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and are very widely used for supplying oil to practically every point in a Diesel engine. At some important points they are used almost exclusively. Figure 4 shows a type of oiler which delivers oil to the piston a t the proper time. To aid in keeping an air-free lubricating pipe to the pistons and preventing gas blow back, several types of check valves have been developed for the cylinder wall inlet. It must be remembered that feed from a mechanical oiler must not fail even for a short time. These forms are the more important ones used to supply main bearings, crank and wrist pins, and cylinders. For lighter drives the bath is common, in which some receptacle. to be filled from time to time by hand or by an overflow system from the crank case, keeps a t least a part of the mechanism running in oil, ample oil being splashed and carried to the rest. Cup and wick oilers are common and often advantageously employed and hand oiling is resorted to in some cases. Oil Grooves
The subject of oil grooves has an important bearing on the success of a lubricating system and is a designer’s problem which can only be mentioned here. Diagonal grooves must be used with care, even though they distribute oil quickly. The position of holes in the crank pin and grooves in the bearing must be placed with regard to load conditions. I n the two-stroke cycle pressure is always in the same direction, while in the four-stroke cycle bearing pressures usually reverse on the exhaust stroke. Oil Cleaning
The question of cleaning lubricating oil is probably one of the most important features of good lubrication and long life of the engine. The causes of fouling of the oil have already been mentioned. Some installations must throw away their oil every 3 or 4 months when unpurified. With capacities for average power plant installations of from 100 to 500 or 600 gallons this is very serious. A number of cleaning methods are used-filtering, settling, chemical sludging, and centrifugal separation.
Vol. 18, No. 5
The m.lue of clean oil is best brought out by the following analysis of sludge taken from an engine in a plant of one of the well-known manufacturers of Diesel engines, which was foriiied a t the rate of one pint per 20 hours for one 400 horsepon-er engine : Bearing temperature Amorphous carbon Paraffin Heavy oil binder Water and volatile oils Silicates Loss
l i 0 ’ F. Per cent 92.2 0.7 5.15 1.21 0.35 0.38
The air mas clean and there was no water seepage. On the ferry “Poughkeepsie” without cleaning it was found necessary to take up the connecting rods at the rate of 0.012 inch every 2 weeks. With clean oil the amount taken up was 0.001 inch on seven rods and 0.003 inch on seventeen in 5 months. Taking up rods and keeping bearings properly close i+ expensive, more so than the extra cost of correct oil and keeping it clean. One oil pumping station has used the same oil for three years after installing proper cleaning facilities. Conclusion
The successful lubrication of any Diesel engine depends upon four factors: Efficient supplying of the proper lubri-
cant, moderation in bearing loads, adequate oil purifying syatein, and thorough supervision during operation. The first three of these factors constitute problems for the engine designer and the manufacturer of lubricants. Obviously the last rests entirely in the hands of the user of the engine. The Diesel engine is still developing and many problems connected with the selection, application, and care of its lubricants yet remain to be solved. It is hoped that the oil companies will take an active part in this development. Diesel engines are more expensive than steam engines and require greater care, but their much higher efficiency is the reason for their rapid development. It is only through cooperation that their development can advance with the greatest posbible rapidity.
A Problem in Diesel Engine Lubrication By Fred Norton and Ralph R. Matthews ROXANAPETROLECM
In the early days of the development of Diesel engines the matter of efficient lubrication was not given the attention it should have had. I t was soon discovered, however, that this neglect was causing considerable trouble to the users, as for this reason the engine often could not be operated under full load successfully for any length of time. This paper considers such a condition as found in one plant and the steps taken to correct it.
HE plant under consideration is a central power plant using five Diesel engines, each unit rated 523 horsepower direct connected to alternating generators having a total connected peak load of 1875 horsepower with a standby steam plant for emergency use, the steam plant being kept ready for instant use at all times. The steam plant was necessary because this particular plant had encountered difficulty in keeping its units in continuous operation. The Diesel engines used in this plant were of the 2-stroke cycle, land type, and were operated a t 300 revolutions per minute. This type of engine is very difficult to lubricate as all moving parts are a t all times under pressure.
