Glossary of Plastic & Piping Terminology
There is no plastic or piping glossary as comprehensive as that shown in the reference. Hundreds of items are listed. If when using this source you cannot find a term you are looking for, please contact the editor. Definitions shown are from industry literature sources including the plastic pipe and fitting association, “Plastic Piping Systems” authored by David A. Chasis and other sources.
Abrasion: Wear or scour by hydraulic traffic.
Abutment: A wall supporting the end of a bridge or span, and sustaining the pressure of the abutting earth.
Acceptance test: An investigation performed on an individual lot of a previously qualified product, by or under the observation of, the purchaser to establish conformity with a purchase agreement.
Acid vent: A pipe venting an acid waste system.
Acid waste: A pipe that conveys liquid waste matter having a pH of 6.9 or less.
Acme Thread: A screw thread, the profile of which is between the square and V threads, used extensively for feed screws. The included angle between the flanks of the thread is 29° as compared to 60° for the unified thread.
Acrylonitrile- butadiene-styrene (ABS) pipe and fitting plastics: Plastics containing polymers and/or blends of polymers, in which the minimum butadiene content is 6%, the minimum acrylonitrile content is 15%, the minimum styrene and/or substituted styrene content is 15%, and the maximum content of all other monomers is not more than 5%: they also contain lubricants, stabilizers, and colorants.
Adapter fitting: (1) Any of various fittings designed to mate or to fit to each other two pipes or fittings that are different in design, when connecting the two together would otherwise not be possible. (2) A fitting that serves to connect two different tubes or pipes to each other, such as copper tube to iron pipe.
Additive: A substance added in a small amount for a special purpose such as to reduce friction, corrosion, and the like.
Adhesive: A substance capable of holding materials together by surface attachment.
Aerial sewer: An unburied sewer (generally sanitary type) supported on pedestals or bents to provide a suitable grade line.
Aging: The effect of exposing plastics to the environment for a length of time. The specific effect and degree of aging depend on the moisture, temperature, and composition of the environment in addition to the length of exposure.
Air vent: Small outlets for preventing gas entrapment.
Ambient temperature: The prevailing temperature in the immediate vicinity, or the temperature of the medium surrounding an object.
Anchor: A device used to fasten or secure pipes to the building or structure.
Angle of bend: In a pipe, the angle between radial lines from the beginning and end of the bend to the center.
Angle of Repose: The angle which the sloping face of a bank of loose earth, gravel, or other material, makes with the horizontal.
Anhydrous: Free of water, especially water of crystallization.
Annulus or Annuli: The gap between the penetrating item and the outside edge of the hole (fire stops).
Antioxidant: A compounding ingredient added to a plastic composition to retard the degradation of the plastics’ properties caused by contact with oxygen (aid), particularly at or exposure to high temperatures.
Artificial weathering: The exposure of plastics to cyclic laboratory conditions involving changed in temperature, relative humidity, and ultraviolet radiant energy, with or without direct water spray, in an attempt to produce changes in the material similar to those observed after long-term continuous outdoor exposure. (Note: The laboratory exposure conditions are usually intensified beyond those encountered in actual out-door exposure in an attempt to achieve an accelerated effect. This definition does not involve exposure to special conditions such as ozone, salt spray, industrial gages, and the like.)
Backer Rod: A cylindrical polyurethane or polyethylene foam material used to provide support and set the proper depth of material for gunned or troweled in place sealant (fire stops).
Backfill: That portion of the trench excavation that is replaced after the buried pipe line has been laid with the material above the pipe (up to the original earth line).
Backfill Density: Percent compaction for pipe backfill (required or expected).
Backing Material: Combustible or noncombustible material used to provide support for gunned or troweled in sealant or caulk.
Ball check valve: A device used to stop the flow of media in one direction while allowing flow in the opposite direction. The closure member used is spherical or ball shaped.
Ball valve: A valve with a ball-shaped disk with a hole through the center of the ball, providing straight-through flow. A quarter-turn of the handle fully opens or closed the valve for quick shut off.
Base (course): A layer of specified or selected material of planned thickness, constructed on the subgrade (natural foundation) or subbase for the purpose of distributing load, providing drainage or upon which a wearing surface or a drainage structure is placed.
Baume gravity: Arbitrary scale for measuring the density of liquids: the unit used is the “Baume” (Be) degree. The scale uses an inverse ration of the specific gravity (sp. gr.) scale:
Formula for liquids lighter than water:
sp. gr. = ____140__________
130 + Be degree
Formal for liquids heavier than water:
sp. gr. = ___145_________
145 – Be degree
This permits the translation of Baume gravity to specific gravity. For instance, when floated in pure water, the Baume hydrometer indicated 10o Be, while the specific gravity scale reads 1.00. The Baume scale is employed by the U.S. National Bureau of Standards for all liquids except oils.
Beam loading: The application of a load to a pipe between two points of support; it is usually expressed in pounds and the distance between the centers of supports.
Bedding: The earth or other material on which a pipe or conduit is supported.
Bell and spigot joints: One side of the fitting or pipe is belled or socket; the other end is plain-ended pipe.
Bell end: The enlarged portion of a pipe that resembles the socket portion of a fitting and that is intended to make a joint by inserting a piece of pipe into it. Joining may be accomplished by solvent cements, adhesives, or mechanical techniques.
Berm: The space between the toe of a slope and excavation made for Bedding – The earth or other material on which a pipe or conduit is supported.
Binder: The part of adhesive composition responsible for adhesive forces.
Biological Corrosion: Corrosion that results from a reaction between the Pipe material and organisms such as bacterial, algae, and fungi.
Blister: The elevated part of the surface of a plastic caused by trapped air, moisture, solvent; it can be caused by insufficient adhesive, inadequate curing time, or excessive temperature or pressure.
Bond: The attachment at the interface or exposed surfaces between an adhesive and an adherent; to attach materials together with adhesives.
Branch: Any part of a piping system other than a main, riser, or stack.
Branch interval: A length of soil or waste stack corresponding in general to a story height-but in no case less than 8 ft (2.4 m) – within which the horizontal branches from one floor or story of a building are connected to the stack.
Branch tee: A tee having one side branch.
Branch vent: A vent connecting one or more individual vents with a vent stack or stack vent.
British thermal unit (Btu): The quantity of energy needed to heat one pound of water from 59o F to 60o F at a standard barometric pressure: 1 Btu = 0.252 kcal = 0.000293 kWh.
Brittleness Temperature: Temperature at which 50% of the tested specimens will fail when subjected to an impact blow.
Bubble tight: The condition of a valve seat that, when closed, prohibits the leakage of visible bubbles.
