GLOSSARY OF TERMS

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

Select the first letter of the word from the list above to jump to appropriate section of the glossary.

- A -

ABS (Acrylonitrile-Butadiene-Styrene) -: A polymer produced from acrylonitrile and styrene liquids, and butadiene gas, which are polymerized together in a variety of ratios to produce the family of ABS resins.

Abrasion Resistance -

- B -

Bleed -: To give up color when in contact with water or a solvent; undesirable movement of certain materials in a plastic (ex: plasticizers in vinyl) to the surface of the finished article or into an adjacent material.

Bleeder -: A device for removal of pressurized fluid. Used to bleed air from system.

Bloom -: A cloudy, greasy film on the surface of a plastic part or film usually caused by the extraction of an additive, such as a lubricant, stabilizer, etc.

Brittle Temperature -: The threshold temperature at which the material will fracture due to cold induced loss of flexibility.

Burning Rate -: A term describing the tendency of plastics to burn at a given temperature. Certain plastics will burn readily at comparatively low temperatures. Others will melt or disintegrate without actually burning, or will burn only if exposed to a direct flame. The latter are referred to as self-extinguishing.

Burst Pressure -: The pressure point at which the tube/hose will suddenly and violently rupture.

Butt Fusion (welding) -: A process of joining the ends of thermoplastic parts by heating the surfaces to be joined to their molten state and then pressing them together to form a homogenous bond.

- C -

Carbon Black -: A multi-functional additive produced by the incomplete burning of natural gas or oil and used in plastics as a conductor of electricity, a pigment, a filler-extender, and a stabilizer.

Catalyst -: A substance which speeds up the polymerization or cure of a compound when added in minor quantity as compared to the primary reactants.

Cavitation -: A gaseous condition within a liquid stream caused when pressure is reduced to the vapor pressure. To be avoided due to destructive effects on pumps and motors.

Cellulose -: A naturally occurring polysaccharide consisting solely of glucose units and found in most plants. It is the main constituent of dried woods, jute, flax, hemp, etc.

Cellulosics -: A family of resins derived from cellulose. The three most common types are: cellulose-acetate (CA), cellulose-acetate-butyrate (CAB), and cellulose-acetate-propionate (CAP).

Circuit; Pilot -: Used to control a main circuit or component.

Circuit; Regenerative -: Used to increase cylinder speed by directing rod end discharge to the piston side of the cylinder. Can be incorporated into directional control valve as fourth position.

Coefficient of Friction -: Resistance to sliding or rolling of surfaces of solid bodies in contact with each other; stated as k=F/W in which F is the force required to move one surface over another and W is the weight pressing the surfaces together.

Co-Extrusion -: The technique of extruding two or more materials through a single die being fed by separate extruders.

Compounding -: The process of mixing the polymer with all the materials necessary for the finished resin to be used by the processor.

Compressed Gas -: Any material or mixture having in the container either an absolute pressure exceeding 40 psia at 70ºF or an absolute pressure exceeding 104 psia at 130ºF.

Compressive Strength -: Maximum load at which compression failure occurs in a specimen divided by the original area of the specimen.

Conductivity -: The property of transmitting electricity, heat, etc.

Copolymer -: A compound resulting from the chemical reaction of two chemically different monomers with each other.

Core -: The inner-most layer of a multi-layered product.

Corona Resistance -: The time that a material will withstand a specified level of field-intensified ionization that does not result in the immediate complete breakdown of the material.

Corrosive -: Any substance which chemically attacks materials with which it comes in contact, such as metals or human tissue.

Crazing -: Minute cracks near the surface of plastic materials.

Creep (cold flow) -: The dimensional change with time of a material under physical load. Creep at room temperature is called “cold flow.”

Cross-Linking -: The establishing of chemical links between the molecular chains in polymers. Cross-linking can be accomplished by chemical reaction, vulcanization, and/or irradiation.

Crystallinity -: A state of molecular structure in some resins denoting uniformity and compactness of the molecular chains. This characteristic is attributable to the existence of solid crystals with definite geometric form.

