Safe region

There are a variety of ways of accomplishing a particular unit operation. Alternative types of process equipment have different inherently safer characteristics such as inventory, operating conditions, operating techniques, mechanical complexity, and forgiveness (i.e., the process/unit operation is inclined to move itself toward a safe region, rather than unsafe). For example, to complete a reaction step, the designer could select a continuous stirred tank reactor (CSTR), a small tubular reactor, or a distillation tower to process the reaction. 

The limits of flammability or explosivity are used to determine the safe concentrations for operation or the quantity of inert material required to control the concentration within safe regions. 

However, several exothermic reactions are characterized by moderate or low values of the B number here, the transition stages from safe to runaway conditions may cover a quite wide range of the parameter values, and the choice of the boundaries for the safe region is very discretional. Hence, not surprisingly, the main discrepancies among the different criteria are found at low B numbers [14, 15]. Moreover, in this case, runaway is a less dramatic phenomenon posing the problem to decide whether a bland explosion still represents a safety issue. In this case, an effective runaway criterion should be more properly determined on the basis of the actual ability of the system to comply with certain levels of temperature and pressure. 

Figure 10.4 Safe regions with regard to crack propagation due to stress-corrosion cracking (6) or mechanical failure (A) In a log

The safe region where Z > 0 and the unsafe region where Z < 0 are both shown in Fig. 5.7. 

This point is well within the safe region of the diagram which indicates that the tie rods can be allowed to vibrate at resonance without failure. 

When operating parameter is departing from the safe region the task of safety systems is to return the safe conditions by actuating the safety functions, such as reactor fast shut-down-system or emergency core-cooling-system. 

The Ultimate level implies changing the concentrate mix into a safe region, i.e. a composition with coarse particles and little impurities. 

It could be that scaling only sets in at energies somewhat higher than PL = 29 GeV/c. On the other hand, firom Table 17.2 we see that at this energy r 0.3 so all the 29 GeV/c points in Fig. 17.25 are way below the safe region in r. In fact, many of the points at 300 GeV/c and 400 GeV/c are also at values of r below Ts- So perhaps it is best not to draw any firm conclusions from these data. 

From the analysis of reactor operation (influence of feed temperature,wall temperature,inlet o-xylene partial pressure) a runaway diagram can be presented showing the safe region of operation as well as the runaway region. 

The minimum amount of steam that needs to be added to a hydrocarbon fuel gas to avoid carbon deposition may be calculated. The principle here is that it is assumed that a given fuel gas/steam mixture reacts via reactions 8.3, 8.4, and 8.5 to produce a gas that is at equilibrium with respect to reactions 8.3 and 8.5 at the particular temperature of operation. The partial pressures of carbon monoxide and carbon dioxide in this gas are then used to calculate an equilibrium constant for the Boudouard reaction 8.9. This calculated equilibrium constant is then compared with what would be expected from the thermodynamic calculation at the temperature considered. If the calculated constant is greater than the theoretical one, then carbon deposition is predicted on thermodynamic grounds. If the calculated constant is lower than theory predicts, then the gas is said to be in a safe region and carbon deposition will not occur. In practice, a steam/carbon ratio of 2.0 to 3.0 is normally employed in steam reforming systems so that carbon deposition may be avoided with a margin of safety. 

Includes sufficient heat removal capability such that fuel temperatures will remain in the proven safe region. 

The long and narrow design of the reactor allows for optimal passive heat removal from the core even under conditions with no coolant flow and the reactor depressurized. Heat flow through conduction and radiation to the RPV, and subsequent removal through the passive heat removal system in the reactor cavity, will limit the maximum fuel temperature and the vessel temperature so that both remain in the safe region. 

In agreement with pervious parts, in order to achieve a proper adoption for engine, all performance points of engine which is equipped to turbocharger should be obtained. As mentioned above, performance points include constant speed lines and constant load which are overlapped on compressor curve. If engine performance condition be at safe region and upper level of compressor efficient curve, it ensures suitable adaptation of engine and compressor. 

In this part we have investigated the effect of this mechanism on performance of system. For this purpose we compared pressure ratio versus modified flow rate curve of a compressor with compressor characteristic curve for totally open wastage in 1,800 2,200 and 3,000 rpm. The comparisons have been illustrated in Figures 3.11 and 3.12. According to Figure 3.11, the performance of compressor in rotation of 3,200 rpm is in safe region and faraway of surge and... 

Since the performance function G is linear, the limit state equation corresponds to a straight line in the R — S coordinate axis, as shown in Fig. 2. This straight line divides the plane into two regions. The first region corresponds to G > 0 and is known as safe region, while the second region corresponds to G < 0 and is known as the unsafe region. ... 

---