Building Sewer: The conduit that connects building wastewater sources to the public or street sewer, including lines serving homes, public buildings, commercial establishments, and industrial structures. The building sewer is referred to in two sections: (1) the section between the building line and the property line, frequently specified and supervised by plumbing or housing officials; and (2) the section between the property line and the street sewer, including the connection thereto frequently specified and supervised by sewer, public works, or engineering officials (Referred to also as “house sewer,” “building connection,)’ “service connection,” or “lateral connection”).
Bulk density: Density of a molding material in loose form, such as granular of nodular, in units of g/cm.
Bulkhead fitting: fitting fixed to a vessel wall that allows fluids to flow through the wall and adapts pipe or tubing to the vessel. One end is usually smooth (inside vessel), and the other end is usually threaded.
Bull head tee: A tee, the branch of which is larger than the run.
Burst pressure: The pressure that can be applied slowly to a valve, fitting, or pipe at room temperature for 30 sec without causing rupture.
Burst strength: The internal pressure required to break a pipe or fitting. This pressure will vary with the rate of buildup of the pressure and the time during which the pressure is maintained.
Bushing: A fitting used to connect a pipe to a female fitting of a larger size.
Butt Fusion: A method of joining thermoplastic pipes wherein the ends of the two pieces to be joined are heated to the molten state and then quickly pressed together.
Butt weld joint: A welded pipe joint made with the ends of the two pipes butting each other.
Butterfly valve: A device deriving its name from the winglike action of the disk, which operates at right angles to the flow. The disk impinges on the resilient seal with low operating torque.
By-pass: An auxiliary loop in a pipeline that divers flow around a valve or other piece of equipment.
By-pass valve: Valve by which the flow or liquid or gas in a system may be directed past some part of the system through which it normally flows (e.g., an oil filter in a lubrication system).
Caisson: A watertight box or cylinder used in excavating for foundations or tunnel pits to hold out water so concreting or other construction can be carried on.
Camber: Rise or crown of the center of a bridge, or Bowline through a culvert, above a straight line through its ends.
Capacity: The maximum or minimum flow obtainable under given conditions of media, temperature, pressure, velocity, and the like. Also, the volume of media that may be stored in a container or receptacle.
Capillary: The action by which the surface of a liquid, where it is in contact with a solid, is elevated or depressed depending on the relative attraction of the molecules of the liquid for each other and for those of the solid.
Cathode: The electrode of an electrolytic cell at which reduction is the principal reaction (Electrons flow toward the cathode in the external circuit). Typical cathodic processes are cations taking up electron and being discharged, oxygen being reduced, and the reduction of an element or group of elements from a higher to a lower valence state.
Cathodic Corrosion: An unusual condition (especially with Al, Zn, Pb) in which corrosion is accelerated at the cathode because the cathodic reaction creates an alkaline condition that is corrosive to certain metals.
Cathodic Protection: Preventing corrosion of a pipeline by using special cathodes (and anodes) to circumvent corrosive damage by electric current. Also a function of zinc coatings on iron and steel drainage products – galvanic action.
Cavitation: Formulation and sudden collapse of vapor bubbles in a liquid; usually resulting from local low pressures – as on the trailing edge of a propeller; this develops momentary high local pressure.
Cell Classification: Method of identifying thermoplastic materials, such as Polyvinyl Chloride, as specified by ASTM, where the Cell Classification is based on these six properties for PVC are: Density, Melt Index, Flexural Modulus, Tensile Strength at Yield, Environmental Stress Crack Resistance, and Hydrostatic Design Basis.
Cement: A dispersion of “solution” of unvulcanized rubber or a plastic in a volatile solvent. This meaning is peculiar to the plastics and rubber industries and may or may not be an adhesive composition. (See also Adhesive and Solvent cement.)
Centipoise: Unit of absolute viscosity; it equals one hundredth of a poise.
Centistoke: Unit of kinematic viscosity; it equals one hundredth of a stoke. Kinematic viscosity in centistokes multiplied by the specific gravity equals absolute viscosity in centipoises.
Char: A grayish black, crusty material formed by burning organic type sealants (fire stops).
Chase: A recess in a wall in which pipes can be run.
Check valve: Device that permits flow in only one direction in pipeline.
Chemical waste system: Piping that conveys corrosive or harmful industrial, chemical, or processed wastes to the drainage system.
Chemical resistance: (1) The effect of specific chemicals on the properties of plastic piping with respect to concentration, temperature, and time of exposure. (2) The ability of a specific plastic pipe to render service for a useful period in the transport of a specific chemical at a specified concentration and temperature.
Circuit vent: A branch vent that serves two or more traps and extends from in front of the last fixture connection of a horizontal branch to the vent stack.
Classification: A series of procedures, usually administered by an independent testing laboratory, by which the consumer is protected and assured that the product that was tested is the same as the product purchased.
Cleaner: Medium strength organic solvent such as methylethyl ketone used to remove foreign matter from plastic pipe and fitting joint surfaces.
Cleanout: A plug or cover joined to an opening in a pipe that can be removed to clean or examine the interior of the pipe.
Close nipple: A nipple twice as long as a standard pipe thread.
Closed System: A piping system that is sealed, typically carrying fluids under pressure, such as hot and cold water distribution.
Coefficient of expansion: The increase in unit length, area, or volume for a unit rise in temperature.
Cohesion: The molecular attraction that holds the body of a sealant or adhesive together. The internal strength of an adhesive or sealant (fire stops).
Cohesive Failure: Failure characterized by rupture within the sealant adhesive or coating (fire stops).
Cold Bend: To force the pipe into a curvature without damage, using no special tools, equipment or elevated temperatures.
Cold flow (see Creep).
Collector Sewer: A sewer located in the public way collects the wastewater’s discharged through building sewers and conducts such flows into larger interceptor sewers and treatment works. (Referred to also as “street sewer.”)
Combined Sewer: A sewer intended to serve as both a sanitary sewer and a storm sewer, or as both an industrial sewer and a storm sewer.
Combined waste and vent system: A specially designed system of waste piping, embodying the horizontal wet venting of one or more floor sinks or floor drains by means of a common waste and vent pipe, adequately sized to provide free movement of air above the flow line of the drain.
Combustion: Burning or rapid oxidation.
Common vent: A vent that connects at the junction of two fixture drains and serves as a vent for both fixtures. Also, known as a dual vent.
Compaction: The densification of a soil by means of mechanical manipulation.
Companion flange: A pipe flange used to connect with another pipe flange or with a flanged valve or fitting. It is attached to the pipe by threads, welding, or other methods and differs from a flange that is an integral part of a pipe or fitting.
Compatibility: The capability of two or more materials when placed in contact or close proximity with one another to maintain their usual physical or chemical properties, or both.
Composite Pipe: Pipe consisting of two or more different materials arranged with specific functional purpose to serve as pipe.
