Timken Lubrication Guide

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Lubrication Guide

Introduction

Lubricant Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Lubrication Information

Mechanical Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Lubricant Types and Characteristics. . . . . . . . . . . . . . . . . . 4 - 7 Shields and Seals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 11 Lubricants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14, 15 Equations and Formulae. . . . . . . . . . . . . . . . . . . . . . . . . 16, 17 Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18, 19

Lubricant Selection

The purpose of this guide is to help you to recognize the relationship of bearings and proper lubrication. Selection of the proper lubricant is an important design function in the use of bearings, since lubricant affects bearing life and operation. The major functions of lubrication in bearing application are:

to minimize friction at points of contact within the bearing

to protect the precision finishes on bearing surfaces from

becoming corroded

to dissipate heat generated within the bearing

to remove or prevent the entry of foreign matter within the bearing

The Timken Company hopes that this guide will help you to identify lubrication problems and take corrective and preventive measures to keep them from recurring.

Mechanical Forces Within the Rolling Bearings

A major source of the frictional resistance in a ball bearing is sliding between the balls, the races, and the retainer. Additional frictional resistance occurs between the rotating parts and the lubricant.

A third factor contributing to frictional resistance is the deformation of the bearing parts under load. When a ball in a bearing is subjected to load, a deformation of both the ball and the race results. This deformation causes an elliptical area of contact between the ball and the race. The amount of deformation is a function of the elasticity of the materials used, the ball size, race geometry, and the magnitude and direction of the applied load.

Rolling Ball Under Vertical and Tangential Load

When a ball is motionless, the load is distributed symmetrically on the ball and the race within the contact area. When a tangential load is applied, causing the ball to roll, the material in the race bulges in front of the ball and flattens out behind the ball. The ball flattens out in the lower front quadrant and bulges in the lower rear quadrant.

Contact Ellipse Formed by Ball and Race

One part of the resistance to rolling is accounted for by this elastic deformation of the rolling elements and the races. Another source of energy loss is the actual slippage within the contact areas of the ball and the races. As shown, all points in the contact area are at different distances from the axis of rotation of the ball and rotate at different velocities. However, two points, A and B, roll true and form a line parallel to the axis of rotation and perpendicular to the direction of rolling. All other points in the contact ellipse slide to varying degrees.

The retainer is another source of sliding friction. Depending upon the bearing design, the retainer may be ball or ring piloted. In both cases, sliding friction will occur between the balls and the ball pockets.

Sliding friction also occurs between the retainer and the controlling ring in the ring piloted retainer. The heat generated within the bearing is a consequence of the frictional resistance of the bearing as well as other effects enumerated above.

High pressures exist in the area of contact. In the absence of lubricant, metal to metal pick-up or welding between the balls and the races can occur. High temperatures due to sliding friction between the balls, races and retainer may also cause surface damage.

To prevent these actions from occurring, lubricants having adequate film strength are required. Insufficient film strength allows metal to metal contact within the contact areas. The hydrodynamics of the lubricant may reduce the stresses in the contact area. This is significant because the amount of deformation of the ball and the race bears a direct relationship to frictional resistance and the fatigue life of the bearing.

In both the ball to race contact area and the retainer rubbing areas, sufficient lubricant flow or movement must be maintained to prevent localized heat build-up in the bearing.

Fluid friction, friction within the lubricant itself, is a function of the chemical and physical composition of the lubricant. Friction between the lubricant and the bearing components is a function of the characteristics of the lubricant and the design of the bearing. All of these factors contribute significantly to the frictional resistance of the bearing and must be considered when selecting the proper lubricant. Of equal importance when selecting a lubricant for a specific application, are the actual operating conditions in addition to the bearing’s characteristics.

Rolling Ball Under Vertical and Tangential Load

Lubricant Types

Two basic types of lubricants–oils and greases–are used with anti-friction bearings. Each has its advantages and limitations.

As a liquid, oil lubricates all the surfaces and is able to dissipate heat from these surfaces more readily. Oil retains its physical characteristics over a wide range of temperatures, making it ideal for high speed and high temperature applications. The quantity of oil supplied to the bearing may be controlled accurately allowing for better circulation, cleansing and cooling.

As a thicker substance, grease can seal a bearing better than oil, while allowing seal design simplification. It can be confined easily in the bearing housing, and permits prelubrication of sealed or shielded bearings.

Advantages of Oil and Grease Oil

Better for high speed operation. Easier dispersion over bearing surfaces. Diffuses heat quicker because of viscosity.



Easier to handle and control amount of lubricant reaching the bearing.

Variety of ways to deliver oil (drip, wick, circulation, batch, air-oil mist) make it easier to introduce into bearing.

Easier to keep clean for recirculating systems.

Easily controlled lubrication. Carries away moisture and particulate matter.

Coatings and Surface Treatments

Grease

Clings to surfaces better. Is squeezed out of roller path to lesser extent.

Easier to retain in bearing. Lubricant loss is lower than oil loss. Generally requires less frequent lubrication.

Lasts longer and protects better than oil.

Acts as an efficient bearing sealant. Allows seal design simplification.

Easily confined in housing, an important plus in food, textile and chemical industries.

Coatings and surface treatments specifically developed to protect bearings from rusting, reduce wear, increase hardness and lubricity are available. Among them:

Electro-Plating

The coating of metal parts with another metal by means of ionic bonding, through the introduction of electric charges in the presence of a chemical agent.

