American Handy Book of the Brewing, Malting, and Auxiliary Trades/Lubricants and Lubrication
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This article represents a section of the classic public domain brewing text "American Handy Book of the Brewing, Malting, and Auxiliary Trades" by Robert Wahl and Max Henius. See the main entry on this book for general information and a complete table of contents. |
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Lubricants and Lubrication
The question of proper lubrication of the different machines used in the brewery and malt-house, in fact, anywhere else, is a matter of no small importance.
The amount of power necessary to drive a machine, and this means the coal pile, as well as the life and proper running of the machines, is greatly influenced by proper lubrication of the sliding surfaces or bearings.
Although it is, of course, good business policy to purchase a lubricating oil. etc., as cheaply as possible, nevertheless, this striving for economy is apt to be carried too far, so that it has in many instances become a "penny wise, pound foolish" policy. A high quality lubricant can be purchased only at a correspondingly high price.
A second mistake often made is to use one kind of lubricant for too many purposes, thereby enabling the purchase of a larger quantity at one time. It is evident that a lubricant best adapted for use on shafting or heavy slow running machines is not suitable for high speed light machinery.
Another error is the application of too much of the lubricant to bearings that do not need it, or would not, if kept properly adjusted. One often finds machinery literally "swimming in oil," which is a wasteful proceeding, and should this excessive application be necessary in order to keep the bearings from heating, it is a reflection either upon the maker of the machine for accuracy and material used, or upon the skill or care of the mechanic in charge. An exception to this are tapping machines and certain types of high speed machinery the bearings of which are lubricated upon the oil-bath principle, but here special construction is provided to prevent the oil from splashing about.
The proper construction of the bearings has also a great deal to do with economical lubrication since a properly adjusted bearing requires less oil and will retain it longer than a loosely constructed one, the latter allowing the oil to run out as fast as it is supplied.
A considerable aid to proper lubrication is given by the oil cups with adjustable feed now in use. by means of which the oil supply can be regulated, and several hours' supply filled at one time.
Theory of lubrication.
If two substances are rubbed against one another their motion is retarded by what is called friction. The smoother the surfaces of these substances can be made, the less friction will there be. This friction is caused by the high points in the surface of the one sinking into the depressions in that of the other and thereby retarding their motion. A surface that may appear smooth to the eye is in reality quite rough, as can be seen if a piece of highly polished steel is examined under a magnifying glass or microscope. This friction, be it ever so small in the beginning, soon becomes greater in an ever increasing ratio. This is due to small particles of the substances being broken off, and the surfaces thereby roughened, the particles assisting in further abrasion or grinding. This can be illustrated by rubbing two pieces of glass together, when it will be found that at first they hardly make any impression upon one another, but if the rubbing is continued they will become "ground" or "frosted," and a layer of powdered glass will be formed between them.
Action of lubricants.
If these surfaces moving past each other can be kept apart so that their high points or ridges cannot strike against each other, it is evident that there can be no abrasion or "wear and tear." This separation is accomplished by means of lubricants, that is, substances that are viscous or "sticky" enough not to be readily squeezed out from between the surfaces, and at the same time fluid enough not to retard the motion of the surfaces. These lubricants form a thin film between the surfaces and keep them apart while moving. The lubricant must, furthermore, be of such a nature as to have no action upon the material of which the moving parts consist, for if it contains acids the latter will attack metallic parts and be likely to cause the opposite result from the one desired.
Anti-friction metals.
If the surfaces of two substances of equal hardness rub together it is likely that they will wear equally. If on the other hand the substances are of different hardness, the softer will be the one that wears more. On this account one of the moving parts is generally made of a softer material, or, where the same material is used for both, one is fitted or lined with a softer material that can be readily removed and replaced.
In modern machinery this softer material is a metal called antifriction metal, and is principally of two kinds: bearing metal, consisting of an alloy of copper, tin and zinc, and babbitt metal, made from tin, antimony and copper.
Kinds of lubricants.
The lubricants, or their substitutes, now in most general use can be classed as follows:
1. Mineral oils.
2. Fixed oils and fats.
3. Blown or thickened oils.
4. Blended oils.
5. Resin (rosin) oil.
6. Lubricants, containing soap.
7. Greases.
8. Solid lubricants.
Mineral oils.
Crude petroleum is the source of the mineral lubricating oils now in general use. Some kinds of crude oil are used in practically their natural state for lubricating heavy bearings, but the bulk of the crude oil is subjected to distillation. This furnishes an almost endless number of different products.
These products are, however, not simple substances, but mixtures of different hydrocarbons, the boiling points of which are limited within narrow confines. Out of the different products obtained the following may be mentioned:
Cymogen.
A gas at ordinary temperature, used in the manufacture of ice.