Cuff -: A smooth end on an irregularly surfaced tube or hose enabling the secure and leak-free fitment of the tube or hose to its termination point.

Cure -: The changing of the physical properties of a material by chemical reaction; usually by the action of heat and catalysts, alone or in combination, with or without pressure.

Cylinder -: A device which converts hydraulic energy into linear mechanical motion and force.

Cylinder; Double Acting -: A cylinder which can apply force and motion in either direction.

Cylinder; Single Acting -: A cylinder which can apply force in one direction only.

Cylinder; Depth Control -: A mechanical or hydraulic device, adjustable, for limiting cylinder stroke.

Cylinder; Rephasing -: A cylinder design which permits the use of two or more cylinders in series, automatically synchronizing cylinder position at the end of each stroke.

- D -

Decay Rate -: The speed in which a material will drain a static electrical charge.

Deflection Temperature -: The temperature at which a standard test bar deflects 0.010” under a load of 66 or 264 psi.

Deformation -: The result when an object does not return to its original form or shape after pressure or stress is removed.

Degradation -: Deleterious change in the chemical structure of a plastic reflected in the appearance or physical properties.

Delamination -: The separation of layers in a laminate through failure of the resin binder or adhesive.

Density -: The mass per unit volume of a substance expressed in pounds per cubic foot, grams per cubic centimeter, etc.

Denier -: a unit of weight for measuring the fitness of threads of silk, rayon, nylon, etc., equal to .05 gram per 450 meters.

Detent -: A spring device which maintains the spool of a directional control valve in position.

Detent Release -: A mechanical, hydraulic or electrical device for releasing the detent.

Die, Extrusion -: Placed at the exit of an extruder barrel through which the resin emerges and is formed into film, rods, pipe, profiles, sheet, tubing, etc.

Dielectric -: 1) any insulating medium which intervenes between two conductors; 2) a material having the property that energy required to establish an electric field is recoverable in whole or in part, as electric energy.

Dielectric Strength -: The electric voltage gradient at which an insulating material is broken down or “arced through,” usually expressed in volts per mil of thickness.

Dimensional Stability -: The ability of a part to retain its shape when exposed to external forces.

D.O.P. (Dioctyl Phthalate) -: An ester plasticizer derived from natural fats and oils; can be modified to meet specific end use requirements.

Ductility -: Amount of plastic strain a material can withstand before it fractures.

Durometer -: A trade name of the Shore Instrument Company for an instrument that measures the hardness of a material. A lower Shore scale number indicates a softer, more flexible material.

- E -

Elastic Deformation -

The portion of deformation of an object under load which can be recovered after the load is removed.

Elasticity -

The property of a material of which it tends to recover its original size and shape after deformation.

Elongation -

The fractional increase in length of a material stressed in tension.

Embossing -

Technique using pressure with or without heat to make a permanent marking in a material's surface.

Encapsulating -

Encasing an article in a closed envelope of plastic by immersing the object in a casting resin and allowing the resin to polymerize, or, if hot, to cool.

End Thrust -

The total force generated at the far end of a conduit by the sudden release of a fluid under pressure (spike pressure) into that conduit; measured in psi and calculated: (¹ x radius [in.]) x spike pressure [psi].

EPDM -

Ethylene Propylene Diene terpolymer

Ester -

The reaction product of an alcohol and an acid.

Ethylene Vinyl Acetate (EVA) -

A copolymer member of the polyolefin family derived from random copolymerization of vinyl acetate and ethylene resulting in a resin with similar properties to that of polyethylene but with greater flexibility and resistance to impact and elongation.

EVA -

Ethylene vinyl acetate

Extender -

A substance added to a plastic compound to reduce the amount of resin required per unit volume.

Extrusion -

The process of compacting and melting a plastic material and forcing it through an orifice (die) in a continuous fashion.

- F -

FDA -: Food and Drug Administration

FEP -: Fluorinated ethylene propylene

FRP -: Fiberglass reinforced plastic.

Filament -: Fiber of extreme length used in yarns and other compositions with little or no twist and usually without the spinning operations required for fibers.