Compound: The admixture of a polymer or polymers with other ingredients such as fillers, softeners, plasticizers, catalysts, pigments, dyes, curing agents, stabilizers, or antioxidants.
Compression fitting: A fitting designed to join a pipe or tube by means of pressure or friction.
Compression joint: A multipiece joint with cup-shaped threaded nuts, which, when tightened, compress tapered sleeves so that they form a tight joint on the periphery of the tubing they connect.
Compression strength: The crushing load at failure of an item divided by the number of square inches of resisting surface. (Figures are given in thousands of pounds.)
Concentric: Having a common center; a pipe centered in the middle of a through-penetration hole results in a concentric annulus (fire stops).
Condensate: Water that has liquefied from steam.
Conductivity: A measure of the ability of a solution to carry an electrical current. Conductivity varies both with the number and type of ions the solution carries.
Continuous vent: A vent that is a continuation of the drain to which it connects.
Continuous waste: A drain from two or three fixtures connected to a single trap.
Control valve: Variable opening valve used with a control instrument to maintain a predetermined flow rate, pressure, temperature, or level. The valve can be electric, electrohydraulic, or air operated.
Copolymer: Formed form two or more monomers. (See also Polymer).
Corrosion: The destruction of a material or its properties because of a reaction with its (environment) surroundings.
Corrosion Rate: The speed (usually an average) with which corrosion progresses (it may be linear for a while); often expressed as though it was linear, in units of mdd (milligrams per square decimeter per day) for weight change, or mpy (milligrams per year) for thickness changes.
Corrosion-erosion: Corrosion which is increased because of the abrasive action of a moving stream; the presence of suspended particles greatly accelerates abrasive action.
Collar: A galvanized sheet metal restricting device used in conjunction with plastic pipe. Its function is to direct and control the intumescent action of the fires stopping material (fire stops).
Corrosion: Deterioration in metals caused by oxidation or chemical action.
Creep: The dimensional change, with time, of a material under continuously applied stress after the initial elastic deformation. The time dependent part of strain due to a constant stress.
Cross: A pipe fitting with four branches in pairs, each pair on one axis, and the axes at right angles.
Cross-linking: Generation of chemical linkages between long-chain molecules; cross-linking can be compared to two straight chains joined together by links. The rigidity of the material increases with the number of links. The function of a monomer is to provide these links.
Cross-over: A fitting with a double offset-shaped like the letter “U” with the ends turned out-used to pass the flow of one pipe past another when the pipes are in the same plane.
Crown: That part of the trap in which the direction of flow is changed from upward to downward.
Crown vent: A vent pipe connected at the topmost point in the crown of a trap.
Dead end: A branch leading from a soil, waste, or vent pipe; building (house) drain; or building (house) sewer that is terminated at a developed distance of 2 ft (0.6 m) or more by means of a plug or other closed fitting.
Deflection temperature: The temperature at which a specimen will deflect a given distance at a given load under prescribed conditions of test (formerly called heat distortion).
Degradation: Deleterious change in a plastic’s chemical structure.
Destiny: Mass of a fluid per unit volume.
Deterioration: Permanent adverse change in the physical properties of a plastic.
Developed length: The length along the center line of the pipe and fittings.
Dew point: The temperature at which liquid first condenses when a vapor is cooled.
Diameter: Unless specifically stated, the nominal diameter as designated commercially.
Diaphragm: A flexible disk used to separate the control medium form the controlled medium; it actuates the valve stem.
Diaphragm valve: A valve used for controlling flow by a flexible elastometric disk.
Diffusion: The movement of a material, such as a gas or liquid, in the body of a plastic. If the gas or liquid is absorbed on one side of a piece of plastic and given off on the other side, the phenomenon is called permeability. Diffusion and permeability are not due to holes or pores in the plastic, but are caused and controlled by chemical mechanisms.
Dimension ratio: The diameter of a pipe divided by the wall thickness. Each pipe can have two dimension ratios depending on whether the pipe’s outside or inside diameter is used. In practice, the outside diameter is used if the standards requirement and manufacturing control are based on this diameter. The inside diameter is used when this measurement is the controlling one.
Disk: The part of a valve that actually closes off the flow.
Dispersion: Heterogeneous mixture in which finely divided material is suspended in the matrix of another material; as in the distribution of finely divided solids in a liquid or a solid (e.g., pigments or fillers).
Displacement: The volume or weight of a fluid, such as water, displaced by a floating body.
Double offset: Two changes of direction installed in succession or series in continuous pipe.
Double ported valve: A valve having tow ports to overcome line pressure imbalance.
Double sweep tee: A tee made with “easy” (long-radius) curves between body and branch.
Drain: Any pipe that carries wastewater or water-borne wastes in a building drainage system.
Drainage fitting: A type of fitting used for draining fluid from pipes. The fitting makes a smooth and continuous interior surface for the piping system.
Dry bulb temperature: The temperature of air as measured by an ordinary thermometer.
Dual vent (see Common vent).
Ductile Failure: A failure mode that exhibits material deformation (stretching, elongation, or necking down) in the area of the break.
Durometer hardness: A material’s hardness as measured by the Shore Durometer.
Eccentric: Off center; an eccentric annulus results when a pipe is not centered in the hole (fire stops)
Effluent: Outflow or discharge from a sewer us sewage treatment equipment.
Elastic Modulus: A measure of the stress buildup associated with a given strain.
Elasticity: Property of materials that tends to retain or recover their original shape and size after undergoing deformation.
Elastomer: A material under ambient conditions that can be stretched and, upon release of the applied stress, returns with force to approximately its original size and shape.
Elevated temperature testing: Tests on plastic pipe above 23oC (73o F).
Elbow (EII): A fitting that makes an angle between adjacent pipes. The angle is 90o, unless another angle is specified.
Elongation: (strain) The increase in length of a material stressed in tension.
Elongation: Extension produced by a tensile stress.
Embankment (or fill): A bank of earth, rock or other material constructed above the natural ground surface.
Embrittlement: Loss of ductility of a material resulting from a chemical or physical change.
End connection: A reference to the method of connecting the parts of a piping system (i.e., threaded, flanged, butt-weld, socket weld).
Environmental stress cracking: Cracks that develop when the material is subjected to stress in the presence of specific chemicals.
Erosion: The gradual destruction of a material by the abrasive action of liquids, gases, solids, or mixtures of these materials.
Exfiltration: The leakage or discharge of flows being carried by sewers out into the ground through leaks in pipes, joints, manholes, or other sewer system structures; the reverse of “infiltration.”
Expansion joint: Joint used in the connection of long lines of pipe; the expansion joint contains a bellows or telescopelike section to absorb the thrust or stress resulting from linear expansion or contraction of the line owing to changes in temperature or to accidental forces.