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At the end of the first 6 months of operating these five units the time lost due to all mechanical troubles had exceeded by far a figure which was considered necessary in good operation. The average running time was 91.71 per cent of the available running time, and it was later found that 87.53 per cent of all lost time was due to faulty lubrication. Analyzing the conditions in the plant a t this time, the following interesting facts were noted: cooling system properly designed and in excellent working condition; mechanical condition of the equipment very good; engines not overloaded; engine room well ventilated; proper grade of fuel being used; engines running a t rated speed. I n fact, all things pertaining to good operating conditions seemed to be in the very best of shape. The actual working conditions of each unit were then investigated. The room temperature was 73” F.; cooling water temperature leaving the jackets, 179” F. A water softener was in use and examination of jackets proved that there was no trouble from mud or scale, indicating rather conclusively that the troubles were not caused by low heat
May, 1926
INDUSTRIAL A N D ENGIIYEERI~VGCHEMISTRY
transmission through cylinder wall, a t least on account of scale. The lubricating oil was a Midcontinent base oil with a Saybolt viscosity of 82 a t 210’ F., of which the consumption was one gallon for 757 horsepower hour developed, this grade of oil being the recommendation of the manufacturer who furnished the engines. Experimental
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and cooling-mater temperature entering the jackets remained the same as when previous data were taken. The oil consumption was materially reduced, 1241 horsepower hours being obtained per gallon of lubricating oil in comparison with previous consumption. I n many instances with more modern equipment being used today lower oil consumption ha? been obtained. Conclusion
After considering all details very thoroughly, one unit wa3 bet aside for experimentation to find the cause of the trouble and the remedy therefor. K a t e r injection had been recommended to eliminate the excessive carbon deposit which had been noted in the cylinders, the theory being that the oxygen in the water would combine with the carbon to form carbon monoxide or carbon dioxide, which would pass out the exhaust. The water was introduced with the air and by emulsifying the desired quantity with the lubricating oil, in order to distribute it uniformly in the cylinders. Running conditions seemed to improve but when the run mas completed and the cylinders were examined they were found to be badly pitted and must be replaced. It was also found that the ports between the transfer chamber and power cylinder were practically closed by a sludgy material which was apparently carbon. The exhaust head and pipe, for a distance of about 18 inches, also contained large amounts of this carbonaceous matter. The cause of the pitting was not determined, but it may have been due to the sulfur in the fuel oil forming compounds which actively attacked the metal or to corrosive action in connection with the formation of the carbon compounds mentioned above. It was also learned that the same trouble, encountered in this case with water injection, had forced several manufacturers of various types of Diesel engines to discontinue their use. Thus it was necessary to consider other means of eliminating the operating troubles. Finally, with the assistance of a lubricating engineer from one of the large oil companies and with the same unit employed in previous tests, it was decided t o use a special lubricating oil for the power cylinders, which was much lower in viscosity and, therefore, had lower flash and fire points. The carbon formation in the cylinders seemed to be caused by high operating temperatures and i t was believed that a n oil with a lower viscosity would bring them down. The flash and fire points of this lubricating oil were lower than had been tried before, and up to this time such oils had been considered dangerous to use. After several weeks of experimenting with different grades of oil and assembling data from tests of reasonable length, it appeared entirely satisfactory to use a n oil with the following approximate specifications: Gravity, ’ A. P. I. Flashb F. Fire F. Saygoit viscosity at 1000 F. Saybolt viscosity at 210’ F.
24.5 405 460
375 56
After this grade of oil had been in continuous use long enough to note that practically all trouble had been eliminated, the engine was completely taken down and all parts carefully examined. Everything was in fine shape with pronounced indication of very good, if not almost perfect, lubrication. This test was continued over a 30-day period, during which time all the following changes were noted which had been brought about by the use of this lower viscosity oil as a lubricant for the power cylinder. The cooling-water temperature leaving the water jackets was 123” F. while the engine mas carrying full load 24 hours per day. Room temperature
S o other type of machine can be damaged
50 easily and quickly by faulty lubrication as the modern Diesel engine and, while it is a fact that the average cost per unit to lubricate any Diesel engine is small, this cost can very quickly be increased beyond reason by using the wrong grade of lubricating oil. Too many users of Diesel engines, and manufacturers as well, pay too much attention to the flash point of lubricating oils which they recommend and use. I t has been found that lubricating oil manufactured from a crude produced in any of the prominent oil fields with a Saybolt yiscosity of from 300 to 500 a t 100” F. will give very satisfactory results. Although most operators today are using an oil with a viscosity of 500 to 750, and some even higher, the lower viscosity oils give much more efficient lubrication. K i t h our modern Diesel engine and its methods of applying lubricating oil, especially to the power cylinder, it would seem logical to assume that a reasonable lubrication efficiency has been reached. However, in most modern Diesel engine plants from two to four lubricating oils of different viscosities are being used to lubricate any one type of engine. This is a condition which recent tests indicate may be eliminated. It is believed that a lubricating oil can be used for the power cylinder which does not have a viscosity high enough to eliminate its use on bearings, and a t the same time gives satisfactory lubrication to the air compressor on engines where solid injection is not used. Undoubtedly, cooperation between the manufacturers of Diesel engines and the refiners and distributors of lubricating oils will result in solution of these and other lubricating problems.
Meeting of the American Refractories Institute The American Refractories Institute will hold its annual meeting at the Bellevue-Stratford Hotel, Philadelphia, Pa., on May 12, beginning a t 1O:OO A . M. (Daylight Saving Time). The following technical papers will be presented: “Service Conditions in Open Hearth Furnaces as Affecting the Life of Refractories,” b y F. W. Schroeder, Assistant Chemist, U. S. Bureau of Mines, PittsbRrgh, Pa. “The Refractories Industry in New Jersey,” by G. H. Brown, Head of the Ceramics Department, Rutgers University, New Brunswick, N. J. “Mullite Refractories,” b y M. L. Freed, Research Fellow, National Bureau of Standards, Washington, D. C. “Industrial Research,” b y E. R. Weidlein, Director, Mellon Institute of Industrial Research, University of Pittsburgh, Pittsburgh, Pa. “The Study a n d Development of Tests for Fire Brick with Special Reference to Spalling,” by S. M. Phelps, Fellow, Refractories Fellowship, hlellon Institute, University of Pittsburgh, Pittsburgh, Pa. “Permeability a s a Measure of the Uniformity of Fire Brick,” b y A. E. R. Westman, Research Fellow, University of Illinois, Urbana, 111. (Dr. \Yestman will also discuss investigations being conducted on checker brick for water-gas sets.)
These papers and talks, together with the discussions that will be presented from the floor, should be of interest t o both consumers and manufacturers of refractories. Arrangements are also being made to have one or two nationally prominent speakers present and talk on subjects of general interest. At noon a luncheon will be served in the hotel, reservation for which should be made through Dorothy A. Texter, secretary, 2202 Oliver Building, Pittsburgh, Pa. The business session will be continued in the afternoon. Invitation to attend this meeting is extended to all who are interested in the program, regardless of membership in the organization.
