Quick estimating checks

Early in the life of a project, information has not been developed to allow definitive cost estimates based on material takeoff and vendor quotes for equipment. Therefore, it is necessary to estimate the cost of a facility using shortcut methods. The first step is to develop or check flow-sheets, major equipment sizes, and specification sheets as described in earlier chapters. From the equipment specification sheets, the cost of each piece of equipment is estimated, using techniques discussed later. Once the major equipment cost has been estimated, the total battery limit plant cost can he quickly estimated using factors developed on a similar project. 

For the purpose of quick estimates or field evaluation of existing systems, consider the curve in Figure 3-27. This curve is not meant to supersede a comprehensive analysis as previously discussed. It should be used in checking vendor proposals or in revising existing installations where a single cylinder is connected to a header without the interaction of multiple cylinders. While not a hard rule, the curve should be conservative for... 

The Fauske nomograph is useful for performing quick estimates and for checking the results of the more rigorous computation. 

After selecting a reactor type and catalyst configuration, the next step is to calculate the reactor volume. Before undertaking a detailed calculation, we need to estimate the reactor volume. A quick estimate is sometimes needed to check an exact calculation or to prepare a budget for a proposal. For packed bed or homogenous reactors, the space velocity is a way of rapidly sizing reactors. Space velocity is defined as the ratio of the volumetric feed flow rate to the reaction volume or the ratio of mass feed flow rate to the catalyst mass. The volu-... 

Concrete and Structural Steel quantities can be easily checked with the quick estimating procedures in Chapter 19. 

In order to help the user in the design of a settling tank (to build or to check), a simple experiment can be proposed (Fig. 13). A wastewater sample is introduced into a2-m-high glass column of 100-L capacity, and aliquots are carefully withdrawn for different heights and times. UV spectra are acquired for a quick estimation of the TSS (after a previous... 

Branan (2005) has given a simplified method for quick estimation of manifold pressure drops. Flare knockout drum sizing needs to be checked for proper vapour-liquid separation and hence prevention of carryover of liquid to the flare stack. Steam injection to the flare stack also needs to be reviewed to prevent potential black smoke and noise. Relief headers ... 

Calculators are wonderful devices they enable you to get to the wrong answer very quickly. Of course, that s not the destination you want. You can take certain steps to avoid putting that wrong answer into your homework set or on an exam. One is to keep track of the units in a calculation and use the correct conversion factors. Second, you can do a quick mental check to be sure that your answer is reasonable you can try to make a ballpark estimate. 

The paper presents an analytical solution to the linear polymer flood problem, which provides a check on accuracy of the numerical model and a quick estimate of additional oil recovery by line-drive polymer floods. The numerical model developed indicates that additional oil recovery by polymer flooding is sensitive to polymer bank size and adsorption level and is insensitive to the extent of dispersion active at the trailing edge of the polymer slug,... 

This study was performed to estimate the additional oil recovery by pattern polymer flooding using Kelzan in a California viscous-oil reservoir. Laboratory experiments were performed to estimate polymer solution viscosity, adsorption and dispersion upon displacement by normal injection water. Waterflood and polymer flood oil recovery curves were obtained for a laboratory core packed with sand representative of the reservoir. A numerical model was developed to simulate polymer floods in linear or five-spot patterns in single-layer or stratified reservoirs- An analytical solution to the linear polymer flood problem was developed to provide a quick estimate of incremental oil obtainable by polymer flooding and to provide a check on the accuracy of the numerical model. 

The spectral exitance M or radiance L can be calculated directly from Planck s law. When only an estimate is needed, values can be read directly or interpolated from graphs as in Figures 2.7 and 2.8 the graphs provide enough accuracy for quick estimates and checks on other sources. (It is always wise to double check a few values from new radiometric code. It is not uncommon to find a value reported to four significant figures, but incorrect by a power of 2, n, or 10 ). 

To check for any possible calculation error, we can estimate the correct answer through a quick mental calculation by using exponential numbers. The answer should be (2 X 10 )(4 x 10 )/(2 X 10 ) 4 x 10 , and it is. Expressing numbers in exponential notation can often help us quickly estimate what the result of a calculation should be. 

