• A.N.S.I. Standard
    American National Standards Institute. A set of specifications, envelope dimensions, for centrifugal pumps manufactured in the United States
  • A.P.I. gland
    A seal gland that incorporates a non sparking disaster bushing along with a vent and drain connection (quench), and a flushing connection.
  • A.P.I. Specifications
    American Petroleum Institute Specifications. Usually adopted by oil refineries for petroleum applications. Includes seal gland and piping recommendations.
  • Abrasion
    Surface loss of a material due to frictional forces. The wearing away of a materiel surface by friction. Particles become detached by a combined cutting, shearing and tearing action. Furnace carbon blacks are the best ingredients found for increasing the resistance of rubber compounds to abrasion.
  • Abrasion resistance
    The resistance of a material to loss of surface particles due to friction.
  • Absolute pressure
    Atmospheric pressure added to gauge pressure.
  • Accelerated aging
    A method in which an attempt is made to produce and measure the effects of natural aging in a shorter period.
  • Accelerator (of vulcanization)
    Any substance, which hastens the vulcanization of rubber causing it to take place in shorter time or at a lower temperature. In earlier days basic oxides such as limes, litharge and magnesia were recognized as having this function. Nowadays the important accelerators are organic substances containing either nitrogen or sulfur or both. According to potency, or speed of action, accelerators are sometimes classified as slow, medium, rapid, semi-ultra and ultra-accelerators. Most accelerators enhance tensile properties, and many improve age resistance.
  • Accelerator Ultra
    An accelerator which causes very rapid vulcanization, even at comparatively low temperatures. Tetramethylthiuram disulfide is a typical ultra-accelerator. The dislkyldithiocarbamates and xanthates are also ultra-accelerators.
  • Acid Resistant
    Withstands the action of acids.
  • Acrylonitrile
    Cyanoethylene, vinyl cyanide, CH2=CHCN a volatile liquid boiling at 178.50 C, prepared by dehydration of ethylene cyanhydrin and by catalytic addition or hydrogen cyanide to acetylene. Used in co-polymerization with butadiene in the manufacture of Buna N or Nitrile rubbers.
  • Activator
    A substance, which by chemical interaction promotes a specific chemical action of a second substance. Most accelerators require activators to bring out their full effect in vulcanization, e.g., zinc oxide or other metallic oxides; some accelerators require a fat acid, especially with zinc oxide.
  • Active metal
    A corrosion resistant metal that has not been passivated. The protective oxide layer has not formed.
  • Adapter
    Connects and aligns the power end of an ANSI pump to the wet end.
  • Adapters
    A “V” shaped ring either male or female to fit together with “V” shaped rings to form a set of adjustable hydraulic packing.
  • Adhesion
    The state in which two surfaces are held together by interfacial forces which may consist of molecular forces or interlocking action, or both.The clinging or sticking of two (2) material surfaces to one another. In rubber parlance, the strength of bond or union between two (2) rubber surfaces or plies cured or uncured. The bond between a cured rubber surface and a nonrubber surface, e.g., glass, metal, wood, fabric.
  • Adhesion Failure
    The separation of two materials at the surface interface rather than within one of the materials itself.
  • Affinity laws
    They predict how capacity, head and horsepower are affected by changes in the centrifugal pump impeller diameter or shaft speed.
  • Aging
    (1)The irreversible change of material properties after environmental exposure for an interval of time; (2) Exposing materials to an environment for an interval of time.
  • Air Checks
    See Air trap
  • Air Curing
    The vulcanization of a rubber product in air as distinguished from vulcanizing in a press or steam vulcanizer.
  • Air ingestion
    Air is coming into the stuffing box because of a negative suction pressure.
  • Air trap
    Surface markings or depressions due to trapping air voids in body or part due to entrapped gas between the materials being cured and the mold or press surface.
  • Alignment
    The center line of the pump is perfectly aligned with the centerline of the driver,usually an electric motor.
  • Alpha sintered
    A type of silicone carbide that does not contain silica. Ambient heat and pressure -The heat or pressure in the area where the equipment is located.
  • Aluminum Seal Rings
    Sealing rings for pistons made from high grade aluminum alloy.
  • Amines
    Derivatives of ammonia in which one or more or (lie hydrogen atoms is replaced by an alkyl or aryl radical. They are called primary, secondary and tertiary amines according to the number of such substitutions. Example: RNH2, R2NH, AND R3N.
  • Aniline point
    The temperature in degrees Fahrenheit at which a kerosene, diesel fuel or distillate is miscible with an equal volume of aniline. Low aniline point hydrocarbons tend to swell rubbers to a greater degree than those with a high aniline point.
  • Annealing
    To soften the metal by heating it to a predetermined temperature somewhere below its melting point.
  • Anodize
    A treatment used on aluminum to put a heavy stable film of oxide on the metal surface.
  • Anti-Extrusion Rings
    Also, called back-up rings or anti-extrusion rings. Used to fit behind rubber o-ring seals to prevent extrusion into the gap between the metal pieces
  • Anti-friction bearing
    Usually referring to a ball or roller bearing
  • Anti-vibration Mounts
    Rubber molded pieces used as padding between a motor and the frame to prevent vibration transfer to the machine to which it is mounted.
  • Antioxidant
    Usually organic and nitrogenous. A substance, which inhibits or retards oxidation and certain other kinds of aging. Some antioxidants cause staining or discoloration of the rubber compound on exposure to light and are used only in black or dark-colored goods. Others (phenolic), described as non-staining, are used in white or light-colored goods.
  • Application
    A description of the fluid and operating conditions that we are trying to pump or seal.
  • Apportionment
    Referred to here as a part of Reliability Engineering. Synonymous with the term Reliability Apportionment, which is the assign- ment of reliability goals from system to subsystem in such a way that the whole system will have the required reliability.
  • AQ Seal
    A special purpose hydraulic seal
  • Assortment Kits
    A convenient package containing several sizes of the same seal, o-ring or retainer ring.
  • Atmospheric pressure
    At sea level, atmospheric pressure is 14.7 psi.
  • Autoclave
    A pressure vessel into which materials or articles can be placed and exposed to steam under pressure. It is commonly used for vulcanization.
  • Automatic U-joints
    Also called u-cups, ucups or u cups. A “U” shaped sealing ring made from a strong pliable plastic or rubber.
  • AVS Standard
    An old, obsolete standard that has been replaced by the A.N.S.I. standard.
  • B.E.P.
    B.E.P. – The best efficiency point. It is the point where the power coming out of the pump (water horse power) is the closest to the power coming into the pump (brake horse power) from the driver. This is also the point where there is no radial deflection of the shaft cause by unequal hydraulic forces acting on the impeller.
  • B.H.P.
    Brake horse power. The actual amount of horsepower being consumed by the pump as measured on a pony brake or dynamometer.
  • Back Plate
    Used in some centrifugal pumps to position the stuffing box and provide an impeller wear surface.
  • Back Pull Out Pump
    A design that allows the wet end of the pump to be left on the piping when the power end and adapter are removed. A.N.S.I. pumps are designed this way.
  • Back to Back Double Seal
    The rotating seal faces are facing in opposite directions. The worst possible configuration. In the past this term was used to describe a higher barrier fluid pressure between dual mechanical seals.
  • Backrinding
    Defect in which the rubber adjacent to the mold parting line shrinks below the level of the molded product, often leaving the parting line ragged and torn.
  • Backringing
    Distortion at the mold parting line usually in the form of wrinkles, folds, tears or indention’s. In severe cases may cause over-all dimensional changes.
  • Baffle Rings
    A ring used to slow the flow of fluids along a shaft.
  • Balance Ratio
    A 70/30 balance ratio means that 70% of the seal face closing area is seeing the stuffing box pressure and 30% is not seeing the pressure.
  • Balanced Seal
    A design in which the seal face closing area is reduced to lower the closing force, and reduce the heat generation between the faces.
  • Ball Bearing
    Consists of an inner race, an outer race, and a series of balls between them. Often called a precision or anti friction bearing.
  • Ball Valve Seats
    A teflon ring shaped to fit against the ball in a flow control valve.
  • Bar
    Metric term for one atmosphere of pressure.
  • Barrier Fluid
    The high pressure fluid that is circulated between two mechanical seals. The fluid should enter the bottom and leave the top to prevent air pockets.
  • Base Plate
    The pump and motor mount on this unit. The pump and motor feet closest to the coupling should be doweled to the base plate.
  • Batch
    The product of the one mixing operation in an intermittent process.
  • Bayonet
    The mechanical seal drive lugs wear into the drive slots and prevent the seal faces from moving forward to compensate for wear.
  • Bearing
    Supports the rotating shaft and allows it to turn with a minimum amount of friction. Could be either sleeve or anti-friction type.
  • Bearing Seals
    A seal ring made to snap-fit into a ball, roller or spherical bearing to exclude dust, dirt or trash.
  • Bearings
    A machined or molded plastic ring used as a guide ring or wear ring in a hydraulic cylinder.
  • Bellows
    A corrogated rubber or plastic piece which can stretch with a shaft to keep the shaft clean.
  • Bellows Plate
    A thin, stamped disc. Two are welded together to form a convolution.
  • Belts
    A v-belt, flat belt or drive belt made from plastic or rubber.
  • Benchmark Data
    The results of an investigation to determine how competitors and/or best-in-class companies achieve their level of performance.
  • Bernoulli’s Law
    A moving stream of liquid or gas exerts less sideways pressure than if it were at rest. The result is that things seem to be drawn into the stream, but they are really being pushed in by the higher pressure from outside.
  • Bias Angle
    (1) Acute angle between the direction of the cut and the diameter of the wrap in the production of wrapping for hose; (2) Acute angle between the direction of the cut and the direction of the cords in the production of fabric plies.
  • Bill of Material
    Total list of all components/materials required to manufacture the product.
  • Blister
    A cavity or sac that deforms the surface of a material.
  • Bloom
    The coating or efflorescence of sulfur, wax or oilier ingredients of vulcanized rubber, which may gradually appear on the surface of some rubber articles. Bloom depends on the solubility of the substance in the rubber.
  • Body Bound Bolts
    The bolt has an interference fit with the bolt hole.
  • Bond
    The union of materials by use of adhesives, usually used in related parts vulcanized after attaching.
  • Bonded Seals
    A flat steel washer with a rubber sealing ring molded into the center to fit over a bolt to provide a seal.
