P X T VALUE
A numerical value resulting from the multiplication of the internal pressure and the temperature of the fluid involved. In English system, usually psi x °F = PTValue.
PACKING GLAND
The space into which a compression packing is inserted. Also known as a Stuffing Box.
PACKING GROOVE
A groove machined into a flange or joint to accommodate a packing ring.
PACKING HOOK
A tool, similar to a corkscrew, for removing packing from a stuffing box.
PACKING SPACE
The distance between the shaft or stem surface and the bore of a stuffing box. Packing space (x) can be calculated by the following equation: x = (OD-ID)/2.
PAN-BASED CARBON
A carbon fiber derived from the carbonization process of a poly acrylonitrile fiber in an inert gas.
PAPER FINISH
Finish resulting from vulcanizing in contact with paper.
PASSIVE INHIBITOR
A type of galvanic corrosion inhibitor added to packing which acts as a protective coating to block the transfer of electrons and keep a galvanic reaction from occurring. Graphite foil can be produced with phosphorus added as a passive corrosion inhibitor. See also "Galvanic Corrosion". Compare with "Active Inhibitor".
PERMANENT SET
The degree to which an elastic material fails to return to its initial form after deformation.
PERMEABILITY
The quality or condition of allowing passage of fluid/gases/air through a material such as rubber.
pH
The measure of the strength of an acid or base. On the pH scale, a neutral solution (neither acidic or basic) has a pH of 7. Solutions with a pH below 7 are acidic; the smaller the pH value, the more acidic the solution. Solutions with a pH above 7 are basic.
PISTON
A cylindrically-shaped part which fits within a cylinder and transmits or receives motion by means of a connecting rod (Cylinder Rod).
PITCH-BASED CARBON
A carbon fiber derived from the carbon residue found at the bottom of a cat cracker in a refinery.
PITTING
Surface cavities that occur on a metal as a result of galvanic corrosion or mechanical erosion.
PLAITED
Braided.
PLASTICIZER
A compounding ingredient which can change the hardness, flexibility or plasticity of an elastomer.
PLATE FINISH
A commercially smooth surface, resulting from vulcanization between press plates (platens).
PLUNGE GROUND
The surface texture of shaft or wear sleeve produced by presenting the grinding wheel perpendicular to the rotating shaft without axial motion.
PLUNGER
A cylindrically shaped part that has a uniform diameter and is used to transmit thrust (as in a hydraulic cylinder) or develop pressure and cause flow (as in a reciprocating pump).
PNEUMATIC SEAL
An extruded or molded elastomeric seal designed to expand and retract to provide a secure, reliable seal that can hold, position, or handle objects in a wide range of applications.
POLYURETHANE
A synthetic elastomeric material made by chemically reacting a polyol and a diisocyanate in such a manner that a high molecular weight polymer is formed.
PRE-ASSEMBLED JOINT
The combination of the metal framework and a bellows, factory assembled into a single assembly.
PRE-COMPRESSION
Compression of the expansion joint during installation (shortening the F/F) so that in the cold position the joint has a given amount of compression in addition to the rated amount of compression. The purpose of pre-compression is to allow for unexpected or additional axial extension.
PRE-SET
Dimension that joints are deflected to insure that desired movements will take place. See Lateral Offset and Manufactured F/F.
PRESS CURE
A method of vulcanizing rubber by the use of heated platens, which can be brought together and separated by hydraulic pressure or mechanical action, to cure rubber sheet under pressure.
PRESS LENGTH
The length of a product that can be vulcanized at one time in a press, limited by the length measurement of the press.
PRESSURE
Force per unit area, usually expressed in pounds per square inch (PSI) or kilograms per square centimeter.
PRESSURE ABSOLUTE
The pressure above zero absolute. (i.e the sum of atmospheric and gage pressure)
PRESSURE CYCLING
The variation of pressure in a system.
PRESSURE, ABSOLUTE (PSIA)
The pressure above zero absolute, i.e., the sum of atmospheric and gage pressure.
PRESSURE, ATMOSPHERIC
Pressure exerted by the atmosphere at any specific location. Sea level pressure is approximately 14.7 lbs./sq.in. absolute.
PRESSURE, GAUGE (PSIG)
Pressure differential above or below atmospheric pressure, expressed as lbs./sq.in. or psig.
PRIMARY LIP
The normally flexible elastomeric component of a lip seal assembly, which rides against the rotating surface and affects the seal.
PROTECTIVE COVER
Outer cover material used to protect boot material during shipment and installation.
psi
Abbreviation for "Pounds per Square Inch", a unit of pressure.
PTFE
Abbreviation for Polytetrafluoroethylene, a polymer having excellent chemical resistance. PTFE dispersion is used as a coating for many styles of packing. Some packing styles are constructed of PTFE fibers. Teflon® is DuPonts trade name for their PTFE materials.
PULP
In the papermaking industry, pulp is the primary raw material from which paper is made. It is a cellulose fiber product produced by the mechanical and/or chemical processing of wood.
PUMP SHAFT
The metal rod connecting the impeller of a pump to the motor.
PURGE FLUID
A clean liquid (usually water) which is injected through a flush port to flush solid particles from the stuffing box area to minimize abrasive wear.
PURGE PORT
A hole in the side of a stuffing box through which a flushing fluid is injected.