Glossary

Click on a letter to see terms beginning with that letter:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

[ top ] A

AMBIENT TEMPERATURE
The temperature of the atmosphere or medium surrounding the gasket in service

ANSI
Abbreviation for American National Standards Institute

API
Abbreviation for American Petroleum Institute

AQUEOUS SOLUTIONS
Any fluid solution containing water

ASME
Abbreviation for American Society of Mechanical Engineers

ASTM
Abbreviation for American Society for Testing and Materials

 

BENCH TEST
A modified service test in which the service conditions are approximated, but the equipment is laboratory equipment and not necessarily identical with that in which the product will be employed

BLISTER
A raised spot on the surface or a separation between layers usually forming a void or air-filled space in the gasketing material

BURST
A rupture caused by internal pressure

 

[ top ] C

CALENDER
A machine equipped with two or more heavy internally heated or cooled rolls, revolving in opposite directions, which is used for continuously sheeting or plying up rubber compound and fractioning or coating fabric with rubber compound

CHECKING
The short, shallow cracks on the surface of a rubber product resulting from damaging action of environmental conditions

CLOTH BOTH SIDES (CBS)
Rubber sheet consisting of a ply of fabric or cloth on each surface, (CDS):  Cloth on just one side

CLOTH INSERTED (CI)
Rubber sheet containing one or more plies of fabric or cloth, in which the fabric is completely covered with rubber

COLD FLOW
The continued deformation under stress

COMPRESSION SHEET
A gasketing material primarily containing fibers, rubber and fillers manufactured on a special calender, known as a “sheeter” in such a manner that the compound is caused to build up under high load as an oriented sheet on one roll of the sheeter

COMPRESSIBILITY
The quality or state of being compressible.  In the case of gasketing, it is the percent loss of thickness when subject to a given load

COMPRESSION SET
The deformation that remains in gasketing after it has been subjected to, and released from a specific compressive stress for a definite period of time at a prescribed temperature.

COUNT
The number of warp ends, or the number of filling picks, or both, in a square inch of fabric

CRAZING
A surface effect on rubber sheet characterized by multitudinous minute cracks

CREEP
A transient stress-strain condition in which strain increases as the stress remains constant

CREEP RELAXATION
A transient stress-strain condition in which strain increases concurrently with the decay of stress.  More simply put, it is the loss of tightness in a gasket measurable by torque loss

CURE
The act of vulcanization

 

[ top ] D

DENIER
A yarn sizing system for continuous filament synthetic fibers.  The denier of filament yarn is the weight in grams of 9000 meters of that yarn

DENSITY
The ratio of mass of a body to its volume or mass per unit volume.  For ordinary practical purposes, density and specific gravity may be regarded as equivalent

DIAPHRAGM PACKING
A packing that spans a gap between a moving and stationary member, permitting limited movement of the former

DIAPHRAGM SHEET
PTFE or sheet rubber (generally fabric reinforced) from which flat diaphragms are cut

DIELECTRIC STRENGTH
The measure of a product’s ability to resist passage of a disruptive discharge produced by an electric stress described in volts/mil

DIN
Abbreviation for Deutsch Industrie Norman.  English translation is German Industry Standard – it is the European equivalent to ASTM

DISHED DIAPHRAGM
A molded diaphragm in which the entire center is depressed below the plane of the rim

DRIFT
(1) the continued deformation under strain (2) the change in rubber hardness after a specified period of time

DRUM CURE
A method of vulcanizing rubber in which the product is wrapped around a drum and cured in hot air or steam, usually with a separator or wrapping jacket.

