Q-Z
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
Q
QPL:
Abbreviation for Qualified Products List (associated with U.S. Government specifications).
QUARTER TURN VALVE:
A valve that will fully open or close with a 90-degree rotation of the stem.
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R
RADIAL:
In the direction perpendicular to a shaft axis.
RADIAL EXPANSION:
The ability for a packing material to spread out in the radial direction of a stuffing box when it is compressed.
RADIAL LIP SEAL:
A type of seal which features a flexible sealing member referred to as a lip. The lip is usually of an elastomeric material. It exerts radial sealing pressure on a mating shaft in order to retain fluids and/or exclude foreign matter.
RADIAL LOAD:
The total force (load) acting on the seal lip which tends to maintain contact of the lip on the shaft. It is the sum of the forces developed from seal interference and the garter spring.
RADIAL WALL VARIATION:
The difference between the minimum and maximum radial wall dimensions when measured around 360I of the seal lip.
RECIPROCATING:
Motion of a shaft back and forth in the direction of its axis.
RECIPROCATING MOTION:
An oscillating, back and forth motion as it normally pertains to a piston rod or valve stem.
RECIPROCATING PUMP:
A type of pump that relies on the reciprocating motion of a plunger, or series of plungers, to generate pressure and cause flow.
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.
REDUCED AREA FULL FACE (RAFF) GASKETS:
Developed by VSP Technologies for low pressure, utility steam systems in U.S. Navy ships per Navy Advisory NR.011-04, MIL-G-24696 GASKET MATERIAL R 031917Z JAN 05.
REGULAR BRAID:
A type of braided construction which yields a soft, flexible packing material having a square cross-section. Also referred to as “Square Braid”.
REMOTE HANDLING:
Handling without direct individual contact, usually done with robotic arms.
RESILIENCE:
The ratio of energy given up by the elastomer upon releasing it from a definite deformation to the energy required to produce the deformation. Unless the deforming is momentary, the result obtained will be complicated by the partially plastic nature of the elastomer.
RESILIENT:
Able to recover rapidly, i.e. elastic.
RETAINING RINGS:
Segmented metal rings installed directly against the back of the expansion joint flange and bolted through to the metal flange of the pipe.
RIB:
A long, narrow projection which is normally triangular in cross-section and which is molded into the outside lip surface of a helix seal. It is oriented at an angle to the shaft axis. One end of the rib forms part of the seal-lip contact surface.
RISING STEM VALVE:
A valve in which the movement of the stem is simply reciprocating, with no rotation.
RISING/ROTATING STEM VALVE:
A valve in which the movement of the stem is both reciprocating and rotating at the same time, usually following a helical path.
RMA:
Abbreviation for the Rubber Manufacturers Association.
RMS (SEE FINISH):
Root Mean Square, or average deviation from a theoretically perfect surface, is used to define surface finish roughness.
ROD:
The metal shaft which extends from the piston to outside the cylinder.
ROLL:
Sheet rubber and gasketing material of a uniform width rolled up on itself from which gaskets and other products of various shapes may be cut.
ROTARY:
The motion of a body turning on an axis.
ROTARY SERVICE:
A dynamic type of sealing application in which one member remains stationary while the other moves past it in a rotating mode. This type of service generally involves a continuous motion between members and higher surface speeds than those encountered in reciprocating applications. The generally higher degree of frictional heating combined with the fact it is concentrated in one area, sometimes lead to heat-related seal problems.
ROTATION (FLANGE):
The warping, bowing or bending of a flange that can occur from too much bolt load.
ROUGH TRIM:
A trimmed surface with irregularities on the outside and inside lip surfaces in the immediate vicinity of the contact line.
ROUGHNESS:
Irregularities in shaft surface texture which result from the production process. (See SAE J448a [June, 1963].)
ROUND BRAID:
A braiding method that yields a hollow tube of yarn. See also “Braid Over Braid” and “Braid Over Core”.
RPM:
An abbreviation for “Revolutions Per Minute”, a measurement of the rotary speed of a rotating shaft.
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 keytone, and ethanoltoluene azeotrope.
RUN OUT:
A measurement of how far a shaft moves in the radial direction.
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S
SAE:
Society of Automotive Engineers.
SCARF CUT:
See “Bevel Cut”.
SCOOP TRIM:
A trimmed surface which is concave.
SCORING:
Gouges on the surface of a shaft, stem, or bore due to mechanical wear.