Cost estimation and screening external MSAs To determine which external MSA should be used to remove this load, it is necessary to determine the supply and target compositions as well as unit cost data for each MSA. Towards this end, one ought to consider the various processes undergone by each MSA. For instance, activated carbon, S3, has an equilibrium relation (adsorption isotherm) for adsorbing phenol that is linear up to a lean-phase mass fraction of 0.11, after which activated carbon is quickly saturated and the adsorption isotherm levels off. Hence, JC3 is taken as 0.11. It is also necessary to check the thermodynamic feasibility of this composition. Equation (3.5a) can be used to calculate the corresponding... 

Table 2-12A is convenient for most air problems, noting that both free air (60°F and 14.7 psia) and compressed air at 100 psig and 60°F are indicated. The corrections for other temperatures and pressures are also indicated. Figure 2-37 is useful for quick checking. However, its values are slightly higher (about 10 percent) than the rational values of Table 2-11, above about 1000 cfm of free air. Use for estimating only. 

A quick check on the probable accuracy of a particular method can be made by using it to estimate the property for an analogous compound, for which experimental values are available. 

In the ultimate monitoring system, every single estimate item would have a corresponding activity shown in the detailed schedule and a value based on hours. This level of precision can only be efficiently achieved with the aid of computer programs and would defeat the purpose of a quick checking system. 

The shortcut techniques included here are very useful for quickly checking estimates as well as developing conceptual estimates. Most have been derived from the analysis of several organic chemical plants, built or estimated others come from personal observations. Table 19.34 reflects the analysis of nine actual chemical projects and five estimates of the following common characteristics ... 

As mentioned in section 19.11 the total field cost factor (TFCF) can be modified and adapted to facilities that differ from those in the original study. The modified factor is developed by adjusting each of its cost components (see Table 19.36) to meet the requirements of specific cases. This approach can be very useful for conceptual estimating as well as for the quick checking of estimates prepared by others. 

Estimating Method Quick Check Check Detailed Detailed Check ... 

Engineering contractors will also find the estimating tools presented in Chapter 12 very useful for the quick preparation of the preliminary estimates frequently submitted with proposals, as well as for checking their own definitive estimates. 

The column converges quickly with the good estimate provided from the shortcut model. The column profiles can be checked by selecting the Performance tab in the column environment and then selecting Plots from the menu on the left and Composition from the list of possible plots, as shown in Figure 4.24. This generates composition profiles like those presented in Figures 4.12 to 4.17. 

Other methods, such as the direct observation of far-infrared transitions, are preferable, but this method permits a quick check on the assignment of infrared or Raman spectra if such spectra have not been obtained or are too weak to observe, it permits a moderately accurate estimate of the energy of the lower vibrational levels. 

SOL VE first checks if all x s are positive, and if not calls LP right away to create a feasible solution. If all x s are positive, the projection technique is applied, to see if a feasible solution can be improved by a quick process of scaling. If this succeeds a message is printed saying that SCALE is 1.0 and the program goes to the first-order method. If it does not succeed, LP is called to provide a starting estimate. 

The detailed procedure is not complicated. First one plots r versus x from experimental data, keeping in mind the general shapes of the curves in Figure 1.28. This gives an indication of the order of reaction, thence the rate constant is evaluated as to/(Co) ", where tq is the initial (x = 0) intercept. For any order, the slope of the initial linear section of the plot (x 0) is given by (-wtq/2). Thus the method provides a quick means for the estimation of reaction order and associated rate constant [E.M. Holleran, Chemtech, 500, August, (1981)]. A check on estimated order is provided by looking at the intercept at x = 1, (r/ro),. This should be equal to To/(l - /2), as shown later. 

A friend once remarked cynically that calculators let you get the wrong answer more quickly. He was implying that unless you have the correct strategy for solving a problem and have punched in the correct numbers, the answer will be incorrect. If you learn to estimate answers, however, you wiU be able to check whether the answers to your calculations are reasonable. 

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