Terminology

  • ACCEPTANCE: The act of an authorized representative of the purchaser by which the purchaser assumes for himself, or as agent of another, ownership of existing and identified supplies tendered, or approves specific services required, as partial or complete performance of the contract on the part of the contractor.
  • ACCEPTANCE NUMBER: A number used in connection with a sampling plan such that if the number of nonconforming test units in the sample taken from the lot is less than or equal to this number, the lot should be accepted.
  • APPLIED SKIN: A thin surface layer of elastomeric material.
  • AQL: Acceptance Quality Level (AQL), combined with a lot/sample size designation is sometimes used for indexing a sampling plan. AQL does not imply that a supplier has the right to knowingly supply a defective unit or product.
  • AUTOCLAVE: A pressure vessel into which materials or articles can be placed and exposed to steam under pressure. It is commonly used for vulcanization.
  • BENCH MARK: Marks of known separation applied to a specimen and used to measure strain.
  • BLISTER: A cavity or sac that deforms the surface of a material.
  • BLOOM: A coating or efflorescence creating a discoloration or change in appearance of the surface of a rubber product caused by the migration of a liquid or solid to the surface.
  • BULK DENSITY: The weight in air, of a unit volume of material, including both permeable and impermeable voids, normal to the material
  • BULKHEAD: A flat boxlike structure used to shut off water flow in a dam that is located upstream from other gates or equipment, enabling repair or maintenance work.
  • CELL: A single, small cavity surrounded partially or completely by walls.
  • CELLULAR MATERIAL: A generic term for materials containing many cells (either open, closed, or both) dispersed throughout the mass.
  • CELLULAR RUBBERS: Cellular rubber is a cellular material made of rubber. Cellular rubber products all contain cells or small hollow receptacles. The cells may either be open and inter-connecting, or closed and not interconnecting.
  • CHLOROPRENE: Commonly referred to as Neoprene, chloroprene was one of the first synthetic materials. It is common for chloroprene to be blended with other polymers and referred to as commercial grade neoprene. The physical properties of a "commercial" neoprene vary widely, yet offer excellent and cost effective options.
  • CLOSED CELL: A cell totally enclosed by its walls and hence not interconnecting with other cells.
  • COLD VULCANIZED SPLICE: A more cost effective method where bonding is completed with a room temperature adhesive. Sufficient to use where splicing is a function to aide in installation or when longevity is not required.
  • COLLAPSE: Inadvertent densification of a cellular material during its manufacture resulting from breakdown of its cellular structure.
  • COMPOUND: An intimate admixture of a polymer with all the ingredients necessary for the finished article.
  • COMPRESSION SET: The residual deformation after removal of the force which has subjected the specimen to compression.
  • CONCENTRICITY: The relationship of two or more circles or circular surfaces having a common center.
  • CONDITIONING OF PARTS: Storing parts at a pre-determined temperature and time typically before taking measurements of dimensions for inspection.
  • CORED CELLULAR MATERIAL: Cellular material containing a multiplicity of holes — usually, but not necessarily cylindrical in shape — molded or cut into the material in some pattern that is normally perpendicular to the largest surface, and extends part or all the way through the piece.
  • CRACKING: A sharp break or fissure in the surface, generally due to excessive strain.
  • CRAZING: A surface effect on rubber articles characterized by innumerable, minute cracks.
  • CURE: The act of vulcanization.
  • CUT: The distance between cuts or parallel faces of articles produced by repetitive slicing or cutting of long pre-shaped rods or tubes — such as lathe cut washers.
  • DUROMETER HARDNESS: An arbitrary numerical value which measures the resistance to penetration of the indentor point of the durometer. Value may be taken immediately or after a very short specified time. Learn more about durometer hardness scales.
  • ELONGATION: Increase in length expressed numerically as a fraction or percentage of initial length.