SCRATCH:
A shallow discontinuity in the seal material whereby no material is removed.
SEAL:
Any device designed to prevent or control the movement of fluid from one chamber to another to exclude contaminants.
SEAL ASSEMBLY:
A group of parts, which includes sealing surfaces, provisions for initial loading, and a secondary sealing mechanism which accommodates the radial movement necessary for installation and operation.
SEAL CAGE:
See “Lantern Ring”.
SEAL CASE:
A rigid member to which the seal lip is attached
SEAL GASKET:
A gasket that is placed between two adjacent metal parts to make a gas tight connection.
SEAL OUTER DIAMETER:
The external diameter of a lip-seal assembly, which normally corresponds to the outer diameter of the outer seal case.
SEAL SOLUTION:
Any gasket or seal, which, when properly installed, prevents the escape of matter.
SEALABILITY:
The measure of fluid leakage both through and across both faces of a gasket. Measured either by using ASTM F-37 or DIN 3535 equipment and procedures.
SEATING LOAD:
The load required to properly compress a seal. This will vary depending on the size and shape of the seal. (This does not include operating hydro end forces.)
SELF-ENERGIZING O-RING:
O-ring with a hole drilled on the pressure side, allowing pressure to equalize inside the O-ring; prevents collapse of the ring.
SET BACK (STAND OF HEIGHT):
The distance the expansion joint is set back from gas stream to allow for lateral movements and to prevent the joint from protruding into the stream or rubbing on the baffle when operating under negative pressure. Set back also reduces the heat input and prevents abrasion from solids or particles in the stream.
SHAFT:
The metal rod connecting the impeller of a pump to the motor.
SHAFT ECCENTRICITY:
The radial distance which the geometric center of a shaft is displaced from the axis of shaft rotation.
SHAFT LEAD:
Spiral grooves on a shaft surface caused by relative axial movement of grinding wheel to shaft.
SHAFT RUNOUT:
See: Dynamic Runout.
SHAFT SURFACE FINISH:
See: Shaft Surface Texture.
SHAFT SURFACE TEXTURE:
A term used to describe the quality, appearance, or characteristics of the shaft surface resulting from operations, such as grinding, polishing, burnishing, etc. See SAE J448a (June,1963) for additional information.
SHEETER:
The special calender used to make compressed sheet.
SHIPPING STRAPS OR BARS:
Braces that are located between the two expansion joint flanges to prevent overcompression or distortion during shipment and joint assembly.
SINGLE-END COATING:
The process of applying a coating to the individual yarns (or “ends”) of a packing before they are braided. This process results in a very thorough, uniform coating throughout the braid.
SIZE, ACTUAL:
Actual dimensions of the part, including tolerance limits.
SIZE, NOMINAL:
Approximate size of part in fractional dimensions.
SKIM COAT:
A layer of rubber laid on a fabric but not forced into the weave. Normally laid on frictioned fabric.
SKIVE:
The process of slicing or veneering off a sheet of PTFE from a billet.
SKIVE CUT:
See “Bevel Cut”.
SLAB:
A thick sheet.
SLEEVE:
A metal cylinder that is placed over a pump shaft in the sealing area. In pumping applications, certain media and packing materials can cause abrasive wear on the rotating surface. A sleeve is a relatively inexpensive, replaceable component which protects the pump shaft from wear.
SLIP STICK:
A friction related phenomena in which the sealing element tends to adhere and rotate with the shaft surface momentarily until the elastic characteristics of the sealing element overcome the adhesive force, causing the seal lip to lose connection with the rotating shaft long enough to allow leakage. This cycle repeats itself continuously and is normally associated with non-lubricated and boundary-lubricated conditions.
SLURRY:
A fluid mixed with solid particles. In packing applications handling slurries, abrasion is a major concern. Steps must be taken to minimize abrasive wear of the packing materials.
SPECIFIC CONTACT PRESSURE:
Seating load divided by seal contact area.
SPECIFIC GRAVITY:
The ratio of the weight of a given substance to the weight of an equal volume of water at a specified temperature.
SPIRAL TRIM:
A trimmed surface which has a spiral pattern.
SPLICES:
Procedure for making endless boot or bellows from open-ended material. Splicing may be accomplished by one or more of the following: cementing, bonding, heat sealing, stitching, vulcanizing, or mechanical fasteners.
SPOOL PACKING:
Packing material that is braided and sold on a spool, as opposed to cut-ring sets or die-formed ring sets.