Electroless-Plating

The coating of metal parts with another metal by means of ionic bonding, through the application of heat and chemical agents.

PVD (Physical Vapor Deposition)

The coating of metal surfaces with low temperature plasma coatings.

CVD (Chemical Vapor Deposition)

The coating of metal with alloys similar to electroless plating.

Solid Lubricants

Coatings and treatments at area of surface-to-surface interface which intentionally wear onto surfaces to ease interaction and contact.

Examples of these coatings are Fafnir TDC™ (Thin Dense Chrome) Electro-less Nickel, Cadmium Plating, Molybnium Disulfide, Titanium Nitride, gold/silver/brass flake and Teflon®/Nomex®.

LUBRICANT TYPES AND CHARACTERISTICS

Lubrication Delivery Systems

Oil-Bath Lubrication

The conventional oil-bath system for lubricating bearings is satisfactory for low to moderately high speed applications. Because this type of system is non-circulating, the static oil-level should never be higher than the center of the lowest positioned rolling element in the bearing being lubricated. A greater amount of oil can cause churning, increase the fluid friction within the bearing and result in excessive operating temperatures.

Unless the running level of the oil is known, oil level should be checked only when equipment is shut down as the running level can drop considerably below the static level depending on the speed of the application.

Because speed, sealing effectiveness, temperature and type of oil are factors that influence the refilling cycle, regular inspection is necessary to determine the frequency of refilling. Applications of this type generally employ sight gages to facilitate inspection.

Wick-Feed Lubrication

Wick-feed oilers, one of the older methods of applying oil to bearings, still enjoy a certain popularity. Properly designed, applied and maintained, then are effective and inexpensive.

Functioning as a filter and quantity regulator, the wick employs either capillary action, or gravity (see illustration) to transfer the oil from the reservoir to bearing.

Paraffinic lubricating oils may also be used with this type oiler although they have a tendency to deposit wax crystals on the wick fibers, destroying the effectiveness of the wick. Because napathetic and synthetic oils do not exhibit this tendency, they are preferred for wick oilers.

Drip-Feed Lubrication

Another one of the older methods of lubrication of oiling bearings is the drip-feed system. This system has been applied successfully to applications where moderate loads and speeds are encountered. The oil introduced through a filter-type, sight feed oiler, has a controllable flow rate which is determined by the operating temperature of the particular application.

Oil -Splash Lubrication

This system of lubrication is used primarily in gear cases where the bearing and gear lubricant is common. The lubrication of bearings in a gearbox, other than one of slow speed, is usually not critical as the oil splash from gear teeth is sufficient to lubricate the bearings.

Because of the constant problem of the oil carrying wear debris, the use of filters and magnetic drain plugs is helpful in reducing the possibility of wear debris contaminating the bearings.

In applications where heavy oil flow or splash is encountered, bearings equipped with shields to reduce the quantity of oil reaching the bearings are sometimes necessary to prevent overheating caused by fluid friction where the bearing is flooded.

In systems where normal splash or washdown is expected to be marginal, oil feeder trails should be designed into the case to direct case washdown into the bearings.

Wick-Feed Lubrication

Drip-Feed Lubrication

Oil-Splash Lubrication

LUBRICANT TYPES AND CHARACTERISTICS

Lubrication Delivery Systems

Circulating-Oil Lubrication

This type of system utilizes a circulating pump to assure a positive supply of lubricant to the bearing and can be used for low to moderately high speed and high temperature power transmission applications.The flow path of the oil in this system is important because bearing churning in a captive amount of oil can generate temperatures capable of causing lubricant breakdown and bearing damage. Due to the inherent possibility of contamination from wear debris in heavy duty applications, suitable oil filters and magnetic drain plugs are necessary to prevent damage to the bearings.

Oil-Jet Lubrication

In applications where a bearing is heavily loaded and operating at high speed and temperatures, a sophisticated variation of circulating oil lubrication, called oil-jet lubrication, may be required. In such cases, it is necessary to lubricate each bearing location individually, under pressure, and to provide adequately large scavenging drains to prevent the accumulation of oil after passage through the bearing. In certain high speed applications where the bearing itself creates a pumping action, the flow of oil must be adjusted to assure passage through the bearing. This is extremely important where the flow of oil from the jet opposes the pumping action within the bearing.

Oil-Mist Lubrication

Oil-Mist Lubrication systems are used in high-speed, continuous operation applications. This system permits close control of the amount of lubricant reaching the bearing. The oil may be metered, atomized by compressed air and mixed with air, or it may be picked up from a reservoir using a venturi effect. In either case, the air is filtered and supplied under sufficient pressure to assure adequate lubrication of the bearings. Control of this type of lubricating system is accomplished by monitoring the operating temperatures of the bearings being lubricated.

The continuous passage of the pressurized air and oil through the labyrinth seals used in the system prevents the entrance of contaminants from the atmosphere into the system.

To insure “wetting” of the bearings and to prevent possible damage to the rolling elements and races, it is imperative that the oil-mist system be turned on for several minutes before the equipment is started. The importance of the “wetting” the bearings before starting cannot be overstressed and has particular significance for equipment that has been idle for extended periods of time.

