versus capacity on logto create economically sound designs — de­ log paper, the plot usually is a straight line. Thus, one can signs that produce high-quality, competitively write the following equation, where n is the size exponent. priced products. This requires the technical and eco­ Capacity sUe2 Costsizei nomic1 study of many different options. When doing ( ) C0Stsj2ei Capacitystzel studies, the design is usually not well defined, so one (1) will often use factor methods for capital estimating. With For equipment, the average size exponent is 0.6, for these methods, one first determines the purchase costplants 0.67. of the equipment and multiplies that by a factor to deter­ To illustrate, if you know the price of a 500 ft2 platemine the capital cost of a process or plant.2 and-frame exchanger is $10,500, you can estimate the The accuracy of factored estimates is usually good price of an 800 ft2 exchanger using Equation (1). Refer­ enough to produce high-quality decisions. ring to Figure 6, note that the size exponent for platePurchase cost data. This article presents up-to-date and-frame exchangers is 0.71. Rearranging Equation (1), equipment purchase cost data for nine different types of the cost is: process equipment. Cost «2 = $10,500 x (800 ft2 / 500 ft2)0-71 = $14,700. • Agitators Adjusting for inflation using the CEPCI. To keep track • Air compressors • Boilers of the effects of inflation, several organizations publish • Cooling towers cost indices. For chemical plant construction, I feel the • Fans CEPCI is the preferred index. Chemical Engineering pub­ • Heat exchangers lishes the index each month. One can use it to escalate costs. The relationship between costs and indices is • Pressure vessels • Pumps, centrifugal given by Equation (2): • Tanks, storage Costa[ tjme 2 lndexat time 2 The cost data are presented for each of these types of lndexat time 1 equipment in Figures 1-9 on p. 52. Each begins with a Costat time 1 (2) general specification. For example in Figure 2 (air com­ pressors) the specification is: Centrifugal, rotary screw For example, if you know the price of a 10,000-gal. and reciprocating compressors that produce 100-150 storage tank in August 2017 (CEPCI = 570) was $33,000, psig oil-free air. The price also includes intercoolers and you can estimate the price in mid-2019 (CEPCI - 590) using Equation (2). Rearranging (2): aftercoolers, a lubrication system and a totally enclosed, fan-cooled (TEFC) motor. Each figure contains a log-log graph plotting purchase $CEPCI, 590 = $33,000 (590/570) = $34,200. cost versus capacity, an equation for cost as a function of capacity, and a size exponent for capacity ratioing. Using the graph factors. Six of the graphs include fac­ Most also contain factors that permit adjusting costs fortors that permit adjusting costs for different materials of different materials of construction, operating pressure or construction, different operating pressures or different equipment type (such as API versus ANSI pumps). equipment variations. Their use is simple. To adjust a All costs are quoted at a Chemical Engineering Priceprice, simply multiply the price by the appropriate factor. Cost Index (CEPCI) of 570, which corresponds to AugustTo illustrate, the small boiler prices in Figure 3 are for 2017. The graphs were developed from actual purchase units generating 150 psig steam. If you wish to price a cost or vendor quotation data. Of special note is that BSI 100-hp unit that produces 15 psig steam, you would Engineering (Cincinnati, Ohio; www.bsiengr.com) allowed multiply the cost from the graph, $82,000, by the 15 psig

Thane R. Brown Procter & Gamble (retired)

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1. For an economic comparison, one usually has to estimate the capital and production cost for each option and use that information to calculate the net present value (NPV) or annualized cost (AC) of each. The NPV or AC is then used to find the economic option. 2. Brown's book [1] explains economic comparison methodology. Lang and Hand factors, plus production cost estimating in depth. CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM JANUARY 2019

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Figures 1-9 depict up-to-date equipment purchase cost data for nine different types of process equipment: agita­ tors (Figure 1); air compressors (Figure 2); boilers (Figure 3); cooling towers (Figure 4); fans (Figure 5); heat ex­ changers (Figure 6); pressure vessels (Figure 7); centrifugal pumps (Figure 8); and storage tanks (Figure 9) Figure \git;Hnis

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