Babbitt: a soft alloy of tin, copper and antimony used for plain bearings.

Backlash (gears): loose motion or play between the nondriving surfaces of adjacent gear teeth, arising from necessary clearance, wear or incorrect adjustment.

Backup roll bearings (Morgan or Mesta design): special sleeve bearings of the Morgoil design, with very large projected areas to reduce unit pressure. These large-diameter oil-film bearings support backup rolls in rolling mills by means of a hydrodynamic film.

Bactericide: additive used with water-soluble cutting fluids to inhibit bacterial growth and unpleasant odors.

Ball bearing: a roller bearing whose rolling elements are balls (see roller bearings).

Bang-bang valve: conventional hydraulic or pneumatic valves operated by solenoids with either two or three distinct positions.

Barium/barium complex grease: a grease thickened with either barium soap or complex barium soap.

Barrel (drum): a standard container size, depending on context, e.g.: a 400-lb open top container (gear lubes and greases are sold by the pound), a 55-gal liquid container (most liquid lubricants) or a 42-gal charge (standard for crude oils).

Base circle (gears): the circle from which the involute tooth profile is derived.

Basic bearing number: for purposes of identification, anti-friction bearings are assigned numbers, referred to as basic bearing numbers. In most cases, they have four digits: the first indicates the TYPE of bearing, the second the bearing SERIES and the third and fourth the BORE SIZE of the bearing. Some manufacturers replace the first digit with letters of the alphabet to identify their bearings, others use numbers and letters.

Basic dynamic capacity: the radial load that 90% of identical bearings will bear for 1,000,000 revolutions before the first evidence of fatigue; also known as basic load rating.

Basic static capacity: the static load endured by a bearing before the most heavily loaded ball or roller experiences sufficient stress to cause a permanent deformation of the element or race equal to 0.0001 in. of the ball or roller diameter.

Beam strength (gears): capability of a gear tooth to withstand repeated bending that occurs whenever it is under load.

Bearing: machine element designed to support or position loads and, properly lubricated, to reduce friction between them. There are two basic designs, rolling element bearings and plain (sliding) types.

Bearing crush: the height by which half of the bearing exceeds the half diameter of the bore into which it is assembled.

Bench test: a modified service test in which the service conditions are approximate in the laboratory.

Bentonite thickener: clay, composed mainly of silicon dioxide and aluminum oxide, used to thicken greases. Such greases have no dropping points because the bentonite does not melt.

Benzene: the simplest aromatic hydrocarbon (C6H6) used in petrochemical processes and as a solvent. It must be used with caution because of its toxicity. For safety considerations, laboratories have substituted other solvents like toluene in its place.

Bernoulli’s Theorem: theory developed by Daniel Bernoulli, 18th century Swiss scientist, one implication of which is that any rise in hydraulic fluid velocity is accompanied by a drop in static pressure and vice versa.

Bevel gears: gears, conical in form, that operates on intersecting axes, usually at right angles.

Biodegradable: capable of decaying through the action of living organisms.

Biodegradability – can be defined as the ability of a substance to degrade over time to carbon dioxide and water in the presence of water, nutrients and microorganisms
Biotoxic: toxic to the environment.

Black oils: dark-colored lubricants containing asphaltic materials, with medium flash points and medium to high viscosity, used in heavy-duty applications requiring adhesiveness under exposed conditions.

Bleeding (grease): the tendency of a liquid component to separate from a liquid- solid or liquid-semisolid mixture, as oil may separate from a grease.

Blending: the process of combining fluid and/or solid components into a finished mixture, particularly with liquid lubricants. Though compounding is similar, the purpose of compounding is to obtain properties not usually attainable with blending.

Block/brick grease: a grease of moderate dropping point, NLGL grade 5 or 6, firm to the touch at normal temperatures, that can be handled in block or stick form. The penetrating powers of such greases are measured at 77°F; grade 6 grease has a penetration range of 85-115.

Blown oils: natural fatty oils, of animal or vegetable origin, are artificially oxidized and thickened by blowing air through them. They are used primarily for compounding petroleum oils, to give them a strong affinity for metal surfaces.

Bomb: in lubrication terminology, a closed container used for conducting tests under elevated pressures.

Bomb oxidation stability: resistance of oils and greases to oxidation when subjected to accelerated oxidation in a sealed unit filled with pure oxygen under pressure and at elevated temperatures. As the lubricant absorbs oxygen, the pressure drops to indicate oxidation resistance. ASTM test D-2272, the Rotary Bomb Oxidation Test, rotates the container during the test.

Bonnet (lube systems): upper portion of packing gland assembly that serves as a viewer for movement of indicator.

Bottoms (residuum): the liquid that collects at the bottom of the distillation column, consisting of high-boiling residual liquids like heavy fuels and asphaltic materials.

Boundary Lubrication: lubrication between two rubbing surfaces in the absence of a full fluid lubricating film. Boundary lubrication is often accomplished with the use of extreme pressure additives. Example – high pressure gears.

Brake valve: a device that permits a machine component driven by a hydraulic rotary motor to revolve unimpeded during operation but restrains the motor return line fluid to slow the machine when it is desired to stop.

Brass: a non-ferrous alloy consisting of varying proportions of tin, zinc and copper; lead is added to attain higher machining speed. Brasses may or may not be lined with babbitt metal (see bronze).

Breather: an air filtering device placed on top of a reservoir to allow it to “breathe” as the oil level rises and falls. All incoming air is thereby filtered to keep out airborne contaminants.

Bright stock: describes high-viscosity lubricating oils that are refined to make them clear products of good color. Bright stocks are made from residuals or bottoms, solvent dewaxed and deasphalted; they may be used for blending.

Brinell hardness: a system to measure the hardness of metals by indentation. A hardened steel ball is pressed into a smooth surface of the metal under a fixed load and the resulting indentation is microscopically measured. With a conversion chart, this number can also be used to determine the approximate tensile strength of the same metal.

BHN: Brinell hardness number

Bromine number: see iodine number.

Bronze: a non-ferrous alloy of copper and a metal other than zinc or nickel. The family of bronzes includes: copper-tin, aluminum (for high tensile strength), phosphor (for corrosion resistance and low friction), leaded phosphor (for machinability) and silicon. ASTM distinguishes five grades of bronze casting alloys.

BS&W: an acronym for the material that settles to the bottom of a storage tank, namely bottoms, sediment and water. Laboratories sometimes quantify and report this information when examining oil in service.

BTU: British thermal unit: the amount of heat required to raise the temperature of a pound of water one degree Fahrenheit.

Buffer solution: a solution that prevents drastic changes in pH values when moderate amounts of acid or alkali are added.

Builder: any substance that increases the effectiveness of a cleaner, e.g., water- softening agents, buffer agents, alkalies.

Bulk appearance (grease): visual appearance when the undisturbed surface is viewed in an opaque container. Bulk appearance should be characterized in the following terms: bleeding (free oil shows on surface or in cracks of a cracked grease), cracked (showing surface cracks of appreciable magnitude), grainy (a surface with small granules or lumps of constituent thickener particles), rough (many small irregularities on the surface), smooth (surface relatively free of irregularities).

Bulk modulus: the resistance to compressibility of a fluid or elastomer; the reciprocal of its compressibility.

Buna-N/S: Buna-N and Buna-S are types of synthetic rubber. Buna-N is a copolymer of butadiene and acetonitrile; Buna-S is a copolymer of butadiene and styrene.

Butyl: copolymer of isobutylene and various amounts of isoprene and butadiene.