The practice of lubrication; an engineering treatise on the origin, nature and testing of lubicants, their selection, application and use

Front matter

Google to make the world's books discoverable online.

It has survived long enough for the copyright to expire and the book to enter the public domain. A public domain book is one that was never subject

to copyright or whose legal copyright term has expired. Whether a book is in the public domain may vary country to country. Public domain books

Contents

Pagb

Pbbface V

Chapter

Chapter I Mineral Lubricating Oils Pbtroleitm Crude

Oa Wells. — Petroleum crudes are secreted by nature and are found in many countries all over the world.

Occasionally, petroleum crude is found Ijdng on the surface of water in pools, but usually it is found at various depths in the earth, from a few himdred feet up to as much as five thousand feet. To bring the crude to the surface a hole is drilled, varying in diameter from a few inches up to 18 inches according to the depth.

Wells may be drilled by the percussion system or by the rotary system, the latter being mostly used for drilling through soft ground. By the perciLssion system a chisel-shaped heavy steel ''bit" is suspended from a cable or a long chain of poles. It is lifted and dropped alternately by means of a steam engine situated on the surface, the steel bit in this way hammering through the eaHh or rock and deepening the bore hole. By the rotary system the drill is attached to the lower end of a length of tubes and is rotated by a steam engine or electric motor situated on the surface. In order to remove from the bore hole sand and fragments of rock a stream of water is continuously pumped through this long tube, and on rising through the hole it carries away the sand and fragments.

When a certain depth has been reached, steel piping called "casing" of slightly less diameter than the hole (from 4 inches to 18 inches in diameter) is driven into the ground. The hole is then continued with a slightly smaller diameter as far as possible, when again a smaller diameter '^ casing" is inserted, so that the deeper the hole the smaller is the diameter at the bottom. Speaking generally, the oil should be reached with not less than a four-inch diameter casing.

It is usual to find confined with the oil a large amount of gas under great pressure, which may be as high as 800 lb. per square inch. Due to this pressure the oil when first reached is forced up the bore hole and rises many feet in the air; such a w«ll is called a "gusher."

Some gushers have produced enormous quantities of crude oil, for example the "Potrero No. 4" well drilled in 1910 by the Mexican Eagle Oil Company. This well was capable of giving about 120,000 barrels of crude oil daily but has now turned into salt water.

Another well, "Dos Bocas," drilled in 1908 by the same Company was probably the largest oil well the world has ever seen; imfortunately it could not be controlled, and drained the field. The gas and oil pressure was so enormous that the heavy casing, 2,000 feet deep, was hurled bodily into the air. This well has probably been the most spectacular well in the world. It burned for 40 days with a flame moimting to 1,800 feet, and newspapers could be read seven miles away by its light. After some months the enormous flow of oil ceased, the original eightinch hole developed into a huge crater many acres in extent, and a daily volume of several million of barrels of salt water is flowing from it at the present day.

When the gas pressure is sufficiently reduced in an old well, it is no longer a "flowing well" but becomes a "pumping well," and the output is reduced to a small fraction of its former value.

Production of Petroleum Crude. — Table No. 1 shows the world's production of petroleum crude oil in metric tons.

The United States, Russia and Mexico are the three great oilproducing countries.

United States.— The production is still increasing in the United States, but will probably not increase much longer; many of the old American fields (Pennsylvania, etc.) are becoming exhausted; the new fields discovered in CaUfornia and Oklahoma have, however, made up for the decreased production in the older fields.

Rv^sia. — ^There are still large possibilities of increased production, but the development of the oil industry is handicapped by the political conditions.

Mexico, — ^The Mexican oil industry has developed rapidly since 1908. The potential resources are enormous, being probably as great as or even greater than the resources of the United States.

Origin of Petroletmi Crude. — There are three theories held concerning the origin of crude oils, but no one is universally accepted.

