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First principles

First principles quickly lifted out of position. The flash, when it occurs, is distinctly visible. For estimation of the fire point, the heating is continued until the oil ignites and continues to burn for five seconds. A series of articles explaining in simple Lubricating oils do not have open flash points of below 300°F. and the average for a good quality language the fundamentals of Lubrication motor oil would be between 400/450°F. The difference between the open flash point and the fire point of an oil may be as much as 60°F. with the No . 4. Flash & Fire Points usual type of straight mineral oil. It could be as much as 80°F. in the case of steam cylinder oils. S O far, in this series, we have only dealt with viscosity, which, whilst being probably the most Flash Point N o Guide t o Oi l Consumption. important test, or series of tests, for any lubricating At one time it was thought that the temperature oil and one tha t figures in every specification, is only at which vaporisation and subsequent burning of an one of many. It is essential that a lubricating oil has oil takes place might indicate the degree of oil con­ the correct viscosity for the purpose for which it is to sumption in an internal combustion engine, but this be used and this is usually the first consideration but is not the case. The reason for this is because flash if the viscosity is correct it does not mean that the and fire points only indicate the temperature a t which oil will be perfectly suitable. For example, since the oil begins to vaporise. They provide no indica­ every liquid has a viscosity and many liquids have tion of the rate of vaporisation or evaporation at any similar viscosity readings to those of lubricating oils, temperature, certainly not at cylinder wall temper­ there must be other tests which an oil must pass atures in an internal combustion engine. before it can be recommended as a suitable lubricant for any particular purpose. The final proof, even after all the chemical and physical tests, can only be Flash Points of Ai r Compressor Oils. ascertained by actual service testing. The flash point test is, of course, extremely valu­ able in many cases. In pointing out any deficiencies, Definition of Flash and Fire Points. it must not be thought that it has no uses. We are only pointing out that its figures must not be wrongly In this article wo will consider the flash and fire interpreted. In no case points of an oil. The terms are self explanatory. would an oil having a The flash point of an oil is the temperature at which flash point of less than its vapour ignites, momentarily, when exposed to a flame. There are two flash points, open and closed about 330°F. be used and both are sometimes mentioned in specifications. for cylinder lubrication of internal combustion The open flash point is the temperature at which the engines since such an vapours ignite momentarily when the oil is heated oil would certainly bo in an open vessel and the closed flash point is the very unstable under temperature at which they ignite momentarily in a high temperature. Oils closed vessel. The vapours do not escape from a closed vessel and so the closed flash point is always to be used for cylinder lubrication of air com­ lower than the open flash point, the difference being pressors are frequently greater for higher flash point oils and is usually specified as having a between five and fifteen degrees. high flash point of over The fire point is the temperature at which the oil 450 or 500°F. A high vapours ignite and continue to burn for five seconds. flash point is certainly The apparatus used for determination is the same as very important for air tha t used for the flash points. compressor cylinder work but too much Determination of Flash Point. reliance should not be The apparatus used in this country for determining put upon this one test. the flash point of an oil is usually the Pensky-Martens. The Cleveland Apparatus is frequently used in the Flash and fire points, nevertheless continue to be U.S.A. The detailed test procedure for use of this demanded in specifications, and not without reason. apparatus is given in "Standard Methods for Testing They are two of the tests that must be made, and an Petroleum and its Products" published by the oil's suitability is finally judged not upon the result Institute of Petroleum. In the Pensky-Martens of these two tests, but upon its average results in apparatus, the test flame is adjusted so tha t it is the several tests. Flash and fire points do give some size of a bead 0.16 in. diameter. Heat is applied indication of the degree to which the lighter fractions gently to the oil under test so that its temperature have been removed during refining of the oil and increases at about 10°F. per minute. Application of provided all other tests are up to standard, but only if the test flame to the vapours is made at intervals of they are, an oil having a high flash point will probably each 5°F. rise and the flame is lowered into position not be consumed so rapidly in service in an internal in half a second, left in position for one second and combustion engine as one with a low flash point. Scientific LUBRICATION May, 1949 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Industrial Lubrication and Tribology Emerald Publishing