Filler -: A very inexpensive material which is typically added to a plastic to make it less costly. They can be inert or can alter various properties of the plastic, particularly hardness, stiffness, and impact strength.

Filter -: A device incorporated into a hydraulic system to remove contaminants from the oil.

Fish Eye (Gels) -: A small globular mass in a transparent or translucent plastic material caused by the incomplete blending of the mass into the surrounding material.

Fitting -: A device for connecting hose or pipe to hydraulic components.

Flame Retardant Resin -: The result of reactive compounds that become an integral part of the polymer structure and/or additive chemicals that are physically dispersed in a polymer to retard or eliminate the polymer's tendency to burn.

Flammability -: The measure of the extent to which a material will support combustion.

Flaring -: The enlargement of a tube/hose diameter by mechanical pressure from the inside.

Flash -: Excess plastic around the area of the parting line on a molded part.

Flexural Modulus -: Ratio of applied stress to strain in outer fibers of plastic specimen during flexure.

Flexural Strength -: The resistance of a plastic material to cracking or breaking during bending expressed as the tensile strength of the outermost fibers at the moment of failure.

Float Spool (Position) -: A spool valve design which connects all ports to the tank (return) port, usually in a detented fourth position, allowing a cylinder or motor to "float".

Flow Rate -: The volume of fluid passing through the system or component in gal. Per min. (or 11m)

Fluid Power System -: The transmission and control of power through the use of fluid pressure.

Fluorescent Pigments -: Colorants which absorb radiation of a given frequency and then emit radiation of a different frequency, creating a glowing effect.

Fluoroplastics -: Polyolefin polymers in which fluorine, fluorinated alkyl groups, or other halogens replace hydrogen atoms in the carbon chain resulting in a material with outstanding electrical properties, excellent resistance to chemical attack, low coefficient of friction, excellent fire resistance, exceptionally good performance at high and low temperatures, low moisture absorption, and outstanding weatherability.

- G -

Gamma Radiation -: An electromagnetic radiation of great penetrating power emitted by the nucleus of a radioactive substance.

Gauge -: Thickness of plastic film measured in decimal inches or mils.

GMP -: Good Manufacturing Process

Gummy -: Having the nature of gum; viscid; sticky.

- H -

Haze -: Cloudiness in a plastic material.

HDPE -: High density polyethylene

Heat Distortion Point -: See: “Deflection Temperature.”

Heat Gun -: An electrically controlled gun for softening, curing, drying, preheating, and welding plastics, as well as shrinking of thermally reducible tubing.

Heat Resistance -: The ability to withstand the effects of exposure to high temperature.

Heat Sealing -: A method of joining plastic films by simultaneously applying heat and pressure to areas in contact.

Homopolymer -: A polymer consisting of only one monomeric species.

Hydrolysis -: The chemical decomposition of a substance by reaction with water.

- I -

Impact Strength -: The ability to withstand shock loading.

Impregnation -: The process of thoroughly soaking a material such as wood, paper, or fabric with a synthetic resin.

Impulse Sealing -: A sealing process in which intense thermal energy is instantaneously applied to the sealing area, immediately followed by rapid cooling.

Inert -: Substances which do not react with other materials under normal temperature and pressure.

Inhibitor -: Substances that slow or halt a chemical reaction; sometimes used in certain types of monomers and resins to prolong product life.

Injection Molding -: A process in which melted plastic is forced into a relatively cool mold cavity which forms the plastic into the desired shape.

IR -: Isoprene rubber

Irradiation -: Subjecting plastics or other compounds to radiant energy to cure or produce a change in the material.

Izod Impact Test -: A test for shock loading wherein a notched sample bar is held at one end and broken by striking.

- J -

Jerk -: The sharp, quick motion used to remove tubing or hose from a bulkhead or other connection point. Also see Yank.

- K -

K factor -: The coefficient of thermal conductivity; the amount of heat that passes through a unit cube of material in a given time when difference in temperature of 2 faces is 1º.

- L -

LDPE -: Low density polyethylene

Light-Resistance -: The resistance of a plastic to change color or other characteristics during exposure to sun or ultraviolet light.