Expansion loop: A large radius bend in a pipe line to absorb longitudinal thermal expansion in the line.
Extrusion: Method of processing plastic in a continuous or extended form by forcing the heat-softened plastic through an opening shaped like the cross section of the finished product.
F Rating: A firestop shall be considered as meeting the requirements for an F rating when it remains in the opening during the fire test and hose stream test within the following limitations: The firestop shall have withstood the fire test for the rating period without permitting the passage of flame through openings, or the occurrence of flaming on any element of the unexposed side of the firestop. During the hose stream test, the firestop shall not develop any opening the would permit a projection of water from the stream beyond the unexposed side (ASTM E 814) (fires stops).
Fabricate: Method of forming a plastic into a finished article by machining, drawing, and similar operations.
Face-to-face dimensions: The dimensions from the face of the inlet port to the face of the outlet port of a valve or fitting.
Fatigue Strength: The stress to which a material can be subjected for a specified number of fatigue cycles.
Female thread: Internal thread in pipe fittings, valves, and the like, for making screwed connections.
Filler: A relatively inert material added to a plastic to modify its strength, permanence, working properties, or other qualities, or to lower costs.
Filter: A device through which fluid is passed to separate contaminates.
Filter element: A porous device that performs filtration.
Finishing: Removal of any defects from the surfaces of plastic products.
Fire Endurance: A measure of the elapsed time during which a material or assembly continues to exhibit fire resistance under specified conditions of test and performance. As applied to elements of building, it shall be measured by the methods and criteria defined in ASTM E 119 Fire Tests of Building Construction and Materials (fire stops).
Fire Rated or Fire Resistance: (1) A system which has been tested by a qualified laboratory in accordance with the appropriate ASTM test standard and has met the mechanical and endurance requirements of that standard. (2) The property of a material or assembly to withstand fire or give protection from it. As applied to elements of buildings, it is characterized by the ability to confine a fire or to continue to perform a given structural function, or both. Systems are rated for 1, 2, 3 or 4 hours, based on the results of the fire test (fire stops).
Fire Resistance Classification: A standard rating of fire-resistance and protective characteristics of a building construction or assembly (ASTM E 119) (fire stops).
Firestop: A through-penetration firestop is a specific combination of components or materials that fill the opening around wall, floor or ceiling penetrating pipes and their means of support for the purpose of preventing the spread of fire (fire stops).
Fire Test Standard: Fire test standards are procedures intended to measure and describe the response of material, products, and systems to sources of heat or flame under controlled conditions. These tests are intended to provide information useful for such purposes as product development, quality control, and specification description. They are not intended to be used alone to provide a measure of the fire hazard of materials, products or systems. Fire test standards are separate and distinct from fire hazard standards, which are used to describe, measure, assess or control the behavior of materials, products and systems in the relevant environment (fire stops).
Fitting: A device or connection that allows a pipe to change direction or size.
Fixture: A device or appliance at the end of a water supply distribution pipe line.
Flammability: The time a specimen will support a flame after having been exposed to it for a given period of time.
Flange: In pipe work, a ring plate on the end of a pipe at right angles to the end of the pipe and provided with holes for bolts to allow fastening the pipe to a similarly equipped adjoining pipe. The resulting joint is called a flanged joint.
Flanged ends: A valve of fitting having flanges for joining to other piping elements. Flanged ends can be plain faced, raised face, large male and female, large tongue and groove, small tongue and groove, or ring joint.
Flange faces: Pipe flanges that have the entire surface of the flange faced straight across and use either a full face or ring gasket.
Flash point: Temperature at which enough of a material is vaporized to produce a flash f burning vapor.
Flexural Modulus: The ratio, within the elastic limit, of the applied stress in the outermost fibers of a test specimen in three point static flexure, to the calculated strain in those outermost fibers (ASTM D 790).
Flexural strength: The pressure in pounds necessary to break a given sample when the pressure is applied to the center of the sample that has been supported at its ends.
Flow coefficient or C: Valve coefficient of flow representing the flow rate of water in gallons per minute that will produce a 1 psi pressure drop through the valve.
Fluorocarbon resins: Material made by the polymerization of monomers composed only of carbon and fluorine.
Foot valve: Check valve located at the inlet end of the suction line at a pump that allows the pump to remain full of liquid when not in service.
Forming: A process in which the shape of plastic pieces such as sheets, rods, or tubes is changed to a desired configuration. (Note: The use of the term “forming” in plastics technology does not include such operations as molding, casting, or extrusion, in which shapes or pieces are made from molding materials or liquids.)
Fouling: An accumulation of deposits. This term includes accumulation and growth of marine organisms on a submerged metal surface and also includes the accumulation of deposits (usually inorganic) on heat exchanger tubing.
Full port valve: A valve in which the resistance to flow, in the open position, is equal to an equivalent length of pipe.
Fungi resistance: The ability of plastic pipe to withstand fungi growth or their metabolic products or both under normal conditions of service or laboratory tests simulating such conditions.
Fusion point: Temperature at which solid and liquid states of a substance can exist together in equilibrium (also called melting or freezing points).
Galvanic Cell: A cell consisting of two dissimilar metals in contact with each other and with a common electrolyte (sometimes refers to two similar metals in contact with each other but with dissimilar electrolytes; differences can be small and more specifically defined as a concentration cell).
Gate valve: Valve with a sliding blank that opens to the complete cross section of the line; used for complete opening or complete shutoff of the flow in pipes. It is not used for throttling or control.
Glass transition temperature: The range of temperatures in which a plastic changes from a rigid to a soft state. (Note: values will depend on the method of test. It is sometimes referred to as softening point.)
Glass Transition Temperature: The temperature below which a plastic is more brittle and glassy.
Globe valve: Valve used for throttling that does not have a straight-through opening.
Grade: The slope or fall of a line of pipe in reference to a horizontal plane. In drainage, it is expressed as the fall in a fraction of an inch or percentage slope per foot (mm/m) length of pipe.
Ground Water Table (or level): Upper surface of the zone of saturation in permeable rock or soil. (When the upper surface is confined by impermeable rock, the water table is absent.)
Haunch: That portion of the pipe barrel extending below the pipe springline.
Haunching: Area from the bedding to the spring line of pipe. Provides the majority of load carrying of underground pipe and also provides side support for flexible and rigid pipe.
Head (Static): The height of water above any plane or point of references (the energy possessed by each unit of weight of a liquid, expressed as the vertical height through which a unit of weight would have to fall to release the average energy posed). The standard inch-pound unit of measure is feet of water. The relation between pressure in psi and feet of head at 68°F is 1 psi = 2.310 ft of head.