First principles

Industrial Lubrication and Tribology , Volume 1 (4): 1 – Apr 1, 1949

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0036-8792
DOI
10.1108/eb052004
Publisher site
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Abstract

quickly lifted out of position. The flash, when it occurs, is distinctly visible. For estimation of the fire point, the heating is continued until the oil ignites and continues to burn for five seconds. A series of articles explaining in simple Lubricating oils do not have open flash points of below 300°F. and the average for a good quality language the fundamentals of Lubrication motor oil would be between 400/450°F. The difference between the open flash point and the fire point of an oil may be as much as 60°F. with the No . 4. Flash & Fire Points usual type of straight mineral oil. It could be as much as 80°F. in the case of steam cylinder oils. S O far, in this series, we have only dealt with viscosity, which, whilst being probably the most Flash Point N o Guide t o Oi l Consumption. important test, or series of tests, for any lubricating At one time it was thought that the temperature oil and one tha t figures in every specification, is only at which vaporisation and subsequent burning of an one of many. It is essential that a lubricating oil has oil takes place might indicate the degree of oil con­ the correct viscosity for the purpose for which it is to sumption in an internal combustion engine, but this be used and this is usually the first consideration but is not the case. The reason for this is because flash if the viscosity is correct it does not mean that the and fire points only indicate the temperature a t which oil will be perfectly suitable. For example, since the oil begins to vaporise. They provide no indica­ every liquid has a viscosity and many liquids have tion of the rate of vaporisation or evaporation at any similar viscosity readings to those of lubricating oils, temperature, certainly not at cylinder wall temper­ there must be other tests which an oil must pass atures in an internal combustion engine. before it can be recommended as a suitable lubricant for any particular purpose. The final proof, even after all the chemical and physical tests, can only be Flash Points of Ai r Compressor Oils. ascertained by actual service testing. The flash point test is, of course, extremely valu­ able in many cases. In pointing out any deficiencies, Definition of Flash and Fire Points. it must not be thought that it has no uses. We are only pointing out that its figures must not be wrongly In this article wo will consider the flash and fire interpreted. In no case points of an oil. The terms are self explanatory. would an oil having a The flash point of an oil is the temperature at which flash point of less than its vapour ignites, momentarily, when exposed to a flame. There are two flash points, open and closed about 330°F. be used and both are sometimes mentioned in specifications. for cylinder lubrication of internal combustion The open flash point is the temperature at which the engines since such an vapours ignite momentarily when the oil is heated oil would certainly bo in an open vessel and the closed flash point is the very unstable under temperature at which they ignite momentarily in a high temperature. Oils closed vessel. The vapours do not escape from a closed vessel and so the closed flash point is always to be used for cylinder lubrication of air com­ lower than the open flash point, the difference being pressors are frequently greater for higher flash point oils and is usually specified as having a between five and fifteen degrees. high flash point of over The fire point is the temperature at which the oil 450 or 500°F. A high vapours ignite and continue to burn for five seconds. flash point is certainly The apparatus used for determination is the same as very important for air tha t used for the flash points. compressor cylinder work but too much Determination of Flash Point. reliance should not be The apparatus used in this country for determining put upon this one test. the flash point of an oil is usually the Pensky-Martens. The Cleveland Apparatus is frequently used in the Flash and fire points, nevertheless continue to be U.S.A. The detailed test procedure for use of this demanded in specifications, and not without reason. apparatus is given in "Standard Methods for Testing They are two of the tests that must be made, and an Petroleum and its Products" published by the oil's suitability is finally judged not upon the result Institute of Petroleum. In the Pensky-Martens of these two tests, but upon its average results in apparatus, the test flame is adjusted so tha t it is the several tests. Flash and fire points do give some size of a bead 0.16 in. diameter. Heat is applied indication of the degree to which the lighter fractions gently to the oil under test so that its temperature have been removed during refining of the oil and increases at about 10°F. per minute. Application of provided all other tests are up to standard, but only if the test flame to the vapours is made at intervals of they are, an oil having a high flash point will probably each 5°F. rise and the flame is lowered into position not be consumed so rapidly in service in an internal in half a second, left in position for one second and combustion engine as one with a low flash point. Scientific LUBRICATION May, 1949

Journal

Industrial Lubrication and TribologyEmerald Publishing

Published: Apr 1, 1949

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