Document n9oMgqYbjBByzk6LnEE52zgpR

880 CHAPTER 37 1956 Guide Table 5 shows the tonnage capacity normally allowed for CCI2F2 liquid lines per foot equivalent length of pipe, and Table 6 the maximum tonnage for suction and discharge CCI2F2 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 881 in water lines, leading to water cooled condensers. Sight glasses which permit visual inspection of the condition of the refrigerant are sometimes installed on factory assembled commercial unit systems. . It is particularly advisable to place such a fitting before the expansion valve, if the evaporator is located above the condenser. Flexible vibration eliminators, usually consisting of a bellows design covered with woven copper wire, are sometimes installed in copper lines where units 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 isolate portions of a system. Fig 14 Performance Characteristics of Compression Refrigeration Machines at Constant Speed 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, acti vated 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 Fig. 15. Performance Characteristics of Compression Refrigeration Machines at Constant Speed EQUIPMENT CHARACTERISTICS AND SELECTION The 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 evapo rator temperature. Thus, both the steam jet and centrifugal machines tend to be more self-regulating than the reciprocating. It is also evident from Fig. 14 that the steam jet equipment is best suited for operation at high evaporator temperatures. The effect of condenser temperature upon the power and capacity of the different types of compressors is shown in Fig. 15. It may be noted