  • Bonding Agents
    Substances or mixtures of substances that are used for attaching rubber to metal, fabrics or other substrates. Generally the rubber compound is vulcanized by heat in the process. Cyclized rubber or rubber isomers, halogenated rubber, rubber hydrochloride, reaction product of natural rubber and acrylonitrile, polymers containing diisocyanates, are all used.
  • Brinnell Hardness
    A method of measuring the hardness of metal parts and hard seal faces. Above 350 the standard machining operations of turning, boring, drilling, and tapping become uneconomical.
  • Brittleness
    Tendency to crack when subjected to deformation.
  • Bronze Piston Bearings
    Guide rings or wear rings made from bronze to fit on a piston in a hydraulic cylinder.
  • Bumpers
    A rubber or plastic part used to prevent metal-to-metal contact.
  • Buna N
    A general term for the copolymers of butadiene and acrylonitrile. Typical commercial polymers are Hycar and Paracril.
  • Buna S
    A general term for the copolymers of butadiene and styrene.
  • Bushing
    A rubber or plastic spacer to provide a wear surface around a shaft.
  • Butadiene
    CH2=CH-CH=CH2. A gaseous hydrocarbon of the diolefin series, boiling at 5~C. Also known as erythrene, divinyl, pyrollylene, Polymerizable to a synthetic rubber, polybutadiene. Butadiene is the chief raw material for making the synthetic rubbers today. Co polymerized with styrene it yields SBR or GR-S; with acrylonitrile the various Buna N or nitrile synthetic rubbers are obtained.
  • Butt Joint
    Joining two ends of material whereby the junction is perpendicular to the ID of an O-ring.
  • Butyl
    A synthetic rubber of the polybutene type exhibiting very low permeability to gases.
  • Butyl Rubber
    A copolymer of isobutylene and isoprene, polymerized almost instantaneously in methyl chloride with aluminum chloride at about
  • Bypass Line
    Used to either re-circulate fluid from the pump discharge to the stuffing box, the stuffing box to the pump suction, or the pump discharge to a lower pressure point in the system.
  • C Frame Adapter
    Used to connect and align the pump to the motor with registered fits. (imperial dimensions. Called the D frame adapter in the metric system)
  • C.I.
    The abbreviation for cloth- inserted, indicating a sheet of rubber containing one or more plies of fabric covered with rubber.
  • C.L.A.
    Center line average. A method of measuring surface finish in the metric system. Uses microns as a unit.
  • Canned pump
    A non seal pump with the shaft, bearings and rotor contained in a can to prevent product leakage. Limited to pumping clean lubricating liquids.
  • Canned Wipers
    A wiper or scraper ring for a hydraulic cylinder which has a metal outside diameter so that it can be press-fitted into a housing.
  • Capacity
    Fluid flow measured in gpm, liters/min, M3/hr. etc.
  • Carbide
    The compound formed when carbon combines with an element. The carbides of metal are very hard and are often used as a mechanical seal face.
  • Carbon Black
    Finely divided carbon formed by the incomplete combustion of natural gas or petroleum in large, closed furnaces.
  • Carbon Bushing
    Used as a restrictive bushing in flushing applications, a thermal barrier in high temperature applications, a disaster bushing in an A.P.I. gland and to support a deflecting shaft in many mechanical seal applications.
  • Carbon/Graphite
    A common mechanical seal face material chemically inert to most fluids with the exception of oxidizers, bleaches, halogens and a few other fluids.
  • Carbonizing
    A reduction of hydrocarbons resulting in the formation of carbonaceous residue that will interfere with the movement of a mechanical seal. Often called “coking”.
  • Carcinogen
    A cancer producing substance.
  • Cartridge Seal
    A self contained assembly containing the seal, gland, sleeve, and both stationary and rotating seal faces. Usually needs no installation measurement. Must be used if impeller adjustments are made. Cartridge seals are the standard for A.P.I. seal applications.
  • Cast Iron Piston Rings
    Piston sealing rings made from cast iron used in hydraulic cylinders.
  • Catalyst
    A chemical in small quantities which accelerates a chemical reaction without itself necessarily becoming part of the final product.
  • Cavitate
    Cavities or bubbles form in the fluid low pressure area and collapse in a higher pressure area of the pump, causing noise, damage and a loss of capacity.
  • Cellular Rubber
    Rubber products which contain cells or small hollow receptacles. The cells may either be open or interconnecting or closed and not interconnecting.
  • Center Line Design
    The pump is suspended on feet attached to the sides of the volute instead of the bottom. Used in higher temperature (> 100
  • Centipoise
    The metric system unit of viscosity.
  • Centistoke
    The kinematic unit of viscosity. Viscosity in centipoises divided by the liquid density at the same temperature, gives kinematic viscosity in centistokes.
  • Centrifugal Pump
    Moves liquid with centrifugal force. Available in circular and volute configurations.
  • Centrifugal Separator
    Sometimes called a cyclone separator. Uses centrifugal force to throw solids out of the fluid. Does not work very well in slurry seal applications.
  • Ceramic
    A hard, chemically inert seal face material that includes products refereed to as silicone carbide.
  • Change of State
    When a liquid flashes into a vapor, solidifies, crystallizes, cokes etc.
  • Characteristics Matrix
    An analytical technique for displaying the relationship between process para- meters and manufacturing stations.
  • Checking
    The short, shallow cracks on the surface of a rubber product, resulting from damaging action by environmental conditions.
  • Checking Sunlight
    The development of minute surface fissures as a result of exposing rubber articles to sunlight, generally accelerated by bending or stretching.
  • Chemical Resistance
    The resistance offered by elastomer products to physical or chemical reactions as a result of contact with or immersion in various solvents, acids, alkalis, salts, etc..
  • Chemraz
    An “elastomer like” material manufactured by Green Tweed of England. Used to seal most solvents and other aggressive fluids.
  • Chevron Packings
    Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple “V” shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end.
  • Chevrons
    See Chevron Packing above.
  • Chloride Stress Corrosion
    Occurs in the 300 series of stainless steel. Caused by a combination of tensile stress, chlorides and heat. No one knows the threshold values.
  • Chloroprene
    2-Chloro-l, 3-butadiene, a volatile, colorless liquid which boils at 59c., synthesized from acetylene. It is used in the manufacture of neoprene, which is obtained by polymerizing chloroprene under suitable conditions.
  • Chrome Carbide
    Forms when chrome forms with carbon in the heat affected zone during the welding of stainless steel. The use of low carbon stainless steel is recommended in these applications.
  • Chrome Oxide
    The passivated layer that forms on the 300 series of stainless steel.
  • Circular Casing
    Used with centrifugal pumps that circulate fluid rather than build head or pressure.
  • Clam Shell
    Used to set the pitch (distance between convolutions) while heat treating a metal bellows core.
  • Clay
    Any naturally occurring mineral substance consisting preponderantly of hydrous aluminum silicates, which divided and mixed with water, yields a more or less plastic mass which can be formed and molded, and which will retain its shape on drying. Clays vary greatly in composition but in their purest forms they approach the composition of Kaolinite, A12O3.2Si2.2H20. They are used as compounding ingredients in rubber, some of them having mild reinforcing properties.
  • Close Coupled
    The pump impeller is mounted directly on the motor shaft. There is no separate bearing case.
  • Coated Face
    A hard coating is plated or welded to a softer base material. Presents problems with different thermal expansion rates, the hard coating can “heat check” or crack. Not recommended as a seal face material.
  • Coefficient of Expansion
    The coefficient of linear expansion is the ratio of the change in length per degree to the length at 0 Celsius. The coefficient of surface expansion is two (2) times the linear coefficient. The coefficient of volume expansion (for solids) is three (3) times the linear coefficient. The coefficient of volume expansion for liquids is the ratio of the change in volume per degree to the volume at 0 Celsius.
  • Coke
    A hard black substance that forms when petroleum products are over heated. It interferes with seal movement and will open the lapped faces.
  • Cold Flow
    Continued deformation under stress.
  • Compact Seals
    Multi-piece seal sets, generally used as piston seals in a hydraulic cylinder. Made to fit in a limit space, compact piston seals contain a primary sealing component, guide rings and back-up rings in one convenient set.
  • Composite
    When used in the content of mechanical seal faces, it refers to either a non metallic material or a combination of non metallic face inserted into a metal holder.
  • Compound
    1). In chemistry, it is the material resulting from the chemical union of two or more elements in definite proportions and in which the properties of the individual elements have disappeared. – 2). In rubber manufacture, it is the composition or formula of stock, the ingredients of which, however, may not all be chemically combined and is therefore more of a physical mixture.
  • Compression Deflection Characteristics
    The tests for compression-deflection characteristics constitute methods of compression stiffness measurement. One compression test involves the determination of a load required to case a specified deflection, and another is a compression test in which a specified weight or compressive force is placed on the specimen and the resulting deflection is measured and recorded.
  • Compression Set
    The residual deformation of a material after removal of the compressive stress.
  • Concentric Dual Seal
    One seal is located inside the other, with a common hard face shared by both of them. Because of its large radial space requirement the seal is usually limited to mixer type applications.
  • Concentricity
    When the parts share the same center line they are concentric to each other.
  • Condensate
    Condensed steam.
  • Conductive
    To conduct or transmit heat or electricity.
  • Contact stain
    Discoloration of a product by another material or by a rubber article in the area directly touching it.
  • Convection
    A natural circulation of fluid. The hot fluid (lighter) rises and the cool fluid (heavier) sinks.
  • Convection Tank
    Used to contain fluid between two mechanical seals. An enclosed heater or cooler can be used to control the barrier or buffer fluid temperature. Pressure or level gages can indicate which seal has failed.
  • Convolution
    Two metal bellows plates welded or formed together. To count the number of convolutions in a metal bellows you count the spaces between the bellows plates.
  • Cooling Jacket
    Surrounds the stuffing box of the pump to control the temperature of the fluid in the stuffing box. Usually molded into the back plate.
  • Copolymer
    A copolymer is a high polymer consisting of molecules containing large numbers of units of two or more chemically different types in irregular sequence. Butadiene (78) and styrene (22) forms a copolymer known as GR-S.
  • Copper Seal Rings
    Rings made from thin copper formed over fiberous filler to seal in high temperature.
  • Corrosion Resistant
    Corrodes at a rate of less than 0.002 inches (0.05 mm) per year.
  • Coupling
    Used to connect the pump to the driver. It transmits torque and compensates for axial growth, but not for radial misalignment.
  • Crazing
    A surface effect on rubber articles characterized by many minute cracks.