LLDPE -: Linear low density polyethylene

Luminescent Pigments -: Special colorants added to a compound to produce eye-catching effects in the dark. Basically there are two types: one is activated by U.V. radiation producing very strong luminescence, and the other is a phosphorescent which does not require a separate source of radiation.

- M -

Mandrel -: A core around which material is wound as in filament winding, which when removed, forms a hollow center in a tube.

Manifold -: Configuration of piping in a block of metal or plastic that takes a single channel flow and divides it into various flow channels to feed more than one outlet.

MDPE -: Medium density polyethylene

Melt Index -: The amount, in grams, of a thermoplastic resin which can be forced through an 0.0825 “ orifice when subjected to 2160 gms force in 10 minutes at 190ºC.

Memory -: The tendency of a thermoplastic material which has been stretched while hot to return to its unstretched shape upon being reheated.

Mer -: The repeating structural unit of any high polymer.

Migration -: The extraction of an ingredient from a material by another material, such as the migration of a plasticizer from one material to an adjacent material with a lower plasticizer content.

Modulus of Elasticity -: The ratio of stress to strain below the proportional limit of the material.

Moisture Vapor Transmission -: The rate at which water vapor permeates through a plastic at a specified temperature and relative humidity.

Mold -: A hollow form or cavity into which molten plastic material is placed to produce the shape of the required component.

Molecular Weight -: The sum of the atomic weights of all atoms in a molecule.

Monomer -: A single molecule which can join with another monomer or molecule to form a polymer or molecular chain.

Motor -: A device which converts hydraulic energy into rotary motion, either fixed or variable.

- N -

Natural Rubber (NR)-: An elastic substance produced by coagulating and drying the milky sap (latex) of various tropical plants, especially a tree (Heva brasiliensis) of the spurge family.

Neoprene -: A synthetic rubber produced by the polymerization of chloroprene providing a high resistance to oil, light, heat, and oxidation.

Nitrile Resin -: Polymers of which the principal monomer is acrylonitrile. This provides the functionality of good chemical resistance and gas barrier properties.

Notch Sensitivity -: Extent to which the sensitivity of a material to fracture is increased by the presence of a surface inhomogeneity, such as a notch.

NSF -: National Sanitation Foundation

Nylon -: The generic name for all synthetic fiber-forming polyamides; characterized by great strength, toughness, and abrasion resistance, good fatigue resistance and lubricity, and low coefficient of friction. They can be formed into a monofilament and yarn. Current types include 6, 6-6, 6-10, 11, & 12.

- O -

Oil Resistance -: Ability to withstand the deteriorating effects of an article by the absorption of oil; usually causing volumetric swell and/or hardening.

Outgassing -: The release of a volatile substance from a compound during curing.

Oxidant -: A gas which supports combustion.

Ozone Resistance -: Ability to withstand the deteriorating effect of Ozone (which generally causes cracking).

- P -

Parting Line -: The line formed by the mating surfaces of the molded part.

Peristaltic Pump -: A type of pump in which the forward movement of material inside a tube is performed in a wave-like fashion caused by the contraction and dilation of the tube in a longitudinal direction.

Permeability -: The rate at which a liquid or gas under pressure passes through a solid material by diffusion and solution.

PFA -: Perfluoroalkoxy

Plasticize -: To impart softness and flexibility in a plastic through the addition of a plasticizer additive or the application of heat.

Plasticizer -: A chemical agent added to a resin to increase its workability during processing, and to impart flexibility and other desired properties to the finished product; usually of an organic ester having a high boiling point.

Polyamides (PA)-: A polymer in which the structural units are lined by amide groupings. Many polyamides are fiber-forming.

Polycarbonate (PC)-: Polymers derived from the direct reaction between aromatic and aliphatic dihydroxy compounds with phosgene or by the ester exchange reaction with appropriate phosgene derived precursors. Structural units are linked by carbonate groups.

Polyester -: A family of resins produced by reaction of dibasic acids with dihydric alcohols or by the polymerization of of a hydroxy carboxylic acid.

