WHAT WE DO

Glossary of Terms

Paper chromatography: a method which involves placing a drop of fluid on a permeable piece of paper and noting the development and nature of the halos, or rings, surrounding the drop through time. The roots of this test can be traced to the 1940s, when railroads used the "blotter spot" tests.

Paraffin: Any hydrocarbon identified by saturated straight (normal) or branched (iso) carbon chains; also called an alkane. The generalized paraffinic molecule can be symbolized by the formula CnH2n+2. Paraffins are relatively non-reactive and have excellent oxidation stability. In contrast to naphthenic oils, paraffinic lubricating oils have relatively high wax content and pour point, and generally have a high viscosity index (VI.). Paraffinic solvents are generally lower in solvency than naphthenic or aromatic solvents.

Parallel Systems: Lubrication systems where the dispensing devices are connected to the main line in parallel. Each dispensing device operates independent of any other in the system.

Particle count: the number of particles present greater than a particular micron size per unit volume of fluid often stated as particles > 10 microns per milliliter.

Particle density: an important parameter in establishing an entrained particle's potential to impinge on control surfaces and cause erosion.

Particle erosion: occurs when fluid-entrained particles moving at high velocity pass through orifices or impinge on metering surfaces or sharp angle turns.

Particle impingement erosion: a particulate wear process where high velocity, fluid-entrained particles are directed at target surfaces.

Particulates: Particles made up of a wide range of natural materials (e.g., pollen, dust, resins), combined with man-made pollutant (e.g., smoke particles, metallic ash); in sufficient concentrations, particulates can be a respiratory irritant.

Pascal: Unit of pressure in the metric (SI) system.

Pascal’s Law: A pressure applied to a confined fluid at rest is transmitted with equal intensity throughout the liquid and that pressure is considered to act at right angles to each surface contacted by the fluid.

Patch test: a method by which a specified volume of fluid is filtered through a membrane filter of known pore structure. All particulate matter in excess of an "average size," determined by the membrane characteristics, is retained on its surface. Thus, the membrane is discolored by an amount proportional to the particulate level of the fluid sample. Visually comparing the test filter with standard patches of known contamination levels determines acceptability for a given fluid.

PCB: Polychlorinated biphenyl, a class of synthetic chemicals consisting of a homologous series of compounds beginning with monochlorobiphenyl and ending with decachlorobiphenyl. PCBs do not occur naturally in petroleum, but have been found as contaminants in used oil. PCBs have been legally designated as a health hazard, and any oil so contaminated bust be handled in strict accordance with state and federal regulations.

Permeability: the relationship of flow per unit area to differential pressure across a filter medium.

Petrochemical: Any chemical substance derived from crude oil or its products, or from natural gas. Some petrochemical products may be identical to others produced from other raw materials such as coal and producer gas.

PH: measure of alkalinity or acidity in water and water-containing fluids. pH can be used to determine the corrosion-inhibiting characteristic in water-based fluids. Typically, pH > 8.0 is required to inhibit corrosion of iron and ferrous alloys in water-based fluids.

Phenol: A white, crystalline compound (C6H5OH) derived from benzene, used in the manufacture of phenolic resins, weed killers, plastics, disinfectants; also used in solvent extraction, a petroleum refining process. Phenol is a toxic material; skin contact must be avoided.

Phosphate ester: Any of a group of synthetic lubricants having superior fire resistance. A phosphate ester generally has poor hydrolytic stability, poor compatibility with mineral oil, and a relatively low viscosity index (VI). It is used as a fire-resistant hydraulic fluid in high-temperature applications.

Pinion: the smaller of two mating or meshing gears; can be either the driving or the driven gear.

Pitting: a form of extremely localized attack characterized by holes in the metal. Pitting is one of the most destructive and insidious forms of corrosion. Depending on the environment and the material, a pit may take months, or even years, to become visible.

Pleated filter: a filter element whose medium consists of a series of uniform folds and has the geometric form of a cylinder, cone, disc, plate, etc. Synonymous with "convoluted" and "corrugated".

PNA (polynuclear aromatic): Any of numerous complex hydrocarbon compounds consisting of three or more benzene rings in a compact molecular arrangement. Some types of PNA’s are formed in fossil fuel combustion and other heat processes, such as catalytic cracking.

Pneumatics: engineering science pertaining to gaseous pressure and flow.

Poise (absolute viscosity): a measure of viscosity numerically equal to the force required to move a plane surface of one square centimeter per second when the surfaces are separated by a layer of fluid one centimeter in thickness. It is the ratio of the shearing stress to the shear rate of a fluid and is expressed in dyne seconds per square centimeter (DYNE SEC/CM2); 1 centipoise equals .01 poise.

Polar compound: a chemical compound whose molecules exhibit electrically positive characteristics at one extremity and negative characteristics at the other. Polar compounds are used as additives in many petroleum products. Polarity gives certain molecules a strong affinity for solid surfaces; as lubricant additives (oiliness agents), such molecules plate out to form a tenacious, friction-reducing film. Some polar molecules are oil-soluble at one end and water-soluble at the other end; in lubricants, they act as emulsifiers, helping to form stable oil-water emulsions. Such lubricants are said to have good metal-wetting properties. Polar compounds with a strong attraction for solid contaminants act as detergents in engine oils by keeping contaminants finely dispersed.

