A-Ad

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Ao-Az

B-Br

Br-Bz

C-Cd

Ce-Co

Co-Cz

D

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F-Fi

Fj-Fz

G

H

I

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K

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M

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P-Pn

Po-Q

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S-Si

Si-Sz

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Single-pass test -- filter performance tests in which contaminant which passes through a test filter is not allowed to recirculate back to the test filter.

Sintered medium -- a metallic or nonmetallic filter medium processed to cause diffusion bonds at all contacting points.

Sleeve bearing -- a journal bearing, usually a full journal bearing.

Sludge -- insoluble material formed as a result either of deterioration reactions in an oil or of contamination of an oil, or both.

Sodium (Na) -- element number 11 on the periodic table of the elements. In the context of oil analysis sodium can be present as a contaminant in various sampled components and the origins can be from such sources as: oil additives, coolant inhibitors, dirt and road salt just to name a few.

Solid -- any substance having a definite shape which it does not readily relinquish. More generally, any substance in which the force required to produce a deformation depends upon the magnitude of the deformation rather than upon the rate of deformation.

Solvency -- ability of a fluid to dissolve inorganic materials and polymers, which is a function of aromaticity.

Specific gravity (liquid) -- the ratio of the weight of a given volume of liquid to the weight of an equal volume of water.

Specific gravity -- the ratio of the weight of a given volume of material to the weight of an equal volume of water.

Spectrographic analysis -- determines the concentration of elements represented in the entrained fluid contaminant.

Spectrographic Oil Analysis Program (SOAP) -- procedures for extracting fluid samples from operating systems and analyzing them spectrographically for the presence of key elements.

Spin-on filter -- a throw-away type bowl and element assembly that mates with a permanently installed head.

Spindle oil -- a light-bodied oil used principally for lubricating textile spindles and for light, high-speed machinery.

Splash lubrication -- a system of lubrication in which parts of a mechanism dip into and splash the lubricant onto themselves and/or other parts of the mechanism.

Static friction -- the force just sufficient to initiate relative motion between two bodies under load. The value of the static friction at the instant relative motion begins is termed break-away friction.

STLE -- Society of Tribologists & Lubrication Engineers - a technical organization intended to advance the knowledge and application of lubrication and related sciences. Formerly known as the American Society of Lubrication Engineers (ASLE).

Stoke (St) -- kinematic measurement of a fluid's resistance to flow defined by the ratio of the fluid's dynamic viscosity to its density.

Strainer -- a coarse filter element (pore size over approximately 40 µm)

Suction filter -- a pump intake-line filter in which the fluid is below atmospheric pressure.

Sulfated ash -- the ash content of fresh, compounded lubricating oil as determined by ASTM Method D 874. Indicates level of metallic additives in the oil.

Sulfur (S) -- element number 16 on the periodic table of the elements. In the context of oil analysis sulfur is a common natural constituent of petroleum and petroleum products. While certain sulfur compounds are commonly used to improve the EP, or load carrying, properties of oil, high sulfur content in a petroleum product may be undesirable as it can be corrosive and create an environmental hazard when burned.

Sulfurized oil -- oil to which sulfur or sulfur compounds have been added.

Surface fatigue wear -- the formation of surface or subsurface cracks and fatigue crack propagation. It results from cyclic loading of a surface.

Surface filtration -- filtration which primarily retains contaminant on the influent surface.

Surface tension -- the contractile surface force of a liquid by which it tends to assume a spherical form and to present the least possible surface. It is expressed in dynes/cm or ergs/cm2.

Surfactant -- surface-active agent that reduces interfacial tension of a liquid. A surfactant used in a petroleum oil may increase the oil's affinity for metals and other materials.

Surge -- a momentary rise of pressure in a circuit.

Swarf -- the cuttings, and grinding fines that result from metal working operations.

Switch, pressure -- an electric switch operated by fluid pressure.

Synthetic lubricant -- a lubricant produced by chemical synthesis rather than by extraction or refinement of petroleum to produce a compound with planned and predictable properties.

