Cooldown period

How long does it take to reach the sterilizing conditions How long is the cooldown period Must the batch size be controlled to achieve the needed sterilizing conditions ... 

The net thermal contraction of the dielectric must be designed so that it contracts evenly with the conductor during the cooldown period. Insufficient dielectric contraction would lead to voids between the inner conductor and the dielectric medium. These voids would permit harmful partial discharges to occur. Excessive contraction would keep the tapes under tensile and compressive load while at operating temperature. This stress could either cause immediate tape fracture, or contribute to accelerated failure owing to a long-term aging process. 

The motors are equipped with ball bearings carefully lubricated to prevent freeze-up of the lubricant during extended cooldown periods. It is worthy of note that these pumps could all be turned by finger pressure against the motor fan after having been full of liquid oxygen for a period in excess of three hours. 

This surge is followed almost immediately by a reversal of flow, another surge and then a more or less gradual transition to the steady flow rate. Figure 6 shows that the mean inlet flow during most of the line cooldown period is much less than the steady-state flow. This fact illustrates how the flow of liquid into the line, during cooldown, is limited by the ability of the transfer line to vent the cooldown gas. 

State 2, At time 0, at the end of the cooldown period, the control volume is filled with liquid in thermal equilibrium with the pipe wall. The mean liquid properties are evaluated at a saturation pressure, which is the arithmetic mean of atmospheric pressure and storage tank pressure, (At the end of cooldown, the liquid at the downstream end of the line is saturated at the local pressure, which is approximately equal to storage tank pressure, since we assume negligible pressure drop in the liquid phase during the cooldown process. The liquid at the upstream end of the line, which has just left the vacuum insulated storage tank, will be saturated at atmospheric pressure. Therefore, the average liquid properties can be determined from the mean saturation pressure mentioned above.)... 

Answer by author We have not compared the quantity of liquid consumed during line cooldown with the cooldown rate. However, we believe that for a given transfer line, the amount of liquid consumed will increase with the length of the cooldown period. This is because the heat input due to the cooldown of concentrated masses and ambient heat leak will increase with cooldown time. 

The total ion chromatogram of the analysis of a Thai jasmine rice is shown in Fig. 2. The samples was desorbed for 5 minutes on a HP 5973 GC/MS system (Agilent Technologies, Palo Alto, CA). The injector temperature was held constant at 270°C. The GC oven temperature was held for 1 min at 50°C, then ramped to 250°C at 10°C/min. A 30 m, 0.25 mm I.D., DB-5 capillary column with 1.0 p,m film was used with helium as the carrier gas under a constant flow of 40 cm/s. The total GC cycle time consisted of a 30-minute run and a 5-minute cooldown period. Following the first GC/MS run, subsequent samples were prepared ahead so that one sample was run every 45 minutes. The mass spectrometer was operated in scan mode from m/z 50 to m/z 350. 

Another potential concern of proper shutdown is the potential formation of coke on the catalyst or in the reactor itself. Coke formation could occur if the 02/C ratio is maintained too low in the absence of steam for an extended period of time. In order to ensure a safe shutdown, the oxidant is removed from the system while fuel and steam continue to flow for a short period to ensure all oxidizants have been removed from the system. Subsequently, the reactor can be blanketed with an inert gas for cooldown. 

For short periods during cool-down, the vapor temperature traces were found to be relatively smooth, and a continuous curve was drawn through these smooth temperature periods. The resulting curve gave the average instantaneous vapor temperatures during cooldown. A typical portion of a temperature trace, demonstrating the method by which vapor temperatures were determined, is shown in Fig. 6. The instantaneous local vapor fractions for the inlet to the test section were calculated by this method. The results of two t3 ical runs at different flow rates are shown in Fig. 7. 

The use of holding periods during the heat-up and cooldown cycles results in relaxation of compressive stresses due to creep. However, this same creep may introduce cracks once the lining is cooled off... 

DBE-7 is a steam in-leak event which starts the same as DBE-6 but goes to completion with RCCS cooldown. In this case, core graphite temperatures remain high for a long period. However, core support graphite temperatures... 

Compensation of shrinkage was investigated in the analysis No. 8. (see Appendix 4) to determine the time of possible feedwater de-isolation by the operator, when the RCS cooldown rate falls below the 60°C/h limit value. This occurs at 19 minutes when the RCPs are running and at 26 minutes when the MCPs are stopped. These time periods are sufficiently long to permit the operator to intervene and de-isolate feedwater flow according to this procedure. However, it should be noted that the normal feedwater reserves will be exhausted by about 25 minutes. 

Those procedures for which all answers are no can be screened out of the review. However, these criteria will generally screen out only a limited number of procedures. If the remaining list of procedures is still beyond the capability of the review team during the available period, then an additional criterion is to look at similar procedures. It often happens that procedures or their selected parts are similar in their writing and content (sequences of identical steps) or strategy. An example is the back end of procedures dealing with plant cooldown and depressurization. For these, the review may look at one representative procedure or part of one to have a complete view. 

Cool down rate After the product has been held at the proper temperature for the proper period of time, which will depend on the type of material used, the rate at which the product is cooled is also important. In general, slower cooldown rates will minimize warpage and residual stress in the finished product. However, slower cooldown rates can adversely impact productivity, so a reasonable balance must be identified. In many cases, a slow cooldown through the Tg of the resin system, followed by a somewhat faster cooling rate after the product cools below Tg, represents a good balance of performance and productivity. 

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