Heat capacity: The quantity of heat required to raise the temperature of a given mass by 1°. This quantity is based on either 1 mole or a unit mass of material.
Heat of fusion: Heat needed to change a quantity of solid to a liquid, without a change in temperature.
Heat joining: Making a pipe joint by heating the edges of the parts to be joined so that they fuse and become essentially one piece with or without additional material.
Home-run: A plumbing design that utilizes a central manifold and distribution piping to each hot and cold water fixture.
Hoop stress: The tensile stress, usually expressed in pounds per square inch (psi), in the circumferential orientation in the wall of the pipe when the pipe contains a gas or liquid under pressure.
Hot soils: Soils having a resistivity of less than 1000 ohm-cm; they are generally very corrosive to base steel.
Hydraulic gradient: The amount of inclination of a drainage line between the trap outlet and the vent connection, not exceeding one pipe diameter in this total length.
Hydrostatic Design Basis (HDB): One of a series of established stress values specified in Test Method D 2837 “Standard Test Method for Obtaining Hydrostatic Design Basis for Thermoplastic Pipe Materials” for a plastic compound obtained by categorizing the LTHS determined in accordance with Test Method D 2837. HDB refers to the categorized LTHS in the circumferential, or hoop direction, for a given set of end use conditions. Established HDBs are listed in PPI TR-4.
Hydrostatic design stress: The estimated maximum tensile stress in the wall of the pipe in the circumferential orientation owing to internal hydrostatic pressure that can be applied continuously with a high degree of certainty that failure of the pipe will not occur.
Hydrostatic strength (quick): The hoop stress calculated by means of the ISO equation at which the pipe breaks due to an internal pressure buildup, usually within 60-70 sec. (See also ISO equation).
Ignition Temperature: Temperature at which the vapors emitted from a material will ignite either without exposure to a flame (self-ignition) or when a flame is introduced (flash ignition).
Impact, Izod: A specific type of impact test made with a pendulum-type machine. The specimens are molded or extruded, with a machined notch in the center. (See also Izod impact strength.)
Impact strength: Resistance, or mechanical energy absorbed by plastic part, to shocks such as dropping and hard blows.
Impact, tup: A falling weight (tup) impact test developed specifically for pipe and fittings. There are several variables that can be selected.
Intumesce: To swell, enlarge inflate or expand as with heat. Intumescent fire stopping sealants swell to close gaps or voids in through-penetration openings when exposed to high heat conditions (fire stops).
Infiltration: The water entering a sewer system, including building sewers, from the ground, through such means as defective pipes, pipe joints, connections, or manhole walls. Infiltration does not include, and is distinguished from inflow.
Inhibitor: Material that retards chemical reaction or curing.
Injection Molding: The process of forming a material by melting it and forcing it, under pressure, into the cavity of a closed mold.
Interceptor Sewer: A sewer which receives the flow of collector sewers and conveys the wastewaters to treatment facilities.
ISO equation: An equation showing the relations among stress, pressure, and dimensions in pipe, namely,
S = P (ID + t)
2t
or P(OD-t)
2t
where S = stress
P = pressure
ID = average inside diameter
OD = average outside thickness
t = minimum wall thickness
Isobaric process: A constant-pressure process.
Isometric process: A constant-volume process.
Isothermal process: A constant-temperature process.
Izod impact strength: The resistance a notched test specimen has to a sharp blow from a pendulum hammer. (See also Impact, Izod.)
Joint: The location at which two pieces of pipe or a pipe and a fitting are connected. The joint may be made by a mechanical device, such as threads or ring seals, or by heat fusion and cementing.
Load factor: The percentage of the total connected fixture unit flow that is likely to occur at any point in the drainage system. Load factor represents the ratio of the probable load to the potential load and is determined by the average rates of flow of the various kinds of fixtures, the average frequency of use, the duration of flow during one use, and the number of fixtures installed.
Long-term burst: The internal pressure at which a pipe or fitting will break due to a constant internal pressure held for 100,000 hr (11.43 years).
Long –term hydrostatic strength: The estimated tensile stress in the wall of the pipe on the circumferential orientation (hoop stress) that when applied continuously will cause failure of the pipe at 100,000 hr (11.43 years). These strengths are usually obtained by extrapolation of log-log regression equations or plots.
Lubricant: A substance used to decrease the friction between solid faces, and sometimes used to improve processing characteristics of rubber or plastic compositions.
Manifold: A device having a series of ports that are used to connect distribution lines for several fixtures.
Manning’s Formula: An equation for the value of coefficient c in the Chezy Formula, the factors of which are the hydraulic radius and a coefficient of roughness: an equation itself used to calculate flows in gravity channels and conduits.
Material Safety Data Sheet (MSDS): A document required by law describing the health and safety aspects of a material as it pertains to its properties, health effects, hazards, handling and disposal.
Melting Point: That temperature at which the plastic transitions to a completely amorphous state.
Mineral Fiber: A noncombustible insulation material made from mineral fibers. It is also known as mineral wool or safing material. It is typically used as a backing and filler material in through-penetrations (fire stops).
Modulus: The ration of stress to strain. Also, the tensile strength at a given elongation.
Modulus of Elasticity (E): ASTM D 638 The ratio of stress (nominal) to corresponding strain below the proportional limit of a material.
Moment, Bending: The moment that produces bending in a beam or other structure. It is measured by the algebraic sum of the products of all the forces multiplied by their respective lever arms.
Modulus: The load in pounds per square inch, kilograms (force) per square centimeter, or, in SI, the modern metric system, megapascals (Mpa) of initial cross-section area necessary to produce a stated percentage elongation; this value is used in the physical testing of rubber or plastics. It is a measure of stiffness, and is influenced by pigmentation, state of cure, quality of raw rubber, and other factors. The modulus at any given elongation is shown by stress-strain curve.
Molding, blow: Method of forming plastic articles by inflating masses of plastic material with compressed gas.
Molding compression: Process of shaping plastic articles by placing material in a confining mold cavity and applying pressure and usually heat.
Molding, high pressure: Molding or laminating with pressures in excess of 200 psi.
Molding, injection: Process of making plastic articles from powdered or granular plastics by fusing the material in a chamber under pressure with heat and forcing part of the mass into a cooler cavity where it solidifies; used primarily with thermoplastics.
Molding, low pressure: Molding or laminating with pressures below 200 psi.
Molding, transfer: Process of molding plastic articles from powered, granular, or performed plastics by fusing the material in a chamber with heat and forcing the mass into a hot chamber for solidification. Used primarily with thermosetting plastics.
Monomer: Reactive material that is compatible with the basic resin. Tends to lower the viscosity of the resin. Simplest repeating structural unit of polymer.
Needle valve: Valve with a cone seat and needle-point plug to control small and accurate flows.
