Document kNQeDb3baG3gJMa98YGaxwQB

856 CHAPTER 37 1954-Guide Table 5 shows the tonnage, capacity normally allowed for Freon-12 liquid lines per foot equivalent length of pipe, and Table 6 the maximum tonnage for suction and discharge Freon-12 lines. Table 7 presents suc tion-line capacity factors for equal pressure drop. ACCESSORIES Dehydrators, oil separators, strainers, vibration eliminators, sight glasses, and various types of valves are accessories frequently needed for the proper Refrigeration 857 in water lines:'leading to water cooleid condensers.* : Sight glasses which permit visual inspection of the condition of the refrigerant are sometimes installed on factory assembled commercial unit systems.: Tti is particularly advisable to place such a fitting before the expansion valve, if the evaporator is located above the condenser. . ! J '' r ` " Flexible vibration eliminators, usually consisting of. a bellows, design covered with woven copper wire, are .sometimes ;instafled ,in <pper.lines where unite such as. compressors are installed on, flexible, mountings, or where vibration is otherwise a problem. Packed or packless shut-off valves are necessary where it may be required to'ik)late portions of a'kysteih^ installation and operation of refrigeration systems. Refrigerant-line de hydrators or dryers usually consist of copper containers fitted with tubing connections at either end, and contain a desiccant such as silica gel, activated alumina, or calcium chloride. The. liquid refrigerant is circulated through the dryer during operation of the system, and the moisture content of the refrigerant charge is thus kept to a minimum. Oil separators are installed between the compressor and condenser to prevent excessive oil removal from the compressor crankcase and its passage; into the condenser and evaporator. The oil is separated from the gaseous; refrigerant by gravity during its passage through a chamber of sufficient size to reduce the velocity. A float-operated valve maintains a maximum, oil level in the separator, and additional oil is forced by pressure difference through a line back to the crankcase. Screen strainers are frequently installed in the liquid line piping before^ solenoid valves and expansion valves, as well as before regulating valves* EQUIPMENT CHARACTERISTICS AND SELECTION Die various types of compression systems have quite different charac teristics of capacity and . power with varying evaporator and condenser temperatures, as may be noted from curves in Figs; 14 and 15. From Fig. 14 it may be observed that power requirements for the. centrif ugal compressor increase much more rapidly than for the reciprocating compressor, with increase in evaporator temperature. Similarly, the ca pacities-of- the steam ejector and centrifugal compressors increase, more rapidly than those of the reciprocating compressor with' increase in evapoIf'uator tt.ePmTYpmenraimtutnrie'o. Thus, Lb-oJ-tth- Athhe* ste---a----m--- je1t and1 centrif"ugal machines mnd to be more self-regulating than the reciprocating. It is' also evident rom pjg that the steam jet equipment is best suited for operation at rugh evaporator temperatures.' ,, effect of condenser temperature upon the power and capacity-of ne different types of compressors is shown in Fig. 15. It may be noted