Synthetic hydrocarbon -- oil molecule with superior oxidation quality tailored primarily out of paraffinic materials.

Thermography -- the use of infrared thermography whereby temperatures of a wide variety of targets can be measured remotely and without contact. This is accomplished by measuring the infrared energy radiating from the surface of the target and converting this measurement to an equivalent surface temperature.

Thermal conductivity -- measure of the ability of a solid or liquid to transfer heat.

Thermal degradation -- thermal degradation or thermal cracking is the breaking of carbon bonds in fluid molecules by heat in excess of the recommended maximum bulk temperature of the fluid. The reaction may either stop at that point, in which case smaller molecules than previously existed are formed, or, the fragments may combine with each other to form polymeric molecules larger than previously existed in the fluid. In heat transfer terminology, the two types of degradation products are known as "low boilers" and "high boilers".

• Low boilers
  The effect of low boilers is to decrease the flash point and viscosity of the fluid as well as to increase its vapor pressure. The increased vapor pressure can affect overall system efficiency and can cause pump cavitation. The reduction in the flash point could also be cause for safety concerns.

• High boilers
  If thermal degradation occurs at extreme temperatures, the effect is not only to break carbon - carbon bonds but to separate hydrogen atoms from carbon atoms and form coke. The effect of the high boilers is to increase the viscosity of the fluid as long as they remain in solution. However, once their solubility limit is exceeded, they begin to form solids which can foul the heat transfer surfaces. In this case, fouling of the heat transfer surfaces is very rapid and the system will soon cease to operate.

Thermal stability -- ability of a fuel or lubricant to resist oxidation under high temperature operating conditions.

Thin film lubrication -- a condition where the thickness of the oil film is so thin that the viscosity of the lubricant plus the properties of the surface determine the friction between the surfaces. Additives may be required in a thin film condition to protect the metal surfaces from wear.

Thixotropy -- that property of a lubricating grease which is manifested by a softening in consistency as a result of shearing followed by a hardening in consistency starting immediately after the shearing is stopped.

Three-body abrasion -- a particulate wear process by which particles are pressed between two sliding surfaces.

Thrust bearing -- an axial-load bearing.

Timken OK Load -- A measure of the EP (extreme pressure) properties of a lubricating oil or grease. The test utilizes a machine (Timken) that consists of a stationary block that is pushed upwards against the rotating outer race of a roller bearing. The test load is increased until a measurable wear scar is formed on the block. The Timken OK load is the heaviest load that a lubricant can withstand before the test block is scored.

Tin (Sn) -- element number 50 on the periodic table of the elements. In the context of oil analysis tin can be present as a wear metal in various sampled components and the origins can be from such sources as: pistons, bearings and bushings just to name a few.

Titanium (Ti) -- element number 22 on the periodic table of the elements. In the context of oil analysis titanium can be present as a wear metal in various sampled components and the origins can be from such sources as: turbine bearings and paint just to name a few.

Total Acid Number (TAN) -- the quantity of base, expressed in milligrams of potassium hydroxide, that is required to neutralize all acidic constituents present in 1 gram of sample. (ASTM Designation D 974.) Term no longer used see Acid number.

Total Base Number (TBN) -- the quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide that is required to neutralize all basic constituents present in 1 gram of sample. (ASTM Designation D 974.) Term no longer used see Base number.

Tribology -- The science and technology dealing with the design, lubrication, friction and wear of interacting surfaces in relative motion. The word Tribology was first introduced in 1966 and originates from the Greek word Tribos meaning to rub.

Triggered test -- an additional test that is performed by the lab when a given test reaches a specific predetermined level (trigger point). Eg. A Karl Fischer Water Titration test may be "triggered" by a positive result on a Crackle test(water contamination).

Turbidity -- the degree of opacity of a fluid.

Turbulent flow sampler -- a sampler that contains a flow path in which turbulence is induced in the main stream by abruptly changing the direction of the fluid.