Lang factors

An overall Lange factor, E- j can be used to relate the battery-limits fixed capital investment Jg to the deHvered equipment cost Eg, so that... 

The ratio of the fixed capital investment to the purchased equipment cost (Lang factor) is taken as 4.83. 

Figure 14.1 Approximate relationship of Lang factor to average main plant item cost. (Redrawn and updated from de la Mare [45].)...

The ISBL costs can be roughly estimated by multiplying the sum of the purchased-equipment costs by a certain factor, the so-called Lang factor ... 

Ce = the total delivered cost of all the major equipment items storage tanks, reaction vessels, columns, heat exchangers, etc., fi = the Lang factor , which depends on the type of process. 

To make a more accurate estimate, the cost factors that are compounded into the Lang factor are considered individually. The direct-cost items that are incurred in the construction of a plant, in addition to the cost of equipment are ... 

The contribution of each of these items to the total capital cost is calculated by multiplying the total purchased equipment by an appropriate factor. As with the basic Lang factor , these factors are best derived from historical cost data for similar processes. Typical values for the factors are given in several references, Happle and Jordan (1975) and Garrett (1989). Guthrie (1974), splits the costs into the material and labour portions and gives separate factors for each. In a booklet published by the Institution of Chemical Engineers, IChemE (1988), the factors are shown as a function of plant size and complexity. 

For the factored estimate a list is made of all pieces of equipment, and the delivered cost of each item is obtained. This could be determined by inquiring from manufacturers, from past records, or from published data. The delivered cost of all the equipment is summed and multiplied by an appropriate factor. According to Lang this factor would be 3.10 for a solids process plant, 3.63 for a solid-fluid plant, and 4.74 for a fluid plant. These factors are referred to as Lang factors. This estimate is often used in the preliminary stages of engineering, but is not extremely accurate. 

To use the Lang factors the engineer must define what type of plant is being built. This is important, since the largest factor is 50% greater than the smallest. It is sometimes difficult, however, because there is a continuum of chemical plants between the two extremes. A coal-briquetting plant is obviously a solids processing plant. Methanol and ammonia plants are fluids plants. Plants that extract chemicals from solids fall between. 

Determine the cost of a fluid plant whose equipment costs are given in Table 9-7 for the year 1975. The Lang factors are to be used. From Table 9-7, the total F.O.B. equipment cost is 1,3 10,000. Let us assume a 4% sales tax and an average freight charge of 5%. The total cost of the delivered equipment is... 

The premise upon which the Lang factors are based is that the equipment costs are a certain fraction of the total cost of the plant. Or conversely, it can be said that the costs of piping, insulation, wiring, site preparation, and so on are a function of the cost of the equipment. However, the cost of equipment is very dependent on the materials used to make it, while most of the other items listed in Table 9-6 are not dependent on materials. 

Similar arguments can be made for high-pressure and low-temperature apparatus. It can also be shown the Lang factor is dependent on the size of the equipment. As the size increases the proportionate cost of all other items decreases, and therefore the Lang factor should be smaller. The net result of the above inaccuracies is that the factored estimate as previously discussed cannot be very accurate. In 1951 W. T. Nichols estimated that the error could easily be as great as 60% of the cost of the plant. 

The cost of a unit is then obtained from Figure 9-4. To obtain the cost of the plant this figure needs to be multiplied by the number of units, a factor (1.33) to account for utilities and general facilities, and the current or projected value of the Engineering News Record Chemical Cost Index. The accuracy of this method is unknown but should be better than the Lang factor and not as good as Miller s. 

For this estimate, the prices of all items on the equipment list except those in the 700 and 800 categories were summed to obtain a 1968 F.O.B. cost of 2,203,000. This was increased by the Ohio sales tax of 4% and then by another 5%, to cover freight costs. This results in a delivered equipment cost of 2,400,000. The Lang factor is between that of a fluids plant and a solid-fluids plant. The value selected was 43. This was updated to 1974, and an 8% factor for waste treatment was added The result is a factored cost estimate of 14,400,000. 

The single factors include piping, automatic controls, insulation, painting, electrical work, engineering costs, etc. (Couper, 2003). Table 9-10 shows the Lang factors for various types of processing plants. The boundaries between the classifications are not clear-cut, and considerable judgment is required in the selection of the appropriate factors. 

Lang method The Lang factor for a fluid processing unit starting with purchased equipment costs is 5.0. Therefore, fixed capital investment is 2,820,000 X 5.0 X 1.035 X 1.040 = 15,177,000. 

The value of the Lang factor (FL) depends upon the type of process. For most plants it has a value of approximately 3. The following values can be used as a guide ... 

If possible, the Lang factor should be obtained from the cost files of the particular company. It is important (although sometimes difficult) to define the type of plant under consideration because of the large difference between the values of FL (3.10 to 4.74). 

METHOD D LANG FACTORS FOR APPROXIMATION OF CAPITAL INVESTMENT. This technique, proposed originally by Langf and used quite frequently to obtain order-of-magnitude cost estimates, recognizes that the cost of a... 

Lang factors to convert from the base cost of the delivered vessel (costed as if it were of carbon-steel material of construction so that weight becomes the primary measure of installation cost) to the cost of the vessel installed with all necessary auxiliaries except special internals such as trays or agitators are 3.0 for vessels installed in a horizontal position and 4.0 for vessels installed in a vertical position. 

The cost for installation (Lang factor of 3.0 by Table 6 of Chap. 14) will be twice the cost of the f.o.b. unit if it is constructed of carbon steel. In this case, the material of construction is carbon steel, so it is not necessary to use a materials cost-conversion factor to obtain the f.o.b. cost thus, the estimated total installed cost of the reactor is 78,000 + (2X 78,000) = 234,000. 

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