  • EMERGENCY LOCK BULKHEAD: A large boxlike structure used to close off an area around a miter lock gate, so water can be pumped out — leaving an area dry for repair work.
  • EPDM: Ethylene Propylene Diene Monomer (EPDM) is a copolymer of ethylene and propylene. It has excellent resistance to aging, ozone, oxygen, and weathering. EPDM also fairs well in applications up to 300°F and has good low temperature stability. It is also known for good resistance to water, steam, hydraulic fluids and, many diluted acids and alkalis.
  • EXPANDED RUBBER: Cellular rubber having closed cells made from a solid rubber compound.
  • FILLET: A narrow, concavely curved strip of rubber at the angle where the rubber and insert meet in a molded rubber product.
  • FINISH: The quality or the appearance of the surface of a rubber product.
  • FISSURE: A split or crack in a cellular material.
  • FLASH: Excess rubber on a molded product, resulting from cavity overflow at the parting lines where the mold sections are separated. Flash has two dimensions — extension and thickness. Flash removal can impact part costs significantly, allowing for the widest possible flash tolerance will help contain costs.
  • FLATNESS: The deviation from a true plane or straight edge.
  • FLUOROCARBON POLYMER: Fluorocarbon (FKM) is often called by its trade name Viton®. It has excellent temperature range to 400°F, compression set, and oil resistance. This polymer performs well against ozone, UV, and oxygen, and is resistant to many chemicals and acids.
  • GASKET: A deformable material clamped between essentially stationary faces to prevent the passage of matter through an opening or joint. (Mechanical)
  • GRAIN: The unidirectional orientation of rubber or filler particles resulting in anisotropy of a rubber compound.
  • HEAD PRESSURE: The pressure exerted by the weight of water per unit of any given depth below the surface. Approximately 4 lbs per square inche per foot of depth. (Hydro Dam Reference)
  • HIGH HEAD(WATER): High water pressure on a gate and seal due to how deep the gate is in a dam.
  • HNBR: Hydrogenated Nitrile Butadiene Rubber (HNBR) is a relatively nitrile butadiene rubber that was engineered for greater resistance to chemicals and oil.
  • HOT VULCANIZED SPLICE: Utilizes a rubber based adhesive and a custom fixture to produce the best quality bond possible. This process is typically more time consuming, however yields a splice that has many of the same properties of the rubber and is less noticeable. This type of splice is the most durable.
  • HYDRO PLANT: A plant built in conjunction with a dam to provide water flow through turbine generators, causing electricity.
  • INSERT: A part — frequently metal — which is placed in a mold and appears as an integral part of the molded product.
  • INSPECTION: The examination and testing of suppliers or services — including raw materials, components and intermediate assemblies — to determine whether they conform to contract requirements.
  • INSPECTION BY ATTRIBUTES: An inspection where a product is classified as conforming or non-conforming, or where the number of departures from requirements is counted and recorded.
  • INSPECTION BY VARIABLES: An inspection where a specific quality product characteristic is measured on a continuous scale, such as pounds, inches, feet per second, etc., and a measurement is recorded.
  • INTAKE GATE: A gate provided to shut off flow of water into a water intake passage or penstock that leads to a turbine.
  • IRHD: International Rubber Hardness (IRHD) is a repeatable test completed as a way to determine the hardness of rubber parts. Used as an alternative to the Shore Hardness test. For a complete definition see ASTM D1415-68 Standard Method of Test for International Hardness of Vulcanized Natural and Synthetic Rubbers.
  • LOT: A specific quantity of similar material, or a collection of similar units, offered for inspection and acceptance at one time. A lot is either accepted or rejected as a whole, on the basis of examination and/or test carried out on a portion of the lot.
  • MANDREL: A bar, serving as a core, around which rubber is extruded. Forms a center hole to the part.
  • MITER LOCK GATE: A gate that consists of two leaves hinged at the outer ends. The two leaves meet at an angle pointing upstream, resembling a miter joing — the joining of two parts, usually at a 45° angle, to form a corner. These gates are usually sealed at the bottom and may also have partial rubber sealing a both the miter/center and hinge/pintle ends.
