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BDIExpress Knowledge Base
Knowledge Base Glossary
Glossary is usually defined as an alphabetical list of technical terms in some specialized field of knowledge. This Knowledge Base Glossary provides a collection of Knowledge Base documents that define many technical terms. These terms are arranged alphabetically, but you can quickly jump to a specific term by selecting its first letter from the index of the Knowledge Base glossary below.
5S Event
5S derives its name from five Japanese terms beginning with “S.” A 5S program creates a workplace suited for visual control in a shared workplace. Collectively, the 5S’s outline how to create a workplace that is visibly organized, free of clutter, neatly arranged, and “like new” conditions. The 5S system is a starting place for implementing lean operations to help drive discipline. 1. Sort: Separate and disposition the unnecessary or unneeded items from the workspace. 2. Set in Order: “A place for everything, everything in its place.” 3. Shine: Return the workplace to “like new” conditions; make waste visible. 4. Standardize: Create standardized, consistent work practices. 5. Sustain: Audit the system to maintain and improve the first 4S’s.

Annular Bearing Engineers Committee. Used as a prefix for tolerance grades of bearings as set up by this committee.

American Bearing Manufacturers Association. This is a non-profit association consisting of American manufacturers of anti-friction bearings, spherical plain bearings or major components thereof. The purpose of ABMA is to define national and international standards for bearing products and maintain bearing industry statistics.

The wearing away of a surface by mechanical action such as rubbing, scraping or erosion.

Abrasive Blasting
Process for removing scale from product after heat treatment and prior to grinding; product pieces are placed in a tumbler that bombards the surface with high-velocity metal shot particles. This process also acts as a tempering or stabilizing process. (Also called Shotblasting)

Alternating Current

Accelerated Life Test
Any set of test conditions designed to reproduce in a short time the deteriorating effect created under normal service condition.

The rate of change in velocity of an object over time.

Acid Etch
The process of checking surface of ground product for cracks or burns by using a series of acids or neutralizers. Also called Nital Etch.

A device attached to a valve which moves the stem, usually my means of a motor or via pneumatics. A valve fitted with an actuator is usually referred to as a control valve.

The process or condition of sticking or staying attached. It also refers to the bond strength between two surfaces.

Undergo changes to physical properties with lapse of time.

All Purpose Bearing
A self-contained pre-assembled, pre-adjusted, pre-lubricated, completely sealed unit. Applied to and removed from an axle without exposing the bearing elements, seal or lubricant to contamination or damage.

Ambient Temperature
The surrounding temperature. Note that ambient temperature is not necessarily the same as atmospheric temperature.

Angular Contact Bearing
A type of ball bearing whose internal clearances and ball race locations result in a definite contact angle between the races and the balls when the bearing is in use.

The American National Standards Institute is a private organization that identifies industrial standards and coordinates their development. Many ANSI standards relate to safe design, performance and practices for equipment.

Anti-Friction Bearing
These bearing types use rolling contact to cut power loss resulting from friction.

Aqueous Solutions
Any fluid solution containing water.

Abbreviation for American Society of Mechanical Engineers.

Assembled Splice
A splice that is constructed of multi layers of materials and connected by use of elastomeric cements, adhesives, etc.

Abbreviation for American Society for Testing and Materials.

Rod or spindle on or with which a wheel revolves; the bar connecting two opposite wheels. The shaft (axle) of an automobile fits through the bore of a cone of the tapered roller bearing.

Business-to-Business. With regards to eCommerce, it means a corporate account

Business-to-Consumer. With regards to eCommerce, it means an individual/personal account

Ball Bearing
An anti-friction bearing that uses a series of steel balls held between inner and outer bearing races.

Ball Detent
A spring-loaded ball mechanism that aligns the needle rollers of a full complement drawn cup bearing before it is pressed into a housing. The rollers are aligned when the ball detent forces the rollers apart, gathering circumferential clearance in one location.

Ball Screw
Precision mechanical component that converts rotational motion to linear motion by rotating the shaft to drive the nut, or by rotating the nut to drive the shaft.

The support and guide for a rotating, oscillating, or sliding shaft, pivot, or wheel. A bearing allows smooth, low-friction motion between two surfaces.

Belt Body
The main part of any belt that generally surrounds, supports and protects the load-carrying tensile cords.