SPRING GROOVE:
A depression formed in the head section of the seal. It is generally semicircular in form and serves to accommodate and locate the garter spring.
SPRING OUTSIDE COIL DIAMETER:
The outer diameter of an individual helical coil of a garter spring.
SPRING RATE:
The force in pounds required to deflect an expansion joint one inch in compression and elongation or in a lateral direction.
SPRING RETAINING LIP:
The portion of the primary lip that restricts the axial movement of the extension spring from a predetermined position.
SPRING WITNESS MARKS:
A series of indentations or depressions remaining in the spring groove of a radial lip seal after the spring has been removed or dislocated.
SQUARE BRAID:
A type of braiding construction that yields a soft, flexible packing material having a square cross-section. Also referred to as “Regular Braid”.
SQUEEZE SEAL:
Also known as “Installation Activated”, a squeeze seal relies on the squeeze or compression it achieves at installation to create a seal. This squeeze or compression is due to its high degree of interference. This type of seal generally seals well at low pressure; however, in dynamic applications, it is characterized by a high wear rate and friction.
STACK HEIGHT:
1) The combined height of all the rings of a packing set. 2) The combined height of all the components in a stack of Belleville washers used to live-load a packing set.
STATIC SEAL:
A seal whose sealing surface sees no motion-the opposite of dynamic seal.
STEM:
The metal rod that connects the internal components of a valve to a handwheel, handle, or actuator.
STOCK:
In the papermaking industry, stock is the wet pulp mixture at any point in the papermaking process.
STRAIN:
The unit change, due to force (stress), in the size or shape of a body compared to its original size or shape-it is 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. inch).
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).
STRONG OXIDIZER:
In packing applications, strong oxidizers cause the degradation of organic packing materials such as carbon, graphite and cellulosic fibers. PTFE packing materials are usually used in these applications due to their oxidation resistance.
STUFFING BOX:
The space into which compression packing is inserted. Also known as a “Packing Gland”.
SUCTION PRESSURE:
The fluid pressure measured on the suction (or inlet) side of the pump where the fluid enters the volute.
SURFACE FINISH:
A measure of the roughness of a surface, usually expressed in microinches or micrometers.
SURFACE SPEED:
The linear speed of a point on the surface of a rotating shaft, usually expressed in FPM or m/sec.
SURGE PRESSURE:
Operating pressure plus the increment above operating pressure that the expansion joint will be subjected to for a very short time period. Surge Pressure is typically due to pump starts, valve closing, etc.
SW:
A Garlock Metallic Gasket style consisting of a winding alone, without a centering ring
SWELLING:
The increase in volume or linear dimension of a specimen immersed in liquid or exposed to a vapor.
SWI:
A Garlock Metallic Gasket style consisting of a winding and an inner ring.
SYMMETRICAL SEALS:
A seal that has the same shape on either side of its center line.
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T
TACKY (RUBBER SURFACE):
Sticky material that will adhere to itself, usually to ply up layers.
TENSILE STRENGTH:
The amount of tensile stress that causes a specimen to rupture; measured in psi.
TEXTURIZATION:
The process of embossing a texture on the surface of graphite foil to achieve better adhesion between layers of graphite foil, and prevent delamination of a die-formed graphite ring.
THERMAL BARRIER:
A layer of insulating material designed to reduce the surface temperature at the gas sealing layer to a level compatible with its heat resistance capability.
THERMAL CONDUCTIVITY:
A measure of the rate at which thermal energy is transferred through a substance. High thermal conductivity is an advantage in pump packing applications where it is important to transfer frictional heat away from the shaft/ packing interface so that the packing does not burn.
THERMAL CYCLING:
The repeated heating and cooling of a tank, vessel or piping system. The duration of the cycle can vary tremendously.
THERMAL EXPANSION:
The increase in volume or length of a material that occurs as a result of a temperature increase.
THERMAL MOVEMENTS:
Movements created within a system caused by a thermal change. Can be axial, lateral, or torsional.
TINSEL:
Fine slit widths of metallic foil. Die-formed rings are made from tinsel and used as junk rings, bushings, and in some cases even as bearings. Garlock manufactures rings made from copper tinsels.
TOLERANCE:
The upper and lower limits between which a dimension must be held.
TORQUE:
Informal Definition: A measure of “twisting force”. In packing applications, one might be concerned with the torque applied to the gland stud nut, or the torque required to overcome friction between the packing and the valve stem.