Polyethylene (PE)-: A thermoplastic composed by polymers of ethylene; normally a translucent, tough, waxy solid which is unaffected by water and a large range of chemicals.

Polymer -: A high molecular-weight organic compound, natural or synthetic, whose structure can usually be represented by a repeated small unit, the MER. Synthetic polymers are formed by addition or condensation polymerization of monomers. Some polymers are elastomers, some plastics, and some are fibers.

Polymerization -: The chemical reaction in which the molecules of monomers are linked together to form polymers.

Polypropylene -: A tough, lightweight, rigid plastic made by the polymerization of high-purity propylene gas in the presence of an organometallic catalyst at relatively low pressures and temperatures.

Polystyrene -: A water-white thermoplastic produced by the polymerization of styrene (vinyl benzene) offering outstanding electrical properties; relatively unaffected by moisture.

Polysulfone -: An amorphous structure; this engineering thermoplastic has inherent resistance to heat, hydrolysis, oxidation, and radiation; self-extinguishing.

Polytetrafluoroethylene (PTFE) -: Member of the fluorocarbon family of plastics created by the polymerization of tetrafluoroethylene and characterized by extreme chemical inertness, very high thermal stability and low frictional properties.

Polyurethane (thermoplastic) -: Polymers which have properties combining the advantages of elastomers and plastics; formed by the reaction of bifunctional polyols with diisocyanates.

Polyvinyl Chloride (PVC) -: Thermoplastic compounds formed by polymerization or copolymerization of vinyl or vinylidene halides and vinyl esters. They are strong, with good abrasion resistance and superior aging properties than that of rubber.

Porosity -: The ratio of the volume of a material's pores (voids) to its total volume; usually expressed as a percentage.

Post-Cure -: The operation on a thermoset part in which the part is subjected to elevated temperatures for a period of time to effect full cure, stress relaxation, etc., and to enhance property levels.

Postforming -: The forming, bending, or shaping of fully cured thermoset laminate.

Port -: The internal or external terminus of a passage. The point where the fitting is attached.

Pressure -: The force per unit area, expressed in pounds per square inch (psi), bars, or atmospheres.

Pressure; Back -: The pressure encountered on the downstream or return side of a component.

Pressure; Cracking -: The pressure at which a pressure operated valve begins to pass fluid.

Pressure Drop -: The difference in pressure between any two points of a component or system.

Pressure; Maximum Rated -: The maximum pressure at which a component should be operated on a continuous basis, usually the relief valve setting at maximum flow rate.

PSI -: Pounds per square inch.

PVDF -: Polyvinylidene fluoride

Pump -: A device which converts mechanical energy into hydraulic. Energy, either fixed or variable.

- Q -

No terms at this time.

- R -

Radiopaque -: Not allowing the passage of X-rays, gamma rays, or other forms of radiant energy.

Random Copolymer -: A copolymer in which the molecules of each monomer are randomly arranged in the polymer backbone.

Reinforced Plastics -: Molded, formed, filament wound, or shaped plastic parts consisting of resins to which reinforcing fibers, mats, fabrics. etc., have been added before the forming operation resulting in enhanced strength properties.

Reinforcement -: A material used to reinforce, strengthen, or give dimensional stability to another material.

Reservoir -: A container which stores the liquid in a fluid power system.

Resin -: An organic substance of natural or synthetic origin characterized by being polymeric in structure and predominantly amorphous. Most resins, though not all, are of high molecular weight and consist of long chain or network molecular structure. Usually resins are more soluble in their lower molecular weight forms.

Resistivity -: The ability of a material to resist passage of electrical current either through its bulk or on a surface. The unit volume resistivity is the ohm-cm, or surface resistivity, the ohm.

Retractable -: The ability to draw back to an original form once tension is relieved.

Rockwell Hardness -: A common method of testing for resistance to indentation in which a diamond or steel ball, under pressure, is used to to pierce the test specimen. The load used is expressed in kilograms (kg) and a 10 kg pre-load is first applied and the degree of penetration noted. The major load (60 to 150 kg) is next applied and a second reading obtained. The hardness is then calculated from the difference between the two loads and expressed with nine different prefix letters to denote the type of penetrator used and the weight of the major load.

