Estimate definitive

Project Control Having made a good estimate of the capital cost and the expected construc tion time, it is essential to introduce an effective system for controlling expenditure of time and money during construction. Good capital-cost control can cut down expenditures even when the definitive estimate is not veiy accurate. It is most important for management to receive early warnings if overruns in expenditure or time are likely to occur. 

Cooling Water System. A list of cooling duties will be available at this point so the cost estimate for this system can be factored or estimated based on a similar operating system. For a more definitive estimate based on initial or detailed layout, it is probably best to use a contractor or consultant skilled in these designs. If a cooling tower is involved, the groundwork will already have been set. This basis can be passed along on specification sheets provided in the Appendix to a vendor for quotes. 

Definitive estimate (project control estimate). "The data needed for this type of estimate are more detailed than those for a preliminary estimate and inclnde the preparation of specifications and drawings. The probable accuracy is -10 to -1-15 percent. 

Analytical Methods Committee (1987), Recommendations for the definition, estimation and use of the detection limit, Analyst, 112,199-204. 

However, their oxidation processes are often complicated and it is not easy to define the positive ends of the potential windows thermodynamically. In aprotic solvents, both the reduction and oxidation processes of solvents are complicated and definite estimation of thennodynamic potential windows is almost impossible. 

Definitive estimates. Definitive cost estimates are the most time-consuming and difficult to prepare, but they are also the most accurate. These estimates require preparation of plot plans, detailed flow sheets, and preliminary construction drawings. Scale models are sometimes used. All material and equipment is listed and priced. The number of labor hours for each construction activity is estimated. Indirect field costs, such as crane rentals, costs of tools, and supervision, are also estimated. This type of estimate usually results in an accuracy of 5%. 

Definitive estimates of the quantities and methods for disposal of closure wastes had not been finalized by the Army when this report was being prepared. However, rough projections of waste that will be generated during closure were available. These are summarized in Tables 4-1 and 4-2. The ultimate end use of each site... 

Definitive estimate (project control estimate) based on almost complete data but before completion of drawings and specifications probable accuracy of estimate within 10 percent. 

Estimating by percentage of delivered-equipment cost is commonly used for preliminary and study estimates. It yields most accurate results when applied to projects similar in configuration to recently constructed plants. For comparable plants of different capacity, this method has sometimes been reported to yield definitive estimate accuracies. 

Definitions of Zinc Deficiency. It is clear that zinc deficiency can be defined only with difficulty since the zinc content of a single body fluid or tissue level cannot provide a definitive estimate of body zinc status (If3 ) It is also not possible to rely on the concentration of zinc in several body tissues to estimate body zinc status since differing concentrations in different tissues lead to non-definitive conclusions. 

The definitive estimates are prepared after the project has been totally defined, including offsites, waste treatment, site conditions, equipment arrangements, etc. This stage of definition requires the involvement of an engineering contractor to complete the so-called basic engineering referred to in Chapter 12. 

It is advisable to complete the definitive estimate before the fabrication of expensive equipment and start of construction as a protection against major, unexpected cost variations which could have a negative influence on project approval. 

The computerized method is an excellent tool for conceptual and even preliminary estimates but should not be used for definitive estimates unless applied by experienced estimators fully familiar with the algorithms and unit prices built into the program for developing takeoffs and calculating material costs and labor hours. 

Equipment Erection - 20% of the equipment account is usually a generous allowance and should be used for preliminary estimate. On appropriation or definitive estimate the individual work hours in Table 19.1 should be used. 

Note For a preliminary estimate, the cost can be calculated in a few minutes with the aid of the charts provided. For definitive estimates intended for appropriation and/or progress monitoring, the cost should be developed with the semi-detailed procedure. Both approaches should result in approximately the same cost. 

Table 19.19 represents the average cost of valves purchased at different times escalated to late 2000. These costs should only be used for conceptual or preliminary estimates when no prices are available. Since the cost variations from one manufacturer to another can be astronomical, definitive estimates should be based on vendors quotes or, at least, on recent purchases. 

This number is very consistent with the actual cost of several organic chemical plants and several definitive estimates. 

Definitive estimates are normally prepared by engineering contractors at considerable cost, in a rather long time. However, with the semi-detailed system propounded in this book, owners could prepare, at a much lower cost and in a much shorter time, in-house estimates of equivalent accuracy. 

The first two were prepared in-house with minimal engineering and very few estimating hours using the techniques proposed in this book. The definitive estimate was prepared by the contractor after several months of engineering (12,000+ hours) using the usual detailed take-off method. 

OF THE FORMAL ESTIMATE AND THE IN-HOUSE, PRELIMINARY ESTIMATE WAS WITHIN 1% OF THE DEFINITIVE ESTIMATE (See Table M.4.)... 

This case also illustrates the value of the quick and semi-detailed estimating techniques proposed in this book. The 1.01 accuracy of the quick estimate versus the contractor s definitive estimate can only be considered a stroke of luck. However, the authors can attest to repeated instances of 0.90-1.10 accuracy of the semi-detailed method recommended for appropriation estimates. 

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. 

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