DUROMETER HARDNESS
An arbitrary numerical value which measures the resistance to indentation (without puncturing) of the indentor into the surface or rubber

 

[ top ] E

ELASTIC LIMIT
The limiting extent to which a body may be deformed and yet return to its initial shape after removal of the deforming force

ELASTOMER
An elastic rubberlike material which, in the vulcanized state, at room temperature can be stretched repeatedly to at least twice its original length and which, upon release of the stress, will immediately return to approximately its original length

ELONGATION
The increase in length expressed numerically as a fraction or percentage of the initial length

EXPANSION
The increase in any linear dimension or volume

EXTRACTION TEST
A test involving the separation of certain components from a solid by dissolving them in a liquid solvent under suitable conditions

EXTRUSION
Permanent displacement of part of a gasket into a gap, under the action of fluid or bolting pressure

 

[ top ] F

FSA
The name of the American-based trade association for the mechanical packing industry.  (Fluid Sealing Association)

FABRIC COUNT
The number of warp ends per inch, and the number of filling picks per inch

FABRIC IMPRESSION
A pattern in the rubber surface formed by contact with fabric during vulcanization (usually during Drum Curing)

FATIGUE
The weakening or deterioration of a material occurring when a repetition or continuous application of stress causes strain

FILLER
Any compounding material, usually in powder form, added to gasketing materials either to improve quality or reduce cost

FLEX LIFE
The relative ability of a rubber article to with stand cyclical bending stresses

FLOW CRACK
A surface imperfection caused by improper flow or failure of stock to knit or blend with itself during the curing process of rubber

FRICTION COATING
A rubber covering applied to the weave of a fabric simultaneously with impregnation

FULL-FACE GASKET
A gasket covering the flange surface and including bolt holes

 

[ top ] G

GASKET
A seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression

GRAPHITED THROUGHOUT
Braided from yarns which have received a prior application of graphite, or, in the case of braid-over-braid construction, an application to each successive braid

 

[ top ] H

HEAD
The height of a column or body of fluid above a given point expressed in linear units.  Head is often used to indicate gage pressure.  Pressure is equal to the height times the fluid’s density

HOMOGENEOUS
Products that are o uniform composition throughout

 

[ top ] I

ID
Symbol for inside diameter

INTERSTICES
Openings, such as between fibers in a cord, or threads in a woven or braided fabic

 

[ top ] J

JOINT
An interstice (crevice) between rigid members of a fluid container

 

[ top ] K

 

[ top ] L

LEAKAGE RATE
The quantity of media passing through and/or over the faces of gaskets in a given length of time. ie cubic feet per minute, cubic centimeters per minute, milliliters per hour or parts per million

 

[ top ] M

MTI
The abbreviation for Material Technology Institute of the Chemical Process Industry

MATTE FINISH
A dull surface, as opposed to a smooth plate finish

MICRO-VOIDS
The spaces in a gasket, on a micro level, that allow media permeation

MIRROR FINISH
A bright, polished surface

MODULUS
In the physical testing of rubber, the pressure is pounds per square inch or Newtons per square meter of initial square cross-sectional area necessary to produce a stated percentage of elongation, compression or shear

“M” FACTOR
The factor that provides the additional preload capability in the flange fasteners to maintain sealing pressure on a gasket after the internal pressure is applied to the joint

 

[ top ] N

 

[ top ] O

OD
Symbol for outside diameter

OIL SWELL
The change in volume of a gasketing product resulting from contact with oil

O-RING
An elastomeric seal of homogeneous composition molded in one piece to the configuration of a torus with circular cross section – more simply, a round ring with a round cross section

 

[ top ] P

PAN BASED CARBON
A carbon fiber derived from the carbonization process of a ply acrylonnitrile fiber in an inert gas

PAPER FINISH
That finish resulting from vulcanizing in contact with paper

PERMANENT SET
The amount by which an elastic material fails to return to its initial form after deformation

PERMEABILITY
The quality or condition of allowing passage of media through a material

PICK
An individual filling yarn of a fabric or jacket

PITCH BASED CARBON
A carbon fiber derived from the carbon residue found at the bottom of a cat cracker in a refinery

PLASTICIZER
A compounding ingredient which can change the hardness, flexibility or plasticity of an elastomer

PRESSURE
Force per unit area, usually expressed in pounds per square inch or kilograms per square centimeter

PRESSURE-ABSOLUTE
The pressure above zero absolute ie the sum of atmospheric and gage pressure

PRESSURE-ATMOSPHERIC
Pressure exerted by the atmosphere at any specific location.  (Sea level pressure is 14.7lbs/sq in. absolute)