  • Creep
    The deformation, in either cured or uncured rubber under stress, which occurs with lapse of time after the immediate deformation.
  • Critical Speed
    Any object made of an elastic material has a natural period of vibration. When a pump rotor or shaft rotates at any speed corresponding to its natural frequency, minor unbalances will be magnified. These speeds are called the critical speeds.
  • Cross Section
    An O-ring as viewed if cut at right angles to the axis showing internal structure.
  • Crush Washers
    A washer made to be crushed to form a seal.
  • Cryogenic
    Very cold temperatures.
  • Cup Packings
    Sealing devices made in the shape of a cup with outer lips curved upward usually made from rubber, fabric reinforced rubber or polyurethane.
  • Cure
    The act of vulcanization. See Vulcanization.
  • Cushioning Seals
    Sealing rings mounted into a cylinder to cushion the stroke or prevent metal to metal contact.
  • Custom Molded Products
    Special shaped parts molded from rubber or plastic made to fit the machine or device it is used in.
  • Cut
    The distance between cuts or parallel faces of articles produced by repetitive slicing or cutting of long preshaped rods or tubes such as lathe cut washers.
  • Cutwater
    Directs the pumped liquid to the discharge piping.
  • Cyclone Separator
    A device used in some seal applications to separate solids from liquid by utilizing centrifugal force. Not very reliable.
  • Cystalinity
    Stretched natural rubber forms a high oriented state and shows X-ray diffraction patterns and other properties common to truly crystalline materials. The amorphous and crystalline regions are not mechanically separable phases, but the same molecule may at the same time have part of its length in a crystalline, and the remainder In an amorphous region.
  • D frame Adapter
    Used to connect and align the pump and motor (manufactured in metric dimensions). The Imperial version is called a “C” frame adapter.
  • D-Gun Process
    A metal spray process used to put a hard surface on a softer metal. This is the normal method of applying nickel base tungsten carbide. It is preferred over the popular Plasma Process if you arre manufacturing a mechanical seal face.
  • D.I.N. Standard
    The German standard for industrial products.
  • Damping
    The physical touching of a component to arrest vibration.
  • Dead Ending
    Isolating the stuffing box. No recirculation or flushing lines in or out.
  • Deflection
    Movement or displacement of the shaft in a radial direction.
  • Density
    Measured in gm/cm2 or lb/in 2 A measure of the weight of the fluid. A better term than specific gravity.
  • Design Failure Mode and Effects Analysis (DFMEA)
    An analytical technique used by a design responsible engineer/team as a means to assure, to the extent possible, that potential failure modes and their associated causes/mechanisms have been considered and addressed.
  • Design for Manufacturability and Assembly
    A simultaneous engineering process designed to optimize the relationship between design function, manufacturability; and ease of assembly.
  • Design Information Checklist
    A mistake proofing checklist designed to assure that all important items are considered in establishing design requirements.
  • Design Reviews
    A proactive process to prevent problems and misunderstandings.
  • Design Validation
    Testing to ensure that product conforms to defined user needs and/or requi- rements. Design validation follows successful design verification and is normally performed on the final product under defined operating conditions. Multiple validations may be performed if there are different intended uses.
  • Design Verification
    Testing to ensure that all design outputs meet design input requirements. Design verification may include activities such as: Design ReviewPerforming Alternate CalculationsUnderstanding Tests and DemonstrationsReview of Design Stage Documents Before Release
  • Dial Indicator
    A tool used to measure concentricity or displacement of a shaft.
  • Diaphragm Seal
    A flexible membrane that seals and isolates an enclosure. The flexible nature of this seal allows pressure effects to cross the barrier but not the material being contained.
  • Dielectric Strength
    The measure of a product’s ability to resist passage of a disruptive discharge produced by an electric stress; the voltage that an insulating material can withstand before breakdown occurs.
  • Dilatant
    A liquid that thickens (increases its viscosity) with agitation.
  • Disaster Bushing
    Used in A.P.I. glands to support the shaft in the event of a bearing failure, or to prevent product from rushing to atmosphere after a seal failure. The close clearance (0.025 inch or 0.5 mm.) directs most of the leakage through a drain connection in the seal gland to an appropriate container.
  • Discharge Recirculation
    Connecting a line from the discharge side of the pump to the stuffing box. Should be used with a close fitting bushing in the end of the stuffing box to increase the stuffing box pressure. A common application when pumping a fluid close to its vapor point.
  • Discs
    Flat, round saucer shaped pieces made from rubber or plastic.
  • Disperse
    To cause particles or molecules of matter to separate and become uniformly scattered throughout a medium. In a rubber compound, the particles of compounding ingredients are dispersed in the rubber. In latex, rubber globules are dispersed in an aqueous medium.
  • Distributor Seals
    Sealing rings used to seal in oil and seal out dust, dirt or trash on an automobile engine electric spark distributor.
  • DN Factor
    Do not use precision bearings if the bearing bore (millimeters) x rpm. is 300,000 or greater
  • Double Acting Seals
    Seal rings which seal in two direction, on the push and the pull stroke of a hydraulic or pneumatic cylinder.
  • Double Balanced Seal
    Hydraulically balanced in both directions. A desirable feature, but seldom provided by seal manufacturers.
  • Double Seal
    An out dated term describing two seals in a pump. The latest terminology is “dual seals”. In the past the term was used to describe a higher pressure barrier fluid between dual seals.
  • Double Suction Pump
    The rotor is suspended between two bearings with the fluid entering on either side of the impeller. Used at higher capacities.
  • Double Volute
    A centrifugal pump design that incorporates two cut waters to prevent shaft deflection when the pump is operating off of the B.E.P. Lowers the efficiency of the pump and therefore seldom used on smaller size impellers.
  • Drive Lugs
    These lugs or pins transmit the torque from the set screws to the seal face.
  • Dry Running
    Running without fluid at the seal face.
  • Dual Seal
    Two seals running in various configurations: back to back, tandem, face to face, or concentric.
  • Duck
    A compact, firm, heavy, plain weave fabric made from cotton or synthetic fibers, or a combination of both. Duck is also known as canvas, army duck, belt duck harvester duck, hose duck and shoe duck.
  • Ductility
    The property of a metal that lets you give it a great deal of mechanical deformation without cracking.
  • Dumb-Bell (Test-Piece)
    In the physical testing of rubber, a strip test-piece is used that is shaped like a dumb-bell, i.e., constricted in the middle and flaring out at the ends, as distinguished from circular or ring test-piece. The dumb-bell is the most commonly used form or test-piece. Dimensions are set by ASTM standards.
  • Duocone Seals
    A special cone-shaped sealing ring.
  • Durability
    The probability that an item will continue to function at customer expectation levels, at the useful life without requiring overhaul or rebuild due to wearout.
  • Durometer
    The most common Durometer. Type A or A-2 is an instrument for determining the hardness or rubber by measuring its resistance to the penetration (without puncturing) of a blunt indentor point impressed on the rubber surface against the action of a spring; a hand and special scale indicate the resistance to penetration 01. “hardness”. The scale reads from zero (0) to 100, zero (0) being very soft and 100 being very hard. The Type D durometer has a sharp indentor point and is used to measure varying degrees of hard rubber up to ebonite.
  • Dust Seals
    Seals used to exclude dust from a machine or device.
  • Dynamic Elastomer
    The rubber part that has to move to move or flex to compensate for seal face wear or shaft movement.
  • Dynamic Head (System Head)
    The pump head created by friction in the piping system.
  • E.P.A.
    Environmental protection agency. A government agency with a mandate to protect the environment.
  • E.P.R.
    Ethylene propylene rubber. The most common elastomer used in the sealing of water based and higher pH materials. Cannot be used in petroleum products.
  • Effective Diameter
    In metal bellows terminology it is the calculated diameter where the pressure penetrates between the metal plates. This number is used to determine the hydraulic balance diameter of the seal face.
  • Efficiency
    Power out of the equipment divided by power in.
  • Elastic Modulus
    The value of the load (in pounds per square inch of original cross-section) required to give an intermediate elongation, is usually called the modulus at that elongation. The expression used is “modulus at 300 percent elongation.” Tensile-stress observations of this sort arc exceedingly useful in characterizing a particular compound, since by indicating the position and shape of the stress-curve. They show the relative toughness of the vulcanizate.
  • Elastic Range
    The stressed part retains its memory and returns to its original shape.
  • Elasticity
    The property of an article which tends to return to its original shape after deformation. Also a property of any material which makes it tend to recover its original dimensions after removal or the force which deforms it.
  • Elastomer
    A rubber like material that, when compressed and then released will return to 90% of its original shape in less than five seconds.
  • Electrolysis
    A process involving chemical change caused by the passage of an electric current through a liquid.
  • Elongation
    Extension produced by a tensile stress. Also, in the physical testing of rubber, the increase in length of a test-piece when stretched, usually expressed as a percentage of the original length; for example a 1″ piece stretched (0 6″ has an elongation of 500%. Elongation at break — the elongation of a test-piece at thc moment of rupture, usually expressed as percentage of the original length.
  • Embrittlement
    A rubber compound becoming brittle during low or high temperature exposure or in the process or aging.
  • Encapsulated O-rings
    A rubber o-ring with a thin jacket of PTFE or Teflon surrounding the softer core material, which allows it to be used in chemical applications.
  • Endurance Limit
    Beyond this point the metal will fatigue without increasing the stress.
  • Excluders
    Also called wipers or scrapers – used in a hydraulic or pneumatic cylinder to exclude and scrape the rod clean.
  • Expanded Rubber
    Cellular rubber having closed cells made from a solid rubber compound.
  • Extrusion
    1) Distortion, under pressure, of portion of seal into clearance between mating metal parts. 2) Material, under pressure, which is forced through the opening of a die in order to obtain a desired cross sectional shape.
  • Eye of the Impeller
    The center of the impeller, where the fluid enters.
  • F.P.M. (fpm.) – feet per minute.
    When used in the context of seals it is measured at the center of the seal face.
  • Face Flatness
    Measured by an optical flat and a monochromatic light. The measurement is read in helium light bands (.0000116 inches or 0,3 microns).
  • Face Lubrication
    The fluid or vapor that sometimes exists between lapped mechanical seal faces.
  • Face Pressure
    The sum of all the loads on the seal face including the spring load, hydraulic load and shaft axial thrust, divided by the area of the seal face. This face load is reduced by friction between the sliding elastomer and the shaft or sleeve.
  • Face Seals
    Rubber rings used like a gasket between two flat pieces of metal.
