Estimating insulation

When very high or very low temperatures are involved, insulation factors can become important, and it may be necessary to estimate insulation costs with a great deal of care. Expenses for equipment insulation and piping insulation are often included under the respective headings of equipment-installation costs and piping costs. 

In the mid-to-late 1980s, growth estimates of the use of polystyrene and polyurethane ceUular plastic insulation materials and products were a healthy 10% per year and greater for phenoHc (40,41). The principal appHcation where strongest growth was forecast for these types was for roofing, especially single-membrane systems (42). 

Principle appHcations of needle-punched nonwovens for the 1990s include automotive, apparel components, blankets, carpeting, carpet pa dding, coating substrates, filtration, furniture, geotextiles, insulation, roofing substrates, and wall coverings. In 1990, the production of needle-punched fabric was estimated to approach 91,000 t and 606 million square meters (15). 

For extended, noncyclic exposures, it can be assumed that the entire piece teaches the temperature of the heating medium and is, therefore, subject to permanent strength losses throughout the piece, regardless of size and mode of stress application. Because dry wood is a good insulator, it often does not teach the daily extremes in temperature of the air around it in ordinary constmction thus, estimates of long-term effects should be based on the actual wood temperatures experienced by critical stmctural parts. 

Fibrous glass insulation products require energy in their manufacture. However, it has been estimated that they save approximately 20 J per year for each joule used in production. In the United States in 1980, approximately 1.9 biUion of insulation fibrous glass was sold, which is over 1.4 biUion kg. 

Equipment Costs. Equipment costs include the purchased cost of process and materials handling equipment, storage faciUties, waste treatment equipment, stmctures, and site service faciUties. Installation costs such as insulation, piping, painting and finishing, foundations, process stmctures, instmmentation, and electrical service connections are estimated or factored separately. Actual quoted prices from suppHers are the best data, but these are not usually available when estimates are made. The quick, inexpensive cost estimates are based largely on personal cost files, internal company cost data, or pubUshed cost correlations. 

A popular overall factor refinement, known as the Hand factor approach, uses a different factor to estimate overall costs for each class of equipment to cover all labor field materials, eg, piping, insulation, electrical, foundations, stmctures, and finishes and indirect costs, but not contingencies. Hand factors range from 4 for fractionating towers down to 2.5 for miscellaneous equipment. 

Because of increased production and the lower cost of raw material, thermoplastic elastomeric materials are a significant and growing part of the total polymers market. World consumption in 1995 is estimated to approach 1,000,000 metric tons (3). However, because the melt to soHd transition is reversible, some properties of thermoplastic elastomers, eg, compression set, solvent resistance, and resistance to deformation at high temperatures, are usually not as good as those of the conventional vulcanized mbbers. AppHcations of thermoplastic elastomers are, therefore, in areas where these properties are less important, eg, footwear, wine insulation, adhesives, polymer blending, and not in areas such as automobile tires. 

The variation in the on and off potentials or the potential difference along the pipeline will usually indicate faults that prevent the attainment of complete cathodic protection. The protection current requirement of the pipeline may be estimated from experience if the age and type of pipeline is known (see Fig. 5-3). Figure 3-20 shows the variation in the on and off potentials of a 9-km pipeline section DN 800 with 10-mm wall thickness. At the end of the pipeline, at 31.84 km, an insulating unit is built in. The cathodic protection station is situated at 22.99 km. Between this and the end of the pipeline there are four pipe current measuring points. The applied protection current densities and coating resistances of individual pipeline sections are calculated from Eqs. (3-40) and (3-41). In the upper diagram the values of... 

Pressure storage tanks should be coirelated using /lb vs. w eight, much the same as other pressure vessels. Materials of construction, of course, would be another variable. Special internals, insulation, and internal heat exchangers should again be separated from the base cost of the tank. The w eight of supports, ladders, and platforms should be estimated and added to the weight of the... 

Some clothing item do values are listed in Table 5.4. For example, the do value of a person wearing a thin shirt, thin trousers, underwear, shoes, and socks estimated by this method would be 0,17 + 0.25 + 0.05 + 0.05 = 0.52 do. If the person were to add a T-shirt under the shirt, the clothing insulation would be expected to increase to 0.6 do. 

ISO EN 9920 C lorhing insulation Estimation of the thermal insulation and evaporative resistance of clothing ensem ble... 

The metabolic rate can be estimated by ISO EN 9886, and the thermal resistance of clothing can be estimated by ISO EN 9920, taking into account the type of work and the time of year. For varying metabolic rates, it is recommended to estimate a time-weighted average during the previous 1 h period. For sedentary people, the insulation of a chair must also be taken into account. 

ISO EN 9920 provides a large database of thermal insulation values, which have been measured on a standing thermal manikin. One set of tables gives the insulation values for a large number of ensembles (Table 6.14).. An-f)ther set of tables gives insulation values for individual garments (Table 6.15), on the basis of which the insulation for a whole ensemble can be estimated. 

These methods for calculating the heating and cooling requirements are conservative estimates assuming that the insulation is on the outside of the towers. The requirements will be less if the towers are insulated internally. 

Pollutants have various atmospheric residence times, with reactive gases and large aerosols being rapidly removed from air. In the London air pollution episode of December 1952, the residence time for sulfur dioxide was estimated to be five hours daily emissions of an estimated 2,000 tons of sulfur dioxide were balanced by scavenging by fog droplets, which were rapidly deposited. Most relatively inert gases remain in the atmosphere for extended periods. Sulfur hexafluoride, used extensively in the electric power industiy as an insulator in power breakers because of its inertness, has an estimated atmospheric lifetime of 3,200 years. 

In most cases, the insulation will be the greatest resistance to heat flow and other materials in the construction and surface resistances are ignored in estimating heat gains through cold store walls, ceilings and floors. 

Solar radiation may fall on outside walls or roofs, raising the skin temperature, and this must he taken into account. Most cold stores are huilt within an outer envelope which protects them from the elements and from direct sunshine. In cases where the insulation itself is subject to solar radiation, an allowance of 5 K higher outside temperature should he taken. Heat load must he estimated through all surfaces including piping, ducts, fan casings, tank walls, etc., where heat flows inwards towards the cooled system. 

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