1. Inorganic Theory, — According to this theory, petroleum is produced deep down in the crust of the earth by the action of high telnperature and pressure on the minerals found there;

Tabub No. 1. — World's Pboduction of Petroleum Crude Oil in Metric

Tons

United States

Russia

Mexico

Roumania

Galicia

Dutch East Indies. .

British East Indies.

Japan

Persia

Peru

Argentine

United Kingdom . . .

Germany

Egypt

Trinidad

Canada

Italy

Other countries, approximately

38,583,063

9,385,000

4,846,471

1,673,145

578,388

1,710,000

1,093,667

415,785

400,000

331,633

91,000

300,000

140,000

33,600

155,000

28,729

5,500

40,000

Total

59,810,981

37,864,031

9,045,700

6,742,480

1,432,296

878,670

1,820,247

1,097,143

399,624

600,000

340,000

130,000

300,000

130,000

54,800

160,000

26,416

5,500

40,000

61,066,907

43,953,560

8,980,790

8,264,260

300,000

780,000

1,700,000

1,100,000

400,000

800,000

340,000

207,000

300,000

140,000

134,500

220,000

25,100

5,500

40,000

67,690,710

40,000

70,541,690

1 Metric Ton » 2,204 lb. == 1,000 kilograms.

carbon and hydrogen are supposed to have combined and formed the hydrocarbons which are the chief constituents of petroleum crude. Only a minority of geologists favor this theory.

2. Vegetation Theory. — According to this theory, vegetable matter has been covered by a layer of impervious material; the air thus being excluded, rotting was prevented, and slow decay during hundreds of thousands of years transformed the vegetable matter into petroleum crude oil and petroleum gas. Several geologists favor this theory.

3. Marine Animal Theory. — According to this theory, dead fishes or tiny marine animals with chalk shells were covered over by a layer of impervious material and gradually transformed into crude oil and gas. Most geologists favor this theory.

Whichever theory is correct, it seems certain that the world's stocks of petroleum crude are practically complete and are being rapidly consumed.

Composition and Character of Petroleum Crude. — When the crude comes to the surface it often contains water (frequently salt water) and dirt, which are separated out in large collecting and settling reservoirs.

The crude is rarely transparent; the color is usually dark brown or black.

Petroleum crude consists chiefly of carbon (C) and hydrogen (H) in the form of hydrocarbons. Besides carbon and hydrogen, there is usually also a certain amount of oxygen, nitrogen and sulphur present.

The percentages of the various chemical constituents vary within limits as indicated in the following table:

Carbon 81.00 to 88 . 0 per cent.

Hydrogen 10 . 00 to 14. 0 per cent.

Oxygen 0.01 to 1.2 per cent.

Nitrogen 0 . 002 to 1.7 per cent.

Sulphur 0 .01 to 5.0 per cent.

Bydrocarbons :

Paraffins (Cn.H2n+2). — The molecules of these hydrocarbons are bound together in the form of chains, and are members of the large family of hydrocarbons known as open-chain hydrocarbons, thus:

II II Ik

H— C— C -C— C C— C— H

u u u

As all the carbon atoms are fully engaged, each carbon atom being tetravalent and attached to four other atoms, the paraffins are called saturated hydrocarbons.

Olefinea (Cn.H2n). — The olefines are also open-chain hydrocarbons, but their molecules have two atoms of hydrogen less than the paraffins, thus:

HH HHHH HH

H-C-C '-O-C = C>-C C— C— H

They are called unsaturated, because they are capable of absorbing hydrogen, oxygen, sulphur, etc., to a value equivalent to two atoms of hydrogen per molecule.

Napthenes (Cn.H2n). — Naphthenes are closed-chain hydrocarbons; they have the same chemical formula as the olefines, but the atoms are not arranged in the form of open chains, but more in the nature of rings or closed chains, in such a manner as to fully saturate all the carbon atoms.

Naphthenes being saturated hydrocarbons are consequently more stable than the olefines.