  • Face to Face Seals
    Two seals running against a common seal face. The barrier fluid pressure is always lower than stuffing box pressure.
  • Failure Modes Analysis (FMA)
    A formal, structured procedure used to analyze failure mode data from both current and prior processes to prevent occurrence of those failure modes in the future.
  • Fastener Seals
    See Bonded Seals.
  • Feasibility
    A determination that a process, design, procedure, or plan can be successfully accom- plished in the required time frame.
  • Fibre Seal Rings
    A gasket or other die cut, water-jet cut or formed ring used to seal between two surfaces.
  • Filled Carbon
    Contains organic or inorganic materials that might be sensitive to temperature, or be attacked by the fluid you are sealing. Usually a low cost carbon.
  • Filler
    Any compounding material, usually in powder form, added to rubber in a substantial volume to improve quality or lower cost. The most important reinforcing filler is carbon black. The most important inert filler, diluent or extender is whiting.
  • Filter
    A devise used to remove solid particles from liquid. It removes smaller paricles than a strainer.
  • Finish, Mold
    The quality or appearance of the machined surface of a mold.
  • Finish, Product
    The quality or appearance of the surface of a rubber product.
  • Finite Element Analysis
    A technique for modeling a complex structure. When the mathematical model is subjected to known loads, the displacement of the structure may be determined.
  • Finite Element Analysis (FEA)
    A computer generated method of predicting seal face distortion.
  • Flange Packings
    A pipe flange gasket.
  • Flange Seals
    A seal used on the bolt-up flange on a hydraulic systems – usually on the hose fitting or pipe flanges.
  • Flash
    Excess rubber on a molded product resulting from cavity overflow at the parting lines where the mold sections are separated.
  • Flashing
    A rapid change in liquid state from a liquid to a gas.
  • Flatness
    Measured by Helium light bands (0.0000116″ or 0,3 microns) as opposed to surface finish that is measured by R.M.S. or C.L.A.
  • Flex Cracking
    A cracking condition of the surface of rubber articles such as tires and footwear, resulting from constantly repeated bending or flexing in service.
  • Flexibility Factor
    Same as L3/D4 Used to predict shaft bending problems.
  • Flexible Member
    The portion of the seal containing the springs or bellows.
  • Flexible Shaft
    A shaft with an operating speed higher than its first critical speed.
  • Flow Marks
    Surface imperfections due to improper flow and failure of stock to knit or blend with itself during the molding operation.
  • Fluid
    The material assumes the shape of its container. It could be either a liquid or a gas.
  • Flurocarbon
    Genetic term for the elastomer called Viton
  • Flush
    Putting an outside liquid into the stuffing box of the pump at a pressure higher than stuffing box pressure. All of this liquid mixes with and dilutes the pumped fluid.
  • Foot
    Supports the wet and power end of the pump and attaches it to the base plate
  • Force
    Created whenever pressure works on an area. The units are pounds. (F = P x A)
  • Formed Metal Bellows
    Manufactured by stretching and compressing the metal bellows material. Not usually used in mechanical seals because of its high spring rate.
  • Francis Vane Impeller
    The most popular impeller shape with a specific speed between 1500 and 4000.
  • Free Length
    The uncompressed axial length of a seal.
  • Frett or Fretting
    Damage or grooving caused by the removal of the protective oxide that is formed on most corrosion resistant metals. It happens when a softer material (rubber) rubs against a hard shaft or sleeve. A common problem with low cost O.E.M. mechanical seals and bearing grease or lip seals.
  • Friction
    Resistance to motion due to the contact of surfaces.
  • Fugitive Emission
    The government has designated certain chemicals as hazardous to the environment. If any of these chemicals is released to the atmosphere they are called fugitive emissions.
  • Galvanic Series
    A list of metals with those on the top of the list being attacked by those lower down in the list. The father apart on the list, the faster the attack.
  • Gap Seals
    A seal ring used to seal between the gaps of metal or plastic.
  • Gasket
    A flat, non-moving, compressible rubber-like device squeezed between two flat sufaces forming a static seal. Gaskets can be made from homogeneous rubber, fabric reinforced rubber, fiberous materials with rubber binders, flexible graphite, PTFE and many other materials. Some gaskets are made from a combination of metal and fiberous materials and some are all metal. An o-ring, while not flat is also referred to as a gasket at times.
  • Gate (rubber injection or transfer mold)
    The orifice used to control the flow of rubber, and through which a shaped cavity in a mold is filled with rubber.
  • Gland
    The part that holds one half of the mechanical seal and attaches to the stuffing box.
  • Gland Bearing Rings
    Also called guide rings or wear rings used as a bearing surface for the rod of a hydraulic ram or cylinder.
  • Gland Seals
    Seals or packings used a the main sealing device in a ram or cylinder.
  • Glandsele
    The brandname of a type of rod seal.
  • Glass Temperature (Tg)
    The temperature at which a rubber becomes glass-like. a more recent name for Second Order Transition point.
  • Glass Transition Point
    Temperature at which a material loses its glass-like properties and becomes a semi-liquid.
  • Globe Valve Discs
    Teflon rings used to seal in a globe valve.
  • Glyd Ring
    Also known as wear rings or guide rings made from plastic, teflon or soft metal to act as a bearing surface for a cylinder rod.
  • Grain
    The unidirectional orientation of rubber or filler particles occurring during processing (extrusion, milling, calendering) resulting in anisotropy of a rubber vulcanizate.
  • Grease Seal
    A spring loaded elastomer seal commonly used to seal bearings. Sometimes called a “lip seal”. Not a good choice for sealing the bearing casing of a pump. A labyrinth or face seal would be a better choice.
  • Grease Seals
    Also called oil seals, rotary seals or shaft seals. Made of rubber to seal grease in a housing with a rotating shaft.
  • Green Strength
    The resistance to deformation of a rubber stock in the uncured state. (2) Uncured adhesion between plied or spliced surfaces.
  • Grommet
    A rubber ring used to fit into a hole in sheet metal aloow wires, shafts or rod to exit the housing without touching the metal.
  • Guide Rings
    See also wear rings, guide rings or bearing rings. Usually made from a form of Teflon or PTFE
  • Guiding Elements
    Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods.
  • H-ring
    Also called H-Wiper. An “H” shaped rod wiper ring made from NBR or polyurethane for a hydraulic or pneumatic cylinder.
  • Halogen
    Elements that attack carbon. Fluorine, bromine, chlorine, astatine and iodine.
  • Hard Face
    A seal face either rotating or stationary. The most common materials are silicone carbide, ceramic, tungsten carbide, Stellite, Ni-resist. The hard face must be the wider seal face.
  • Hardness
    The relative resistance of rubber to the penetration (without puncturing) of a blunt point impressed on its surface.
  • Harmonic Vibration
    Vibtrating in harmony with something near by. This can be a big problem for bearings in stationary or non running equipment.
  • Hastelloy “C”
    A nickel rich, corrosion resistant metal used for mechanical seal springs and metal bellows because it is not sensitive to chloride stress corrosion.
  • Hastelloy “C” Halogen
    Elements that attack carbon. Fluorine, bromine, chlorine, astatine and iodine.
  • Hat Packings
    Usually made from leather, it is ised as a rod seal or ram seal in a hydraulic cyinder.
  • Head
    The equivalent height of the liquid. 20
  • Heat History
    The accumulated amount of heat a rubber stock has been subjected to during processing operations, usually after incorporation of the vulcanizing agents. Incipient cure or scorch can take place if heat history has been excessive.
  • Helium Light Band
    A method of measuring seal face flatness. One helium light band equals 0.0000116 inches or 0.3 microns. Seal faces are normally lapped to within three helium light bands of flatness.
  • HiClean
    A brand name for rod wipers.
  • High Pressure Seals
    Seals to be used in high pressure hydraulic applications made from teflon, urethane or fabric reinformced material.
  • Horse Power
    33,000 foot pounds per minute. A common method of measuring work.
  • Hydraulic Balance
    A method of reducing mechanical seal face loading by reducing the seal face closing area.
  • Hydraulic Cylinder Kits
    A selection of seals used to completely repair a cylinder or ram.
  • Hydraulic Force
    Occurs any time pressure acts on a seal face area. Force times distance divided by time is a measurement of work done.
  • Hydraulic Packings
    Packing rings used in a hydraulic ram or cylinder
  • Hydrocarbon
    A petroleum product consisting of hydrogen and carbon.
  • Hydrodynamic Force
    Generated at the seal faces because, for all practical purposes, liquid is not compressible.
  • Hydrodynamic Seal
    Special geometric features on the seal face that provide lift by taking advantage of the rotation of one seal face upon the other.
  • Hydrogen Embrittlement
    A premature fatigue of metal caused by the presence of free hydrogen. This is a major cause of ceramic breakage in hot water seal applications, and bearing fatigue if moisture penetrates into the bearing case.
  • Hydrolysis
    Chemical decomposition of a substance involving the addition of water.
  • Hydronium Ion
    An ion formed by the transfer of a proton from one molecule of water to another. Used to determine the pH of a substance. Each step increases by a factor of ten.
  • Hydrostatic Seal
    Maintains a controlled gap between the seal faces by balancing the open and closing forces. There is a small amount of leakage across the faces when the shaft is rotating. Used in some compressor applications, but not very practical for the chemicals found in the process industry.
  • Hysteresis
    The delay or lag that causes seal faces to open.
  • Hysteresis (a)
    The heat generated by rapid deformation of a vulcanized rubber part. It is the difference between the energy of the deforming stress and the energy of the recovery cycle.
  • Hysteresis (b)
    Hysteresis or energy loss is the difference between the work input and the work output as measured under the curves or extension and retraction (stress and elongation curves). The difference becomes heat build-up.
  • I.D.
    Inside diameter.
  • I.S.O.
    International standards organization. Sets pump and seal standards for the metric community.
  • Impeller
    Attaches to the end of the shaft to impart energy to the fluid being pumped. Available in open, semiopen and closed designs.
  • Impeller Eye
    The center of the impeller or the point where fluid enters the impeller.
  • Impeller Setting
    Open impellers require a clearance between the volute or the pump back plate depending upon design. This clearance must be set when the pump is at operating temperature and must be reset to compensate for wear. (0.015″ to 0.020″ or 0,04 mm to 0,05 mm is typical)
  • Impeller Shroud
    The plates located on one or both sides of the impeller vanes. Prevents solids from penetrating behind the vanes.
