Document KGRB2d9qMkw5bV0e3gBn2LV80

290 CHAPTER 19 Tgble 17 .... Effect,of Temperature on-Capacity* (Constant Compressor Oitptowurf--4 cfia.) Crop. Temp. Capacity--fife, per Hour Condensing Temperahire, F , 80 I" 100 Refrigerant 12 120 5,240 2 8,280 - 12,590 18,510 4,790 7,590 11,580 17,080 - Refrigerant 22 4,320 6,890 10,550 15,620 3,841 6;160 9,470 14,090 -20 ... o 8,672. 20,303 29,553 3 .7,987 12,479 18,782 27,386 7,279 11,402 17,203 25,139 6,536 22;789 1965 Guide And Data Book . Table 18.... Effect of Temperature on Theoretical Horsepower per Ton* F -20 40 -20 40 Condensing Temperature F 60 | 80 | 100 j -120 Refrigerant 12 1.03 0.70 0.43 0.20 1.36 0.99 0.68 0.42 Refrigerant 22 1.76 1.33 - . * 0.97 0.67 2.24 1.73 1:31 0.95 1.03 0.71 0.44 0.20 1.37 I 1.01 : 0.G9 0.42 - -1-.77 . : . .I:34i . 0.98 =: 0.67 ' 0.97 aemg Ubleo in Chapter 2a Table 19 .... Relative Safety of Refrigerants Under- ASA-69 -- Safety Code Group CtassiGcetion- Exphare Units to Air % Sy VofutM SO 14 1150 744A 13 Methane Tetrafiuoromethai e Ethylene Nitrous Oxide Monoehlorotri' fluoromethane 3*. 5b ... ! ' 6* 3* 5b 1- ' 6* *' 4.9 to 15.0 . Nonflammable 3.0 to 25.0 Nonflammable Nonflammable 170 744 13B1 290 22 Ethane Carbon Dioxide Monobromotri- fluoromethane Propane Monochlorodi fiuoromethane 3 5b* 1 -5* 1* 6 3.3 to 10:6 Nonflammable Nonflammable . 3 : 5b* , 2.3 to 7.3 1 5a** Nonflammable 717. 500 12 Ammonia Dichlorodifluoromethane 2 `' 2* 1 5a T ; 6* . 16.0 to 25.0 Nonflammable Nonflammable 40 Methyl Chloride 601.. Isobutane 764 600 114 21 160' 11 611 30 113 1130 Sulfur Dioxide Butane Dichlorotetra- fluoroethane ` Dichloromono- fluoromethane! Ethyl Chloride. - Triehloromono-.. . fluoromethane Methyl Formate. MethyleneChloride Triehlorotrifluord- | ethane , Dicbloroethylene 2 , - 4* 3 <.` 5b .. 2 1* 3 5* 1 - . 6* ,i! *. 4-r5f; 2 4a* ' 1.1 to 17.2 1.8 to 8.4 Nonflammable 1.6 to 6.5 \2 i r iv : 5* : ! 3* *.' 4a* * 4-5 J i 2 4* .5.6 to 11.4 * Underwriter*' laboratories Report MH-2375. 7*.yterwriter' Laboratories Report MH-3I34. I Laboratories Report MH-2630. | gwwriteM' laboratories Report Mil-3072. Table 20.... Underwriters* laboratories Cfassifrcatioh of Comparative Hazard to Ufe of Gases.and Vapors' Gnp 1 Deflnrfioo Gases or vapors which in concen trations of about l to I percent for durations of exposure of about 5 minutes are lethal or produce seri ous injury. Examples, Sulfur Dioxide . -2 Gases or vapors which in concen trations of about J to 1 percent for durations of exposure of . about l hour are lethal or produce serious injury. Ammonia ' Methyl-Bromide 3 Gases or vapors which in concen Carbon Tetra trations of about 2 to 2$ percent chloride for durations of exposure of about Chloroform: ' 1 hour are lethal or produce serious injury. ' Methyl Formate 4 Gases or vapors which in concern Dichlorbethyiene trations of about 2 to 2j percent . Methyl Chloride for durations of exposure of about 'Ethyl Bromide .2 hours are lethal or produce seri ous injury. Between . 445 Appear to classify as somewhat" leas toxic than Group 4. Methylene Chlo- -ride Ethyl Chloride . r Much less toxic than Group 4 but somewhat more toxic than Group5; Refrigerant 113 6a ' Gases or vapors much less toxic Refrigerant 11.- than Group 4 but more toxic than Group 6. Refrigerant 22 Carbon Dioxide 5b Gases or vapors which available Ethane:' 'data indicate would classify.'as Propane - either Group 5a or Group 6. Butane- 6 Gases or vapors which in concen Refrigerant 12 trations up to at .least about 20 Refrigerant 114 percent- by volume for durations Refrigerant 13B1 of exposure of about 2 hours do not appear to produce injury Refrigerants: Safety *11x6 characteristics of a number of refrigerants are suin- rearimd in Table 19.with respect to,toxicity and flamma bility. In ASA Standard B9.1-1864, refrigerants are classified in three groups, depending on the hazard. Group 1. refriger ants are considered the least hazardous and Group 3 the.most hazardous. The Underwriters' Laboratories' Classification System is based on acute toxicity tests'on guinea pigs.'The significance of the Underwriters' Groups is shown in Table 20. LEAK DETECTION .The detection of leaks in refrigeration equipment is a major problem for both manufacturers and service engineers. Sev eral methods of leak detection will be described. Electronic Detector The electronic detector is widely used in the manufacture and asembly of refrigeration equipment. The operation of the instrument depends on the variation in current flow due to ionization of decomposed refrigerant between two oppositelycharged platinum-electrodes. This instrument can be used to detect any of the halogenated refrigerants .except Refrigerant 14. It is not recommended for use in atmospheres containing explosive or flammable vapors. Some other vapors, such as alcohol and carbon monoxide, may interfere with' the test/ ' The electronic detector is the most sensitive of'the various leak detection methods, ,reportedly capable of sensing a leak of 1/100 os per year of Refrigerant 12, or approximately 1 X 10-*ccperBecond.' 