Non-Pressure Pipe: Pipe designed for gravity-conveyed medium that must resist only intermittent static pressures and does not have a pressure rating.
Non-Sag Sealant: A compound that exhibits little or no flow when applied in vertical or inverted joints (fire stops).
Nonrigid plastic: Plastic whose apparent modulus of elasticity is not greater than 10,000 psi at room temperature in accordance with the Standard Method of Test for Stiffness in Flexure of Plastics.
Notch Sensitivity: The extent to which an inclination to fracture is increased by a notch, crack, scratch, or sudden change in cross-section.
Nylon plastics: Group of plastics comprised of resins that are primarily long-chain synthetic polymeric amides. These resins have recurring amide groups as an integral part of the principle polymer chain.
Offset: A combination of pipe, pipes, and/or fittings that join two approximately parallel sections of the line of pipe.
Olefin plastics: Plastics based on resins made by the polymerization of olefins or copolymerization of olefins with other unsaturated compounds, the olefins being in greatest amount by weight. Polyethylene, polypropylene, and polybutylene are the most common olefin plastics encountered as pipe.
Open System: An open system or sometimes referred to as a vented system is a piping system which allows air flow to the exterior of the building to prevent back flow or vacuum.
Out-of-Roundness: The allowed difference between the maximum measured diameter and the minimum measured diameter (stated as an absolute deviation).
Outdoor exposure: Plastic pipe placed in service or stored so that it is not protected from the elements of normal weather conditions, i.e., the sun’s rays, rain, air, and wind. Exposure to industrial and waste gases, chemicals, engine exhausts, and the like, are not considered normal “outdoor exposure.”
Permanence: The property of a plastic that describes its resistance to appreciable changes in characteristics with time and environment.
Permeability (see Diffusion).
pH: A scale ranging from 0 to 14 that ranks how acidic or alkaline a liquid is; fluids with a pH below 7 is considered acidic and fluids with a pH above 7 is consider alkaline.
Pitch: The amount of slope or grade given to horizontal piping and expressed in inches of vertically projected drop per foot (or mm/m) on a horizontally projected run of pipe.
Pitting: Highly localized corrosion resulting in deep penetration at only a few spots.
Pipe stiffness: A measure of how a flexible conduit will behave under burial conditions.
Plastic (n): A material that contains as an essential ingredient an organic substance of large molecular weight, is solid in its finished state, and, at some state in its manufacture or in it’s processing into finished articles, can be shaped by flow.
Plastic (adj.): The adjective plastic indicates that the noun modified is made of, consists of, or pertains to plastic. (Note 1: This definition may be used as a separate meaning to the definitions contained in the dictionary for the adjective “plastic.” Note 2: The plural form may be used to refer to two or more plastic materials, for example, plastics industry. However, when the intent is to distinguish “plastic products” from “wood products” or “glass products,” the singular form should be used. As a general rule, if the adjective is to restrict the noun modified with respect to type of material, “plastic” should be used; if the adjective is to indicate that more than one type of plastic material is or may be involved, “plastics” is permissible.)
Plastic conduit: Plastic pipe or tubing used as an enclosure for electrical wiring.
Plastic pipe: A hollow cylinder of plastic material in which the wall thickness is usually small compared to the diameter and in which the inside and outside walls are essentially concentric. (See also Plastic tubing.)
Plastic, semirigid: Plastic having apparent modulus of elasticity in the range of 10,000-100,000 psi at 23°C, as determined by the Stanford Method of Test for Stiffness in Flexure Plastics.
Plastic tubing: A particular size of plastic in which the outside diameter is essentially the same as that of copper tubing. (See also Plastic pipe.)
Plastic welding: Joining of finished plastic components by fusing materials either with or without the addition of plastic from another source.
Plasticate: Softening by heating or kneading.
Plasticity: Property of plastics that permits the material to undergo deformation permanently and continuously without rupture from a force that exceeds the yield value of the material.
Plasticize: Softening by adding a plasticizer.
Plasticizer: Material added to a plastic to increase workability and flexibility. Plasticizers tend to lower the melt viscosity, the glass transition temperature, and or the elastic modulus.
Plough-in Piping: Installation procedure that splits the earth and pulls the pipe into position.
Plug valve: Valve mainly used in gas service; consisting of a rotating cylindrical plug in a cylindrical housing with an opening running through the plug.
Polybutylene: A polymer prepared by the polymerization of butane-1 as the sole monomer. (See also Polybutylene plastics.)
Polybutylene plastics: Plastics based on polymers made with butane-1 as essentially the sole monomer.
Polyethylene: A polymer prepared by the polymerization of ethylene as the sole monomer. (See also Polyethylene plastics.)
Polyethylene plastics: Plastics based on polymers made with ethylene as essentially the sole monomer. (Note: In common usage for this plastic, polyethylene plastics essentially means no less than 85% ethylene and no less than 95% total olefins.)
Polymer: A compound formed by the reaction of simple molecules having functional groups that permit the combination to proceed to high molecular weights under suitable conditions. Polymers may be formed by polymerization (addition polymer) or polycondensation (condensation polymer). When two or more monomers are involved, the product is called a copolymer.
Polymerization: A chemical reaction in which the molecules of a monomer are linked together to form large molecules whose molecular weight is a multiple of the original substance. When two or more monomers are involved, the process is called copolymerization heteropolymerization.
Polyolefin: A polymer prepared by the polymerization of an olefin(s) as the sole monomer(s). See also Polyolefin plastics and Olefin plastics.)
Polyolefin plastics: Plastics based on the polymers made with an olefin(s) as essentially the sole monomer(s).
Polypropylene: A polymer prepared by the polymerization of propylene as the sole monomer. (See also Polypropylene plastics and Propylene plastics.)
Polypropylene plastics: Plastics based on polymers made with propylene as essentially the sole monomer.
Polystyrene: A plastic based on a resin made by polymerization of styrene as the sole monomer. (See also Styrene plastics.) (Note: Polystyrene may contain minor proportions of lubricants, stabilizers, fillers, pigments, and dyes.)
Polyvinyl chloride: A resin prepared by the polymerization of vinyl chloride with or without the addition of small amounts of other monomers.
Polyvinyl chloride plastics: Plastics made by combining polyvinyl chloride with colorants, fillers, plasticizers, stabilizers, lubricants, other polymers, and other compounding ingredients, other polymers, and other compounding ingredients. Not all of these modifiers are used in pipe compounds.
Powder blend (See Dry-blend).
Pressure: When expressed with reference to pipe, the force per unit area exerted by the medium in the pipe.
Pressure rating: The estimated maximum pressure that the medium in the pipe can exert continuously with a high degree of certainty that failure of the pipe will not occur.