  • Impeller Vane
    Located between the eye and the discharge side of the impeller. Directs the flow of the liquid to the outside diameter of the impeller.
  • Implode
    The opposite of explode. Bubbles implode in the higher pressure areas of the pump making noise and causing damage to the metal parts. This is normally called cavitation.
  • Inclusion
    A non metallic slug of material which has become entangled in the metal during its manufacture. A severe problem in thin cross section metal bellows manufacture.
  • Inducer
    A small axial flow vane that attaches to the impeller of a centrifugal pump to increase the N.P.S.H. available.
  • Induction Motor
    The most common type used in industry. Has a slippage of 2 to 5 percent compared to synchronous motors.
  • Inline Pump
    Mounted in the piping. No base plate or alignment required.
  • Insert
    A part, usually metal, which is placed in a mold and appears as an integral part of the molded product.
  • Intergranular Corrosion
    A corrosion of the grain boundaries in the body of the material.
  • Internal Mixer
    An enclosed mixing machine for rubber or other suitable material, inside or which are two (2) heavy mixing rotors which revolve in opposite directions with a small clearance between themselves and tine enclosing walls. The mixing chamber is jacketed or otherwise arranged for water-cooling, and is provided with a feeding hopper which can be closed by means of a pneumatically operated, vertical ram. Leading examples are the Banbury, the Boiling and the Shaw mixers.
  • Internal Recirculation
    A loss of efficiency caused by liquid flowing through wear rings or the impeller to volute clearances.
  • IRHD (International Rubber Hardness)
    For complete definition see ASTM D 1415-68 Standard Method of Test for International Hardness of Vulcanized Natural And Synthetic Rubbers.
  • Isolators
    A term used to describe a bearing seal which replcases an oil seal providing more reliable sealing.
  • Iteration
    A technique used in impeller design. You repeat the action until you get to the final result. Very difficult to do until the new computer programs became available.
  • Jacket
    Usually refers to the heating/ cooling jacket surrounding the stuffing box on some pumps. May also refer to the sealing material (u-cup) around a metallic spring or elastomeric energizer.
  • Joule
    A metric unit for the measurement of heat. Defined as the energy required to move one Newton over one meter.
  • K-Type Fluid Seals
    A “K” shaped sealing ring used in a hydraulic or pneumatic cylinder.
  • Kaizen
    Taken from the Japanese words kai and zen where kai means change and zen means good. The popular meaning is continual improvement of all areas of a company not just quality.
  • Kalrez
    An “elastomer like” material manufactured by E.I. Dupont that is used to seal most solvents and other aggressive fluids. It is available in several different grades.
  • Kantseal
    A brandname of a special seal.
  • Kilowatt
    One thousand watts. The normal unit for work in the metric system
  • Knit Mark
    Where raw stock did not unite into a homogeneous mass during the vulcanization. This is also called poor knitting. See Flow marks
  • kPa
    A metric unit for pressure. 100 kPa = one atmosphere.
  • L3 / D4
    A guide line for determining pump shaft stiffness where the length of the shaft is compared to its diameter. This number should be below 60 in imperial units and 2.0 in metric units.
  • Labyrinth Seal
    A non contacting seal utilizing a tortured path for the escape of the fluid. Utilizes a series of pressure drops to reduce the leakage.
  • Labyrinth Seals
    A non-contacting, rotary seal with a series of internal grooves to divert the flow and lubricating fluids in the direct of its source used on a shaft.
  • Lantern Ring
    A device used to supply lubricant to packing. Usually located in the middle of the packing ring set.
  • Lantern Rings
    A spacer ring with grooves and port holes used in the stuuffing box of a pump or other rotating equipment utilizing braided packings, to allow an outside source of lubrication.
  • Lathe Cut Seals
    A seal or gasket ring cut square on a lathe.
  • Line Bearings
    Position the rotor or shaft radially. Normally of the sleeve type.
  • Line Bored
    When the drilling or boring is done on a jig that insures every component is in a straight line.
  • Linear Pressure Drop
    A straight line pressure drop across the lapped seal faces. Seldom happens.
  • Lip Packing & Rings
    Could be the description of a u-cup or of an oil seals. A seal with a lip design to provide sealing.
  • Lip Seal
    See grease seal.
  • Lip Seals
    Seal rings having lips to provide a flexible, dynamic sealing against a shaft.
  • Loaded Lip Seals
    A hydraulic u-cup which has an o-ring or quad ring fitted into the u-shaped groove to assure good low pressure sealing on a reciprocating shaft.
  • Loaded U-Cups
    Same as loaded lip seals.
  • Low Film
    A thin film of oil on the shaft of a hydraulic cylinder.
  • Low Flow
    A condition that can cause excessive heat inside the pump volute. A temperature rise of 10
  • Low Temperature Flexibility
    The ability of a rubber product to be flexed, bent, or bowed at specified low temperature without loss of serviceability.
  • Lubricant
    Any fluid that will maintain a film thickness of one micron or more at its operating temperature and load
  • Mach Number
    The relationship between a moving body and the speed of sound in that locality which can vary with temperature, altitude and there fore pressure.
  • Magnesia
    Heavy calcined: Magnesium oxide by calcination of magnesite (natural magnesium carbonate), and then ground for use as a compounding ingredient for molded goods and hard rubber. (b)Light calcined: Magnesium oxide by calcination of purified magnesium carbonate and/or magnesium hydroxide. It has a fine particle size and a bulk factor of 10 to 30 pds. per cubic ft. Used chiefly in neoprene stocks. (c)Extra light calcined: Prepared similarly by calcination of magnesium carbonate, but with a bulk factor of 4 to 6 pds. per cubic ft. Used chiefly in neoprene stocks.
  • Magnetic Drive
    A type of seal less pump that is pretty much limited to pumping clean lubricating liquids. Similar in concept to a canned pump.
  • Magnetic Seal
    Uses magnetic materials rather than springs to keep the lapped seal faces together. Limited to non corrosive fluids because of the magnets.
  • Magnetite
    Iron oxide ( Fe3O4). A protective coating the forms on iron pipe to prevent further rapid corrosion. Usually black or maroon in color. Can be very destructive to mechanical seal components until the oxide stabalizes. We often find these iron pipes in new hot water systems
  • Maintainability
    The probability that a failed system can be made operable in a specified interval or downtime.
  • Mandrel
    A bar, serving as a core, around which rubber is extruded, forming a center hole.
  • Master Batch
    A mixture of rubber with one (1) or more ingredients in definite but higher concentrations than those in which they normally occur in a complete rubber mix. Used for efficiency in compounding, and also to avoid the handling of small quantities of accelerators, antioxidants, color, etc…
  • Masterbatch
    A preliminary mixture of rubber and one or more compound ingredients for such purposes as more thorough dispersion or better processing, and which will later become part of the final compound in a subsequent mixing operation.
  • Masticate
    To work rubber on a mixing mill or in an internal mixer till it becomes soft and plastic. To break down. MASTICATOR – A machine for plasticizing rubber by mechanical work.
  • Mating Ring
    Another name for the hard face in a mechanical seal. It can be either rotating or stationary.
  • Mean Diameter
    The middle diameter. Usually refers to the center of the seal face. The term is commonly used with metal belows seals to describe the middle diameter of the bellows plate.
  • Mechanical Seal
    A positive sealing device used to seal all fluids (liquids and gases). The primary seal is a set of lapped seal faces that are installed perpendicular to the shaft.
  • Metal Bellows
    Used in mechanical seal designs to eliminate the need for a dynamic elastomer.
  • Metal Fatigue
    A breakage of the metal caused by the bending and flexing of a metal part beyond its endurance limit.
  • Metal O-rings
    An o-ring usually made from hollow stainless steel tubing, with a small vent hole.
  • Micro Organisms
    Used in a variety of chemical processes. Can cause corrosion of stainless steel if they penetrate the passivated layer and attack the carbon content of the stainless steel.
  • Mill
    A machine consisting of two (2) adjacent, heavy, chilled iron rolls set horizontally, and which revolve in opposite directions (i.e., upper surfaces rotate), used for the mechanical working of rubber Mills are of different types. For masticating, and mixing compounds the rolls are smooth and revolve with differential speed. For crepeing and washing rubber, mills have scored or fluted rolls and differential speeds and may be equipped to spray the rubber with water. Mills with even-speed rolls are occasionally used for different purposes. Mills are corridor hollow and equipped for internal heating with steam or cooling with water.
  • Minimum Flow
    A condition that can cause excessive heat inside the pump volute. A temperature rise of 10
  • Miscible
    When one liquid mixes or blend with another liquid. Same as soluble.
  • Mixing
    The process of incorporating the ingredients or a rubber compound into the rubber, usually done on a mixing mill or in an internal mixer. The mixing process consists in (1) breaking down the rubber, (2) gradual incorporation or compounding ingredients, (3) final working of the rubber after all ingredients are in, and (4) removing the mixed compound from the mill in sheets.
  • Modulus
    In the physical testing of rubber, the ratio of stress to strain, i.e., the load in pounds per square inch or kilos. per square cm. of initial cross-sectional area necessary to produce a stated percentage-elongation. It is a measure of toughness, is influenced by pigmentation, state of cure, quality or rubber and other factors. The ratio of stress to strain. In the physical testing of rubber, the load necessary to produce stated percentage of elongation, compression or shear.
  • Modulus of Elasticity
    Refers to the stiffness of the material. The higher the modulus the stiffer the shaft. Most pump shafts have similar modules numbers. Also called Young’s modulus. The relationship of stress to strain. If seal faces have a high modulus they are less likely to distort under pressure.
  • Mold Register
    Means used to align the parts of a mold.
  • Moment of Inertia
    Referring to rotation about an axis. In the pump business it refers to a formula that describes the shape of the shaft. A solid shaft would have a different moment of inertia than a hollow shaft.
  • Monochromatic Light
    A single color light used with an optical flat to read seal face flatness.
  • Mooney Scorch
    A measure of the incipient curing characteristics of a rubber compound using the Mooney viscometer.
  • Mooney Viscometer
    A laboratory testing machine for measuring the plasticity of raw rubber or unvulcanized rubber compounds. A knurled steel rotor disc winch is centrally embedded iii the heated rubber specimen firmly held in a cavity under pressure is caused to rotate at a low speed (2 rpm). The resistance offered by the plastic rubber mass to the rotation of the rotor disc is the measure of the plasticity of the rubber. The machine is also used to determine the scorch characteristics of rubber mixes.
  • Mooney Viscosity
    A measure of the viscosity of a rubber or rubber com- pound determined in a Mooney shearing disc viscometer.
