Range of operation

Above the top limit the total efficiency no longer increases with increasing pressure drop and it may actually decline due to re-entrainment of dust from the dust outlet orifice. It is, therefore, wasteful of energy to operate cyclones above the limit. At pressure drops below the bottom limit, the cyclone represents 

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Many empirical correlations have been pubHshed in the Hterature for various types of Hquid atomizers, eg, one book (2) provides an extensive coUection of empirical equations. Unfortunately, most of the correlations share some common problems. Eor example, they are only vaHd for a specific type of atomizer, thereby imposing strict limitations on thein use. They do not represent any specific physical processes and seldom relate to the design of the atomizer. More important, they do not reveal the effect of interactions among key variables. This indicates the difficulty of finding a universal expression that can cover a wide range of operating conditions and atomizer designs. 

Pure zirconium tetrachloride is obtained by the fractional distillation of the anhydrous tetrachlorides in a high pressure system (58). Commercial operation of the fractional distillation process in a batch mode was proposed by Ishizuka Research Institute (59). The mixed tetrachlorides are heated above 437°C, the triple point of zirconium tetrachloride. AH of the hafnium tetrachloride and some of the zirconium tetrachloride are distiUed, leaving pure zirconium tetrachloride. The innovative aspect of this operation is the use of a double-sheU reactor. The autogenous pressure of 3—4.5 MPa (30—45 atm) inside the heated reactor is balanced by the nitrogen pressure contained in the cold outer reactor (60). However, previous evaluation in the former USSR of the binary distiUation process (61) has cast doubt on the feasibHity of also producing zirconium-free hafnium tetrachloride by this method because of the limited range of operating temperature imposed by the smaH difference in temperature between the triple point, 433°C, and critical temperature, 453°C, a hafnium tetrachloride. 

Process variables do not change G and, therefore, Mj- is constant over modest ranges of operating conditions. 

Range of Operation Because of the wide variety of pump types and the number of factors which determine the selection of any one type for a specific installation, the designer must first eliminate all but those types of reasonable possibility. Since range of operation is always an important consideration. Fig. 10-26 should be of assistance. The boundaries shown for each pump type are at best approximate, as unusual applications for which the best selection contradicts the chart... 

FIG. 10-26 Pump coverage chart based on normal ranges of operation of commercially available types. Solid lines use left ordinate, bead scale. Broken lines use right ordinate, pressure scale. To conveii gallons per minute to cubic meters per hour, multiply by 0.2271 to conveii feet to meters, multiply by 0.3048 and to conveii poiinds-force per square inch to Idlopascals, multiply by 6.895. 

For lubricated plug cocks, the lubricant must have limited viscosity change over the range of operating temperature, must have low solubility in the fluid handled, and must be applied regularly. There must be no chemical reaction between the luBricant and the fluid which... 

Data for determining the size of natural-draft towers have been presented by Chilton [Proc. Inst. Elec. Eng., 99,440 (1952)] and Rish and Steel (ASCE Swuposium on Thermal Power Plants, October 19.58). Chilton showed that the duty coefficient Df of a tower is approximately constant over its normal range of operation and is related to tower size by an efficiency factor or performance coefficient as follows ... 

The symbol Ot represents the average specific cake resistance, which is a constant for the particular cake in its immediate condition. In the usual range of operating conditions it is related to the pressure by the expression... 

Cooling of gas stream possibly required to get to the usual range of operation (less than 49 C [120 F])... 

While it is, of eourse, entirely possible to prediet expander-eompressor off-design performanee using modern eomputer software, tliere are a large number of variables to be eonsidered and it is not always easy to obtain a rapid overview. However, sereening smdies will benefit from graphieal metliods that allow tlie proeess designer to quiekly determine tlie expander and eompressor performanee over the enthe range of operation. 

The efficiency of the steam section in many of these plants varies from 30-40%. To ensure that the steam turbine is operating in an efficient mode, the gas turbine exhaust temperature is maintained over a wide range of operating conditions. This enables the HRSG to maintain a high degree of effectiveness over this wide range of operation. 

Temperature Range" refers to the range of operating temperatures, heat treatment temperatures, or temperatures developed in welding which can produce the type of embrittlement shown. 

For wide ranges of operation, multiple valves help keep the efficicncic high (see Figure 7-15). As power output is increased, the lower curve flow... 

The excellent corrosion resistance over a wide range of operating conditions and readily available methods of fabrication by welding and other means of shaping metals make these steels the most extensively used throughout the chemical and allied industries. 

Use materials that are applicable over the full range of operating conditions such as normal, startup, routine shutdown, emergency shutdown, and draining the system. For example, carbon steel may be acceptable for normal operating conditions but may be subject to brittle fracture at low temperatures under abnormal conditions (as in the case of a liquefied gas). Cold water, of less than 60°F, during hydrotest may cause brittle fracture of carbon steel. 

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