Ejector Arrangements

Several ejectors are used in parallel when the load is variable or because the process system gradually loses tightness between maintenance shutdowns—then some of the units in parallel are cut in or out as needed. 

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Ejector and Vacuum Systems 162 Ejector Arrangements 162 Air Leakage 164 Steam Consumption 165 Ejector Theory 166 Glossary for Chapter 7 166 References 167... 

Install pre-condensers cooled with cooling/chilled water. Use multi-stage steam ejectors arranged in series/series-parallel arrangement. Use liquid ring or dry vacuum pumps... 

Figure 6-8 illustrates various arrangements of ejectors with inter and aftercondensers. The condensers can be barometric or nonbarometric types. 

Installation arrangements, 351 Pump-down time, 380 Selection procedure, 374 Specification form, 377 Specifications, 373 Steam jet comparison, 356 Types of loads, 359 Ejectors, 346 Applications, 353 Barometric condenser, 249, 376 Booster, 370 Calculations Actual air capacity, 362 Air equivalent, 360... 

Figure 7.30. Arrangements of two-stage ejectors with condensers, (a) Identification of the parts of a two-stage ejector (Croll-Reynolds Co.). (b) A two-stage ejector with interstage barometric condenser (Elliot Co.), (c) A two-stage ejector with surface condensers interstage and terminal (Elliot Co.).

Steam-Jet (Ejector) Systems These systems substitute an ejector for a mechanical compressor in a vapor compression system. Since refigerant is water, maintaining temperatures lower than the environment requires that the pressure of water in the evaporator must be below atmospheric. A typical arrangement for the steam-jet refrigeration cycle is shown in Fig. 11-104. 

When the steam supply to one ejector of a group is closed, some means must be provided to for preventing the pressure in the condenser and flash tank from equalizing through that ejector. A com-partmental flash tank is frequently used for such purposes. With this arrangement, partitions are provided so that each booster is operating on its own flash tank. When the steam is shut off to any booster, the valve to the inlet spray water to that compartment also is closed. 

In the arrangements described, the air has free access to the goods which have to be dried. In some cases it may be desirable to carry on the drying in a closed system this could easily be effected by providing any of the before-mentioned apparatus with a lid. In that case it will be necessary to carry off the vapours by means of a mechanical arrangement, such as a pump, a fan, or an ejector. 

Ejector pins are used in the moving die to release the casting. The ejector pins will leave small marks on the surface of the casting and should be positioned so that these will not appear on a visible face of the finished casting. If a casting has a face which is to be machined, then, where possible, the ejector-pin marks should be arranged on that face, to be removed by the machining. 

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