  • NATURAL RUBBER: Natural Rubber, also known as Polyisoprene, has very good tear strength and tensile, as well as good abrasion resistance and stiffness range. This compound has good low-temperature flexibility and excellent resistance to cold flow. While natural rubber is not naturally ozone resistant, additives can be added to improve ozone resistance
  • NEOPRENE: See Chloroprene.
  • NITRILE (NBR): Nitrile Butadiene Rubber (NBR) is a copolymer of butadiene and acrylonitrile. It is known for having excellent resistance to petroleum oils and gasoline, as well as excellent resistance to mineral and vegetable oils. However, it has poor resistance to the swelling action of oxygenated solvents such as acetone, methyl ethyl ketone, and other ketones.
  • OPEN CELL: A cell not totally enclosed by its walls, connects with other cells.
  • OXIDATION: The reaction of oxygen on a rubber product. Usually detected by a change in the appearance or feel of the surface, or by a change in the physical properties.
  • OZONE CRACKING: Surface cracks, checks, or crazing caused by exposure to an atmosphere containing ozone.
  • PARALLELISM: The relationship of surfaces in different planes. To be parallel, the planes passing through the surfaces must be in the middle of each other at all points when measured at 90° to the planes.
  • PENSTOCK: A gate used to regulate the flow of water, or a channel used for conveying water to a waterwheel or turbine.
  • PIECE: The portion of the sample that is prepared for testing.
  • POLYISOPRENE: See Natural Rubber.
  • POROSITY: The prescence of numerous small cavities, or open spaces, in the product.
  • POST CURE: A second cure that is sometimes given to products after an original shaping, or preforming partial cure.
  • PREFERRED NUMBERS: The conventially rounded off term values or geometric series that includes the integral powers of 10 and has ratios with the following factors: 5√10, 10√10, 20√10, 40√10, and 80√10.
    Source: International Standards Organization (ISO) Recommendation R-3, Preferred Numbers.
  • PUMP STATION: A plant built with diesel or electric powered pumps to move water for drainage or storage. Such stations are also built to move sewage to a treatment plant.
  • RADIAL GATE: A device used for controlling the flow of water over spillways or into canals by having the upstream face curved in the form of an arc at the center of the gate hinge.
  • REJECTION NUMBER: A number used in connection with a sampling plan such that if the number of nonconforming units in the sample taken from the lot is equal to or greater than this number, the lot should be rejected.
  • ROLLER GATE: A gate used in a levee opening for flood control, usually so wide or long that rollers are required at the bottom to support it during opening and closing.
  • RUBBER: A material that is capable of recovering from large deformations quickly and forcibly. It can be modified to a state in which it is essentially insoluble, but can swell, in a boiling solvent — such as benzene, methyl ethyl-ketone, and ethanol-toluene a zoetrope. Rubber in its modified state, free of dilutions, will retract within 1 minute to less than 1.5x its original length, after being stretched at room temperature to twice its length and held for 1 minute before release.
  • RUBBER LATEX: Colloidal aqueous/water emulsion of an elastomer.
  • SAMPLE: A unit, collection of units, or a section of a unit taken from a sampling lot.
  • SAMPLE INSPECTION: The number of units taken from a lot for the purpose of examination or test.
  • SAMPING PLAN: A procedure which specifies the number of units of product from a lot which are to be inspected, and the criterion for acceptability of the lot.
  • SBR: Styrene Butadiene Rubber (SBR) is a synthetic copolymer of styrene and butadiene. SBR has good resistance to abrasion and water. It bonds well to itself and many other materials.
  • SHORE A HARDNESS: An indentation method of rating the hardness of rubber using a shore durometer with the A scale from 0-100. Learn more about durometer hardness scales.
  • SHRINKAGE: Contraction of molded rubber upon cooling.
