Calculating Service Life

This equation shows that both plasticizer type and type of carbon affect performance. On the plasticizer side, its density, affinity, saturated vapor pressure and its actual concentration determine adsorption. On the carbon side, its porous stmcture and surface area available for adsorption determine the capacity of a particular filter. The data for the parameters of the equation can be found in chettucal handbooks and therefore the equation can be used for predicting the adsorption capacity of a filter. The capacity of coimnercial filters is normally rated by an experimental method in which the amount of the plasticizer adsorbed by filter is determined under conditions which specify concentration of the plasticizer, rate of flow, and time. Vapor pressures of plasticizers are very low, therefore calculated service life of filters is usually very long. 

Figu re 1.73 S-N line and damage curves as a basis for calculating service life [ 148]... 

The installation costs for a single impressed current anode of high-silicon iron can be taken as Kj = DM 975 (S550). This involves about 5 m of cable trench between anodes so that the costs for horizontal or vertical anodes or for anodes in a common continuous coke bed are almost the same. To calculate the total costs, the annuity factor for a trouble-free service life of 20 years (a = 0.11, given in Fig. 22-2) should be used. For the cost of current, an industrial power tariff of 0.188 DM/kWh should be assumed for t = 8750 hours of use per year, and for the rectifier an efficiency of w = 0.5. The annual basic charge of about DM 152 for 0.5 kW gives about 0.0174 DM/kWh for the calculated hours of use, so that the total current cost comes to... 

Once the variability risks, and q, have been calculated, the link with the particular failure mode(s) from an FMEA for each critical characteristic is made. However, determining this link, if not already evident, can be the most subjective part of the analysis and should ideally be a team-based activity. There may be many component characteristics and failure modes in a product and the matrix must be used to methodically work through this part of the analysis. Past failure data on similar products may be useful in this respect, highlighting those areas of the product that are most affected by variation. Variation in fit, performance or service life is of particular interest since controlling these kinds of variation is most closely allied with quality and reliability (Nelson, 1996). 

Before commencing calculations the worst case is assumed. For example it is assumed that the component operates continuously at the maximum temperature and under the maximum load encountered in its service life. 

Example 2.2 A polypropylene beam is 100 mm long, simply supported at each end and is subjected to a load W at its mid-span. If the maximum permissible strain in the material is to be 1.5%, calculate the largest load which may be applied so that the deflection of the beam does not exceed 5 mm in a service life of 1 year. For the beam / = 28 mm and the creep curves in Fig. 2.5 should be used. 

Traditionally, the penetration of chlorides and sodium is measured destructively by grinding layers of concrete and chemically analyzing the powder samples. These data are used to calculate diffusion coefficients for the ions. This procedure is very slow, has low spatial resolution, and is destructive. The measured data are critically important for the development of service life models and therefore a rapid, high-resolution method to monitor the ingress of these ions is desirable. 

Today, a modified bearing service life calculation is increasingly in use. It takes into account the possible use of special materials, special production qualities, lubricant composition and purity, as well as operating temperatures. With the measures commonly used today, modified bearing service life can be approx. 2.5 times the LhlO service life. However, to obtain similar values, it is advisable to adopt the LhlO value when assessing a bearing design. 

Service life. The using time calculated in larger current experiment test. 

The use of high power lithium batteries has so far been limited mostly to military applications and to expensive appliances, such as sophisticated cameras and computers. Low rate lithium batteries are widely used where long service life is important (wrist watches, calculators, memory backup in computers, etc). 

The greater the temperature difference between service life and accelerated test, the smaller the error in activation energy must be for a given error in scaled rate. In the oxidation of polystyrene between 225 C and 275 C, the final averaged activation energy is 21.5 0.2 kcal/mole. Using an error value of 2a 0.4 kcal/mole for a 95% confidence level, we estimate by interpolation in Table I that an error of 31% would be introduced into the calculated rate if the rates observed at v- 225 C were scaled to room temperature. 

T q)ically, cost analysis should be done on the basis of installed cost plus operating cost considering the useful service life of the equipment. It is also possible to base the selection solely on the initial cost of the equipment which consists of equipment and installation costs. A more accurate basis would consider the cost of the equipment over its useful life. This calculation is based on some discounted cash flow considerations and depreciation of the cost overthe life ofthe equipment. Tables 12.1-12.3 compare the costs of piping, vessels, and lining systems for different material selections. The reader should consult these tables to compare the initial equipment cost. 

The total cost calculations of a product made of polymer blends includes the materials, compounding, forming, assembling, decorating, customer satisfaction, esthetics, service life-spans, ease of disposal, and recycling. Thus, recycling enters into the initial part design. Before a part... 

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