Exposure temperature

Stress relaxation performance is usually determined in bending, where the initially imposed stress is 50 to 100% of the yield strength at the tension side of the stressed samples. Test details are presented in Reference 23. Data is presented as the percentage of the initial stress that remains as a function of time at exposure temperature. 

MI Cables (mineral insulated cables. Fig. 10-181) are the electric heat tracers of choice for high-temperature applications. High-temperature applications are generally considered to maintain temperatures above 250°F or exposure temperatures above 420°F where self-regulating heaters cannot be used. MI cable consists of one or two heating wires, magnesium oxide insulation (from whence it gets its... 

Figures 7 and 8 show thermal conductivity data for CBCF after exposure to temperatures of 2673, 2873, 3073, and 3273 K, for 5.7 and 15 7 seconds, respectively. The symbols in the Figs. 7 and 8 represent measured thermal conductivity values, and the solid lines are the predicted behavior from Eqs. (5) through (8) The model clearly accounts for the effects of measurement temperature, exposure tune, and exposure temperature The fit to the data is good (typically within 10%). However, the fit to the as fabricated CBCF data (Fig 6) was less good (-20%), although the scatter in the data was larger because of the much lower heat treatment temperature (1873 K) in that case.

The time required to produce a 50% reduction in properties is selected as an arbitrary failure point. These times can be gathered and used to make a linear Arrhenius plot of log time versus the reciprocal of the absolute exposure temperature. An Arrhenius relationship is a rate equation followed by many chemical reactions. A linear Arrhenius plot is extrapolated from this equation to predict the temperature at which failure is to be expected at an arbitrary time that depends on the plastic s heat-aging behavior, which... 

Records can quickly be grouped by generic family, exposure medium or trade name and grade. In addition, records can be searched, sorted and displayed by exposure temperature, exposure time, exposure medium concentration, and supplier or using the PDL resistance rating. Complete information can then be viewed on any individual record. 

Again, bacterial spores are much more resistant than vegetative cells, and their recorded resistance varies markedly depending upon their degree of dryness. In many early studies on dry heat resistance of spores their water content was not adequately controlled, so conflicting data arose regarding the exposure conditions necessary to achieve effective sterilization. This was partly responsible for variatiorrs in recommended exposure temperatures and times in different pharmacopoeias. 

Incapacitating concentrations (ICtso) for dermal exposure to these agents at moderate temperatures (i.e., between 65 and 85°F) are as low as 2 ppm for a 30-minutes exposure. Temperatures above 85°F reduce the concentration necessary to produce similar effects. 

These were plotted and are compiled in API RP 520, Chart D-2 (page 55). The data plotted is for vessels constructed of ASTM A-5I5, Grade 70 steel, a steel typically employed for process vessels. If other materials are used an allowance for their stress characteristics under heat application needs to be made. Therefore a general determination of the need for protective measures, such as depressurization, can be made for a particular vessel by comparison to the D-2 chart and selected fire exposure temperatures. It should be noted that this is the best available fire test exposure data in the public domain. Improved methods and test data may be available in the future to refine the calculation methods. 

Underwriters Laboratories (UL) high rise (hydrocarbon) fire test UL 1709, has an average fire temperature of 1093 °C (2,000 °F) after 5 minutes. Therefore unless the an actual fire exposure heat radiation input calculation has been made, either a worst case fire exposure temperature could be assumed or a standard temperature to the limits of UL 1709 could be applied. 

With filtering to cut out the radiation below 300 nm and to reduce the infrared, xenon lamps provide a quite good simulation of sunlight across the spectrum. They are now considered the preferred source where the total solar spectrum is required and the method, ISO 4892-2 [27], is nominated in ISO 11403-3 [23]. Unfortunately, xenon lamp apparatus is very expensive and the exposure temperature is usually rather high. 

The hardness of each compound was plotted against time for different exposure temperatures (Figures 12.5 and 12.6). Compound B showed relatively complicated behaviour with the shape of the hardness-time plot changing with temperature, whilst compound R showed relatively consistent increase of hardness with time. 

Even when using LDPE and PP, the diffusive losses of most nonpolar solvents may be unacceptably large for A designs that exceeded 1 cm . This is especially true at higher exposure temperatures because both solute diffusion and polymer free volume increase with temperature (Comyn, 1985). Even when solvent losses were not excessive, uptake of HOCs by membrane-enclosed solvents appeared to become curvilinear well before thermodynamic equilibrium was approached. This phenomenon is likely due to the outward flux of sampler solvent with elevated HOC levels (relative to water), which appears to facilitate residue... 

Adopted from Komp and MacLachlan (1997), evaluated at the exposure temperature. 

PP photoperiod ET = exposure temperature EL exposure light GL growth light. Time of light treatment. 

Early reports suggested a positive correlation between plant response to ozone and increasing exposure temperature, to about 30 C. These results were shown for pinto bean when exposures were under green-... 

TABLE 11-10 Response of Plants to Ozone, as Conditioned by Growth or Exposure Temperature... 

The sterilization cycle exposure time, exposure temperature, minimum lethality, and spore log reduction with acceptance criteria and results are provided in Table 2. 

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