TORSIONAL ROTATION:
The twisting of one end of an expansion joint with respect to the other end about its longitudinal axis. Such movement being measured in degrees as is angular rotation.
TRIM:
The removal of superflous parts from a molded product, usually removal of parting line flash or feed sprues.
TRIM CUT:
Damage to the elastomeric portion of the seal during trimming.
TRIMMED LIP DIAMETER:
The lip diameter in the free state (no spring) developed by knife trimming the molded portion of the sealing element to form the contact line.
TRIMMING ANGLE:
The angle between the trimmed face of a seal lip and the seal axis.
TUBE:
The inner ply of the expansion joint that is in direct contact with the system media.
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U
U-SEALS:
A packing in which the element has a “U”-shaped cross-section.
ULTIMATE ELONGATION:
The maximum elongation prior to rupture.
UNBONDED FLASH:
Flash which does not properly adhere to the mating material to which it is intended to be bonded.
UNCOMPRESSED HEIGHT:
The height of a packing set or packing ring before being compressed in the stuffing box.
UNDER-CURE:
A degree of cure less than desired.
UNIROTATIONAL SEAL:
A seal, designed for applications having a single direction of shaft rotation.
UNITIZED SEAL:
A seal assembly in which all components necessary for accomplishing the complete sealing function are retained in a single package.
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V
VACUUM:
Negative pressure, when a gasket or seal is used to prevent the passage of external media or air into the system.
VALVE BODY:
The part of a two-piece valve that houses the internal workings of the valve. The flanges that attach the valve to a pipeline are also part of the body.
VALVE BONNET:
The part of a two-piece valve that attaches to the valve body. It houses the stuffing box and provides support to guide the valve stem.
VALVE STEM:
See “Stem”.
VHAP:
Abbreviation for “Volatile Hazardous Air Pollutant”.
VIBRATION:
The ability of a flexible connector to absorb mechanical oscillations in the system.
VISCOSITY:
A manifestation of internal friction opposed to mobility. The property of fluids and plastic solids by which they resist an instantaneous change of shape, i.e., resistant to flow.
VOC:
Abbreviation for “Volatile Organic Compound”.
VOLUME SWELL:
Increase in physical size caused by the swelling action of a liquid.
VOLUTE:
The internal area (housing) of a centrifugal pump where the fluid comes in contact with the impeller.
VSP ANTI-BUCKLING SPIRAL WOUND GASKET DESIGNS:
A revolutionary spiral gasket design that eliminates radial buckling at the source. Patented gasket design redirects gasket compression, thus eliminating the need for expensive inner rings and allowing for full gasket compression, even on lightly loaded ASME class 150 flanges. Currently available as Garlock EDGE® gasket.
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.
VULCANIZED SPLICE:
A splice that is bonded with heat and pressure.
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W
WEAR SLEEVE:
A replaceable metal ring generally used in assemblies to eliminate expensive shaft replacement caused by grooving that may occur at the seal-shaft interface.
WEATHERING:
The surface deterioration of a rubber article during outdoor exposure, such as cracking, crazing, or chalking.
WEEPAGE:
A minute amount of liquid leakage by a seal.
WELD IN BAFFLE:
A baffle that is designed to be welded to the duct wall. This design can be either single or double acting type.
WELDING BLANKET:
A fire resistant blanket that is placed over the expansion joint to protect it from weld splatter during field welding operation.
WHIP:
Deflection of a shaft (usually on a mixer or pump) due to a rotating mechanical load. A long shaft that is not supported by bearings is more susceptible to whip than a short shaft or one that is supported by bearings.
WICKING:
Leakage through a gasket, not around it.
WIPER RING:
A ring of braided packing, used in conjunction with graphite foil rings to wipe a reciprocating valve stem clean of graphite particles and keep the graphite contained in the stuffing box.
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.
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Y
“Y” FACTOR:
The minimum design seating stress in either psi or megapascals over the contacted area of a particular gasket. The stress required to provide a sealed joint with a 2 psig (virtually 0 psig) internal pressure in the joint.
YARN:
Generic term for continuous strands of textile fibers or filaments in a form suitable for weaving or otherwise intertwining to form a textile fabric.
YIELD:
The length of a packing material of a specified weight (Ft/ Lb). The inverse of this value (Lb/Ft) is also sometimes referred to as yield.
YIELD STRENGTH:
The amount of stress which causes a material to permanently lose its elasticity.
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