Detailed-item estimates

METHOD A DETAILED-ITEM ESTIMATE. A detailed-item estimate requires careful determination of each individual item shown in Table 1. Equipment and material needs are determined from completed drawings and specifications and are priced either from current cost data or preferably from firm delivered quotations. Estimates of installation costs are determined from accurate labor rates, efficiencies, and employee-hour calculations. Accurate estimates of engineering, drafting, field supervision employee-hours, and field-expenses must be detailed in the same manner. Complete site surveys and soil data must be available to minimize errors in site development and construction cost estimates. In fact, in this type of estimate, an attempt is made to firm up as much of the estimate as possible by obtaining quotations from vendors and suppliers. Because of the extensive data necessary and the large amounts of engineering... 

Detailed-estimate designs, 14, 17, 162 Detailed-item estimates, 179-180 Deteigenf manufacture of 23-34... 

The methods used to estimate the capital investment depends on the degree of accuracy required by the project and on the available data. An accuracy of +/- 5% can be achieved by means of a detailed-item estimation, in which equipment costs are computed from detailed sizing and material specifications. This method can be applied at best by using specialised computer package, as ICARUS . 

Having selected a suitable site for the chemical plant, it is possible and necessary to make a preliminary decision regarding the layout of the plant equipment. Although the equipment has not been designed in detail, preliminary estimates of the physical size of each item should be available in the equipment list (Chapter 4). Any sizing differences between the initial and final estimates should not be too excessive, and appropriate areas should be allowed around the plant items when determining the layout. 

Aspen IPE estimates the purchase and installed cost of each equipment item individually or provides estimates for all of the equipment items (i.e., the entire project) using a single command. For an individual unit, right click on the unit in the List View and select Evaluate Item. Aspen IPE produces a detailed item report for the unit. For the depropanizer tower, by scrolling about a third of the way down the report, the following summary of the cost estimates appears ... 

Other items such as interest, taxes and depreciation are also included in the detailed cost estimate. 

The capital cost estimates are generated by the Engineering function, often based on 50/50 estimates (equal probability of cost overrun and underrun). It is recommended that the operating expenditure is estimated based on the specific activities estimated during the field lifetime (e.g. number of workovers, number of replacement items, cost of forecast manpower requirements). In the absence of this detail it is common, though often inaccurate, to assume that the opex will be composed of two elements fixed opex and variable opex. 

Factor Methods. A more detailed product cost estimation method is to relate manufacturing cost items to a few calculated items, such as raw materials, labor, and utihties by means of simple factors (1,2). Internal accounting groups often develop factors to use with this method. This factor method is very popular. 

At the end of each month, the field cost engineer collects all current information on a detailed cost report form. As these are actual costs, they can be used to estimate future job costs to completion. Daily reports of unit-cost progress for concrete, excavation, masonry, steel, piping, and electrical work, etc., are then used to predict possible overruns or underruns for the various items. Analysis and comparison with the original estimate point out trouble spots for early attention. If an item is running into difficulty, it is red-flagged to the resident and projec t engineers for remedial action. 

Once the sizes of the major equipment items are known, there are several ways to get the cost of each. By far the most accurate is to get quotations from vendors. This is difficult to do in the early stages of a project because many equipment details are not known. Also, the time between making the preliminary study and purchasing the equipment is so long that the quotation ages, and vendors cannot afford to prepare quotations on every preliminary study. However, many vendors are very cooperative in providing verbal prices or " estimating quotations. Often, the vendor is the only source for accurate cost information. 

Because of the magnitude of the task of preparing the material for this new edition in proper detail, it has been necessary to omit several important topics that were covered in the previous edition. Topics such as corrosion and metallurgy, cost estimating, and economics are now left to the more specialized works of several fine authors. The topic of static electricity, however, is treated in the chapter on process safety, and the topic of mechanical drivers, which includes electric motors, is covered in a separate chapter because many specific items of process equipment require some type of electrical or mechanical driver. Even though some topics cannot be covered here, the author hopes that the designer will find design techniques adaptable to 75 percent to 85-1- percent of required applications and problems. 

Definitive effort-hour estimating data is used to develop specific detail estimates. Composite effort-hour data is presented as a guide for quick estimating methods. All material quantities have been consolidated into an average for a given amount of material and do not include any specialty items. All effort-hour units and material quantities are based on a typical installation, and each material type should be reviewed carefully for various differences. 

Capital cost estimates for chemical process plants are often based on an estimate of the purchase cost of the major equipment items required for the process, the other costs being estimated as factors of the equipment cost. The accuracy of this type of estimate will depend on what stage the design has reached at the time the estimate is made, and on the reliability of the data available on equipment costs. In the later stages of the project design, when detailed equipment specifications are available and firm quotations have been obtained, an accurate estimation of the capital cost of the project can be made. 

Pikulik and Diaz (1977) give a method of costing major equipment items from cost data on the basic components shells, heads, nozzles, and internal fittings. Purohit (1983) gives a detailed procedure for estimating the cost of heat exchangers. 

An accurate estimate can be made by detailing and costing all the items needed, based on experience with similar plants. As a rough guide the cost of miscellaneous materials can be taken as 10 per cent of the total maintenance cost. 

In summary, there are three important generalizations about error estimation in protein crystallography. The first is that the level of information varies enormously as a function primarily of resolution, but also of sequence knowledge and extent of refinement. The second generalization is that no single item of information is completely immune from possible error. If the electron density map is available or indicators such as temperature factors are known from refinement, then it is possible to tell which parameters are most at risk. The third important generalization is that errors occur at a very low absolute rate 95% of the reported information is completely accurate, and it represents a detailed and objective storehouse of knowledge with which all other studies of proteins must be reconciled. 

Preliminary estimate (budget authorization estimate). More details about the process and equipment, e.g., design of major plant items, are required. The accnracy is probably -20 to -1-25 percent. 

Detailed Estimate Method For estimates in the detailed category, a code of account needs to be used to prevent oversight of certain significant items in the capital cost. See Table 9-15. Each item in the code is estimated and provides the capital cost estimate then this estimate serves for cost control during the construction phase of a project. 

Electrical This item consists of transformers, wiring, switching gear, as well as instrumentation and control wiring. The installed costs of the electrical items may be estimated as 20 to 40 percent of the delivered equipment costs or 5 to 10 percent of the fixed capital investment for preliminary estimates. As with piping estimation, the process design must be well along toward completion before detailed electrical takeoffs can be made. 

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