- S -

SAE -: Society of Automotive Engineers

Santoprene® -: A thermoplastic rubber with good fluid and flex fatique resistance. Commonly used in peristaltic pumps for both medical and general industry.

SBR -: Styrene butadiene rubber

Seal -: A device which prevents or controls the escape or passage of hydraulic fluid.

Self-Extinguishing -: A loosely-used term describing a material's ability to stop burning once the source of the flame is removed.

Shear Strength -: The stress at which a material fails in shear or the ability of a material to withstand shear stress.

Shelf Life -: The period of time during which a material or product may be stored at ambient temperature and humidity without measurable degradation of its physical properties.

Shore Hardness -: A common method of determining the hardness of a plastic material as developed by the Shore Instrument Company. The device used, called a durometer, consists of a small conical hammer fitted with a diamond point and acting in a glass tube. The hammer is made to strike the material under test and the degree of rebound is noted on a graduated scale. Generally, the harder the material, the greater the rebound.

Silicone -: One of the family of polymeric materials in which the recurring chemical group contains silicon and oxygen atoms as links in the main chain. These compounds are derived from silica (sand) and methyl chloride. Silicones are characterized by their resistance to heat and low thermal expansion.

Sintering -: The process of holding a fusible pressed-powder article at a temperature just below its melting point for a period of time to fuse (sinter) the particles together.

Slitting -: The process of making a long, straight, lengthwise cut in an article.

Solvent Bonding -: A process of joining articles made of thermoplastic resins by applying a solvent to soften the surfaces to be joined, and then the surfaces are pressed together. Adhesion comes from evaporation of the solvent, absorption of solvent into the material surfaces, and/or polymerization of the solvent.

Specific Gravity -: The ratio of the mass of any volume to the mass of an equal volume of another substance taken as a standard. The standard for solids and liquids is usually water, and for gases the standard is air.

Specific Heat -: The amount of heat required to raise a specified mass by one unit of a specified temperature at constant pressure.

Stabilizer -: An ingredient included in the compounding of some polymers to assist in maintaining desirable physical and chemical properties of the compounded material throughout the life of the material; ex: heat or U.V. stabilizers.

Sterilization -: The process of applying great heat or chemical action to an article in order to clean it of all living microorganisms.

Strain -: Elastic deformation due to stress; measured as the change in length per unit of length in a given direction, and expressed in percentage or inches per inch, etc.

Stress -: The unit force or component of force at a point in a body acting on a plane through the point; expressed in psi.

Stress Crack -: External or internal cracks in a plastic caused by tensile stresses; often appear as a network of fine cracks known as crazing.

Stress Relaxation -: Time dependent decreases in stress for a specimen constrained in a constant strain condition.

Synthetic Resin -: Any complex organic liquid or solid formed from simpler molecules by polymerization or condensation; any of various chemically modified natural resins.

- T -

Tack -: Stickiness of a material, measurable as the force required to separate an adherend.

Talc -: An inert refined mineral product (hydrated magnesium silicate) that is a reinforcing filler extender. Because of its platy configuration, it tends to add stiffness to the resin, while its low cost categorizes it as an extender. Talc is also commonly applied to reduce the tackiness of some plastic materials.

Tear Resistance -: The resistance of a material to a force acting to initiate and then propagate a failure at the edge of a test specimen.

Tensile Strength -: The maximum tensile stress sustained by the specimen before failure in a tension (pull) test; usually expressed in pounds per square inch (psi).

Thermal Conductivity -: Ability of a material to conduct heat.

Thermoforming -: Any process in which thermoplastic material is heated to its softened point and then drawn and/or forced against an open mold. Depending on the technique, the mold can either be male or female, and the method of forming either vacuum and/or pressure.

Thermoplastic -: A material which has a linear macromolecular structure that will repeatedly soften when heated and harden when cooled.

Thermoset -: A material that will undergo or has undergone a chemical reaction by the action of heat, ultraviolet light, catalysts, etc., leading to a relatively infusible and cross-linked state.