  • Mounts
    A rubber molded part used as a motor mount or to mount device against a frame without allowing vibration to pass through the mounting.
  • N.P.S.H.A.
    The net positive suction head available to prevent cavitation of the pump. It is defined as: Atmospheric pressure + gage pressure + static pressure – vapor pressure – friction loss in the suction piping.
  • N.P.S.H.R.
    Net positive suction head required to stop a pump from cavitating. This number is given to you by the pump manufacturer. Since the number was generated by testing with cold fresh water, it can be lowered in some cases if you are pumping hot water or some hydrocarbons.
  • Negative Pressure
    Less than atmospheric pressure.
  • Newton
    A metric unit of force. Kilogram x gravity.
  • Newtonian Fluid
    A fluid that does not change viscosity as it is agitated.
  • Non Lubricant
    The fluid that will not maintain a film thickness of at least one micron at its operating temperature and load. A concern with mechanical sealing
  • O-ring Groove
    The space into which an O-ring is inserted. Dynamic O-ring grooves use a different dimension than static O-ring grooves.
  • O.D.
    Outside diameter.
  • O.E.M.
    Original equipment manufacturer. The pump or seal company, not the distributor of the products.
  • Oil Analysis
    A sensible preventative maintenance technique to check the oil for solids, water etc.
  • Oil Life
    Lubricating oil has a useful life of about thirty years at thirty degrees centigrade if it is not contaminated.
  • Oil Mist
    A lubrication system where oil and air are mixed and sent into the pump bearing case. Not friendly to the environment.
  • Operating Length
    Measured after the seal has been compressed the proper amount. The measurement is usually made from the face of the stuffing box.
  • Optical Flat
    A high quality glass lapped flat on one side and used with a monochromatic light to read seal face flatness.
  • OSHA
    Occupational and Safety Health Act. Government regulations that affec the sealing business. OSHA 1910 is one of the more important that impacts the training of seal mechanics and operators.
  • Over Hung Impeller
    Not supported with bearings on either side of the impeller.
  • Oxidizer
    Combines with carbon to form carbon monoxide or carbon dioxide. The oxidizers attack all forms of carbon including the seal face and any black O-rings in the system.
  • Ozone
    Created by oxygen atoms combining with oxygen molecules in a high energy atmosphere. Will prematurely age Buna rubber. Ozone forms in the shop as a result of the sparking of electric motor brushes.
  • P.D. Pump
    Positive displacement pump. It can pump a high pressure or head, but at a low volume.
  • P.V. Factor
    An attempt to correlate the relationship between the pressure and the velocity at the mechanical seal faces. Unfortunately carbon graphite is sensitive to P, but not to V so the correlation does not work too well.
  • Packing
    The soft rings that mechanical seal replace to stop leakage. Packing must leak because it works on the theory of a series of pressure drops to reduce the stuffing box pressure to the point where the leakage is acceptable. A minimum of five rings of packing is required to do this.
  • Parallel Operation
    The pumps are discharging to a common header. It is important that the impeller speed and outside diameters be the same or one of the pumps will throttle the other.
  • Pascal
    A metric unit for pressure. 100 kPa = one atmosphere.
  • Passivated
    The protective oxide layer (ceramic) has formed on the metal surface.
  • pH
    A measure of the acidity or the alkalinity of a fluid. The scale ranges from 0 (acid) to 14 (alkali) with 7 considered neutral.
  • Physicals
    Same as the specifications.
  • Pipe Strain
    The strain on the pump volute caused by the piping. It will cause excessive mechanical seal movement and can cause contact between rotating and stationary pump and seal components.
  • Pitting
    Surface voids caused by corrosion, erosion or cavitation.
  • Plasma Spray
    A method of putting a hard coating on a base material. Not recommended for mechanical seal faces.
  • Plastic Range
    The metal has been stressed beyond its yield point and will not return to its original shape.
  • Positive Displacement Pump
    Called a PD pump. Gear, sliding vane, progressive cavity, lobe etc. the capacity determined by the pump speed. The maximum head is determined by the horsepower available and the casing strength.
  • Power End
    The end of the pump that attaches to the power source and does not get wet from the pumpage. The bearings are in this part.
  • Power Factor
    A measure of how the voltage leads or lags the amperage.
  • Precision Bearing
    Ball or roller bearing as opposed to a sleeve or babbitt bearing.
  • Press Fit
    The best way to insert a carbon/graphite face into a metal holder. The carbon will shear to conform to the holder’s irregular shape. Usually done with an arbor press.
  • Pressure Drop
    Referring to the loss of pressure from the outside to the inside of the mechanical seal faces or across the individual rings of packing.
  • Pressure Gradient
    The pressure drop between the seal faces. Usually illustrated by a wedge.
  • Pressure Head
    The pump head exerted by atmospheric pressure or any additional pressure that might be in the vessel.
  • Pump Curve
    A diagram supplied by the pump manufacture to describe the relationship between the head and the capacity of a particular pump using various size impellers. The curve also include information about efficiency, horse power consumption, N.P.S.H. required, etc.
  • Pump Out Vane
    Located behind the impeller shroud in some impeller designs to lower stuffing box pressure. Should no be used in hot well condensate pumps or any pump running with a negative stuffing box pressure.
  • Pumping Ring
    Used with a convection system to get circulation between two mechanical seals. Absolutely necessary if oil is used as a barrier fluid because of oil’s poor specific heat.
  • Pusher Seal
    A design that has a spring loaded dynamic elastomer or rubber like part. A very poor design that should be avoided.
  • Quench
    The introduction of a fluid outside the seal to cool the product, or dilute any leakage across the seal faces.
  • Quill Shaft
    A hollow shaft with another shaft inside it.
  • Raco Seal
    A Saint-Gobain (formerly Fluorocarbon Company, Furon) trademarked name for an engineered face seal utilizing a special Raco spring and manufacturing process
  • Radial
    90 degrees to the centerline of the shaft.
  • Radial Bearing
    In an end suction centrifugal pump it is the bearing located closest to the stuffing box. This bearing handles most of the radial loads put on the impeller.
  • Radial Shaft Seals
    Also called grease seals, rotary seals or shaft seals. Made of rubber to seal grease in a housing with a rotating shaft. OmniLip seal by Saint-Gobain.
  • Reaction Bonded
    A method of manufacturing silicone carbide mechanical seal faces. These materials are sensitive to caustic and some other high pH liquids.
  • Rebound
    Rebound is a measure of the resilience, usually as the percent- age of vertical return of a body which has fallen and bounced.
  • Rebound Test
    Method of deter- mining the resilient properties of vulcanized rubber, by measuring rebound of a steel ball or pendulum falling from a definite height onto a rubber sample.
  • Register
    The accurate matching of the plates of a mold.
  • Reinforcing Agent
    In rubber compounding, a finely-divided substance or filler which, when properly dispersed in rubber, produces improved physical properties in the vulcanized product, i.e., greater energy of resilience, greater resistance to abrasion, higher modules of elasticity and tensile strength Certain grades of furnace blacks are the most important reinforcing agents for black stocks. For light-colored stocks, calcium silicate, precipitated calcium carbonates, silica and clay are the most commonly used.
  • Reliability
    The probability that an item will continue to function at customer expectation levels at a measurement point, under specified environmental and duty cycle conditions.
  • Reliability Apportionment
    The breakdown or allocation of reliability goals or objectives to elements within the product.
  • Renkin Scale
    Used to measure low temperatures in the Fahrenheit scale. Similar to Kelvin which is used to measure low temperatures in the Centigrade system.
  • Repeller
    A second impeller used to lower the stuffing box pressure.
  • Reproducibility
    The variation in the average of measurements made by different operators using the same gage when measuring identical characteristics of the same parts.
  • Resilience
    The property of a material that enables it to return to its original size and shape after removal of the stress which causes the deformation. The energy returned by vulcanized rubber when it is suddenly released from a state of strain or deformation. The returned energy, expressed as a percentage of the original potential energy, is a measure of the resilience. Various rebound testers are used to measure rebound (Bashore, Lupke).
  • Retarder
    Any substance whose presence ill relatively small proportion retard a chemical reaction. Specifically, a substance which when added in small proportion to a rubber compound, retards the rate of vulcanization. An anti-scorching agent; examples, phthalic anydride, salicylic acid.
  • Reverse Balance
    A common type of hydraulic balance used on outside mounted mechanical seals.
  • Reversion
    A deterioration of physical properties that may occur upon excessive vulcanization of some elastomers, evidenced by a decrease in hardness and tensile strength, and an increase in elonga- tion; (2) A similar change in proper- ties after air aging at elevated temperatures. Natural rubber, butyl, polysulfides and epichlorobydrin polymers exhibit this effect (extreme reversion may result in tackiness). Most other polymers will harden and suffer loss of elongation on hot air aging. The softening of some vulcanized rubbers when they are heated too long. Usually accompanied by an increase in extensibility, a decrease in tensile strength and a lowering of the stress required to produce a given elongation. Extreme reversion may result in tackiness; the rubbers “revert” to an unvulcanized then to a non-polymeric condition.
  • Rheology
    The science of deformation and flow of matter. Deals with the laws of plasticity, elasticity and viscosity and their connections with paints, plastics, rubber, oils, glass, cement, etc…
  • Rheometer (Monsanto)
    An oscillating disk cure meter used for determining vulcanization characteristics of a rubber compound.
  • Rigid Shaft
    A shaft with a rotating speed lower than its first critical speed.
  • Rimseal
    A sealing device used on the rim of round plate or rim of a wheel.
  • Rings
    Round sealing devices.
  • RMS (Root Mean Square)
    A measure of surface finish or smoothness. Metric uses C.L.A. or centerline average for the same purpose.
  • Rockwell “C”
    The scale most often used to measure hardness of the hard seal face.
  • Rod Seals
    Any seal used on the rod of a hydraulic or pneumatic cylinder made from rubber or plastic.
  • Rollers
    A round, flat ring used as a wheel or guide.
  • Rotary Seals
    Seals used on rotating shafts – see lips seals, grease seals, oil seals.
  • Rotating Seal
    When the spring loaded or moveable portion of the seal rotates with the shaft.
  • Roto Glyd
    A flat plastic, PTFE or Teflon ring used on a rotating shaft.
  • Rotocure
    Rotory press.
  • Rubber
    A material that exhibits elastic properties that allow recovery from large deformations quickly and forcibly. A tough, waterproof substance obtained through polyme- ric synthesis or in natural form from the sap of various species of plants or trees.
