Ejectors Steam pressure factor

Air/water vapor mixture, chart, 364,365 Air/water vapor, 359 Capacity at ejector suction, 369 Capacity for process vapor, 362 Evacuation time, 371, 380 Load for steam surface condenser, 367 Non-condensables, 362, 363 Size selection, 371 Steam pressure factor, 373 Steam requirements, 372 Steain/air mixture temperature, 361 Total weight saturated mixture, 362 Capacity, 358 Discharge, pressure, 358 Effect of excess steam pressure, 358 Effects of back pressure, 359 Effects of wet steam, 356 Inter-and-after condenser, 351 Load variation, 370 Materials of construction, 347 Molecular weight entrainment, chart, 360 Performance, 358, 370, 375 Relative comparison, 357... 

Figure 7.31. Steam requirements of ejectors at various pressure levels with appropriate numbers of stages and contact intercondensers. Steam pressure 100 psig, water temperature 85°F. Factor for 65 psig steam is 1.2 and for 200 psig steam it is 0.80 (Worthington Corp).

Figure 2-44. Friction factor for streamlined flow of air at absolute pressures from 50 microns Hg. to 1mm Hg. By permission, Standards for Steam Jet Ejectors, 3rd. Ed., Heat Exchange Institute, 1956 [54] and Standards for Steam Jet Vacuum Systems, 4th Ed., 1988. Note f on same basis as Figure 2-3 [58].

Reasonable factors of safety should be applied to the various loads in order to insure adequate capacity. Excess ejector capacity can be handled by pressure control and some adjustment in steam flow and pressure, but insufficient capacity may require ejector replacement. Factors of 2.0 to 3.0 are not uncommon, depending upon the particular qqte of system and knowledge of similar system operauons. 

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