Cnff 2tt— 2, CnH2n—4:y etc. Most hydrocarbons of the formulas CnH2n— 2, CnH2n— 4, etc., are more or less unsaturated, and the more so the less hydrogen they contain.

Hydrocarbons having from 1 to about' 15 carbon atoms per molecule represent the light products of petroleum crude, viz. petroleum gas, gasolenes, kerosenes, and light transformer and spindle oils.

Most lubricating oils are mixtures of hydrocarbons possessing more than 15 carbon atoms per molecule; the greater the number of carbon atoms, the greater is the viscosity of the oil. Comparing two hydrocarbons having the same number of carbon atoms, the one containing the least hydrogen is the more viscous of the two, but its viscosity is less stable, i,e,, it changes more rapidly with changes in temperatiu'e.

Most petroleum crudes are v^ry complicated in character, and it is difficult to classify them; they contain hydrocarbons of practically all types, but the proportions vary considerably according to the origin of the petroleum.

Petroleum crudes are, however, referred to as Paraffin Base Crudes, Asphaltic Base Crudes, Russian Crudes, and Mixed Base Crudes.

Paraffin base crudes are so called because they contain paraffin hydrocarbons (CnH2n+2). There are only a few lubricating oils of low viscosity which are actually paraffin hydrocarbonSy as paraffins from CnHse and upward represent the hydrocarbons present in paraffin waxes. The heavy viscosity lubricating oils which are found in paraffin base crudes are largely composed of olefines and naphthenes (CnH2n) and acetylenes (CnH2n— 2). As paraffin base crudes always contain a certain amount of paraffin wax, usually about 2 per cent, lubricating oils made from such crudes have high setting points.

The most important supplies of paraffin base crudes come from Pennsylvania and Ohio in the United States. They are fairly fluid, rich in gasolenes and kerosenes, usually contain only a little asphalt, sulphur, oxygen or nitrogen, and have a low specific gravity.

Asphaltic base crudes are so called because they contain a large amount of asphalt; they usually contain certain small percentages of sulphur, oxygen and nitrogen. The crudes from California, Mexico, Texas, and South America belong to this class.

They are very viscous, black in color, rich in lubricating oils, fuel oils and asphalt, and have a high specific gravity; they often contain complex sulphur compounds, which are difficult to extract.

The lubricating oils produced from non-paraffinic asphaltic base crudes have low setting points and possess a wide range of viscosity, ranging from quite thin oils to exceedingly viscous oils.

The hydrocarbons in asphaltic base crudes are lower in hydrogen than the paraffins, although paraffins are often present. For example, California crudes contain olefines (CnH2n), asphaltic hydrocarbons (CnH2n-4) and also some benzenes (CnH2-6).. Texds crudes are rich in asphaltic hydrocarbons.

Russian crudes are in a class by themselves, consisting chiefly of naphthenes (CnH2n) ; they also contain a small percentage of acetylene hydrocarbons (CnH2n— 2).

Russian crudes contain little or no paraffin wax; hence produce lubricating oils with low setting points.

Mixed base crudes are crudes of a character intermediary between paraffin base crudes and asphaltic base crudes, containing both paraffin wax and asphalt. Mexican crudes are the most important mixed base crudes.

DISTILLATION AND REFINING

Petroleum crude is a mixture of many hydrocarbons, all having different boiling points.

The crude is gradually heated in cylindrical stills and the hydrocarbons distil over as their boiling points are reached; the vapors escape through a dome at the top of the still, pass a coil of pipes immersed in cold water, become liquefied and run through an inspection box with glass windows in the "tail '' house, whence the various ''fractions" are directed into their respective collecting tanks. The specific gravity and color form a sufficient • guide for the attendant to enable him to judge when to "cut" the various fractions.

The distillation may be carried out by the intermittent system or the continuous system.

By the Intermittent System batches of oil are treated in separate cylindrical stills, the crude stills being as much as 45 feet long and 12 feet in diameter, holding about 1000 barrels of crude. The distillation may be carried to a finish in the crude stills, as in the Tower vertical still, or the crude may only be freed from the lighter fractions (gasolenes and kerosenes), and the residue, known as tar, transferred to other stills (tar stills), holding about 250 barrels each, in which the final distillation takes place.