Pressure tubing: Tubing used to convey fluids at elevated temperatures and/or pressures. Suitable for head applications, it is fabricated to exact outside diameter and decimal wall thickness in sizes ranging from ½ to 6 in. outside diameter inclusive and to ASTM specifications.
Primer: Coating that is applied to a surface before application of an adhesive, enamel, and the like; its purpose is to improve bonding.
Propylene plastics: Plastics based on resins made by the polymerization of propylene or copolymerization of propylene with one or more unsaturated compounds, the propylene being in greatest amount by weight.
Pump: Mechanical device for transporting liquids in pipelines; major types are centrifugal, reciprocating, turbine, rotary, and proportioning.
Qualification test: An investigation, independent of a procurement action, performed on a product to determine whether or not the product conforms to all requirements of the applicable specification. (Note: The examination is usually conducted by the agency responsible for the specification, the purchaser, or facility approved by the purchaser, at the request of the supplier seeking inclusion of his or her product on a qualified products list.)
Quick burst: The internal pressure required to burst a pipe or fitting due to an internal pressure buildup, usually within 60-90 sec.
Quick Burst Test: (ASTM D 1599) An internal pressure test designed to produce rupture (bursting) of a piping component in 60-70 seconds determined in accordance with ASTM D 1599.
Reinforced plastic: According to ASTM, those plastics having superior properties over those consisting of the base resin, owing to the presence of high-strength fillers embedded in the composition. Reinforced fillers are usually fibers, fabrics, beads, or mats made of fibers.
Relief valve: Safety device for automatic release of fluid at a predetermined pressure.
Resin: A solid, semisolid, or pseudosolid organic material that has an indefinite and often high molecular weight, exhibits a tendency to flow when subjected to stress, usually has a softening or melting range, and usually fractures conchoidally (radially).
Reworked material (thermoplastic): A plastic material that has been reprocessed, after having been previously processed by molding, extrusion, and the like, in a fabricator’s plant.
Reworked Plastic: A plastic from a manufacturer’s own production that has been reground or pelletized for reuse by that same manufacturer.
Riser: A water supply pipe that extends vertically one or more stories to transport water to fixtures or branches.
Roughness Coefficient: A factor in the Kutter, Manning, and other flow formulas representing the effect of channel (or conduit) roughness upon energy tosses in the fl owing water.
Rubber: A material that is capable of recovering from large deformations quickly and forcibly. (See also Elastomer.)
Saddle Fitting: A fitting used to make lateral connection to a pipe in which a portion of the fitting is contoured to match the OD of the pipe to which it is attached.
Sample: A small part or portion of a plastic material or product intended to be representative of the whole.
Sanitary Sewer: A sewer intended to carry only sanitary and industrial wastewaters from residences, commercial buildings, industrial parks, and institutions.
Schedule: A pipe size system (outside diameters and wall thickness) originated by the Iron Pipe Industry.
Sealant: A material that has the adhesive and cohesive properties to form a seal (fire stops).
Sealant Backing: A compressible material placed in a joint before applying a sealant (fire stops).
Self-extinguishing: The ability of a plastic to resist burning when the source of heat or flame that ignited it is removed.
Self-Leveling Sealant: A compound that exhibits flow sufficient to seek gravitational leveling (fire stops).
Service factor: A factor that is used to reduce a strength value to obtain an engineering design stress. The factor may vary depending on the service desired and the properties of the pipe.
Shelf life: Period of time over which a material will remain usable during storage under specified conditions such as temperature and humidity.
Socket Fusion Joint: A joint in which the joining surfaces of the components are heated, and the joint is made by inserting one component into the other.
Softening range: The range of temperature in which a plastic changes from a rigid to a soft state. (Note: Actual values will depend on the method of test. It is sometimes referred to as softening point.)
Solvent cement: In the plastic piping field, an adhesive that contains a solvent which dissolves or softens the surfaces being bonded so that the bonded assembly becomes essentially one piece of the same type of plastic.
Specific gravity: Weight of a unit of fluid volume.
Specimen: An individual piece or portion of a sample used to make a specific test. Specific tests usually require specimens of specific shape and dimensions.
Spool piece: A measured length of piping usually flanged on both ends.
Stabilizer: A compounding ingredient added to a plastic composition to retard possible degradation on exposure to high temperatures, particularly in processing. An antioxidant, for example, is a specific kind of stabilizer.
Stack: The vertical main of a system of soil, waste, or vent piping extending through one or more stories.
Standard dimension ratio (SDR): A selected series of numbers in which the dimension ratios are constants for all sizes of pipe.
Standard Time/Temperature Curve: A graphical representation derived from prescribed time-temperature relationships and used to control burn test furnace temperatures with progressing time (fire stops).
Steel Sleeve: A form used when pouring concreted to provide space for a penetrating item. Also may be used inside hollow construction walls to prevent firestopping materials from entering wall cavities unnecessarily (fire stops).
Stiffness factor: A physical property of plastic pipe that indicates the degree of flexibility of the pipe when subjected to external loads.
Strain: The ratio of the amount of deformation to the length being deformed caused by the application of a load on piece of material.
Stress crack: An internal or external crack in a plastic caused by tensile or shear stresses less than the short term tensile strength of the material. The development of such cracks is frequently related to, and accelerated by the environment to which the material is exposed. More often than not, the environment does not visibly attack, soften or dissolve the surface. The stresses may be internal, external, or a combination of both.
Strength: The stress required to break, rupture, or cause a failure.
Street elbow: Pipe fitting with a male thread on one end and a female thread on the other end.
Structural Sealant: A sealant capable of transferring dynamic or static loads, or both across joint members exposed to service environments typical for the structure involved (fire stops).
Styrene plastics: Plastics based on resins made by the polymerization of styrene or copolymerization of styrene with other unsaturated compounds, the styrene being in greatest amount by weight.
Styrene-rubber (SR) plastics: Compositions based on rubbers and styrene plastics, the styrene plastics being in greatest amount by weight.
Styrene-rubber (SR) pipe and fitting plastics: Plastics containing at least 50% styrene plastics combined with rubbers and other compounding materials, but not more than 15% acrylonitrile.
Substrate: A material upon which film, treatments, adhesives, sealants, membranes, and coatings are applied (fire stops).
Sustained pressure test: A constant internal pressure test for 1000 hr.
T Rating: A firestop shall be considered as meeting the requirements for a T rating when it remains in the opening during the fire test and hose stream test within the following limitations: The transmission of heat through the fires during the rating period hall not have been such as to raise the temperature of any thermocouple on the unexposed surface of the fires or on any penetrating item more than 325°F above its initial temperature. Also, the firestop shall have withstood the fire test for the rating period without permitting the passage of flame through openings, or the occurrence of flaming on any element of the unexposed side of the fires. During the hose stream test, the firestop shall not develop any opening that would permit a projection of water from the stream beyond the unexposed side (fire stops).