The successful operation of this type of system is based upon the following factors:

proper location of the lubricant entry ports in relation to the bearings being lubricated

avoidance of excessive pressure drops across void

systems within the system

the proper air pressure and oil quantity ratios to suit the particular application

the adequate exhaust of the air-oil mist after lubrication has been accomplished

Circulatory-Oil Lubrication

Air-Oil-Mist

Lubrication Delivery Systems

Oil Quantity

Normally, not more than a thin film of oil is required to lubricate a bearing. Experience has shown that when the oil quantity is increased to more than just enough to form a film on the bearings, fluid friction and friction torque will increase. In applications where generated heat is a critical factor, increased quantities of oil are used as a heat transfer medium.

Pre-Packed Bearings

Bearings which are utilized in moderately high speed applications are supplied with the proper amount and type of grease pre-packed in the bearing. Prelubricated Timken® Torrington® bearings are prepacked with greases which have chemical and mechanical stability and that have demonstrated long-life characteristics in rotating bearings. Greases are filtered several times to remove all harmful material and accurately metered so that each bearing receives the proper amount of grease.

Prelubricated shielded and sealed bearings are extensively used with much success on applications where:

Grease might be injurious to other parts of the mechanism

Costs and space limitations preclude the use of a

grease-filled housing

Housings cannot be kept free of grit, water or other contaminants

Relubrication is impossible or would be a hazard to satisfactory use

Housed Bearings

Applications utilizing grease lubrication should have a grease fitting and vent on opposite sides of the housing near the top. A drain plug should be located near the bottom of the housing to allow purging of the old grease from the bearing.

Relubricate at regular intervals to prevent damage to the bearing. Relubrication intervals are very difficult to determine. If plant practice or experience with other applications is not available, consult your lubricant supplier or a Timken sales engineer.

Grease Quantity

There is no set formula to determine the exact amount of grease necessary to lubricate a bearing because the quantity is directly dependent upon such factors as the application, the bearing and retainer design and the type of grease used. Certain bearings of the high precision types used in high speed applications may have as little as 20 percent of the bearing void filled with grease. Other bearings of the types used in low speed applications may have as much as 80 percent of the bearing void filled with grease. Aircraft bearings of the oscillating types may be 100 percent filled with grease. Even within the limits of a given application, the quantity of grease may be dependent upon the type of grease selected. For example, two different grades of grease, one a NLGI Grade #1 and the other a NLGI Grade #4, have proved to be suitable lubricants for machine tool spindle bearings. However, because the Grade #1 grease has a tendency to churn, a lesser amount must be used in a given bearing as compared to the amount of a Grade #4 grease is a channeling type which does not churn; consequently, the amount used in the bearing is less critical. Overgreasing may cause a rapid temperature rise in the bearing that can damage both the lubricant and the bearing.

If the operating temperature must be outside of the above range or if the seals are exposed to unusual fluids please consult your nearest Timken sales associate.

Compatibility of Seals and Lubricants

Buna N

Buna N is also known as Acrylonitrile which is often shortened to Nitrile. Buna N has greater resistance to petroleum oils, fuels and solvents at higher temperatures than Neoprene. Its compatibility with diester fluids and diester fluid greases made Buna N rubber an immediate success for bearing seals. The changeover from Neoprene to Buna N Ply-Seals began in early 1946. Because of its compatibility with fuels and lubricants, its excellent wear characteristics, easy moldability and low cost, Buna N has been and still is the most widely used seal material.

Buna N becomes stiff and brittle with extended exposure at 250°F so it is generally limited to service below that temperature.

Polyacrylic

Polyacrylic, also referred to as PA, is a copolymer of ethyl acrylate and chlorethylvinyl ether. Polyacrylic has excellent wear characteristics, petroleum oil and fuel compatibility and is capable of withstanding temperatures up to 320°F. Polyacrylic seals are not compatible with diester oils or greases.

Fluoro-Elastomer

The increased demand for equipment to operate at higher temperatures has led to the development of the Fluoro-Elastomer type seals. This group includes materials such as the fluorinated hydro-carbons which are copolymers of vinylidine fluoride and hexafluoropropylene (Viton) and also fluorinated silicone which, as the name implies, is a fluorine containing silicone elastomer. This family is noted for its exceptional heat resistance and compatibility with various fluids, especially petroleum products at higher temperatures than the other elastomers discussed.

This family of elastomers includes many trade names such as Viton, Teflon, Kel F, and Fluorothene. Although some of these are more correctly classified as plastics, they are used as sealing materials. Of this group only Viton and Teflon have been used in any quantity for bearing seals.

The cost of these materials is sufficiently higher than other elastomers so that very special applications are required to justify their use. Temperature range is –65°F to +450°F

Bonded Teflon Seals

Teflon or polytetrafluoroethylene (PTFE) is a relatively soft, white, waxy, inert non-toxic resin closely resembling a thermoplastic.

PTFE is used as bearing seal material because of its chemical inertness and wide thermal range (–125°F to +500°F). PTFE is a less effective seal material than elastomers primarily because it lacks wear or abrasion resistance.

Pillow Block Seal

The Dustac™ Shaft seal is for extremely contaminated environments, such as might be encountered by roller bearing pillow blocks located in taconite mines.

A Dustac seal shuts out residual and air-borne contaminants even better than the triple ring labyrinth shaft seal.

The Dustac shaft seal is a patented device utilizing a V-shaped nitrile ring which rotates with the shaft and applies pressure to the cartridge face to exclude contaminants. The geometry of this seal also enhances the excluding effect of centrifugal force.