Rhigoline.
Also a gas, used for medicinal purposes.
Petroleum Ether.
Liquid, boils at 160° to 190° F.; used as solvent for fatty oils, etc.
Gasoline.
Liquid, boils at 160° to 190° F.: used for oil extraction from seeds, etc.
Naphtha.
Liquid, boils at 176° to 250° F.; used for burning, and as a solvent for resins.
Ligroine.
Liquid, boils at 176° to 250° F.; used as a solvent.
Benzine.
Liquid, boils at 250° to 300° F.; used for cleansing and as a substitute for turpentine.
Kerosene or Burning Oil.
(Standard white, prime white and water white.) Used for burning in lamps; must stand "fire test," that is, it must not develop ignitable gases below a certain temperature (110° to 150° F.).
Lubricating Oils.
What remains of the natural oil after the removal of the above named substances by distillation is called residuum, and is used for the manufacture of lubricating oils, paraffine and vaseline.
Distilled Oils.
The residuum, after the removal of the lighter oils, is allowed to stand for some time, and then transferred to so-called "tar stills." in which the lubricating oils are distilled off by superheated steam or in vacuo. Oils produced in such manner are called distilled or paraffine oils. The first distillate furnishing light lubricating oil for light machinery is called " neutral oil," and is used for mixing with fixed oils. Upon further distillation the heavier oils called "spindle oil" and "engine oil" are obtained, and finally an oil distills over at about 600° F., which is used as "cylinder oil." What is now left behind is further treated and furnishes paraffine wax and vaseline. The distilled oils are then chemically treated for further purification and bleaching with dilute sulphuric acid, which is then removed by water and a solution of caustic soda.
To avoid decomposition by high heat the petroleum is preferably distilled with steam under high pressure or in vacuo. After the lighter oils have been driven out, and the volume reduced, the remaining black, viscous oil is also called "reduced oil," and is used for heavy machinery. It may contain tarry matter, which is objectionable. For the manufacture of cylinder oils special kinds of petroleum are used, which are carefully reduced at low temperature and in vacuo: the reduced oil is then filtered through animal charcoal repeatedly.
The removal of the light oils is sometimes carried out in open shallow tanks, in which the oil is exposed to sunlight while floating upon water warmed by steam. Such oil is called "sunned oil."
A characteristic of nearly all mineral lubricating oils is their fluorescent appearance when contained in bottles or transparent vessels.
Shale Oil.
Crude shale, a substance similar to petroleum, found mostly in Europe, gives products similar to crude petroleum by which it is now mostly replaced.
Paraffine
is found native as a fossil wax, and is contained in the least volatile part of petroleum residues, from which it is obtained by cooling to a low temperature. It is also largely made from bituminous shale.
Paraffine is a white, waxy substance, without taste or odor. It is insoluble in water and cold alcohol, soluble in petroleum ether, kerosene and warm fixed oils. It is not acted upon to any extent by acids or alkalies.
Vaseline
or petroleum jelly is also prepared from the least volatile portions of petroleum. It is separated from the crystallizable paraffine, and purified. Vaseline is a pale, yellow, translucent substance. It finds some use as a lubricant, but its principal application is for medicinal purposes.
Fixed oils.
These are so called on account of being fixed, that is, not volatile, or capable of being evaporated or distilled.
Fats.
Fixed oils and fats derived from animal and vegetable tissue are practically identical except in consistency, the fats being solid. Fats, however, become oils when heated, and fixed oils become fats when cooled.
Fixed oils and fats differ from mineral oils in their behavior toward oxygen. The former combine with it, thereby becoming thicker, even solid, while the mineral oils are inert toward oxygen.
Spontaneous Combustion.
This absorption of oxygen by fats and oils is accompanied by a rise in temperature, the more so, the larger the surface of the oil. Rags or machinist's waste saturated with oil present a large oxidizing surface and will, on this account, especially if inclosed in a box, etc., absorb oxygen so fast as to become ignited by what is generally termed spontaneous combustion.
Mineral oils, as they have no affinity for oxygen, are not subject to spontaneous combustion, and when mixed with fixed oils reduce the liability to combustion in proportion to the amount present. This oxidizing or "drying" property renders some of the fixed oils unfit for lubrication, prominent among which is linseed oil, being on that account most useful as a paint oil. Those possessing this oxidizing property the least, and that are used, therefore, mostly as lubricants, are cottonseed, olive, castor and rape oil of the vegetable oils, and sperm, neatsfoot and lard oil, also tallow, among animal oils.
The mineral lubricating oils are not acted upon by caustic alkali, that is, do not saponify. Fixed oils can on that account be easily distinguished from them.
Blown or thickened oils.
