The Load Factor Method

It is significant that both the methods considered in the previous sections are derived directly from tlie available methods of structural response analysis. The permissible stress method results from the use of elasticity, the load factor method from the use of ultimate load theory and plasticity. In both of them, the specification of the loads is not a direct part of the method, and the way in which the safety is assessed, results very simply from the structural response analysis. In comparision to the effect Involved in developing the theories of response analysis, the effort put in to the safety assessment is trivial. 

Since the recovery yield achieved rmder the experimental conditions giving the maximum production rate is of the order of 60%, a first-order approximation of the loading factor giving a recovery yield Y is Lf = 0.6L /Y. Then the column efficiency is adjusted to achieve the required recovery yield. This method has been adopted because the results of numerical optimization suggest that there is a quasi-linear relationship between the recovery 5deld and both the mobile phase velocity and the loading factor [7]. 

The GEM method is based upon the assumption that the size and shape of the testing chamber does not influence the emission. During the testing the formaldehyde concentration in the chamber will rise and stabilize at a steady state concentration. At constant climate the steady-state concentration or emission rate from the test object depends on the relation between the loading factor and the air change rate. Good air circulation in the chamber is also essential ( ). 

The capacities of these demonstration power plants are very small by utility standards. To examine the economy-of-scale effect of Energy Plantation-produced electricity, different-sized "high-performance" power plants were analyzed at one location where an intermediate electricity cost prevails, viz., Natchitoches. Louisiana. The load factor used in these calculations was 33 percent. The results are shown in Figure II. These costs show a marked economy-of-scale effect, with "utility-method" costs dropping from 43 to 32 mills/kWhr over the same range of generator capacities. 

There is one immediate difficulty, however. What happens if there is not sufficient data available with which to draw the probability distribution This is, in fact, just the situation which has faced standards committees rewriting codes of practice into the limit state format. Firstly, it must be forcibly argued that surveys of the various classes of structural type must be undertaken in order to remedy the situation and obtain some data, but inevitably this takes time and money and competes with other demands upon limited resources. Surveys have been undertaken but the information is still rather sparse. The British codes of practice for buildings, written in the limit state format, have in fact been written to take as characteristic loads the same mixture of median, maximal and statistical estimates of dead loads, imposed loads, and wind loads as used for the limiting stress and load factor methods. This is plainly inconsistent and has led to some confusion where the basis of the method has not been clearly understood. 

In order to demonstrate clearly the differences in approach between (a) the permissible stress, (b) the load factor, and (c) the limit state methods, a numerical... 

An alternative method by Stichlmair [2.97] to compute the column diameter d and the tray spacing A.Z is explained in Table 2-23. Since the loading factor k, is not used, the use of this method is advantageous. 

Comparison the two Factor Method (TF) of SRM with single Factor Method (SF) of SRM, the ultimate load of TF was closer to the ultimate value of ICM than the value of SF. The error of the ultimate load of TF to the ultimate value of ICM was 3.85%, and the error of the ultimate load of SF... 

Crack velocity versus stress intensity factor (V-Kf) curves were obtained by two general tests, so called constant loading and relaxation tests [4. In the load relaxation method, the pre-cracked specimen was subjected to fast loading, followed by subsequent stopping of the crosshead at a certain displacement. Hence, the crack propagation resulted in a load relaxation and the load versus time curve allows the determination of the V-Kj curve with a single experiment, for crack rates down to 10 m/s [4]. The stress intensity factor can be calculated from expression (2) pro-... 

The most common design procedure, the partial factor method, is a semi-probabilistic method based on a design value which is a function of a characteristic value and of a partial factor. The partial factors depend mainly on relevant uncertainties in resistances and load effects, and on the class of failure consequences (reflected by a target reliability level). Designing new types of structures without specific guidelines, using partial factors that do not fit the characteristics of the structure can lead to an uneconomic (non-optimal) design. 

For ordered, or structured, packings, pressure-drop estimation methods have been reviewed by Fair and Bravo [Chem. Eng. Progr, 86(1), 19 (1990)]. It is not common practice to use the packing factor approach for predicling pressure drop or flooding. For operation below the loading point, the model of Bravo et [Hydrocarbon... 

However, power systems that cater to almost fixed loads at a time and whose variations occur only at specific times of the day may not reejuire it fast response. In such cases, it is possible to provide manual switching methods which will give enough time between two switchings. Manual switching, how ever, has certain shortcomings, due to the human factor such as its accuracy and diligence, as noted above. The recommended practice is therefore to select fast reactive controls as noted below. 

The rapid increase in the separation factors observed for the individual series of columns reflected not only the improvement in the intrinsic selectivities of the individual selectors but also the effect of increased loading with the most potent selector. Although the overall loading determined from nitrogen content remained virtually constant at about 0.7 mmol g for all CSPs, the fractional loading of each selector increased as the number of selectors in the mixture decreased. Thus, the whole method of building block selection and sublibrary synthesis can be also viewed as an amplification process. 

Power factor adjustment Although related to the average power factor of the load, the method of calculation may be based directly on measured power factor or on the measurement of reactive kVA over the period. Values at which power factor charges are incurred vary from 0.8 to 0.95 lag. 

The second method of improving the power factor of an installation is to provide static capacitor banks. These can be installed as a single block at the point of supply busbar, as a set of switchable banks or as individual units connected to specific loads. For an installation where no synchronous machines are installed for other purposes (i.e. as prime movers or generators) then static capacitor banks are almost invariably the most cost-effective way of improving the power factor. 

Electricity is normally charged for on the basis of power (kilowatts) and the supply authority must install plant whose rating (and therefore cost) is a function of the voltage of the system and the current which the consumer takes (i.e. kilo-volt-amps). The relationship between the two is kW = kVA x cos (j> where cos (j> is the power factor and is less than 1.0. In the case of loads which have a low power, factor the supply authority is involved in costs for the provision of plant which are not necessarily reflected in the kWh used. A penalty tariff may then be imposed which makes it economically worthwhile for the consumer to take steps to improve his power factor. Low power factors occur when the load is predominantly either inductive or capacitive in nature (as opposed to resistive). In most industrial circumstances where the load includes a preponderance of motors, the load is inductive (and the power factor is therefore lagging). Consequently, if the power factor is to be brought nearer to unity the most obvious method is to add a significant capacitive component to the load. 

Previous chapters have outlined the methods of estimating loads, choosing methods to achieve the required conditions, and howto select and balance plant for correct operation. Theyhave also mentioned the factors which will give economy in running costs. 

It should be evident that the full spectrum of the possible materials and applications in load-bearing situations involves many factors that may have to be taken into account. Fortunately, most products involve only a few factors, and others will not be significant or relevant. Regardless, the methods of design analysis must be made available to handle any possible combinations of such factors as the materials characteristics, the product s shape, the loading mode, the loading type, and other service factors and design criteria. 

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