Properties of Seal Materials

Property Type of Material Base

Nitrile (Buna N) Poly-acrylic Viton Teflon Neoprene

Tear Resistance Fair Good Good Good Good

Abrasion Resistance Good Good Good Poor Excellent

Aging Sunlight Oxidation Heat (max. temp.) Static (shelf) Poor Fair 250°F Good Good Excellent 350°F Good Excellent Excellent 400°F Good Excellent Excellent 500°F Excellent Excellent Good 225°F Good

Flex Cracking Resistance Good Good Good Good Excellent

Compression Set Resistance Good Good Excellent Poor Excellent

Lubricant Resistance Low Aniline Mineral Oil High Aniline Mineral Oil Silicones Diesters Phosphate Esters Silicate Esters Excellent Excellent Fair Fair Poor Fair Excellent Excellent Good Poor Poor Poor Excellent Excellent Excellent Good Good Good Excellent Excellent Excellent Excellent Excellent Excellent Fair Good Fair Poor Poor Poor

Solvent Resistance Aliphatic Hydrocarbon Aromatic Hydrocarbon Halogenated Solvent Keytones Good Fair Poor Poor Excellent Poor Poor Poor Excellent Excellent Good Poor Excellent Excellent Excellent Excellent Fair Poor Poor Poor

Gasoline Resistance Aromatic Non-Aromatic Good Excellent Good Good Excellent Excellent Excellent Excellent Poor Good

Acid Resistance Dilute (under 10%) Concentrated Good Poor Poor Poor Good Good Excellent Excellent Fair Poor

Alkali Resistance Dilute (under 10%) Concentrated Good Fair Poor Poor Good Poor Excellent Excellent Good Poor

Low Temperature Flexibility (max.) –65°F –55°F –65°F –125°F –65°F

Resistance to Gas Permeation Fair Good Good Excellent Good

Water Resistance Good Poor Good Excellent Fair

Resilience Fair Fair Good Fair Good

Lubricant Selection

The successful application of lubricating fluids in bearings depends on the physical and chemical properties of the lubricant as they pertain to the bearing, its application, installation and general environmental factors.

Viscosity

Generally, the most important single property of a lubricating fluid is its viscosity. Viscosity is the measure of the relative resistance of a fluid to flow.

The measurement of viscosity can be made by any of a number of different instruments called viscosimeters. A common unit of measure is the Saybolt Universal Second (SUS). This is the time, in seconds, required for 60 c.c. of a fluid to flow through a standardized orifice under a standard head, at a given temperature. The common temperatures for reporting viscosity are 100°F to 210°F. The higher the viscosity number, the greater the resistance to flow.

Experience indicates that a lubricating fluid with a viscosity of at least 100 SUS at the operating temperature of the application will be adequate for normal lubrication of bearings.

Viscosity Index

The ideal oil (as far as viscosity is concerned) would be the same viscosity at all temperatures. All oils become less viscous (thin-out) when heated and more viscous (thicken) when cooled.

However, all oils do not vary in viscosity to the same extent. Some thicken more rapidly or thin more rapidly than others.

The term “viscosity index” or VI is used to rate oils according to their temperature-viscosity behavior.

Oils with the highest viscosity index are more resistant to changes in viscosity with changes in temperature than lower viscosity index oils. Obviously high viscosity index lubricants are most suitable for bearing applications experiencing wide temperature variations.

NLGI Grease Grades Penetration Number

0 1 2 3 4 5 6 355-385 310-340 265-295 220-250 175-205 130-160 85-115

Pour Point

The pour point is the lowest temperature at which a fluid will flow or can be poured. It is important in applications exposed to low temperatures that the lubricating fluid selected has a pour point lower than the minimum ambient temperature.

The Oil Viscosity Selection Chart may be used to approximate

the proper oil viscosity for all bearing applications.

To use the chart proceed as follows:

1.

Determine the DN value – Multiply the bore diameter of the bearing, measured in millimeters, by the speed of the shaft, measured in revolutions per minute.

2.

Select the proper temperature – The operating temperature of the bearing may run several degrees higher than the ambient temperature depending upon the application. The temperature scale of this chart reflects the operating temperature of the bearing.

3.

Enter the DN value in the DN scale on the chart.

4.

Follow or parallel the “DOTTED” line to the point where it intersects the selected “SOLID” temperature line.

5.

At this point follow or parallel the nearest “DASHED” line downward and to the right to the viscosity scale.

6.

Read off the approximate viscosity value – expressed in Saybolt Universal Seconds at 100°F

Lubricant Selection

Oxidation Resistance

The most important property of an oil, from a quality standpoint, is its chemical or oxidation stability.

All lubricating fluids are subject to a continual chemical combination with oxygen to form a multitude of compounds. The initial reaction generally results in the formation of unstable hydroperoxides which react to form such compounds as alcohols, aldehydes, keytones, acids and oxyacids. Subsequently, through polymerization and condensation reactions, oil in soluble gum, sludge and varnish will be formed. This can reduce bearing clearances, plug lines, increase operating temperature and further accelerate lubricant deterioration which will end with bearing failure.

Lubricating fluids vary in ability to resist oxidation effects. Oxidation stability is dependent upon the fluid type, refining methods and whether or not, oxidation inhibitors are present. In a circulating or splash system the oxidation rate is not only a function of the oil, but also of the operating conditions. Temperature, contaminants, water, metal surfaces and agitation all favor oxidation and all are present in lubrication systems.

