Automatic switch over

If, as the result of leakages in components containing primary coolant, gas-bome radioactivity is released into the reactor building or the reactor auxiliary building, the facility is automatically switched over to the subpressure maintenance system with its activated carbon and aerosol filters. It has to be noted that these action are not necessary in order to meet allowable dose limits, but they are carried out as a matter of precaution due to the principle of minimization. 

The general plant arrangement is for a duty dosing pump to inject the liquid chemical into a water transfer main, most commonly proportional to flow to ensure consistent dosing. A standby dosing pump should also be available, preferably with automatic switch-over if the duty pump fails. 

In the suction and pressure lines, simple ball valves are provided as manual shut-off valves (AA06, AA08, AAll and AA14). Driven valves or non-return valves are not required for the automatic switch-over of the pumps, as the pumps con-... 

A cavity temperature signal, however, is precisely measured when the melt reaches the sensor. In this way, the position of the melt is always known and can be used for control purposes as automatic switch over to holding pressure. In contrast to the cavity pressure sensor, the cavity temperature sensor can be placed where it is needed. 

The extrudable adhesives are supplied in the larger sized containers, 22-5 or 200 litres, which have been filled under controlled conditions to avoid the occlusion of air. The adhesive is distributed to the work locations from a centrally sited pump-house through a manifolded pipe network at moderate pressure. Care must be taken in the design of the pipework to ensure that there are no features which may lead to eventual partial or full blockages. A dual pumping system is normally used the adhesive is transferred from one container at a time and as the end is approached the system will automatically switch over to the other thereby providing a constant material supply. 

Table 1.12.1 shows also Tke/n, which is the sum of all measurements divided by the number of measurements. After 4.3 h, Tice drops in 1 h by 2.5 °C below the highest TicJn (-23.4 °C). As shown in Figure 1.78.3, this decrease in ice temperature marks the end of main drying and can be used to switch over manually or automatically to secondary drying. 

As smart d/p transmitters became available, the orifice rangeability could be increased at a lower cost by using dual-span transmitters. Some smart d/p transmitters are currently available with 0.1% span accuracy, and their spans can be automatically switched based on the value of measurement. Therefore, a 100 1 pressure differential range (10 1 flow range) can theoretically be obtained by automatically switching between a high (10-100%) and a low (1-10%) pressure differential span (in practice, some overlap is recommended). The overall result can be a 1% of AF accuracy over a 10 1 flow range. 

A version of this optimization problem was to compute the optimum values of t and (at given (Ns)inax Ng and Ng in the absence of an automatic tracking system for switching over the design parameters. The optimality criterion was the maximum daily integral hydrogen production by the plant,... 

The fraction collector 23 normally contains sixty 20 ml receiving tubes and is buUt into a vacuum desiccator with a wire-gauze safety cover. It can be employed at atmospheric pressure and at reduced pressures down to 1mm. After 30 tubes have been filled a signal sounds alternatively, the apparatus may be made to switch over automatically to the next circle of tubes. When all the tubes are full there is another signal and the reflux controller is switched off so as to stop the distillate take-off. 

This can require a bank of batteries, inverters, switch for an immediate automatic change over when main power supply fails due to any reason. This system can be quite costly depending on the connected electrical loads and the duration for which the assured supply is required. 

The action of the commutator is to reverse the generated e.m.f. every half-cycle, rather like an automatic change-over switch. However, this simple arrangement produces a very bumpy d.c. output. In a practical machine, the commutator would contain many segments and many windings to produce a smoother d.c. output similar to the unidirectional battery supply shown in Fig. 2.9. 

Recuperators with high alumina bricks Alter the temperature of the exit air starts falling below a certain predetermined value, the unit is taken up for passing hot gases again. The hot gas and cold air streams are thus passed alternately by operating butterfly valves in the ducts which are switched over manually or automatically (can be by timers) as per temperature patterns desired. 

For proper combination tower control, it would appear that a feedforward computer-controlled system is required since conventional automatic control seems to lag behind heat-loss effects caused by coke drum warm-up and switch-over. Many refiners have implemented such advanced control schemes with good success. 

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