Economic circuit

Other options for gas dispensing cryogenic tanks are manifolds that can connect two to six cylinders together. These manifolds can provide flow rates of 250 cfh (cubic feet per hour), can set up a reserve of gas for uninterrupted flow when changing cylinders, and (with an economizer circuit) can cut loss due to evaporation. For extra-high-capacity gas demands, there are external vaporizing manifolds, which are a combination of the external heat exchanger and manifold n... 

Figure 2.1 Economic circuit (adapted from http //de.wikibooks.org/wiki/Betriebs-wirtschaft/ Grundlagen/ Wirtschaftsteilnehmer).

In the gas cleaning sections of spent acid or metaUurgical sulfuric acid plants, the weak acid scmbbing circuit is typicaUy handled by plastic or glass fiber reinforced plastic (ERP) pipe. The contaminants in weak acid usuaUy vary too greatly to aUow use of an economical aUoy. 

The.se arc similar to stator resistance starters, as discussed in Section 4.2..3 and can be used in the rotor circuit to control the rotor side resistance. Figure 5.10 shows the smooth variation of resistance by electrolytic vaporization compared to a conventional metallic resistance variation. I hc self-variable resistance of electrolyte is equivalent to almost three or four steps of a metallic resistance and makes such starters economical. Normally one step is sufficient for motors up to 160 h.p. (For spccd-torquc... 

With the availability of 3.3 and 6.6 kV vacuum contactors the control of HT motors up to 6.6 kV systems has now become easier and economical, compact and even more reliable. For 11 kV. systems, vacuum as well as SF (Sulphur hexafluoride) breakers can be used. The HT motor s switching and protection through a vacuum contactor provides a replica of an LT system. The earlier practice of using an HT OCB, MOCB, or an air blast circuit breaker for the interruption of an HT circuit is now a concept of the past. 

In most applications, a bar primary CT is generally used and a normal CT may be suitable. But for too small ratings, where the use of a wound primary CT is imperative, short-circuit effects must be considered, except the CTs for an LT system, where the fault level for such small ratings may be very low and may not matter (Section 13.4.1(5)). For applications on an HT system, where a wound primary CT is imperative, choice of a CT from standard wound primary CTs may still be possible, meeting the minimum requirements of class of accuracy, VA burden and short-time rating. lEC 60044-1 indicates for measuring and protection CTs the maximum short-time factors (STF) that can be obtained economically for a normal wound primary CT where... 

Nevertheless, unbalance is a major occurrence in either case and an unbalanced protection, in addition to short-circuit protection is imperative in all types of capacitor units. Hence it is also possible to design series protected capacitor units in larger sizes and for higher voltages, which are more economical, compared to smaller units. 

In single-phase bridge circuits for ac connections and for very low ac output voltages below 5 V, single-phase center tap circuits are used as rectifier circuits for CP transformer-rectifiers. They have an efficiency of 60 to 15% and a residual ripple of 48% with a frequency of 100 Hz. A three-phase bridge circuit for three-phase alternating current is more economical for outputs of about 2 kW. It has an efficiency of about 80 to 90% and a residual ripple of 4% with a frequency of 300 Hz. The residual ripple is not significant in the electrochemical effect of the protection current so that both circuits are equally valid. 

When the plant distribution voltage is above utilization levels, Itjr instance 23 kV or higher, economics will usually favor the 2,300- relative cost of alternate schemes sometimes favors 4.100 volts. This is true particularly with motors in the 4,000 hp and larger si/.es. and short circuit levels are above 150 MVA. 

It would be possible to remove all of the heat by pumping cold reflux from the distillate drum to the top of the tower and thus eliminate the cost of the pumparound circuit. Where more than one sidestream is withdrawn, however, it is usually economical to withdraw part of the heat in a pumparoimd reflux system farther down the tower. The following economic factors affect the choice ... 

The etched printed circuit boards are washed out with water to dilute the concentration of the contaminants on the board surface to an acceptable level. The extraction of copper from the effluent rinse water is essential for both environmental and economic reasons since decontaminated water is returned to the rinse vessel. 

Make up water for these refrigeration units is at 80°F, and feed water for the gas cooler unit is available at 90°F. Barometric water is 90°F. Items 1 and 2 are for a closed-circuit operation with return water at 68°F and total 175 gpm. Note that in order to consolidate the temperature levels of water, it is economical to establish a temperature, such as 55°F, which satisfies the bulk of the requirement, and then design the other phases of the plant process to also use this water temperature. Item 3 is an open-circuit operation because the water is sent to waste after absorbing certain corrosive vapors and cooling the bulk of the gas. 

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