Temperature Impact on Lubricant

Temperature is primarily an accelerator of oil oxidation. The rate of any chemical reaction including the oxidation of hydrocarbons will double for every 18°F increase in temperature. It is estimated that the life of an oil be decreased 50% for every 18°F temperature rise above 140°F and increased 50% for reductions in temperature of 18° below 140°F.

Metal Effect on Lubricant

Metal, particularly copper, and copper containing alloys are known catalysts for oil oxidation and their catalytic effect is greatly enhanced by water or water containing contaminants.

Additives to Lubricants

Present day lubricating fluids are formulated with chemical additives to increase the viscosity index, increase oxidation resistance, provide detergent properties, resist corrosion, provide extreme pressure properties and lower the pour point.

Grease Selection

Sodium, lithium and polyurea base greases are normally preferred for general purpose bearing lubrication. Lime base greases are advantageous for high moisture applications but should not be operated above 150°F. Lithium complex greases have good water resistant characteristics and may be operated through the same temperature range as sodium base greases. Polyurea greases have excellent water resistance and can be used at higher temperatures.

The grease must be carefully selected with regard to its consistency at operating temperature. It should not exhibit thickening, separation of oil, acid formation or hardening to any marked degree. It should be smooth, non-fibrous and entirely free from chemically active ingredients. Its melting point should be considerably higher than the operating temperature of the bearing.

Frictional torque is influenced by the quantity and quality of lubricant present. Excessive quantities of grease causes churning. This results in excessive temperatures, separation of the grease components and break-down in lubricating valves. On normal speed applications the housings should be kept approximately one-third to one-half full.

Only on low speed applications may the housing be entirely filled with grease. This method of lubrication is a safeguard against the entry of foreign matter, where sealing provisions are inadequate for exclusion of contaminants or moisture.

During periods of non-operation, it is often wise to completely fill the housings with grease to protect the bearings surfaces. Prior to subsequent operation, the excess grease should be removed and the proper level restored.

Lubricating Grease Temperature Ranges

Typical Dropping PT Usable* Temp. Typical Water Resistance

Thickener F C F C

Sodium Soap Lithium Soap Polyurea Lithium Complex Soap 500+ 380 460 500+ 260+ 193 238 260+ 250 220 300 250 121 104 149 121 Poor Good Excellent Good

* Continuous operation with no relubrication. Depending on the formulation, the service limits may vary. The usable limit can be extended significantly with relubrication.

Note: The properties of a grease may vary considerably depending on the particular oil, thickener and additives used in the formulation.

By expanding the formula:

Fluids + Thickening + Special = Lubricating Agents Ingredients Grease

it is possible to show the combinations possible for formulating greases to meet a wide range of operating conditions.

Fluids + Thickening Agents + Special Ingredients = Lubricating Grease

Mineral Oils Soaps Oxidation Inhibitors

Esters Lithium, Sodium Rust Inhibitors

Organic Esters Barium, Calcium VI Improver

Glycols Strontium Tackiness

Silicones Non-Soap (Inorganic) Perfumes

Microgel (Clay) Dyes

Carbon Black Metal Deactivator

Silica-gel

Non-Soap (Organic)

Urea compounds

Terepthlamate

Organic Dyes

Lubrication Terms

Additive A chemical compound or compounds added to a lubricant for the purpose of imparting new properties or of enhancing those properties which the lubricant already has.

Channeling The tendency of grease to form an unobstructed path or channel following the movement of the rolling elements in a bearing.

CVD – Chemical Vapor Deposition A method of thin coating (3-5 microns) metal parts with metallic alloys through a gaseous medium. The coating adds to the hardness while reducing wear and increasing lubricity of base metal.

EP (Extreme Pressure) Lubricants Lubricants which impart to rubbing surfaces the ability of carrying appreciably greater loads than would be possible with ordinary lubricants without excessive wear or damage.

Fiber Grease Grease having a distinctly fibrous structure which is noticeable when a sample of the grease is pulled apart. Greases having this fibrous structure tend to resist being thrown off gears and out of bearings.

Flash Point (Cleveland Open Cup) The temperature to which a combustible liquid must be heated to give off sufficient vapor to form momentarily a flammable mixture with air when a small flame is applied under conditions. (ASTM Designation D 92-57).

Grease A lubricant composed of an oil or oils thickened with a soap, soaps or other thickener to a semi-solid or solid consistency.

Lime Base Grease A grease prepared from a lubricating oil and a calcium soap.

Lithium Base Grease A grease prepared from a lubricating oil and a lithium soap.

Lubricant Any substance interposed between two surfaces in relative motion for the purpose of reducing the friction and/or wear between them.

NLGI National Lubricating Grease Institute

Oil A viscous, unctuous liquid of vegetable, animal, mineral, or synthetic origin.

Penetration or Penetration Number The depth, in tenths of a millimeter, that a standard cone penetrates a semi-solid sample under specified conditions (ASTM Designation D 217-60T.) (See Worked Penetration.)

Polyurea Base Grease A grease prepared from a lubricating oil and a polyurea thickener.

Pour Point The pour point is the lowest temperature at which a fluid will flow or can be poured.

PVD – Physical Vapor Deposition A thin metal-plasma coating (2-5 microns) that is applied in a low heat temperature environment (350°F to 600°F) which can be applied to standard metal surfaces to help resist wear while increasing lubricity and hardness.

SAE Numbers – SAE Viscosity Classification. Numbers applied to crankcase, transmission and rear axle lubricants to indicate their viscosity range.

