– P –
Pad Lubrication – A system of lubrication in which the lubricant is delivered to a bearing surface by a pad of felt or similar material.
Paraffin Base Oil – A characterization of certain petroleum products prepared from paraffinic type crudes (crudes containing a high percentage of straight chain aliphatic hydrocarbon molecules). Lubricating oils made with these crudes are normally distinguished from similar oils from other crudes (both oils equally well refined) by higher API gravity and higher viscosity index.
Penetration or Penetration Number – The depth, in tenths of a millimeter that a standard cone penetrates a solid or semisolid sample under specified conditions. This test is used for comparative evaluation of grease and grease-like materials. (See Worked Penetration)
Petrolatum – A jelly-like product obtained from petroleum and having a microcrystaline structure. Often used in rust preventatives.
Plain Bearing – Any simple sliding type bearing as distinguished from tapered land, tilting pad, or antifriction bearings, etc.
Poise – The standard unit of absolute viscosity in the c.g.s. system expressed in dyne sec. Per sq. cm.
Pour Point – The pour point of a lubricant is the lowest temperature at which the lubricant will pour or flow when it is chilled without disturbance under specified conditions.
Power Factor – A measure of the dielectric loss, or ability to perform as an electrical insulating oil.
Pour Point Depressant – An additive that retards wax crystallization, and lowers the pour point.
Process Oils – A lube base stock that receives additional processing to impart a very specific hydrocarbon composition in addition to viscometrics. Process oils are not used as lubricants; they are used as chemical components in the manufacture of rubber, plastics, and other polymeric materials.