PRESSURE GAGE
Pressure differential above or below atmospheric pressure (Expressed as lbs/sq in. or P.S.I.G)

PSI
The abbreviation of pounds per square inch

PTFE
The abbreviation for Polytetrafluoroethylene.  DuPont’s trademarked name for this is Teflon

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

 

[ top ] Q

QPL
Abbreviation for Qualified Products List (associated with US Government specifications)

 

[ top ] R

RECOVERY
The degree to which a product returns to its normal dimensions or shape after being distorted

RECOVERY (GASKETING)
The increase in thickness of a gasket after a load is removed

ROTATION (FLANGE)
The warping, bowing or bending of a flange that can occur from too much bolt load

RMA
Abbreviation for the Rubber Manufacturers Association

RUBBER
A material that is capable of recovering from large deformations quickly and forcibly and can be, or already is, modified to a state in which it is essentially insoluble (but can swell) in boiling solvent such as benzene, methyl ethyl ketone and ethanoltoluene aezotrope

 

[ top ] S

SEAL
Any device designed to prevent or control the movement of fluid from one chamber to another to exclude contaminants

SEALABILITY
The measure of fluid leakage both thru and across both faces of a gasket.  Measured either by using ASTM F-37 or DIN 3535 equipment and procedures

SHEETER
The special calender used to make compressed sheet

SKIM COAT
A layer of rubber laid on a fabric but not forced into weave.  Normally laid on fractioned fabric

SKIVE
The process of slicing or veneering off a sheet of PTFE from a billet

SLAB
A thick sheet

SPECIFIC GRAVITY
The ratio of the weight of a given substance to the weight of an equal volume of water at a specified temperature

STRAIN
The unit change, due to force (stress), in the size or shape of a body referred to its original size or shape – it is a non-dimensional quantity, but is frequently expressed in inches per inch, centimeters per centimeter, etc

STRESS
The intensity at a point in a body of the internal forces or components of force that act on a given plane through the point (lbs, sq. in.)

STRESS RELAXATION
The loss of initial bolt load or bolt stress.  Often accelerated by thermal cycling

STRESS-STRAIN
The relationship of load and deformation in a body under stress.  In rubber this is most commonly the relationship of tension (stress) and elongation (strain)

SWELLING
The increase volume or linear dimension of a specimen immersed in liquid or exposed to vapor

 

[ top ] T

TACK
The ability to adhere to itself

TENSILE STRENGTH
The maximum tensile stress during stretching a specimen to rupture measured in PSI

THERMAL CYCLING
The repetitious heating and cooling of a tank, vessel or piping system.  The duration of the cycle can vary tremendously

TOLERANCE
The upper and lower limits between which a dimension must be held

TORQUE
A force that either attempts, or actually does, product rotary movement.  With reference to bolts, it is the work to produce an axial clamping force on a gasket

 

[ top ] U

ULTIMATE ELONGATION
The maximum elongation prior to rupture

UNDERCURE
A state of vulcanization less than optimum.  May be evidenced by tackiness or inferior physical properties

 

[ top ] V

VHAP
The abbreviation for Volatile Hazardous Air Pollutant

VULCANIZATION
An irreversible process during which a rubber compound, through a change in its chemical structure becomes (1) less plastic and (2) more resistant to swelling by organic liquids; and elastic properties are conferred, improved or extended over a greater range of temperature

 

[ top ] W

WARP
The lengthwise yarns in a woven fabric

WEATHERING
The surface deterioration of a rubber article during outdoor exposure, such as cracking, crazing or chalking

WEFT
An English term for filling

WICKING
Leakage thru a gasket (not around it)

WIRE REINFORCED
A product containing wire(s) to give added strength, increased dimensional stability or crush resistance

WORK PRESSURE
The maximum operating pressure encountered during normal service

 

[ top ] X

 

[ top ] Y

“Y” FACTOR
The minimum design seating stress in either psi or megapascals over the contacted area of the gasket.  The stress required to provide a sealed joint with a 2 psig (virtually 0 psig) internal pressure in the joint

YIELD STRENGTH
The stress at which a product exhibits a specified limiting permanent set

 

[ top ] Z