Excessive acceleration

Caution should be taken to prevent excessive acceleration. One solution is to provide for opening of the compressor discharge vent valve to increase the compressor flow and increase blower horsepower. This is effective with a centrifugal compressor, however, not with an axial compressor unless the compressor is provided with adjustable stator vanes that are reliable. This can be seen from the performance curve. The head versus flow curve for a given vane setting is extremely steep and opening the vent valve is ineffective. However, if the vanes operate fully open and the vent valve opens, the combined effect is satisfactory. The vent valve must not be oversized. 

Another solution is to eliminate the air exiting the unit on the assumption that if no air goes in, no flue gas comes out to drive the expander. Again, this is not very effective because the unit acts as a large surge bottle and the large flue gas valves are relatively slow. Before the flue gas back-pressure valves have acted, excessive acceleration may result. 

Cracks in suction or discharge lines (10 cm) of a charging positive displacement pump in the Diablo Canyon 1 power station (1990), due either to excessive acceleration of the suction and to defective operation of the pressure peak damping chambers or bellows in the discharge side. 

Portland cement of rather fine grain is preferred, but not too fine, so as to avoid excessive acceleration of all processes of hydration. Ultra-fine cement (cf. Section 4.1) is used only for special purposes. The compatibility of cement with other components should be verified as well as low shrinkage and heat of hydration. 

The functional safety concept that has been chosen to achieve the safety goal, named Distributed detection and mitigation of torque errors, is based on degradation whereby all faults that can lead to excessive acceleration are detected within an acceptable time interval. On detection of a fault, the vehicle acceleration is limited to a value below that specified in the safety goal. The concept is based on the assertion that only malfunctioning behaviour of the Item that can violate the safety goal (which is specified in terms of vehicle- QVQ behaviour acceleration) is the delivery of... 

Since an enzyme is a biological catalyst and therefore merely accelerates a reaction, it cannot alter the position of equilibrium in a reversible reaction. The hydrolysis of p-methylglucoside is reversible and emulsin should therefore be capable also of synthesising this compound frc n glucose and methanol. This synthesis can actually be carried out by the action of the enzyme on glucose dissolved in an excess of methanol, the excess of the alcohol throwing the equilibrium over to the left. Owing to experimental difficulties, this reaction is not here described. 

In a 1 litre flask mix 53 -5 g. of p-toluidine and 400 ml. of water, and then add cautiously 98 g. (53 6 ml.) of concentrated sulphuric acid warm until the p-toluidine dissolves. Cool the flask in a bath of ice and salt to 0-5° add about 100 g. of crushed ice to the contents of the flask in order to accelerate the cooling. Add slowly and with frequent shaking a solution of 35 g. of sodium nitrite in 60 ml. of water until a slight excess of sodium nitrite is present (.see Section IV,60) keep the temperature of the mixture below 10°. 

Likewise, the influence of the ligand catalyst ratio has been investigated. Increase of this ratio up to 1.75 1 resulted in a slight improvement of the enantioselectivity of the copper(L-tryptophan)-catalysed Diels-Alder reaction. Interestingly, reducing the ligand catalyst ratio from 1 1 to 0.5 1 resulted in a drop of the enantiomeric excess from 25 to 18 % instead of the expected 12.5 %. Hence, as anticipated, ligand accelerated catalysis is operative. 

The nonbonding electron clouds of the attached fluorine atoms tend to repel the oncoming fluorine molecules as they approach the carbon skeleton. This reduces the number of effective coUisions, making it possible to increase the total number of coUisions and stiU not accelerate the reaction rate as the reaction proceeds toward completion. This protective sheath of fluorine atoms provides the inertness of Teflon and other fluorocarbons. It also explains the fact that greater success in direct fluorination processes has been reported when the hydrocarbon to be fluorinated had already been partiaUy fluorinated by some other process or was prechlorinated, ie, the protective sheath of halogens reduced the number of reactive coUisions and aUowed reactions to occur without excessive cleavage of carbon—carbon bonds or mnaway exothermic processes. 

Sulfur. Low sulfur stocks and EV sulfur-accelerated systems have better aging resistance. Normally, the oxidation rate increases with the amount of sulfur used in the cure. The increased rate may be due to activation of adjacent C—H groups by high levels of combined sulfur. Saturated sulfides are more inert to oxidation than aHyUc sulfides. Polysulfidic cross-links impart excessive hardening of SBR as compared to more stable monosulfidic cross-links. 

Because of hydrate formation, the sodium salts tend to be difficult to dry. Excess water over that of hydration is beheved to accelerate the decomposition of the xanthate salts. The effect of heat on the dryiag of sodium ethyl xanthate at 50°C has been studied (84) ... 

Liquid-phase chlorination of butadiene in hydroxyhc or other polar solvents can be quite compHcated in kinetics and lead to extensive formation of by-products that involve the solvent. In nonpolar solvents the reaction can be either free radical or polar in nature (20). The free-radical process results in excessive losses to tetrachlorobutanes if near-stoichiometric ratios of reactants ate used or polymer if excess of butadiene is used. The "ionic" reaction, if a small amount of air is used to inhibit free radicals, can be quite slow in a highly purified system but is accelerated by small traces of practically any polar impurity. Pyridine, dipolar aptotic solvents, and oil-soluble ammonium chlorides have been used to improve the reaction (21). As a commercial process, the use of a solvent requites that the products must be separated from solvent as well as from each other and the excess butadiene which is used, but high yields of the desired products can be obtained without formation of polymer at higher butadiene to chlorine ratio. 

Decomposition to styrene and carbon dioxide has been observed upon heating the acid to temperatures in excess of 150°C. The decarboxylation process can be accelerated with the addition of a bicycHc amine base (9). 

Handling and Storage. Cyanamide solution dimerizes to dicyandiamide and urea with the evolution of heat and a gradual increase in alkalinity accelerating the reaction. Storage above 30°C without pH stabilizer leads to excessive dimerization and can result in violent exothermic polymerization. Cyanamide should be stored under refrigeration and the pH tested periodically. Stabilized cyanamide can be kept at ambient temperature for a few weeks. 

Catalysts for dielectric surfaces are more complex than the simple salts used on metals. The original catalysts were separate solutions of acidic staimous chloride [7772-99-8J, used to wet the surface and deposit an adherent reducing agent, and acidic palladium chloride [7647-10-17, which was reduced to metallic palladium by the tin. This two-step catalyst system is now essentially obsolete. One-step catalysts consist of a stabilized, pre-reacted solution of the palladium and staimous chlorides. The one-step catalyst is more stable, more active, and more economical than the two-step catalyst (21,23). A separate acceleration or activation solution removes loose palladium and excess tin before the catalyzed part is placed in the electroless bath, prolonging bath life and stability. 

Acceleration modifies the surface layer of palladium nuclei, and stannous and stannic hydrous oxides and oxychlorides. Any acid or alkaline solution in which excess tin is appreciably soluble and catalytic palladium nuclei become exposed may be used. The activation or acceleration step is needed to remove excess tin from the catalyzed surface, which would inhibit electroless plating. This step also exposes the active palladium sites and removes loose palladium that can destabilize the bath. Accelerators can be any acidic or alkaline solution that solubilizes excess tin. 

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