By the Continuous System the crude oil passes slowly but continuously through a row of stills, perhaps ten in number, all connected together. The stills are placed at lower and lower levels, so that the crude flows by gravity from the first to the last still, passing through all the stills one after the other. Each still is heated to a higher temperatiu^ than the previous one, so that a definite distillate is being taken out from each still, and the character of the distillates can be varied at will by regulating the temperatures of the various stills and the rapidity of the flow of crude. This system is largely used in Russia and is rapidly gaining favor in America and Mexico.

Cracking. — The crude itself or certain distillates are cracked when it is desired to produce a maximum amount of light fractions. When hydrocarbons are suddenly heated to a temperature above their boiling points and not given time to distil in the ordinary way, they decompose into simpler hydrocarbons which possess lower boiling points; this process is called '' cracking. '^

When crude oil (after gasolenes and kerosenes have been removed) is slowly heated for a prolonged period, the oil falls back from the cooled top of the stills into the hot liquid, and in this way a large portion of kerosene is produced from the heavier fractions of. the crude. This process is, however, slow, and experience has shown that quicker and more effective results can be obtained in special cracking stills, heated to a high temperature, into which the kerosene, gas oil, or other heavy oil is sprayed. The effect of cracking on the lubricating oils is that viscous oils are decomposed into low-viscosity oils. In certain cracking processes the oil is cracked under a pressure of several atmospheres, which further increases the yield of lower boiling point fractions. These improved cracking stills are responsible for the large increase in production of cracked motor spirits and kerosenes which has taken place during recent years to meet the increased demand for motor spirits.

With every cracking process a certain amount of unsaturated hydrocarbons is formed, but most of the undesirable ones may be removed by treatment with sulphuric acid or by filtration through Fuller's earth or like material.

Steam DistiUation. — When it is desired to produce a maximum amoimt of lubricating oils and to minimize cracking, the stills in addition to being heated by fire externally are heated internally by live superheated steam, introduced directly into the body of the oil near the bottom of the stills, so as to mix well with the oil and also to prevent overheating of the still bottom. To increase further the yield of lubricating oils and to prevent overheating, the oils may be distilled under a partial vacuum, as the vacuum causes the various fractions to distil over at lower temperatures.

When the distillation is assisted by the application of steam with or without vacuum, a lower percentage of imsaturated hydrocarbons is formed than when distilling without steam, and less acid or treatment is therefore required when refining the distillates.

Redistillation. — Usually the crude is split into only a few fractions, which may be further separated into a greater number of fractions by redistillation. For example, crude gasolene is redistilled by steam distillation into light and heavy gasolene, and the residue may be used as first-grade turpentine substitute or kerosene stock. Crude kerosene is similarly redistilled into the particular grades of kerosene desired, and if the crude kerosene contains too light fractions, these may be utilized as a second-grade turpentine substitute, whereas too heavy fractions are mixed with the gas oil distillates. Lubricating oil distillates are also redistilled, by fire and live steam distillation with or without vacuum, and separated into heavier and lighter lubricating oils.

PBTROLEITM PRODUCTS

When the light fractions, viz. gasolenes (distilling over up to 150®C.) and kerosenes (distilling over between 150®C. and 300^C.) have been distilled off, the next distillate is a high flash burning oil called 300 fire test oil, mineral colza, mineral sperm, or mineral seal; but if the quality of this distillate is not such as to produce a satisfactory burning oil, the distillate is called solar oil or gas oil, and is used for making oil gas or carburetted water gas, or as a high class fuel oil for semi-Diesel or Diesel oil engines. Also, when mixed with heavy black residual oils (asphaltic or non-asphaltic) it is used as fuel oil in Diesel engines, or in furnaces using liquid fuel.