These oils are manufactured by blowing a jet of air through heated fixed oils, principally cottonseed and rape oil. The oils thereby become thicker and more viscous. These oils are not used alone as lubricants, but mixed with mineral oils to increase the body or viscosity of the latter.
Blended oils.
Mixed or blended oils consist of varying proportions of mineral and fixed oils mixed so as to be best adapted for the purpose for which they are to be used.
As mineral oils are cheaper than fixed oils, and as the latter are not suitable for every purpose, this mixing has the advantage of furnishing an oil that is better suited for many purposes than would either alone. As mineral oils are best adapted for high speed and light pressure moving parts, and fixed oils for slow speed and heavy pressure parts, the best results for intermediate speeds and pressures can, therefore, be obtained with properly mixed or blended oils. This mixing cannot, however, be always resorted to, as the solid hydrocarbons, paraffines, etc., contained in some mineral oils are precipitated by this mixing.
Resin (rosin) oil.
Resin oil is the product of destructive distillation of common resin. It is a viscid liquid of dark brown color, with a strong fluorescence. It contains a considerable proportion of unchanged resin, carried over by the oil. Its specific gravity is high, ranging from 0.96 to 0.99, and sometimes much higher. It is not used by itself as a lubricant, but to some extent as an adulterant for other lubricants.
Lubricants containing soap.
These are often used as a thickening medium for mineral oils. If enough soap is added a gelatinous grease is formed. The soap generally used is aluminum soap, made by saponifying various fixed oils with caustic soda and stirring this into a solution of alum. A precipitate of oleate of aluminum is thereby obtained which, after drying, etc.. is added to the lubricant.
Aluminum soap has practically no lubricating quality and is therefore considered as an adulterant; in fact, it is claimed by some to decrease the efficiency of the lubricant. Regular soaps, made with oils and caustic soda alone, arc also used, but mostly as an addition to oils to produce lubricating grease.
Greases.
These nearly all have tallow as their base mixed with various oils, although various soaps are also used instead of the tallow.
Axle Grease.
This consists usually of resin grease prepared by treating resin oil with slaked lime, and stirring this into more resin oil, or with petroleum or coal tar oil.
Solid lubricants.
These consist mostly of talcum or soapstone, and plumbago and graphite, the latter being the one almost exclusively used. Solid lubricants are used for very slow speeds and great pressures, and will remain in some bearings where grease or oil would run out. Solid lubricants are also used for lubricating link belting running over sprocket wheels, which, if lubricated with oil, would throw off or splash the oil by centrifugal force, or if running in dusty places gather grit, etc., which would cause undue wear.
Oils for hot or cold use.
Besides selecting oils best adapted for speeds or pressures, the temperature of the moving parts must also be considered.
Cold Test Oils.
These oils are used for lubrication of refrigerating machines, and must have the property of remaining liquid at temperatures of from 15° to 0° F. without congealing or solidifying.
Hot Test Oils.
Cylinder oils, used for lubricating piston and valves in the steam cylinder, must have the opposite property of cold test oils, viz., they must remain viscous and not decompose at the high temperatures of pressure steam in the cylinder. Cylinder oils should have an evaporating or decomposing point much higher than the temperature at which used, this ranging from 500° to 600° F.
Chemical and physical properties of lubricants.
The properties to be considered in judging the fitness of a lubricant are (see also "Brewers' Chemical Laboratory"):
1. Viscosity or "body" of the lubricant at the temperature at which it is used;
2. Temperature of solidifying or thickening point;
3. Flash point, the temperature at which the lubricant begins to give off inflammable vapors, which, however, are extinguished if flame is removed;
4. Fire test point, at which these vapors burn continuously;
5. Amount of volatile substances contained;
6. Drying, gumming or oxidizing property of the lubricant;
7. The proportion of admixtures of other fats or oils;
8. Acidity, effect on metal surfaces;
9. Mineral admixtures or adulterants.
Lubricants for different purposes (Thurston).
Low temperatures, as rock drills, etc.—Light mineral lubricating oils.
Very great pressures, slow speed.—Graphite, soapstone (talcum) and other solid lubricants.
Heavy pressures, slow speed.—The above, and lard, tallow and other greases.
Heavy pressures, high speed.—Sperm oil, castor oil, heavy mineral oils.
Light pressures, high speed.—Sperm, refined petroleum, olive, rape, cottonseed oils.
Ordinary machinery.—Lard oil. tallow oil, heavy mineral oils, and the heavy vegetable oils.
Steam cylinders.—Heavy mineral oils, lard, tallow.
Watches and other delicate machinery.—Clarified sperm, neats-foot, porpoise, olive and light lubricating oils.
For mixture with mineral oils, sperm oil is best, lard oil much used, and olive and cottonseed oils are good.
