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.