Tank adapter (See Bulkhead fitting).
Temperature: A measure of the degree of hotness of a material detected most commonly with a liquid-in-glass thermometer.
Tensile strength: 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 variously as “breaking load”, “breaking stress,” “ultimate tensile strength,” and sometimes erroneously as “breaking strain.” In rubber and plastics testing, it is the load in pounds per square inch, kilograms per square centimeter, or newtons per square millimeter in modern SI metric, of original cross-sectional area, supported at the moment of rupture by a piece of test sample on being elongated.
Thermal conductance: Also called “conductance,” it is the amount of heat transmitted by a material divided by the difference in temperature of the surfaces of the material. Where heat is transferred by several mechanisms through a structure of mean cross-sectional area Am, conductance equals the gross rate of heat transfer divided by the temperature drop between its faces.
Thermal conductivity: Measure of the ability of a material to conduct heat; measured in flow of Btus per hour through a unit cross section or unit thickness with 1°F of temperature difference across this thickness. For refractory and insulation materials, typical units are Btu-in./ft2-hr-°F. Other acceptable units are Btu-ft2-°F.
Thermal expansion: An increase in volume of linear dimensions caused by heating the material.
Thermal shock: Denotes a sudden temperature change.
Thermal Stabilizers: Compounds added to the plastic resins when compounded that prevent degradation of properties due to elevated temperatures.
Thermoelasticity: Rubberlike elasticity that a rigid plastic displays; it is caused by elevated temperatures.
Thermoplastic (n): A plastic that repeatedly can be softened by heating and hardened by cooling through a temperature range characteristic of the plastic, and that in the softened state can be shaped by flow into articles by molding or extrusion.
Thermoplastic (adj.): Capable of being repeatedly softened by heating and hardened by cooling through a temperature range characteristic of the plastic, and that in the softened state can be shaped by flow into articles by molding or extrusion. (Note: Thermoplastic applies to those materials whose change upon heating is substantially physical.)
Thermoset (n): A plastic that, when cured by application of heat or by chemical means, changes into a substantially infusible and insoluble product.
Thermoset (adj.): Pertaining to the state of a resin in which it is relatively infusible.
Thermosetting: Capable of being changed into a substantially infusible or insoluble product when cured by application of heat or by chemical means.
Tolerance: The total range of variation permitted; the upper and lower limits between which a dimension must be maintained.
Tooling: The act of compacting and contouring a sealant in a joint (fire stops).
Tooling Time: The time interval after application of a one-component sealant or after mixing and application of multi-component sealant during which tooling is possible (fire stops).
Trap: A fitting or device designed and constructed to provide, when properly vented, a liquid seal that will prevent the back passage of air without materially affecting the flow of sewage or waste water through it.
Through Penetration: Consist of three items: 1) wall or floor construction, 2) penetrating item or absence thereof, 3) the hold or void (fire stops).
Tuberculation: Localized corrosion at scattered locations resulting in knob-like mounds.
Tubing (plastic): A particular size of plastic pipe in which the outside diameter is essentially the same as that of copper tubing.
Ultraviolet Stabilizers: Compounds that when mixed with thermoplastic resins selectively absorb ultraviolet rays protecting the resins from ultraviolet attack.
Urethane plastics: Group of plastics composed of resins derived from the condensation of organic isocyanates with compounds containing hydroxyl groups.
UV Degradation: Sunlight contains a significant amount of ultraviolet radiation. The ultraviolet radiation that is absorbed by a thermoplastic material may result in actinic degradation (i.e., a radiation promoted chemical reaction) and the formation of heat. The energy may be sufficient to cause the breakdown of the unstabilized polymer and, after a period of time, changes in compounding ingredients. Thermoplastic materials that are to be exposed to ultraviolet radiation for long periods of time should be made from plastic compounds that are properly stabilized for such conditions.
Vacuum: Any pressure less than that exerted by the atmosphere; it may be termed a negative pressure.
Vacuum forming: Fabrication process in which plastic sheets are transformed to desired shapes by inducing flow; accomplished by reducing the air pressure on one side of the sheet.
Valve: A device that regulates the flow of fluids through piping by opening, closing, or obstructing ports or passageways.
Valve positioner: Auxiliary servo device that allows precision positioning of a control valve stem. It is used in conjunction with a standard valve operator (e.g., a diaphragm motor). Its purpose is to overcome stuffing box friction and stem thrust caused by fluid pressure.
Van Stone flange: A fitting flange whose drilled back plate turns 360° in order to facilitate the joining of one flange to another flange.
Velocity: Time rate of motion in a given direction.
Velocity head: Velocity pressure expressed in feet of column of the flowing of the flowing fluid.
Vinyl chloride plastics: Plastics based on resins made by the polymerization of vinyl chloride and copolymerization of vinyl chloride with other unsaturated compounds, the vinyl chloride being in greatest amount by weight.
Vinyl Plastics: Compositions of polymers and ingredients that are based on polymers of vinyl chloride, or copolymers of vinyl chloride with other monomers, the vinyl chloride being in the greatest amount by mass.
Virgin material: A plastic material in the form of pellets, granules, powder, floc, or liquid that has not been subjected to use or processing other than that required for its original manufacture.
Viscosity: A measure of the tendency of a fluid to resist shear. The unit of viscosity is the poise, which is defined as the resistance (in dynes per square centimeter of its surface) of one layer of fluid to the motion of a parallel layer one centimeter away and with a relative velocity of one centimeter per second.
Water absorption: The percentage of water absorbed by an immersed specimen in a given time.
Waterhammer: The forces, pounding noises, and vibration that develop in a piping system when a column of incompressible liquid flowing through a pipe line at a given pressure and velocity is stopped abruptly.
Waterhammer arrester: A device, other than an air chamber, designed to provide protection against excessive surge pressure.
Weathering: Exposure of a plastic to outdoor conditions.
Weld-or knit-line: A mark on a molded plastic formed by the union of two or more streams of plastic flowing together.
Wire Mesh: Galvanized steel hardware cloth used to support backing material in gypsum wallboard and hollow concrete block construction (fire stops).
Working (“pot”) Life: The time interval after opening a container of a single component sealant or after mixing the components of a multi-component sealant, during which application and tooling is possible (fire stops).
Working Pressure (WP): The maximum anticipated, sustained operating pressure applied to the pipe exclusive of transient pressures.
Yield value: Also called yield stress; force necessary to initiate flow in a plastic.
Young’s modulus of elasticity: The modulus of elasticity in tension. The ratio of stress in a material subjected to deformation.