Torsion -: The stress produced by twisting one end of an object along its longitudinal axis while the other end is held firm or twisted in the opposite direction.

Toxic -: Substances which chemically produce injurious or lethal effects to humans; poisons.

TPE -: Thermoplastic Elastomer

TPR -: Thermoplastic Rubber

- U -

UHMWPE -: Ultra high molecular weight polyethylene

U.L. -: Underwriters' Laboratories

Ultrasonic Welding -: A method of joining plastics using ultrasonic vibrations which are produced by the mechanical motion of a converter expanding some 20,000 times per second. The vibratory energy creates frictional heat which is channeled through a horn and applied to thermoplastic materials to produce a molecular interaction that welds the materials.

USDA -: United States Department of Agriculture

U.S.P. -: United States Pharmacopoeia

U.V. (Ultraviolet Light) -: The radiation from sunlight or artificial light having wavelengths shorter than those of visible light and longer than those of x-rays (250-400 millimicrons).

- V -

Valve -: A device which controls fluid flow rate, direction, or pressure.

Valve;
Directional Control- A device for directing or preventing the oil flow in a system.

Open Center (Tandem) Type - Has the inlet port connected to the outlet (tank) port in neutral.

Closed Center Type - Has the inlet port blocked from the outlet and work ports in neutral.

Two-Way - A 2 port valve with inlet and outlet ports.

Three-Way - A 3 port valve (in, out ~r,d work) normally used with a single acting cylinder or uni-directional motor.

Four-Way - A 4 port valve (in, out and 2 work) used with double acting cylinders, bi-directional motors.

Two, Three, Four Position - The number of positions in which a valve can be positioned.

Series Type - A multiple spool valve in which the return oil from the first spool is directed to the inlet of the second spool (and from the second to the third, etc.). This type valve permits simultaneous operation of two or more functions with the same oil flow. However, the total pressure requirements of all functions are accumulative.

Parallel Type - A multiple spool valve in which the inlet oil is connected to all spools simultaneously. If more than one spool is actuated, the function requiring the lowest pressure will operate first.

Series-Parallel Type - A multiple spool valve which has all spools connected to the open center passage in neutral. However, when actuated, the upstream valve takes full priority. The return oil is directed to downstream spools as in a series type valve.

Power Beyond (High Pressure Carryover) - A sleeve attachment which permits the oil flow from one valve (when in neutral) to be used by another valve downstream. Hence, a 3-spool valve cou1d be connected to a 2-spool valve to create a 5-spool valve, The first valve takes priority and thrust have a separate outlet port to return oil from an activator back to the reservoir.

Load Check (Lift Check) - A device which prevents a load from dropping when a valve is shifted, until ample pressure and flow is available to hold or move the load
Vicat Softening Point -: The temperature at which a flat-ended needle of 1 mm2 circular cross section will penetrate a thermoplastic specimen to a depth of 1 mm under a specified load using a selected uniform rate of temperature rise.

Viscosity -: The measure of the resistance of a fluid flow (either through a specific orifice or in a rotational viscometer). The absolute unit of viscosity measurement is the poise (or centipoise). Kinematic viscosity is expressed in stokes.

Vulcanization -: The chemical reaction which induces extensive changes in the physical properties of a rubber or plastic and which is brought about by the reaction of the material with sulphur and/or other suitable agents. The changes typically include decreased plastic flow, solubility, and surface tackiness, along with increased elasticity and much greater tensile strength.

- W -

Weld Lines -: The marks visible on a finished part made by the meeting of two flow fronts of resin during molding.

Welding -: Joining pieces by one of several heat-softening processes.

Working Life -: The period of time during which a material or product retains the physical properties for which it was created.

Working Pressure -: The maximum recommended pressure at ambient temperature for continuous operation.

- X -

X-Ray Specs -: Used to obtain visual contact with flow.

- Y -

Yield Strength -: The lowest stress at which a material undergoes plastic deformation. Below this stress the plastic is elastic; above it , viscous.

Yank -: The sharp, quick motion used to remove tubing or hose from a bulkhead or other connection point. Also see Jerk.

- Z -

No terms at this time.