'A portable model is available for use in-field testing.'Qther models, are available with an automatic balancing, system which corrects for refrigerant vapors that might,be present in the atmosphere around the test area. ' Halide Tordi ' ' The halide torch has been used for many years as a fast and reliable method of detecting leaks of halogenated refrigerants. Air is drawn over a oopper element heated by a'.methyl alco-^ hoi or hydrocarbon flame. If halogenated vapors are present, they will be decomposed and the color of the flame will change to bluish-green. 'Although not as sensitivej as .the electronic detector, this method is suitable for most'purposes.. , Bubble Method The object.to be tested is pressurised'wito-ab,or nitrogen. A pressure corresponding to operating conditions is generally used. The 'object cap be immersed in a water bath ami any leaks detected by observing the forination of bubbles in the 291 liquid. Addition of a detergent to the water, win decrease the surface tension and prevent escaping gas from clinging to the iHft of the object and will promote the formation of a regular stream of small bubbles. Kerosine or other organic liquids are sometimes used for the same reason. A solution of soap or de tergent can be brushed or poured onto jointe or other spots where leakage is suspected, flaking gas will form soap bubbles which can be readily detected. .- Detection of Ammonia and Sulfur Dioxide Leaks Ammonia' can be detected by burning a sulfur candle in .the vicinity of the suspected* leak or by bringing a solution of hydrochloric acid near the object. If ammonia vapor is present, a white-cloud or smoke of ammonium sulfite or am monium chloride will be formed. Ammonia can'alto be de tected with any indicating paper which changes color in the presenceof a base. , Sulfur dioxide can be detected by the appearance of a white smoke when aqueous ammonia is brought near the leak. The presence of Wfe* can also be determined by pressurizing or evacuating and observing the'change in pressure or vacuum over a period of time. This is a good practice in checking'on the Fightnpsg of a system but is of. little help in locating the point of leakage. EFFECT ON CONSTRUCTION MATERIALS Metals .: The'halogenated refrigerants-can be used satisfactorily under normal conditions with most of the common metals, such as steel, cast iron, brass, copper;tin, lead and aluminum:'- Under more severe conditions, the various metals will affect such properties as hydrolysis and thermal decomposition in' differing degrees.' The tendency of metals to promote thermal decomposition of:the halogenated compounds is in the follows ing general order.... ,*- (least decomposition) Inconel < 18-8 stainless steel < nickel < copper < 1340 ' steel < aluminum < bronze < brass < zinc < silver (most decomposition).'' This order is' only approximate and exceptions may befound for individual compounds or for special conditions of use. The-effect'of metais on hydrolysis would probably be similar. *'*' -s - Magnesium, zinc, and aluminum alloys containing more than 2 percent magnesium are not recommended for use with! halogenated compounds.where even trace amounts of water may be present . Methyl chloride should never Be used with aluminum in' Table 21 .... Swelling of Elastomers in Liquid Refrigerants at Room Temperature17 Refrigerant No. Name Buna N 11 Tricbloromonofluoromethane 12 DichlorodiAuoromethftn* 13 Mouochlorotnfluoromethane 21 Dichloromonofluoromethane 22 Monochlorodifluoromethane 6 2 1 48 26 30 Methylene Chloride 40 Methyl Chloride 113 Trichlorotrifiuoroethane 114 Diehlorotetrafluoroethane 600 Butane 52 35 1 0 1 (GR-S) 21 3 1 49 4 26 20 9 2 8 linear Swell, Percent Butyl (GR-I) Rubber 41 23 66 01 24 34 16 23 34 16 26 21 17 20 20 16 .. GN 17 0 0 28 2 37 22 3 2 3 s FA 2 1 0 28 4 59 11 1 0 0