The lubricating oil fraction or fractions (from which spindle oils, engine and machinery oils are manufactured) now distil over and if the crude contains wax the distillate containing wax is chilled to about 20~25°F., and in the wax filter press the oils are squeezed out and the wax left in the press. Lubricating oils made^from ^ jiaraffin base crude, therefore, have setting points of about 20-2fi^F. unless they are specially treated to remove "niore of the wax; they may also be blended with other oils having very low setting points so as to produce oils with low setting points.

The wax when removed from the press contains as much as 50 per cent, of oil which is removed by "sweating," viz. slow prolonged heating of the wax. The melting points of the sweated wax range from lOO^F. to 130**F.; it is melted, crystallized in molds, and sold as white paraffin wax used chiefly for making candles, also for preserving fruit and jellies, for polishing floors, etc.

The pressed lubricating oils are redistilled into heavier and lighter oils and either treated by sulphuric acid or filtered through FtMer's earth or bone black (animal charcoal) in order to remove unstable hydrocarbons or other undesirable elements, and to lighten the color.

Sunbleaching, exposing the oil in shallow troughs, has the effect of forming a heavy sludge of the unstable elements, which sinks to the bottom and the oil becomes lighter in color. After exposure for some time the oil commences to darken, and the sunbleaching process should then be stopped, as otherwise the oil is injured.

After the oil has been treated with acid in vertical, lead-lined agitators it is washed with water, neutralized with an alkali, washed again with water to remove the alkali, and finally blown with hot air to remove the last traces of moisture; it should then be bright and transparent, and be free from acid or alkali.

When filtered through Fuller's earth or animal charcoal the first few gallons of oil which come out are colorless, but as the filtering material becomes saturated with the absorbed impurities and coloring matter the color of the oil gradually darkens. Each grade of oil is filtered to be within the standard j^olocJimit^ for that particular grade.

Dark Cylinder Stock. — ^When the distillates containing the light and heavy lubricating oils have passed off there remains in the still a very heavy viscous dark oil used principally for internal lubrication of steam engine cylinders and valves. If it contains more than a trace of asphalt it should not be used as a cylinder oil, but may be mixed with light viscosity lubricating oils to produce dark lubricating oils.

Filtered cylinder stock is produced from dark cyUnder stock

;' by filtration; the color becomes green, amber; the heavy gravity

tarry matter is removed, the viscosity is reduced 15 per cent.

to 25 per cent, and the specific gravity is likewise reduced, but the

I setting point is increased.

1 Petroleum jeUy (mineral jelly, petrolatum) is an amorphous wax produced by slow cooling of dark cylinder stock diluted with gasolene; the petroleum jelly separates out and is afterwards refined (decolorized) by hot filtration. Petroleum jelly is used in the manufacture of cordite (an addition of 2 per cent, of jelly makes the cordite less brittle), as an anti-rust grease, for ointments (veterinary purposes), etc., etc. Vaseline is the proprietary name given to a certain high grade petroleum jelly.

Cold Test Cylinder Stock. — ^By distilling oflf the gasolene from the liquid portion a low cold test cylinder stock is produced, which may be further refined by filtration.

Cylinder stocks are almost exclusively produced from paraffin base crudes^ When a paraSin base crude is crScBeT* during" [stillation and it is not desired to produce cylinder stock, the cracking of the heavy distillates produces carbon, so that as much as 5 per cent, of the crude may remain in the still in the form of petroleum coke, which is used for smelting furnaces, for electric arc carbons, or as refinery fuel, according to its quality.

When asphaltic base crudes are distilled, cylinder stock can rarely be produceJ"; the residue consists ©rasphaltic matter.' Heavy liquid asphaltic residues are used as road spraying ma'^ terial in place of coal tar, and are also used in the manufacture of various liquid fuels.

Petroleum pitch or bitum^en has found a most important use, chiefly in the making of wearing surfaces for modem roads; also for roofing felts, bituminous paints, etc. It is also used in the making of hot neck greases for steel works rolling mills.

