Temperature Control Required

Temperature control required—accurate (within 4—5 °C of set value), moderately acceptable range (10-15 °C), within a larger variation (20-30 °C). 

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Because temperature control can be so critical to safety and quality, highly trained operators -- "human controllers", so to speak --are often assigned to control chemical processes. But human operators have other responsibilities and thus may not be able to monitor the temperature during the entire process. Even the finest operator may not be able to achieve the kind of temperature control required for certain demanding specialty products. 

P, I, D system (Figure 9.10). This type of temperature control requires careful tuning of the control parameters, in order to avoid oscillations, which may lead to loss of control of reactor temperatures in cases where an exothermal reaction is carried out. The main advantage of the isothermal control is to give a smooth and reproducible reaction course, as long as the controller is well tuned. 

Since the temperature control required is not very stringent, it is possible to place the detector and the column in a well-insulated oven, the temperature of which is controlled by the amount of heat supplied. A Transite box wound with nichrome wire and insulated with glass wool has been found to be quite satisfactory. For carefully cen-... 

Identification and quantification of the desired reaction conditions, particularly temperature and concentration, are necessary to evaluate what may happen if these conditions are not met. This is particularly true where equilibrium considerations are a significant factor in a rate determining step between or among competing reactions. Where multiple products are possible, temperature variations will often significantly alter the ratios of these products. If one of these is unstable or more toxic, this could lead to more stringent temperature control requirements in the process and equipment design. 

Such operating lines exist for all multi-port PFRs. There is no requirement that idealized conditions, such as adiabatic or isothermal, be present during reactor operation. Therefore the data from a TS-PFR need not be gathered under idealized operating conditions in order to construct valid operating lines from which rates can be calculated. This greatly simplifies the temperature control requirements in TSR operation and makes the TS-PFR relatively simple to build. 

Temperature control requiring additional heat input is normally controlled by regulating the flow rate of steam to the process heat exchanger. A desuperheater should be installed to prevent steam quality variation from causing heat exchanger fouling due to temperature spikes at constant flow. 

Temperature-Control Requirements, The temperature control needed in the TT apparatus depends upon the results desired. It is often possible to obtain useful endpoints in titrations simply by bringing both the sample and titrant to room temperature. However, for precise calorimetric results, the titrant and sample must be as close to the same temperature as possible. This is the main purpose of the thermostat. 

Shock or friction sensitive Temperature control required ... 

Temperature Control.—For moderate accuracy, the temperature of the column should be controlled to within 0.2 K if the solute vapour pressure is known to be better than 1 per cent. A good air thermostat is capable of this control. It is, however, much easier to control the temperature of the water bath, and a simple on-off relay in conjunction with a toluene regulator and backing heater is capable of controlling the temperature to 0.01 K. This is the order of temperature control required for the accurate determination of activity coefficients. 

Cold runner systems have a similar temperature control requirement to the plasticising and injection unit, since the cold runner acts as an extension to the nozzle, controlling the rubber temperature to preclude any build up of scorched material while it awaits injection into the mould. 

Accuracy of temperature control required (within 5 °C is possible when it is being heated by oil firing). It is difficult with coal firing. 

Mold temperature control requires a circulating cooling fluid and cooling channels in the mold in order to remove heat from the molten polyethylene at a controlled but rapid rate. 

Dependence on a large reference set Influence of sample morphology Slow and costly method development Need for quantitative calibration model Troublesome calibration transfer Strict sample temperature control required Spectroscopic complexity (lack of specificity no characteristic absorption bands)... 

Inadequate temperature controls, requiring employees to work in extreme heat or cold without means of personal protection. 

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