  • SILICONE RUBBER: Silicone elastomers can be compounded to withstand temperatures as high as 600°F without serious deterioration, and retains flexibility 150°F. Silicone has lower strength than other elastomers, yet exhibits excellent fatigue and flex resistance.
  • SKIN: A relatively dense layer at the surface of a cellular material.
  • SLUICE GATE: Usually a smaller, rectangular type of gate used to control water level or flow. May also be a small radial type of gate.
  • SPECIFIC GRAVITY: The ratio of the weight of a given substance to the weight of an equal volume of water at a specified temperature.
  • SPILLWAY: An opening in a dam for water overflow usually closed off with some type of gate (radial or vertical lift), but may be uncontrolled. An open area for high water to overflow.
  • SPLICE/SPLICING: The uniting of two parts of a rubber product to form a continuous length or piece.
  • SPONGE RUBBER: Cellular rubber consisting predominantly of open cells made from a solid rubber compound.
  • SQUARENESS: The quality of being at an angle of 90°.
  • STOPLOG: Similar to a bulkhead. Smaller and stacked in sections on top of each other, usually removable one at a time.
  • SURFACE GROUND: The grinding of the surface of a rubber product to produce close dimensional tolerances.
  • SWELLING: The increase in volume or linear dimensions, of a specimen immersed in a liquid or exposed to a vapor.
  • SWING GATE: A small to medium sized gate, used in a levee opening. Gate is equipped to swing on hinges from one end to open or close for flood control.
  • TAINTER GATE: See Radial Gate.
  • TAINTER VALVE: A radial type gate used in a submerged location, such as in a navigation lock, that is used to open or close water passages which floor or drain the lock.
  • TEAR STRENGTH: The maximum load required to tear apart a specified specifmen. The load acting substantially parellel to the major axis of the test specimen.
  • TENSILE STRENGTH: The maximum tensile stress applied during stretching to rupture a specimen.
  • TENSILE STRESS: The applied force per unit of the original cross-sectional area of a specimen.
  • TENSILE STRESS AT GIVEN ELONGATION: The tensile stress required to stretch a unifrom section of a specimen to a given elongation.
  • TENSION SET: The extension remaining after a specimen has been stretched and allowed to retract.
  • TESTING: An element of inspection that generally denotes the determination of the properties and components, including functional operation. Involves the application of established scientific principles, procedures, and equipment.
  • THERMOPLASTIC RUBBER: Rubber that does not require chemical vulcanization and will repeatedly soften when heated and stiffen when cooled. This type of rubber will exhibit only slight loss of original characterstics.
  • THERMOSETTING RUBBER: Chemically vulcanized rubber that cannot be remelted or remolded without destroying its original characteristis.
  • TRASH RACK: A metal grid structed placed upstream of a gate such as an intake gate to catch trash and debris from entering a water passage where it could damage equipment such as a turbine.
  • ULTIMATE ELONGATION: The maximum elongation prior to rupture.
  • VITON®: See Fluorocarbon Polymer.
  • VOID: A cavity unintentionally formed in a cellular material, that is substantially larger than the characteristic individual cell.
  • VULCANIZATION: An irreversible process during which a rubber compound, through a change in its chemical structure (i.e. cross-linking), becomes less plastic and more resistant to swelling by organic liquids and where elastic properties are conferred, improved, or extended over a greater range of temperature.
  • WAIVER REQUEST: A formal document submitted by a contractor to a purchaser for the purpose of requesting acceptance of the designated nonconforming supplies or services, or for requesting temporary relief from a technical requirement of the contract.
  • WATER ABSORPTION: The increase in weight and volume after immersion in water.
  • WHEEL GATE: A rectangular, vertical lift, gate designed with a number of wheels fixed on axles on each side, which move up and down slots built in on either side of the gate opening. This type of gate is usually provided for water closure under high heads, such as a service or emergency gate.