When the liquid bitumen in the stills is "blown" with air, it oxidizes into blown asphalt, which has a rubbery nature and finds an important use as rubber substitute, for roofing felt, etc.

SHALE OIL

Oil shale is a dark grey or black mineral yielding about 23 gallons of crude shale oil per ton of shale. By distillation is produced crude naphtha, green oil, and coke. The crude naphtha is redistilled and yields mainly motor spirit. The green oil yields paraffin wax, kerosene, fuel oil, gas oil, and lubricating oils.

The lubricating oils are of very low vicosity and are chiefly used as batching oils (for softening the fibres of flax, jute, etc., during their process of manufacture into yarns) ; they contain a large percentage of unsaturated hydrocarbons (olefines). The setting point is about 32®F. When used as lubricants they are rarely used alone but are usually mixed with 5 per cent, to 15 per cent, of fixed oil (sperm, whale or lard) to increase their oiliness; they can then be used for lubricating light, quick running spindles and machinery, but are inclined to gum on account of the presence of highly unsaturated hydrocarbons.

CLASSIFICATION OF LUBRICATING OILS

Dark Cylinder Ofls. — Dark cylinder oils are the undistilled dark residues left in the stills (by steam distillation chiefly of non^asphaltic crude), freed from solid impurities but not filtered. They are chiefly used for lubrication of steam engine cylinders and valves, either alone or mixed with from 3 per cent, to 10 per cent, of acidless tallow oil. The ordinary characteristics are as follows:

Flash point open From 600°F. to 620°F. (>^^>^ ^^^^ )

Specific gravity From 0.900 to 0.916

Saybolt viscosity at 212*'F 135 sec. to 260 sec.

Color, in reflected light Dark brown or dark green to black

Color in transmittent light Dark brown to black

Filtered Cylinder Oils. — Filtered cylinder oils are made from dark cylinder oils by filtration. They represent the highest quality oils used for internal lubrication of steam engines; they are used either alone or mixed with from 3 per cent, to 12 per cent, of acidless tallow oil. They are also largely used for mixing with lower viscosity oils to produce heavy viscosity oils for internal combustion engines, or heavy viscosity engine and machinery oils, air compressor oils, circulation oils, etc. *

Specific gravity From 0.876 to 0.895

Saybolt viscosity at 212*F 100 sec. to 160 sec.

Color, in reflected light Green, amber

Color in transmittent light Deep red

Red Oils. — ^Red oils are fire-distilled (with or without steam) acid treated oils. They represent a large portion of the medium and heavy viscosity oils used for general lubrication of engines, shafting and machinery of all kinds. Mixed with filtered cylinder oil, red oils produce very heavy viscosity engine and machinery oils.

They must not be used for circulation service as in steam turbines, because they do not separate well from water, causing emulsification and objectionable deposits.

Red oils, made from paraffin base crude, are not very satisfactory for making oils for internal combustion engines, as they produce a great deal of hard and brittle carbon. When made from asphaltic base crudes, they produce less carbon deposit and it is of a soft crumbly nature.

The heavy red oils, when mixed with from 5 per cent, to

A a

20 per cent, of fixed oil (blown or unblown) produce some of the lighter viscosity marine and railway engine oils.

Flash point open 380**F. to 440^F. (ws-*ax>^ A

Specific gravity ' 0.900 to 0.916 ^^'^ J

Saybolt viscosity at 70''F 600 sec. to 1,600 sec.

Color Red

Setting point (paraffin base) 20''F. to 30*F.

Setting point (asphaltic base) O^'F. to 20''F.

Pale Oils. — Pale oils are fire distilled (with or without steam) , heavily acid treated or heavily filtered oils. They are of light to medium viscosity, and are used for lubricating quick-running machinery, such as high speed shafting, electric motors, textile machinery, also for manufacturing yellow lubricating greases. Further, they are used largely for lubricating small and medium size internal combustion engines of all kinds, either alone or mixed with from 3 per cent, to 10 per cent, of fixed oil, or filtered cyUnder oil (when a heavy viscosity oil is required).