Polishing (bore): excessive smoothing of the surface finish of the cylinder bore or cylinder liner in an engine to a mirror-like appearance, resulting in depreciation of ring sealing and oil consumption performance.

Polyglycols: Polymers of ethylene or propylene oxides used as a synthetic lubricant base. Properties include very good hydrolytic stability, high viscosity index (VI), and low volatility. Used particularly in water emulsion fluids.

Polymer : A substance formed by the linkage (polymerization) of two or more simple, molecules, called monomers, to form a single larger molecule having the same elements in the same proportions as the original monomers; i.e. each monomer retains its structural identity. A polymer may be liquid or solid; solid polymers may consist of millions of repeated linked units. A polymer made from two or more similar monomers is called a copolymer; a copolymer composed of three different types of monomers is a terpolymer. Natural rubber and synthetic rubbers are examples of polymers. Polymers are commonly used as viscosity index improvers in multi-grade oils and tackifiers in lubricating greases.

Polymerization: the chemical combination of similar-type molecules to form larger molecules.

Polyol ester: A synthetic lubricant base, formed by reacting fatty acids with a polyol (such as a glycol) derived from petroleum. Properties include good oxidation stability at high temperatures and low volatility. Used in formulating lubricants for turbines, compressors, jet engines, and automotive engines.

Polyol Esters: Synthetic lubricants made by reacting fatty acids with polyhydric alcohols.

Polyolefin: A polymer derived by polymerization of relatively simple olefins. Polyethylene and polyisoprene are important polyolefins.

Pore: a small channel or opening in a filter medium which allows passage of fluid.

Pore size distribution: the ratio of the number of effective holes of a given size to the total number of effective holes per unit area expressed as a percent and as a function of hole size.

Porosity: the ratio of pore volume to total volume of a filter medium expressed as a percent.

Positive crankcase ventilation (PCV): system for removing blow-by gases from the crankcase and returning them through the carburetor intake manifold to the combustion chamber where the recirculated hydrocarbons are burned. A PC valve controls the flow of gases from the crankcase to reduce hydrocarbon emissions.

Pour point: lowest temperature at which an oil or distillate fuel is observed to flow, when cooled under conditions prescribed by test method ASTM D 97. The pour point is 3°C (5°F) above the temperature at which the oil in a test vessel shows no movement when the container is held horizontally for five seconds.

Pour point depressant: an additive which retards the adverse effects of wax crystallization, and lowers the pour point.

Pour stability: The ability of a pour depressed oil to maintain its original ASTM pour point when subjected to long-term storage at low temperature approximating winter conditions.

Power unit: a combination of pump, pump drive, reservoir, controls and conditioning components which may be required for its application.

Predictive maintenance: a type of condition-based maintenance emphasizing early prediction of failure using non-destructive techniques such as vibration analysis, thermography, and wear debris analysis.

Pressure: force per unit area, usually expressed in pounds per square inch.

Pressure Drop: Resistance to flow created by the element (media) in a filter. Defined as the difference in pressure upstream (inlet side of the filter) and downstream (outlet side of the filter).

Pressure gage: pressure differential above or below atmospheric pressure.

Pressure line filter: a filter located in a line conducting working fluid to a working device or devices.

Pressure, absolute: the sum of atmospheric and gage pressures.

Pressure, atmospheric: pressure exerted by the atmosphere at any specific location. (Sea level pressure is approximately 14.7 pounds per square inch absolute.)

Pressure, back: the pressure encountered on the return side of a system.

Pressure, cracking: the pressure at which a pressure operated valve begins to pass fluid.

Pressure, rated: the qualified operating pressure which is recommended for a component or a system by the manufacturer.

Pressure, system: the pressure which overcomes the total resistances in a system. It includes all losses as well as useful work.

Preventive maintenance: maintenance performed according to a fixed schedule involving the routine repair and replacement of machine parts and components.

Proactive Maintenance: a maintenance strategy for stabilizing the reliability of machines or equipment. Its central theme involves directing corrective actions aimed at failure root causes, not active failure symptoms, faults, or machine wear conditions. A typical proactive maintenance regiment involves three steps: (1) setting a quantifiable target or standard relating to a root cause of concern (e.g., a target fluid cleanliness level for a lubricant), (2) implementing a maintenance program to control the root cause property to within the target level (e.g., routine exclusion or removal of contaminants), and (3) routine monitoring of the root cause property using a measurement technique (e.g., particle counting) to verify the current level is within the target.

Process oil: An oil that serves as a temporary or permanent component of a manufactured products. Aromatic process oils have good solvency characteristics; their applications include proprietary chemical formulations, ink oils, and extenders in synthetic rubbers. Naphthenic process oils are characterized by low pour points and good solvency properties. Paraffinic process oils are characterized by low aromatic content and light color.

Pump, fixed displacement: a pump in which the displacement per cycle cannot be varied.

Pump, variable displacement: a pump in which the displacement per cycle can be varied.

Pumpability: the low temperature, low shear stress-shear rate viscosity characteristics of an oil that permit satisfactory flow to and from the engine oil pump and subsequent lubrication of moving components.

Pusher seal: A mechanical seal in which the secondary seal is pushed along the shaft or sleeve to compensate for misalignment and face wear.