Overload conditions

High-voltage contactor-type motor controls depend on power fuses for short-circuit protection. The fuses are coordinated with the overload relays to protect the motor circuit over the full range of fault conditions from overload conditions to solid maximum-current short circmts. 

Figure 3.14 Thermal curves to set the relay for over-temperature protection corresponding to different overload conditions...

During an overload condition, the relay may be set to give alarm if normal conditions do not restore by Ibe end of the cycle. 

An overload characteristic say, 50-200%, matching the thermal withstand characteristic of the generator. This operates during an overload condition when the generator voltage is normal. 

Contemporary development of chromatography theory has tended to concentrate on dispersion in electro-chromatography and the treatment of column overload in preparative columns. Under overload conditions, the adsorption isotherm of the solute with respect to the stationary phase can be grossly nonlinear. One of the prime contributors in this research has been Guiochon and his co-workers, [27-30]. The form of the isotherm must be experimentally determined and, from the equilibrium data, and by the use of appropriate computer programs, it has been shown possible to calculate the theoretical profile of an overloaded peak. 

A better solution for preparative columns is the development of separation media with substantially increased selectivities. This approach allows the use of shorter columns with smaller number of theoretical plates. Ultimately, it may even lead to a batch process in which one enantiomer is adsorbed selectively by the sorbent while the other remains in the solution and can be removed by filtration (single plate separation). Higher selectivities also allow overloading of the column. Therefore, much larger quantities of racemic mixtures can be separated in a single run, thus increasing the throughput of the separation unit. Operation under these overload conditions would not be possible on low selectivity columns without total loss of resolution. 

As a protection for equipment against overload, sprockets are sometimes provided for silent chains with a shearing pin or a break-pin hub. A pin of a known strength is used, and an overload of sufficient magnitude shears the pin and leaves the plate free to turn on the hub. After the overload condition is remedied, a new pin may be easily inserted and the drive again made ready to operate. 

Cause of failure Tooth shear caused by belt overload condition from improper application or shock loads (Figure 58.25). 

A molecule that binds iron through coordinating moieties (e.g., carboxylates or amines). They are used to inhibit iron-catalyzed free radical reactions or to treat iron overload conditions. Desferrioxamine and defer-iprone are two widely used iron chelators. 

The lower isotherm represents the overload condition that can occur in liquid/liquid or gas/liquid systems under somewhat unique circumstances. If the interactions between solute molecules with themselves is stronger than the interactions between the solute molecules and the stationary phase molecules, then, as the concentration of solute molecules increases, the distribution coefficient of the solute with respect to the stationary phase also increases. This is because the solute molecules interact more strongly with a solution of themselves in the stationary phase than the stationary phase alone. Thus, the higher concentrations of solute in the chromatographic... 

Finally, an officially updated definition of the retardation factor, R, issued by lUPAC is important to the whole field of planar chromatography (the linear and the nonlinear TLC mode included). The importance of such a definition has two reasons. First, it is promoted by the growing access of planar chromatography users for densitometric evaluation of their chromatograms and second, by the vagueness of the present definition in the case of skewed concentration profiles with the samples developed under mass overload conditions. 

Figure 4.40 Separation of alkylbenzyl alcohol Isoeers by reversed-phase senipreparative HPLC In a nass overload condition. The dotted line is the equivalent analytical sepeuration on the same column. (Copyright Whatman Inc.)...

Xt is very difficult to provide an optimum set of conditions for operation of a liquid chromatograph under overload conditions due to the coiq>lex interactions among a large number of parameters [591,592,595,608,620,625]. The following general observations seem to be applicable in most cases. The column efficiency should be as high as possible and separatimis should be carried out using concentration overload conditions. The production rate of a... 

When translated to the SMB conditions, these features imply that increasing feed concentration lead to an increasing degree of non-linearity due to the fact that the adsorption columns increasingly are operated under overload conditions. This effect is predicted by the approach summarized in the previous section, in particular by Eqs. (8) to (19), which allow the calculation of the constraints on m1 and m4 and the boundaries of the complete separation region in the (m2, m3) plane as a function of feed composition [19]. 

Experimental results obtained in the high-g rotor in fluidized state under overload conditions at 500 rpm (8.3 Hz)(20)... 

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