  • Rubber Latex
    Colloidal aqueous emulsion of an elastomer
  • Run Out
    Twice the distance that the center of the shaft is displaced from the axis of rotation.
  • Scorch
    Premature vulcanization of a rubber compound, generally due to excessive heat history. Also see Mooney Scorch;
  • Scorching
    A term frequently used to denote premature vulcanization of a rubber compound, occurring on a mill or calender, or in an extruder. Same as burning or “setting up”.
  • Scraper Rings
    A ring which rides tight against a rod, with a sharp lip to scrape or wipe off excess oil, dirt or dust in a hydraulic or pneumatic cylinder.
  • Scrapers
    Also, called a wiper ring – A ring which rides tight against a rod, with a sharp lip to scrape or wipe off excess oil, dirt or dust in a hydraulic or pneumatic cylinder.
  • Seal
    An elastomeric ring-shaped component used in a constantly moving, dynamic application – either reciprocating or rotating shaft – providing a near positive no leak mode in a hydraulic cylinder, ram, mixer or gear box – as examples. (Note: no sealing device is absolutely 100% positive). Seal rings can be u-shaped, v-shaped, o-shaped, metal inserted, radial lipped, multiple lipped or a simple flat ring. Master Machine Instant Seal Making Machine – A special CNC controlled machine for making seals instantly.
  • Seal Cages
    A special device used to assist a seal ring.
  • Seal Faces
    The lapped faces that that provide the primary sealing in a mechanical seal.
  • Seal Kits
    Any group of seals, o-rings, wiper rings and back-up rings used to repair a specific hydraulic cylinder.
  • Seal Life
    Seals should run leak free until the sacrificial face (usually carbon/ graphite) is worn away. More than 85% of the mechanical seals in use today fail prematurely.
  • Seal Only Pump
    The pump does not have a conventional stuffing box so it could not be supplied with soft packing.
  • Seats
    A stationary ring which is pressed into a housing and acts as the matching face of a mechanical seal.
  • Self Align
    A method of keeping both mechanical seal faces square to the rotating shaft.
  • Self Sintered Silicone Carbide
    Same as Alpha sintered. No free silica present. Can be used in caustic and higher pH liquids.
  • Series Operation
    The pumps are connected with the discharge of the first pump discharging to the suction of the other. The speed and impeller widths must be the same or the difference in capacities could cause cavitation or over heating problems.
  • Shaft Packing
    The soft packing supplied by pump manufacturers. Most of these leaking packings are being replaced by mechanical seals.
  • Shaft Repair Kits
    A package of seals which includes all seals needed to repair the rod end of a hydraulic or pneumatic cylinder.
  • Shaft Seal & Packings
    Any seal ring used on the rod of a hydraulic ram.
  • Shallex
    A brand name for vee packings, chevron or parachute packings.
  • Sheet Materials
    Rubber or fiberous material used to make gaskets.
  • Shelf Life
    Usually refers to the seal elastomer. Buna “N” is the biggest problem because of Ozone attack.
  • Shims
    Flat, thin metal gasket-like parts used as spacers to position machiery or align equipment.
  • Shore “A”
    A scale used to measure elastomer hardness.
  • Shore A Hardness
    An indentation method of rating the hardness of rubber using a Shore Durometer with the A scale from 0 to 100.
  • Shrinkage
    Contraction of molded rubber upon cooling.
  • Shut Off Head
    The maximum head that the pump can generate with a given impeller outside diameter and horsepower driver.
  • SiC
    Silicon carbide. A common mechanical seal face material. A type of ceramic.
  • Simulation
    The practice of mimick- ing some or all of the behavior of one system with a different, dissimilar system.
  • Simultaneous Engineering
    A way of simultaneously designing products, and the processes for manufacturing those products, through the use of cross functional teams to assure manufacturability and to reduce cycle time.
  • Single Acting Seals
    Rings which are designed to seal only in one axial direction.
  • Sintered Material
    Formed from a powder as opposed to being melted and poured into a mold.
  • Skidding
    A term used in describing how an impeller slides on the solids in the bottom of a mixer.
  • Skin
    A relatively dense layer at the surface of a cellular material.
  • Sleeve Bearing
    A non precision bearing. Usually manufactured from carbon, Teflon. brass etc., Allows too much axial and radial movement for most mechanical seal applications.
  • Slenderness Ratio
    Another name for L3/D4
  • Slip O-rings
    A type of ring which fits over an o-ring to relieve friction.
  • Slip Stick
    An alternating slipping and sticking of the seal faces caused by a poor lubricant between the faces. Will cause vibration problems at the seal face unless the vibration is dampened.
  • Slurry
    Solids in liquid. It is impossible to define when the quantity and size of the particles becomes too much for the mechanical seal.
  • Smoke Sheets
    Plantation natural rubber sheets that, after passing through a mill that puts the conven- tional ribbing design on them, are washed and hung on racks in a smoke house where they undergo a combined smoking and drying process.
  • Snap-in Wipers
    A rod wiper which is made from one homogeneous material, either rubber or polyurethane, which is designed to snap-fit into a matching machined groove.
  • Soft Foot
    The tendency for one of the pumps feet to rise when the hold down bolt is loosened. Very bad for alignment.
  • Solosele
    The brand name of a particular single acting u-cup seals.
  • Soluble
    When one liquid dissolves or mixes with another liquid.
  • Spacers
    A ring with flat sides to provide specific dimensional spacing between two components.
  • Span
    The width of the metal bellows. The distance from the inside diameter to the outside diameter.
  • Special Characteristics
    Product and process characteristics designated by the customer including govern- mental regulatory and safety; and/or selected by the supplier through knowledge of the product and process.
  • Specific Gravity
    The ratio of the mass of a unit volume of a material to that of the same volume of water at a specified temperature.
  • Specific Heat
    Refers to the amount of calories or BTUs required to raise a quantity of a liquid one degree.
  • Specific Speed
    A formula that describes the shape of a pump impeller. The higher the specific speed the less N.P.S.H. required.
  • Speed of Sound
    In air it is 1090 feet per second, in water it is 4800 feet per second.
  • Speedi Sleeves
    The name of a thin, round tube which slips over a rotating shaft to provide a new, clean sealing surface for a rubber lip oil or grease seal.
  • Splice
    A joint or junction made by lapping or butting edges, straight or on a bias, and held together through vulcanization or mechanical means.
  • Spool Piece
    Usually refers to a seal and bearing combination that is supplied for some mixer applications. It depends upon the application, but this is not a good idea if there are already two anti-friction bearings already installed on the shaft
  • Spring Energized Seal
    SES, Omniseal
  • Spring Energized Seals
    Any sealing ring that utilizes a metal garter spring or finger spring to assist in energizing the seal when there is not sufficient pressure.
  • Spring Force
    The force on the seal faces caused by the spring compression.
  • Spring Loaded Seals
    See spring energized seals above.
  • Sprue
    The primary feed channel that runs from the outer face of an injection or transfer mold to mold gate in a single cavity mold or to runners in a multiple cavity mold; (2) The piece of material formed or partially cured in the primary feed channel.
  • Sprue Mark
    A mark, usually elevated, left on the surface of an injection or transfer molded part, after removal of the sprue.
  • Squeeze
    Cross section diametrical compression of O-ring between bottom surface of the groove and surface of other mating metal part in the gland assembly.
  • Stainless Steel
    Alloy steels containing a high percentage of chromium.
  • Stat-O-Seals
    See bonded seals.
  • State of Cure
    The cure condition of a vulcanizate relative to that at which optimum physical properties are obtained.
  • Static Head
    The maximum height the liquid is being pumped as long as you take into consideration the siphon affect in some piping systems.
  • Stationary Seal
    The spring loaded or moveable portion of the seal does not rotate with the shaft. Must be used when the seal surface speed exceeds 5000 fpm. or 25 meters per second.
  • Stem Packing
    A type of homogeneous or multi-braided packing used on the stem of a valve to stop leakage.
  • Stepseal
    A seal ring with a step cut groove to match up against a housing machine to fit.
  • Stiffness Ratio
    Another name for L3/D4
  • Stoppers
    See plugs.
  • Strain
    A measure of the amount of deformation produced in a substance when it is stressed.
  • Stress
    Force per unit of original cross sectional area required to stretch a specimen to a stated elongation.
  • Stress Relaxation
    The decrease in stress after a given time of constant strain.
  • Stress Relieve
    To take residual stress out of an object. This is very important with lapped seal faces; especially those that have been inserted into a metal holder.
  • Stuffing Box
    That portion of the pump that held the packing and now holds the mechanical seal.
  • Stuffing Box Pressure
    Between suction and discharge pressure but closer to suction pressure.
  • Substrate
    A material upon the surface of which an adhesive promo- ter is applied for any purpose such as bonding or coating.
  • Subsystem
    A major part of a system which itself has the charac- teristics of a system, usually consisting of several components.
  • Suction Head
    The head on the suction side of the pump. You subtract it from the discharge head to determine the head being produced by the pump. It is a sum of the static, pressure and friction heads.
  • Suction Recirculation
    Piping from the bottom of the stuffing box back to the suction side of the pump. Used to lower pressure and circulate liquid in the stuffing box.
  • Suction Specific Speed
    A formula that will predict one of the types of cavitation. Pumps should be purchased with a number below 8500 (10,000 metric)
  • Surface Speed
    A measure of the feet per minute the seal face or some other component is moving.
  • Swelling
    The increase in volume or linear dimensions of a specimen immersed in a liquid or exposed to a vapor. The property of raw or unvulcanized rubber absorbing organic liquids such as benzene, gasoline, etc., arid swelling to many times its original volume. in a general sense, it may be any increase in volume of a solid substance caused by the absorption of a liquid.
  • Switch Seals
    Seals used in electrical switching devices to keep moisture out.
  • Synchronous Motor
    Runs with out slippage. Used in elevators and compressors frequently, but seldom used in pumping. Pumps mostly use induction or “squirrel cage” motors.
  • System
    A combination of several components or pieces of equipment integrated to perform a specific function.
  • System Curve
    A description of what the pump is required to perform. The pump will pump where the system curve intersects the pump curve.
  • System Head
    The head caused by friction in the piping. valves and fittings.
  • T-Seals
    A “T” shaped rubber sealing ring with harder back-up rings on each side for rod or piston sealing.
  • T.D.H.
    Total discharge head. A combination of the suction head and the head being produced by the pump.
