Temperature worst-case

Endurance Burn Under certain cou(itious, a successfully arrested flame may stabilize on the unprotected side of an arrester element. Should this condition not be corrected, the flame will eventually penetrate the arrester as the channels become hot. An endurance burn time can be determined by testing, which specifies that the arrester has withstood a stabilized flame without penetration for a given period. The test should address either the actual or worst-case geometry, since heat transfer to the element will depend on whether the flame stabilizes on the top, bottom, or horizontal face. In general, the endurance burn time identified by test should not be regarded as an accurate measure of the time available to take remedial action, since test conditions will not necessarily approximate the worst possible practical case. Temperature sensors may be incorporated at the arrester to indicate a stabilized flame condition and either alarm or initiate appropriate action, such as valve closure. 

Worst-case atmospheric conditions occur to maximize (C). This occurs with minimum dispersion coefficients and minimum wind speed u within a stability class. By inspection of Figs. 26-54 and 26-55 and Table 26-28, this occurs with F-stability and u = 2 m/s. At 300 m = 0.3 km, from Figs. 26-54 and 26-55, <3 = 11m and <3 = 5 m. The concentration in ppm is converted to kg/m by application of the ideal gas law. A pressure of 1 atm and temperature of 298 K are assumed. 

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. 

Before performing any calculations, a thorough examination of the possible causes and flow conditions of temperature and pressure should be evaluated. From this list, select the most probable and perhaps the worst case possibility and establish it as a design basis, Figure 7-14. See [80]. 

All finishes should be selected to be resilient to expected average and worst-case environmental exposure such as high/low humidity or temperature, airborne contaminants, vibration, possible aggressive liquid spillages, cleanliness/hygiene requirements, etc. 

Checking the absence of external mass transfer limitations is a rather easy procedure. One has simply to vary the total volumetric flowrate while keeping constant the partial pressures of the reactants. In the absence of external mass transfer limitations the rate of consumption of reactants does not change with varying flowrate. As kinetic rate constants increase exponentially with increasing temperature while the dependence of mass transfer coefficient on temperature is weak ( T in the worst case), absence... 

GP 2] [R 2] The radial temperature distribution was determined by modeling, using a worst-case scenario (5 Nl h stoichiometric mixture without inert 100% conversion 80% selectivity) [102], The maximum radial temperature difference amounts to approximately 0.5 K. Thus, isothermal behavior in the radial direction can be diagnosed. 

The core temperature. We expect that there will be hot spots inside the capacitor since we have less-than-perfect thermal conductivity inside it. As a worst case, that... 

Capacitor manufacturers recommend that in general we don t pass any more current than the maximum rated ripple current. This ripple current is the one specified at the worst case ambient (e.g., 105°C). Even at lower temperatures we should not exceed this current rating. No temperature multipliers should be used. Because only then is the case to core temperature differential within the design specifications of the part. And only then are we allowed to apply the simple 10°C doubling rule for life. 

Rather than take the case temperature as the local ambient temperature of the capacitor, which is more of a worst-case calculation, we could try to actually measure the local ambient. Assume that the general ambient is Lamb ext- The local ambient near the capacitor is Lamb. The procedure to factor out the heat from nearby components (i.e., heat which is not due to ripple current) is as follows ... 

For example, suppose the estimated dissipation is 1.5W. We want to ensure that, at a worst-case ambient of 55°C, the case of the part does not rise above 100°C (safe temperature for the PCB material—do not exceed ). Therefore the Rth we are looking for here, is... 

The flow behaviour of rubber on a mill is dependent on the material, nip width, roll speed and temperature, and certain combinations can give flow instabilities, the worst case from the mixing point of view being bagging , i.e., loss of adhesion of the rubber compound to the mill rolls. A decrease in nip width, an increase in speed or temperature, can overcome this problem. 

A total of ca. 60 simulations were run and in the vast majority of them PVC decomposition plays a negligible, if any, role. In only two of the single plenum simulations was there a high enough plenum temperature for PVC decomposition to take place over a period of more than 1 min. Those worst cases, viz. 2, and 13, were analysed further, by considering various rates of PVC decomposition (HC1 generation), depending on upper level temperatures. 