Lubrication Terms

Saybolt Universal Viscosity, SUV (or Saybolt Universal Seconds, SUS) The time in seconds required for 60 cubic centimeters of a fluid to flow through the orifice of the Standard Saybolt Universal Viscometer at a given temperature under specified conditions. (ASTM Designation D 88-56.)

Soda-Base Grease A grease prepared from lubricating oil and sodium soap.

Thixotrophy The characteristic of grease to soften under shear and return to original state when shearing force is removed.

Viscosity That property of a fluid, semi-fluid or semi-solid substance which causes it to resist flow. It is defined as the shear stress on a fluid element divided by the rate of shear. The standard unit of viscosity in the English system is the dyne which has units of 16 sec/in2. The standard unit of viscosity in the CGS. system is the poise which has the units of dyne sec/cm. 1 dyne = 6.895 x 104 poises.

Viscosity Index (VI) A commonly used measure of a fluid’s change of viscosity with temperature. The higher the viscosity index the smaller the relative change in viscosity temperature.

“Wetting” Bearings The pre-lubrication of bearing surfaces prior to starting a machine that has been idle for an extended period of time. Prevention of possible brinel damage to bearing components upon sudden dry start of a machine.

Worked Penetration The penetration of a sample of lubricating grease immediately after it has been brought to 77° F and then subjected to 60 strokes in a standard grease worker. (ASTM Designation D217-60T).

Newton’s Law

Force = dynamic viscosity x area x velocity film thickness

F= . • A • V h

F = Force, Newton (N)

. = dynamic viscosity

A = area, square meters (m2)

V = velocity, meters per second (m • s-1)

h = film thickness, meter (m)

Dynamic Viscosity

Fh

. =•

AV FN

= consists of units of pressure or pascal (Pa) -SI System. A m2

hm

= consists of units of time or seconds (s) -SI System.

s-1

V m •

therefore: dynamic viscosity, . = pascal seconds, Pa · s.

or

cgs system unit of dynamic viscosity - poise (P)

for convenience both systems can be related as follows: 1 millipacal second = 1 centipoise or 1 mPa • s = 1 cP

Kinematic Viscosity

Kinematic viscosity = dynamic viscosity density

or

.

v=

p

v = kinematic viscosity kg

. = dynamic viscosity, Pa • s = (in base units) m • s

p = density, kg m3

Conversion of Pa • s to kg

m • s

Pa = Nm2 by definition

N= kg • m s2 by definition

therefore:

Pa• s = N • s = kg • m • s = kg

m2 m2 • s2 m • s

therefore:

v = . p = kg • m • s m3 kg = m2 s (square meters per second)

In the cgs system, v = stoke (st) For most common uses units are related in lower common denominators: 1 millimeter squared per second = 1 centistoke 2

mm

1 = 1 cSt

s

Examples of Viscosity

Examples of the viscosities in the SI units of lubricating mineral oils are shown in the table.

Oil Viscosity

Dynamic Kinematic m Pa · s mm2 · s-1

40°C 100°C 40°C 100°C

Light 7.9 2.1 9.2 2.5

Heavy 1065 50.8 1162 55.4

Viscosity Grade Comparisons

Kinematic Viscosity Saybolt Viscosity

cSt @ 40°C Universal Seconds @ 100°F 10,000

250

—5000

140

—3000

—2000

—1000

—500

—300

—200

2000

1000 —

500 —

300 —

200 —

100 —

50 —

30 —

1500

1000

680

460

320

220

150

100

68

46

32

22

15 8A

8

7

6

5

4

3

2

1 80W

50

40

30

20W

20

10W

5W

90

85W

75W

20 —

—100

10 —10 —60

ISO/ASTM AGMA SAE SAE Viscosity Grades Crank Case Oils Gear Oil

18 / Lubrication Guide

Conversion Tables

TO CONVERT FROM TO MULTIPLY BY VISCOSITY CONVERSION TABLE

Acceleration SUS R’ E cSt

foot/second2 . . . . . . . . . . . . . . . . . . . . . . . . . . meter/second2 . . . . . . . . . . . . . . . . m/s2 . . . . . . . . . . . . . . . . . . . . . . . 0.3048 Saybolt Redwood Engler Centistokes

inch/second2 . . . . . . . . . . . . . . . . . . . . . . . . . meter/second2 . . . . . . . . . . . . . . . . m/s2 . . . . . . . . . . . . . . . . . . . . . . . 0.0254 (sec.) (sec.) (deg.)

Area 35 32.2 1.18 2.7

foot2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . meter2 . . . . . . . . . . . . . . . . . . . . . . . . . m2 . . . . . . . . . . . . . . . . . . 0.09290304 40 36.2 1.32 4.3

inch2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . meter2 . . . . . . . . . . . . . . . . . . . . . . . . . m2 . . . . . . . . . . . . . . . . . . 0.00064516 45 40.6 1.46 5.9

inch2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . millimeter2 . . . . . . . . . . . . . . . . . . . mm2 . . . . . . . . . . . . . . . . . . . . . . . 645.16 50 44.9 1.60 7.4

yard2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . meter2 . . . . . . . . . . . . . . . . . . . . . . . . . m2 . . . . . . . . . . . . . . . . . . . . . 0.836127 55 49.1 1.75 8.9

mile2 (U S. statute) . . . . . . . . . . . . . . meter2 . . . . . . . . . . . . . . . . . . . . . . . . . m2 . . . . . . . . . . . . . . . . . . . . . 2589988 60 53.5 1.88 10.4

