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Deaerator -- a separator that removes air from the system fluid through the application of bubble dynamics. Degas -- removing air from a liquid, usually by ultrasonic and/or vacuum methods. Degradation -- the progressive failure of a machine or lubricant. Dehydrator -- a separator that removes water from the system fluid. Delamination wear -- a complex wear process where a machine surface is peeled away or otherwise removed by forces of another surface acting on it in a sliding motion. Demulsibility -- the ability of a fluid that is insoluble in water to separate from water with which it may be mixed in the form of an emulsion. Demulsifier -- an additive that promotes the oil-water separation in lubricants that are exposed to water or steam. Density -- the mass of a unit volume of a substance. Its numerical value varies with the units used. Deposits -- oil-insoluble materials that result from oxidation and decomposition of lube oil and contamination from external sources and engine blow-by. These can settle out on machine or engine parts. Examples are sludge, varnish, lacquer and carbon. Depth filter -- a filter medium that retains contaminants primarily within tortuous passages. Desorption -- opposite of absorption or adsorption. In filtration, it relates to the downstream release of particles previously retained by the filter. Detergent -- in lubrication, either an additive or a compounded lubricant having the property of keeping insoluble matter in suspension thus preventing its deposition where it would be harmful. A detergent may also redisperse deposits already formed. Dewaxing -- a refining process for removal of wax from a base oil to improve low temperature properties, especially the cloud and pour points. DEXRONŽ -- Registered trademark of General Motors Corporation used to identify automatic transmission fluids (ATF) approved for use in GM vehicles. Dibasic Acid Ester (Diester) -- synthetic lubricant base oil. An organic ester formed by reacting a dicarboxylic acid and an alcohol. Properties include a high viscosity index, low volatility and long oxidation life. With the addition of additives they may be used as a lubricant in compressors, hydraulic systems and internal combustion engines. Dielectric -- nonconductor of electricity, such as insulating oils for transformers. Dielectric Strength -- a measure of the ability of an insulating material to withstand electric stress (voltage) without failure. Fluids with high dielectric strength (usually expressed in volts or kilovolts) are good electrical insulators. (ASTM Designation D 877.) Differential pressure indicator -- an indicator which signals the difference in pressure between any two points of a system or a component. DIN -- Deutsche Industrie Norm Dirt capacity (dust capacity) (contaminant capacity) -- the weight of a specified artificial contaminant which must be added to the influent to produce a given differential pressure across a filter at specified conditions. Used as an indication of relative service life. Dispersant -- in lubrication, a term usually used interchangeably with detergent. An additive, usually nonmetallic ("ashless"), which keeps fine particles of insoluble materials in a homogeneous solution. Hence, particles are not permitted to settle out and accumulate. Disposable -- a filter element intended to be discarded and replaced after one service cycle. Dissolved gases -- those gases that enter into solution with a fluid and are neither free nor entrained gases. Distillation method (ASTM D-95) -- a method involving distilling the fluid sample in the presence of a solvent that is miscible in the sample but immiscible in water. The water distilled from the fluid is condensed and segregated in a specially-designed receiving tube or tray graduated to directly indicate the volume of water distilled. dN Factor -- is determined by multiplying the bore of an antifriction bearing (d) in millimeters by the speed (N) in rpm of the shaft. It can be used with the operating temperature to determine the appropriate viscosity of the bearing lubricating oil. Dropping point -- the temperature at which grease passes form a semisolid to a liquid state under specific test conditions (ASTM D 566). The test is however of limited significance in predicting overall service performance. Drum -- a container with a capacity of 205 litres (approx. 55 U.S. gallons). Duplex filter -- an assembly of two filters with valving for selection of either or both filters. Dynamic viscosity -- see absolute viscosity. Dyne -- the force which, acting upon a mass of one gram, produces and acceleration of 1 cm per second.
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