In the worst case, an enthalpy of decomposition of 50 to 70 cal/g results in an adiabatic temperature rise of approximately 100 to 200°C which is, as a rule-of-thumb, not regarded as critical under the condition that die substance does not easily produce a significant quantity of gas and thus, in a very general way, will not lead to a hazardous situation [23]. However, this has to be evaluated for each individual process. 

For reaction systems without solvents, the time at the test temperature is important. In these cases, the elected period of time and temperature should be based on the worst case operating conditions. 

Reaction calorimetry provides information on the maximum heat generation at process temperatures and on the adiabatic temperature rise. This ATad provides insight into the worst-case temperature consequences. 

Worst-case analysis based on the DSC data, namely, the test with the lowest onset temperature, resulted in a graph showing the relationship between initial temperature and time-to-maximum rate under adiabatic conditions. For an initial temperature of 170°C, it would take 2 hours to reach the maximum rate. Venting simulation tests were undertaken on a larger scale to detect safe venting requirements for the separator and for the MNB hold tank. Several vent sizes were tested. It was found that a 10-cm rupture disc with a burst pressure 1 bar above the operating pressure was adequate. 

The following conclusions were drawn. Microcalorimetry can be used to evaluate the heat generation characteristics of a solid material directly at the temperature of practical interest. However, in order to determine the worst case, the variability between batches of the substance must be determined which requires a considerable number of tests (over 100 trials in this specific case). Having obtained the heat generation as a function of temperature for with worst case, the safe storage diameter of storage vessels can be calculated and the equipment appropriately designed. 

Credible cases are identified when the probability of decomposition is low. Energy calculations of known or proposed chemical reactions and side reactions are carried out to determine a more likely level of energy release than the worst-case scenario. Therefore, it is necessary to define the most energetic reactions. Enthalpies of reaction are calculated, followed by calculations of the adiabatic temperature rise of the system and the corresponding pressure rise. 

The calculations of the Inherent Safety Index (ISI) are made on the basis of the worst situation. The approach of the worst case describes the most risky situation that can appear. A low index value represents an inherently safer process. In the calculations the greatest sum of flammability, explosiveness and toxic exposure subindices is used. For inventory and process temperature and pressure the maximum expected values are used. The worst possible interaction between chemical substances or pieces of equipment and the worst process structure give the values of these subindices. 

Endurance burn testing generally implies that the ignited gas mixture and flow rate are adjusted to give the worst-case heating (based on temperature observations on the protected side of the element surface), that the burn continues for a specified duration, and flame penetration does not occur. Continuous flame testing implies a gas... 

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. 

A temperature increase to about 85 °C would require a pressure of about 43.8 MPa in the vehicle tank (or a pressure of about 44.8 MPa in the high pressure bank). If the vehicle tank should be filled to the upper level at all conditions, the worst case (85 °C) has to be considered. In this case, the maximum pressure of the storage banks must be well above 45 MPa. 

It is possible to assume that the worst case conditions will prevail at all times, but this will probably lead to an unrealistically short lifetime. For example, the design temperature can be taken as the maximum. 

Worst-case scenario. When considering the stationary source s worst-case scenario, there are selection factors to be considered. In addition to the largest inventories of a substance, the following conditions must also be considered smaller quantities handled at higher process temperatures and pressures, and proximity to the boundary of the stationary source. Sources must analyze and report additional worst-case scenarios for a hazard class if the worst-case scenario from another covered process affects a different set of public receptors than the original worst-case scenario. It is interesting to note that worst-case release data indicate that the distances and thus the populations that could be threatened are greater for toxic substances than for flammable substances. 

A statistical significant effect is not always relevant from the practical point of view. Therefore, a worst-case level combination experiment with regard to the studied response (e.g., resolution) is determined and performed with replicates. In this experiment, only the method parameters with major effects (both statistically significant and almost significant) are considered. As can be seen in Figure 15, the major effect, temperature and pH, are easily detected. The worst-case combinations... 

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