Bending Moment or Torque dyne-centimeter . . . . . . . . . . . . . . . . . newton-meter . . . . . . . . . . . N • m . . . . . . . . . . . . . . 0.0000001 kilogram-force-meter . . . . . . . . . . . . . newton-meter . . . . . . . . . . . N • m . . . . . . . . . . . . . . . 9.806650 pound-force-inch . . . . . . . . . . . . . . . . newton-meter . . . . . . . . . . . N • m . . . . . . . . . . . . . . 0.1129848 65 70 75 80 57.9 62.3 67.6 71.0 2.02 2.15 2.31 2.42 11.8 13.1 14.5 15.8

pound-force-foot . . . . . . . . . . . . . . . . newton-meter . . . . . . . . . . . N • m . . . . . . . . . . . . . . . 1.355818 85 75.1 2.55 17.0

Energy B.T.U. (International Table) . . . . . . . . joule . . . . . . . . . . . . . . . . . . . . . J . . . . . . . . . . . . . . . 1055.056 foot-pound-force . . . . . . . . . . . . . . . . joule . . . . . . . . . . . . . . . . . . . . . J . . . . . . . . . . . . . . . 1.355818 kilowatt-hour . . . . . . . . . . . . . . . . . . . megajoule . . . . . . . . . . . . . . . . MJ . . . . . . . . . . . . . . . . . . . . 3.6 90 95 100 110 79.6 84.2 88.4 97.1 2.68 2.81 2.95 3.21 18.2 19.4 20.6 23.0

Force 120 105.9 3.49 25.0

kilogram-force . . . . . . . . . . . . . . . . . . kilopond-force . . . . . . . . . . . . . . . . . . pound-force (lbf avoirdupois) . . . . . . newton . . . . . . . . . . . . . . . . . . . N . . . . . . . . . . . . . . . newton . . . . . . . . . . . . . . . . . . . N . . . . . . . . . . . . . . . newton . . . . . . . . . . . . . . . . . . . N . . . . . . . . . . . . . . . 9.806650 9.806650 4.448222 130 140 150 160 114.8 123.6 132.4 141.1 3.77 4.04 4.32 4.59 27.5 29.8 32.1 34.3

fathom . . . . . . . . . . . . . . . . . . . . . . . . Length meter . . . . . . . . . . . . . . . . . . . . . m . . . . . . . . . . . . . . . . . 1.8288 170 150.0 4.88 36.5

foot . . . . . . . . . . . . . . . . . . . . . . . . . . meter . . . . . . . . . . . . . . . . . . . . . m . . . . . . . . . . . . . . . . . 0.3048 180 158.8 5.15 38.8

inch . . . . . . . . . . . . . . . . . . . . . . . . . . microinch . . . . . . . . . . . . . . . . . . . . . micron (µn) . . . . . . . . . . . . . . . . . . . . millimeter . . . . . . . . . . . . . . . mm . . . . . . . . . . . . . . . . . . . 25.4 micrometer . . . . . . . . . . . . . . . um . . . . . . . . . . . . . . . . . 0.0254 millimeter . . . . . . . . . . . . . . . mm . . . . . . . . . . . . . . . . . 0.0010 190 200 220 167.5 176.4 194.0 5.44 5.72 6.28 41.0 43.2 47.5

mile (U.S. statute) . . . . . . . . . . . . . . . meter . . . . . . . . . . . . . . . . . . . . . m . . . . . . . . . . . . . . . 1609.344 240 212 6.85 51.9

yard . . . . . . . . . . . . . . . . . . . . . . . . . . meter . . . . . . . . . . . . . . . . . . . . . m . . . . . . . . . . . . . . . . . 0.9144 260 229 7.38 56.5

nautical mile (UK) . . . . . . . . . . . . . . . meter . . . . . . . . . . . . . . . . . . . . . m . . . . . . . . . . . . . . . . 1853.18 280 247 7.95 60.5

kilogram-force-second2/meter Mass 300 325 265 287 8.51 9.24 64.9 70.3

(mass) . . . . . . . . . . . . . . . . . . . . . . . kilogram . . . . . . . . . . . . . . . . . kg . . . . . . . . . . . . . . . 9.806650 350 309 9.95 75.8

kilogram-mass . . . . . . . . . . . . . . . . . . kilogram . . . . . . . . . . . . . . . . . kg . . . . . . . . . . . . . . . . . . . . 1.0 375 331 10.7 81.2

pound-mass (Ibm avoirdupois) . . . . . kilogram . . . . . . . . . . . . . . . . . kg . . . . . . . . . . . . . . 0.4535924 400 353 11.4 86.8

ton (long, 2240 Ibm) . . . . . . . . . . . . . kilogram . . . . . . . . . . . . . . . . . kg . . . . . . . . . . . . . . . 1016.047 425 375 12.1 92.0

ton (short, 2000 Ibm) . . . . . . . . . . . . kilogram . . . . . . . . . . . . . . . . . kg . . . . . . . . . . . . . . . 907.1847 450 397 12.8 97.4

tonne . . . . . . . . . . . . . . . . . . . . . . . . . kilogram . . . . . . . . . . . . . . . . . kg . . . . . . . . . . . . . . . 1000.000 475 419 13.5 103

Power 500 441 14.2 108

BTU (International Table)/hour . . . . . watt . . . . . . . . . . . . . . . . . . . . . . W . . . . . . . . . . . . . . . 0.293071 550 485 15.6 119