  • Tack
    The ability to adhere to itself; a sticky or adhesive quality.
  • Tandem Seals
    The seals are facing in the same direction with a low pressure barrier fluid circulating between them.
  • Team Feasibility Commitment
    A commitment by the Product Quality Planning Team that the design can be manufactured, assembled, tested, packaged, and shipped in sufficient quantity at an acceptable cost, and on schedule.
  • Tear Resistance
    Resistance to tearing, measured as the force required to tear completely across a specially-designed nicked rubber test piece or right-angled test piece by elongating it at a specified rate. Express in lbs. per inch of thickness of specimen.
  • Tear Strength
    The maximum load required to tear apart a specified specimen, the load acting substantially parallel to the major axis of the test specimen.
  • Teflon
    A DuPont tradename for polytetrafluoroethylene.
  • Telescopic Packing
    Packing sets used on telescopic cylinders, each stage having a different diameter.
  • Temperature Range
    Lowest temperature at which rubber remains flexible and highest temperature at which it will function.
  • Tensile Strength
    Force in pounds per square inch required to cause the rupture of a specimen of a rubber material. The capacity of a material to resist a force tending to stretch it. Ordinarily the term is used to denote the force required to stretch a material to rupture, and is known as “breaking load”, “breaking stress “ultimate tensile strength”. lit rubber testing, it is the load in lbs. per square inch or kilos per square centimeter of original cross-sectional area, supported at the moment of rupture by a piece of rubber being elongated at a constant rate.
  • Tensile Stress
    The applied force per unit of original cross sectional area of a specimen.
  • Tensile Stress at Given Elongation
    The tensile stress required to stretch a uniform section of a specimen to a given elongation.
  • Tension Set
    The extension remaining after a specimen has been stretched and allowed to retract.
  • Thermal Conductivity
    A measure of the material’s ability to conduct heat. This is a very important factor in the selection of mechanical seal faces.
  • Thermal Deterioration
    The elongation at the moment of rupture.
  • Thermal Imaging
    A troubleshooting piece of equipment that will let you see hot spots in the quipment.
  • Thermoplastic
    A plastic material that can be softened or melted repeatedly without change of properties. Injection molded parts are manufactured with Thermo-plastic materials.
  • Thermoplastic Rubber
    Rubber that does not require chemical vulcanization and will repeatedly soften when heated and stiffen when cooled; and which will exhibit only slight loss of its original charac- teristics.
  • Thermosetting
    A plastic material that can be softened and molded but cannot be re-used or reverted to its original state.
  • Thermosetting Rubber
    Chemically vulcanized rubber that cannot be remelted or remolded without destroying its original characteristics.
  • Thixotrophic Fluid
    The viscosity of the fluid decreases with agitation. Non drip paint is an example of such a fluid.
  • Thorseals
    A brand name for a polyurethane hydraulic u-cup seal.
  • Thrust
    In a centrifugal pump it refers to the axial movement of the shaft. The thrust can be towards the wet or power end of the pump and at start up it thrusts in both directions.
  • Thrust Bearing
    Designed to take the axial thrust in pump applications. It is usually located next to the coupling and is often supplied in a “double row” configuration.
  • Timing Plan
    A plan that lists tasks, assignments, events, and timing required to provide a product that meets customer needs and expectations.
  • Tips
    A rubber cup-shaped part used on the end of a rod or shaft to provide shock resistance or cushioning.
  • Torr
    One millimeter of mercury. Used in both the imperial and metric systems a a unit of measurement in vacuum service.
  • Total Head
    The amount of head produced by the pump. Discharge head minus suction head. If suction head is a negative number it is added to the discharge head.
  • Transducer
    Attached to the pump and used to send a vibration signal to a meter where it can be read.
  • Trim
    The process Involving removal of mold flash.
  • Tube Springs
    A rubber or plastic cushioning device used to assist spring or cover the outer portion of a coil spring.
  • Tungsten Carbide
    A common hard face seal material available in several grades depending upon hardness and corrosion resistance. Cobalt and nickel are the two most common types.
  • Turbulence
    Disturbed fluid. Can cause cavitation problems in a centrifugal pump. Often caused by an elbow located too close to the pump suction inlet.
  • Two Way Balance
    A method of balancing a mechanical seal in two directions. A very important consideration in dual seal applications.
  • U-Cup
    Type of seal used in a hydraulic or pneumatic cylinder. It’s cross section is U-shaped to allow oil to energize the seal body to properly block oils and seal correctly.
  • U-Cups
    “U” shape cup sealing ring designed to seal in one direction along a shaft or rod in a hydraulic or pneumatic cylinder.
  • U-Packings
    A “U” shape cup sealing ring designed to seal in one direction along a shaft or rod in a hydraulic or pneumatic cylinder.
  • U.S.C.S.
    United States Customary System. All dimensions are in inch units.
  • UHMW
    Ultra High Molecular Weight Polyethylene
  • Ultimate Elongation
    The maximum elongation prior to rupture.
  • Unbalanced Seal
    Not hydraulically balanced to generate low heat at the seal faces.Typical of original equipment designs.
  • Undercure
    State of vulcanization less than optimum. It may be evidenced by tackiness or inferior physical properties.
  • Unfilled Carbon
    Containing carbon/ graphite and nothing else. Filled carbons contain inorganics that will be sensitive to some chemicals and temperature extremes. Unfilled carbons are the prefereed seal faces.
  • V-Packing
    Also known as Vee Packing, Vee Sets, Chevron Packing, Parachute Packing. A multiple ring set of packings whose center rings or sealing rings are V-shaped to form sealing lips. The V-rings stack on top of each other and have a male and female adaptor on each end to make the set flat. This packing type is adjustable.
  • V.D.M.A.
    A German standard for mechanical seals.
  • Vacuum
    Any pressure less than atmospheric. Can present a problem for the elastomer in many seal applications.
  • Value Engineering (Value Analysis)
    A planned, clean sheet approach to problem solving, focusing on specific product design and process characteristics. Where value analysis is employed to improve value after production has begun, value engineering is employed to maximize value prior to expend- itures of facilities and tooling money.
  • Valve Discs
    A PTFE or Teflon disc used on a valve as a seat to provide positive sealing whn shut off.
  • Valve Packing
    Braided packing used in the stuffing box of a valve stem to make a positive seal.
  • Valve Seats
    A PTFE or Teflon disc or ring used on a valve as a seat to provide positive sealing whn shut off.
  • Valve Stem Packing
    Braided packing used in the stuffing box of a valve stem to make a positive seal.
  • Vane Passing Syndrome
    A type of cavitation caused by the impeller/ cutwater clearance being too small.
  • Vapor Pressure
    Below this pressure, the liquid at this temperature will vaporize.
  • Vaporize
    The fluid passes from a liquid to a gaseous state. If this happens at the seal faces the seal faces will be blown open.
  • Variable Speed Motor
    Used to control flow in a system by varying the frequency of the motor. Recommended for circulating systems and any other system where the main head is friction losses in the piping system.
  • Velocity
    A measurement of the speed of the liquid in the system. Measured in feet or meters per second. The pump is a constant velocity device.
  • Velocity Head
    Part of the total head calculation. Derived from the formula h = V2/2g
  • Vent
    To remove air or gas from the system. It is important to vent the stuffing box in vertical pumps to prevent the seal faces from running dry.
  • Vibration Damping
    Important in metal bellows seal designs. The elastomer acts as a vibration damper in the other seals. The vibration can chip carbon faces, destroy anti-rotation drive lugs, and open the lapped seal faces.
  • Viscosity
    Resistance to pouring. Higher viscosities can restrict seal movement. Centrifugal pumps can handle a maximum viscosity similar to 30 weight oil at room temperature. Above this viscosity a positive displacement pump should be used.
  • Viton
    An E.I. Dupont Dow manufactured elastomer widely used in the sealing industry. The generic name is fluorocarbon. Many of these compounds are attacked by water and steam.
  • Volute Casing
    Derives is name from a spiral shaped casing surrounding the pump impeller. It converts velocity energy to pressure energy.
  • Vortex Pump
    A type of pump used for excessive solids. The impeller is recessed into the volute. A very low efficiency design, but practical in many applications.
  • Vortexing Liquid
    Creating a “whirlpool affect” that can draw air into the suction of the pump.
  • Washers
    Round, flat rings used as spacers, gaskets or slip devices under the head of a bolt.
  • Water Absorption
    The increase in weight and volume after immersion in water.
  • Water Horse Power (W.H.P.)
    The calculated horse power coming out of the pump using the formula WHP = head x gpm/3960
  • Water Resistance
    The ability to withstand swelling by water for a specified time and temperature.
  • Watt
    A measure of power. 746 watts equals one horsepower.
  • Wave Spring
    A disc washer used when axial space is at a premium. Does not allow very much axial travel of the seal.
  • Wear Ring
    Used with closed impeller pumps to restrict leakage from the high pressure side of the pump to the low pressure side. Should be replaced when the recommended clearance is doubled.
  • Wear Rings
    Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods.
  • Wear Sleeves
    Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods.
  • Wear Strips
    Strips of abrassion resistant plastic, PTFE or Teflon material – Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods.
  • Welded Metal Bellows
    A seal design used to eliminate the use of elastomers. Excellent for cryogenic and hot applications. Not as effective for hot petroleum applications because of “coking” problems
  • Wet End
    The part of the pump that gets wet from the pumping fluid. Includes the volute, stuffing box, impeller wear rings, and shaft or sleeve .
  • Wetting
    Completeness of contact between particles dispersed in a medium, such as carbon black rubber.
  • Wheels
    Round rollers to provide easy movement of a machine or component.
  • Wiper Rings
    Also, called a wiper ring – A ring which rides tight against a rod, with a sharp lip to scrape or wipe off excess oil, dirt or dust in a hydraulic or pneumatic cylinder.
  • X-Rings
    Also called quad rings or quatro rings, rubber rings of a special shape ised to replace o-rings and eliminate the rolling found when using o-rings.
  • Yield Point
    Where the metal passes from the elastic to the plastic range
  • Young’s Modulus
    The ratio of normal stress to corresponding stress or compressive stresses below the proportional limit of the material
  • Zinc Oxide Activator
    Accelerators of vulcanization do not always exert their full influence unless the rubber mixture contains substances known as activators. Zinc oxide is an activator and gives its best activity in the presence of an organic acid like stearic acid with which it forms a rubber-soluble soap.
  • Zurcon
    A type of material used to make guide rings, wear rings, bearings or seals.