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with increasing total pressure, and also with increased temperatures, and is undoubtedly due in large part to the actual solubility of part of the water in the crude oil. That this may be quite appreciable is shown by the results of Groschuff.2 The increase at higher temperatures and pressures is, of course, characteristic of immiscible liquids. The presence of dissolved salt in the water would also have a slight effect in lowering the observed vapor pressures, especially when the water is nearly all vaporized. At moderate pressures and a t temperatures above 300' F. the volume of vapors produced is so large that it must certainly be taken into account in calculating heat consumption, rates of heat transfer, and pressure drops to be anticipated in all equipment where a moving stream of oil is heated. The serious effect of even small slugs of water or highly emulsified crude is readily apparent from the results on crude containing only 1.75 per cent water as compared with dry crude. 2
Leslie, "Motor Fuels," p. 646; C. A , , I , 2550 (1911).
Power and the Viscosity of Oil' By William F. Parish PARISH & TEWKSBURY, INC., 17
H E interest shown in lubricating oils of late years prompts this author to place in a convenient record some work in Germany, which was reported in part by Philip Kessler before the Verein deutscher Chemiker in 1910. This work was in answer to theories personally advanced by Professors Engler, Holde, Ubelholde, and others, that viscosity was the main characteristic of a lubricant for determining its lubricating power. The popular lubricants for industrial machinery in Germany came from Russia, these oils being the cheapest on the market. In making power tests against these heavy bodied oils and showing very considerable power reductions by the use of American oils, the technical fraternity in Germany became much interested. In certain textile mills power reductions of over 15 per cent were shown through the use of the American oils, resulting in their permanent establishment. One mill required a second demonstration again to supplant Russian oils, which, however, had been mixed to secure lower viscosity, when the power saving with American oils was about 8 per cent. The theory was then advanced that viscosity was the main factor in making power tests. A later examination of the lubricants a t the same mill showed that the viscosity of the mixed local spindle oil was identical with that of the American oil. The author then changed the program of testing and established a method of showing that, irrespective of viscosity, a properly refined and finished oil would wear longer without decomposition than an oil made up by mixing heavy and light distillates to suit a specification based entirely upon viscosity. It is admitted that two oils of the same viscosity in the bearing will show the same coefficient of friction on a handoiled testing machine as long as speed, temperature, and pressure will not allow either oil to decompose or change in the slightest degree. It is only when the more modern methods of severe service and continuous application are used that the oil shows changes in character. These changes are in no way indicated in a preliminary examination of the oil by its viscosity alone. The work done was decisive and has influenced the German technical opinions on the subject. One test was on a ring
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spinning machine in a cotton mill (Chart 1). The power measurements were made with an absorption dynamometer, other measurements by standard instruments of the finest kind. The machine was cleaned in the same manner before each oil was put in. The two new oils were analyzed in the laboratory of an oil company. No. 1 is the American oil and No. 2 is the oil made up locally to duplicate it. The American oil is taken as the basis of performance-power and temperature being increased and speed reduced by use of the mixed oil No. 2. Spinning Frame Test Properties No. 1 No. 2 0.880 0.855 Specific gravity 150' C. 142O C. Flash (Pensky-Martin) Fire 176' C. 166' C. - 8 . 5 ' C. - 7 . 5 ' C . Pour Acidity (SOJ) 0.008 0.02 Natural Mirbane Odor 54 sec. 5 3 . 5 sec. Viscositv. at 40' C. .. Savbolt . Performance Hours run Dynamometer horsepower: Empty machine Machine spinning Speeds per minute: Empty machine' Drum Spindle Ratio Machine ;pinning: Drum Spindle Ratio Relative humidity Temperatures, O C . : Room Spindle base Frictional heat (R-Sb)
348 1.416 2.570
Difference
342 1.517 2.695
0 . 1 0 1 (7.15%) 0.125 ( 4 . 9 % )
810.6 808.7 8863.0 8838.6 10.934 10.929
0.005 (0.05%)
808.0 806.0 8841.2 8784.0 10.942 10.898 71% 73% 26.68 29.87 3.19
25.25 29.48 4.23
0 . 0 4 4 (0.402%)
1 . 0 4 (32.6%)
Another series of tests were made on a cotton twisting machine. This machine has larger and heavier spindles, but the oils were substantially the same as those used on the dynamometer test, though the No. 2 oil was slightly changed. The appearance and odor suggested quite clearly what had been done in blending it, though nothing was shown in the analysis that in any way indicates the peculiarity. The oils were examined in the laboratory of an oil company. Each oil had run in the same machine for four weeks. As before, the American No. 1 oil was taken as the basis of per-
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formance. The power readings were taken by the engineers of the State Electro Technical Department with their instrument,s. ,411 the work was under control conditions (Chart 2 ) . Twisting Frame T e s t Properlies . No. 1 No. 2 Specific eravity 0.880 Flash (Pensky-Martin) 152: C . Fire 176 Pour -8.5‘ Acidity (SOJ) 0.008 3 Color Viscosity, Saybolt at 40° C. 54 sec. at2O0 C. 2 .75 Viscosity, Engler at 50’ C . 1.50
{
Hours run Electrical horsepower Revolutions per minute: Motor Spindles Ratio Relative humidity Temperatures, C.: Room Spindle Shaft Frictional heat (R-Ss) : Spindle Shaft
0.865 151; C. 177 -5.5’ 0.013 4 54 sec.
creased somewhat. The oil was suitable for further continuous operation. The made up oils showed a much greater physical change, as had been anticipated. Gum had formed in considerable quantity. The acid value had greatly increased. The greatest change was in the viscosity which was as high as the increased heat and power and lower speed of the test indicated. Conclusion
Holde,* the German authority, has this to say on the subject:
2.75 1.50
The practical man is interested in knowing how to cut down power losses by lubrication. Unfortunately this question cannot be answered directly from a consideration of either viscosity or the behavior of the oil on a mechanical (laboratory) testing machine. While the viscosity of a n oil is probably most important in determining the lubricating power, other factors are undoubtedly concerned.* * The oil should not lose its power of reducing friction by evaporation or by acting chemically on the metal of the bearing* * and should not contain drying oils.
Difference
288 4.76
288 5.82
1 . 0 6 (22.3%)
1435 3176 2.213 49.4%
1451 2996 2.065 55,0%
0.148 ( S . i % )
21.9 23.51 24.67
19.6 25.25 24.80
1.74 (7.4%) 0 . 1 3 (O.a%)
1.61 2.77
5.65 7.20
4 . 0 4 (251%) 4 . 4 3 (160%)
A complet’eanalysis was made of the oil that was removed from the spindles on all of the four tests, though the figures do not appear in the record. These analyses show that there was but little change in the American oil, the viscosity was but little greater, the oil was dark, and acidity had in-
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This introduces a very practical element in the lubrication problem; one oil may change more than another, even if both are of the same viscosity when new. Therefore the value of the lubricant for use under modern conditions in the continuous lubrication systems is not entirely indicated by the viscosity of the oil when new. 2 “The Examination of Hydrocarbon Oils and Saponifiable Fats and Waxes,” 5th ed., 1922.
Time f o r Read;ngs - P . M . Chart 2