Pale oils produce less carbon deposit than red oils when used for lubricating internal combustion engines.

Flash point open 275**F. to 420^F.

Saybolt viscosity at TO'^F 60 sec. to 860 sec.

Color. . . . : Pale

Setting point (paraffin base) 16*F. to 26**F.

Setting point (asphaltic base) O^F. to 16**F.

Neutral Oils. — Neutral oils are steam or fire distilled oils (freed from paraffin wax, if wax is present), sunbleached and filtered through Fuller's earth and when not acid treated are called filtered neutral oils. Most neutral oils are filtered rather than acid treated.

Neutral oils are of light or medium viscosity and used for similar purposes as pale oils; neutral filtered oils are more suitable than pale oils for self oiling bearings, where the oil is used over and over again. Neutral filtered oils are largely used as circulation oils (for enclosed typQ steam engines and steam turbines) either alone or mixed with filtered cylinder oil, as they separate well from water.

By redistillation, or "reducing, " the neutral oils are separated

into (a) viscous and (b) non-viscous neutral oils.

(a) Viscous NeiUral Oils,

Flash point open 350**F. to 400°F.

Saybolt viscosity at 70**F 180 to 600 sec.

Color Pale to light red

Setting point (paraffin base) 16'*F. to 26**F.

Setting point (asphaltic base) O^'F. to 16'*F.

(b) NonMSCOtis Neutral Oils,

Flash point open 320°F. to 360°F.

Saybolt viscosity at TO'^F 70 to 180 sec.

Color Pale

Setting point (paraflBn base) 15**F. to 26'*F.

Setting point (asphaltic base) O^'F. to Id^'F.

Dark Lubricating Oils. — Dark lubricating oils are such undistilled residues from the crude or from the redistillation of lubricating oil distiUates which, because of too low a viscosity or for other reasons, are considered unsuitable as cylinder oils. Dark lubricating oils are usually mixtures of such residues with low viscosity lubricating oils to produce the required viscosity.

Dark lubricating oils are used for rough machinery in collieries and steel works, as cheap oils for lubricating the axles of railway carriages and for making black lubricating greases, for rough service.

Flash point open SOO'^F. to 460°F.

Saybolt viscosity at UO^'F 200 sec. to 350 sec.

Color Dark green or brown to black

Setting point lO^F. to OO'^F.

Asphalt Less than 5 per cent.

Viscous Low Setting Point Ofls. — These oils are fire distilled and made from non-paraffinic base crude, acid treated and filtered. They are chiefly used in the manufacture of heavy viscosity railway and marine engine oils, compounded with from 10 per cent, to 25 per cent, of fixed oil (blown or unblown) ; they are also largely used in the manufacture of heavy viscosity oils for internal combustion engines, as they produce only a little carbon deposit, and the carbon is soft. As motor car oils they give easy starting from cold on account of their low setting points.

Flash point open 385**F. to 416^F.

Saybolt viscosity at 70*'F 1200 to 4000 sec.

Color Pale to red

Setting point Zero F. to 20°F.

Non-viscous Low Setting Point Oils. — These oils are either fire distilled or steam distilled, acid treated or acid treated and filtered; they may possess a naturally low setting point (when made from a non-paraffinic base crude) or they are cold pressed at zero or an even lower temperature to extract the wax and to give the desired low setting pomt.

Non-viscous low setting point oils are chiefly used in the manufacture of oils for refrigerator compressors on account of their low setting points; very low setting point oils are used for lubricating certain parts of high-flying aeroplanes.

Flash point open 280**F. to SSO^'F.

Saybolt viscosity at TO'^F 80 to 360 sec.

Color Pale or red

Setting point — 40®F. to zero F.

Bloomless Oils. — Bloomless oils are neutral oils which have been highly filtered and may also have been sunbleached; they are very light in color and of Ught viscosity.