8TU (International Table)/minute . . . . watt . . . . . . . . . . . . . . . . . . . . . . W . . . . . . . . . . . . . . . 17.58426 600 529 17.0 130

horsepower (550 ft lbf/s) . . . . . . . . . . kilowatt . . . . . . . . . . . . . . . . . . kW . . . . . . . . . . . . . . . 0.745700 650 573 18.5 141

BTU (therrnochemical)/minute . . . . . watt . . . . . . . . . . . . . . . . . . . . . . W . . . . . . . . . . . . . . . 17.57250 700 617 19.9 152

Pressure or Stress (Force/Area) 750 661 21.3 163

newton/meter2 . . . . . . . . . . . . . . . . . . . . . . . . pascal . . . . . . . . . . . . . . . . . . . Pa . . . . . . . . . . . . . . . . . 1 .0000 800 705 22.7 173

kilogram-force/centimeter2 . . . . . . . . . . . kilogram-force/meter2 . . . . . . . . . . . . . . . . pascal . . . . . . . . . . . . . . . . . . . pascal . . . . . . . . . . . . . . . . . . . Pa . . . . . . . . . . . . . . . Pa . . . . . . . . . . . . . . . 98066.50 9.806650 850 900 749 793 24.2 25.6 184 195

kilogram-force/millirneter2 . . . . . . . . . . . . pascal . . . . . . . . . . . . . . . . . . . Pa . . . . . . . . . . . . . . . . 9806650 pound-force/foot2 . . . . . . . . . . . . . . . . . . . . pascal . . . . . . . . . . . . . . . . . . . Pa . . . . . . . . . . . . . . . 47.88026 pound-force/inch2 (psi) . . . . . . . . . . . megapascal . . . . . . . . . . . . . . MPa . . . . . . . . . . . . 0.006894757 950 1000 1200 837 882 1058 27.0 28.4 34.1 206 217 260

Temperature degree Celsius . . . . . . . . . . . . . . . . . . degree Kelvin . . . . . . . . . . . . . . °K . . . . . . . . . . . . tk = tc+ 273.15 1400 1600 1234 1411 39.8 45.5 302 347

degree Fahrenheit . . . . . . . . . . . . . . . degree Kelvin . . . . . . . . . . . . . . °K . . . . . . . . k = 5/9 (tf + 459.67) 1800 1587 51 390

degree Fahrenheit . . . . . . . . . . . . . . . degree Celsius . . . . . . . . . . . . . °C . . . . . . . . . . . . tc = 5/9 (tf - 32) 2000 1763 57 433

Velocity foot/minute . . . . . . . . . . . . . . . . . . . . meter/second . . . . . . . . . . . . foot/second . . . . . . . . . . . . . . . . . . . . meter/second . . . . . . . . . . . . m/s . . . . . . . . . . . . . . . . 0.00508 m/s . . . . . . . . . . . . . . . . . 0.3048 2500 3000 3500 2204 2646 3087 71 85 99 542 650 758

inch/second . . . . . . . . . . . . . . . . . . . . meter/second . . . . . . . . . . . . m/s . . . . . . . . . . . . . . . . . 0.0254 4000 3526 114 867

kilometer/hour . . . . . . . . . . . . . . . . . . meter/second . . . . . . . . . . . . m/s . . . . . . . . . . . . . . . . 0.27778 4500 3967 128 974

mile/hour (U.S. statute) . . . . . . . . . . . meter/second . . . . . . . . . . . . m/s . . . . . . . . . . . . . . . . 0.44704 5000 4408 142 1082

mile/hour (U.S. statute) . . . . . . . . . . . kilometer/hour . . . . . . . . . . . km/h . . . . . . . . . . . . . . . 1.609344 5500 4849 156 1150

Volume 6000 5290 170 1300

foot3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . meter3 . . . . . . . . . . . . . . . . . . . . . . . . . . m3 . . . . . . . . . . . . . . . . . . 0.02831685 6500 5730 185 1400

gallon (U.S. liquid) . . . . . . . . . . . . . . . liter . . . . . . . . . . . . . . . . . . . . . . . l . . . . . . . . . . . . . . . 3.785412 liter . . . . . . . . . . . . . . . . . . . . . . . . . . meter3 . . . . . . . . . . . . . . . . . . . . . . . . . . m3 . . . . . . . . . . . . . . . . . . . . . . . . . 0.001 7000 7500 6171 6612 199 213 1510 1630

inch3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . meter3 . . . . . . . . . . . . . . . . . . . . . . . . . . m3 . . . . . . . . . . . . . . 0.00001638706 8000 7053 227 1740

inch3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . centimeter3 . . . . . . . . . . . . . . . . . . . . cm3 . . . . . . . . . . . . . . . . . . . . . 16.38706 8500 7494 242 1850

inch3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . millimeter3 . . . . . . . . . . . . . . . . . . . mm3 . . . . . . . . . . . . . . . . . . . . . 16387.06 9000 7934 256 1960

ounce (U.S. fluid) . . . . . . . . . . . . . . . centimeter3 . . . . . . . . . . . . . . . . . . . . cm3 . . . . . . . . . . . . . . . . . . . . . 29.57353 9500 8375 270 2070

yard3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . meter3 . . . . . . . . . . . . . . . . . . . . . . . . . . m3 . . . . . . . . . . . . . . . . . . . 0.7645549 10000 8816 284 2200

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