Bench Test
A modified service test in which the service conditions are approximated using laboratory equipment not necessarily identical with the equipment in which the product will be employed.

Bevel Cut
An angled cut at the seam (or joint) of a ring.

A mark, deformity, or injury which impairs the appearance.

Bolt Torque
The amount of twisting or turning effort (expressed as Ft- Lb or N-m) required to turn the nuts on a gland follower. The load that the gland follower exerts on a valve packing set can be expressed in terms of a specific bolt torque.

The inside diameter of the inner ring or cone.

Bore Diameter
The outside dimension of the annular space.

Bore Size
The inner diameter of a cone, which accommodates a shaft.

Boundary Lubrication
A state of lubrication that occurs when, due to speed, load or lubricant combination, the “thick film” or hydrodynamic conditions do not completely separate the rubbing surfaces. Special additives sometimes are used for bearing protection under these conditions.

Break-In Lubricant
A lubricant added to the surface of braided packing. Break-in lubricants are used to protect the packing from charring during the initial start-up of rotating equipment, such as pumps and mixers.

A rupture caused by internal pressure.

A type of plain bearing. It is metallic or carbon ring used to take up excessive space and reduce vibration.

Cage Deformation
Improperly installed or dropped bearing.

Cage Pocket Wear
Heavy contact between the rollers and cage pocket surfaces caused by a bearing’s operating too loosely.

Caged Bearing
Similar to a full complement bearing, except that there are fewer rollers, allowing room for the cage.

The reduction of a material to carbon.

Centrifugal Pump
A type of pump which relies on the rotation of an impeller to generate pressure and cause flow.

Customer Economic Value Add -- a methodology that uses global best practices and experience to explore customer logistics and purchasing processes. This information, combined with other surveyed data, enables BDI to formulate a CEVA report indicating potential cost savings and productivity enhancements. 

Closed-End Bearing
A drawn cup bearing where one end of the cup has a solid face, which fully encloses that end of the bearing. This allows the housing to be through bored (straight housing). The closed end of the installed bearing seals the housing.

Coefficient of Friction
The ratio of the force that maintains contact between an object and a surface and the frictional force that resists the motion of the object.

The molecular attraction between grease particles that causes them to stick together. This attraction contributes to its resistance to flow.

Combined Load
Both radial and thrust loads applied to the same bearing at one time.

Mixtures of rubber, plastics and other materials that are used to form the body of the belt.

Compression Packing
A deformable material used to prevent or control the passage of a pressurized fluid between surfaces that move in relation to each other.

Conrad Deep-Groove Ball Bearing
Standard single-row deep-groove bearing. Also referred to as a radial ball bearing.

An inventory management strategy where supplier-owned material is stored on the client’s premises.

Continuous Operating Temperature (COT)
Actual operating temperature of service.

A conveyor is a system of mechanical handling devices that moves materials from one location to another. Conveyors are especially useful in applications involving the transportation of heavy or bulky materials.

A chemical attack on metals by acids, alkalies, oxygen, chlorine, sulfur or other chemicals. This is distinct from metal destruction by wear and may be evident by either discoloration or pitting.

Corrosion Inhibitor
An ingredient added to packing, which decreases or eliminates the possibility of galvanic corrosion in the stuffing box. Corrosion inhibitors may be classified as either passive or active.

A sharp break or fissure in the surface, generally due to excessive strain.

Crib Crawl
An exercise that takes place at the customer plant level, where representatives from a distributor such as BDI "poke through inventory in search of clues to wasteful spending."

1) The view of a part as if it were cut to show its internal structure. 2) The distance between the shaft or stem surface and the bore of a stuffing box. 3) The shape of a packing ring at a cut. A packing ring could have a square, rectangular, or round cross-section.

Cycle and Adjust Procedure
A procedure used to consolidate a packing set after it has been installed in a stuffing box. This procedure helps to reduce the amount of gland load relaxation that occurs after the valve has been put into service.

Cylinder Bore
The internal diameter of the cylinder.

Cylinder Double Rod
A cylinder with a piston rod extending from each end.

Cylinder Single Rod
A cylinder with a piston rod extending from one end.

Direct Current

Dead-End Housing
A housing that is not through bored. The machining stops part way through the housing forming a blind hole.

A stress induced change of form or shape.

Design Temperature
The maximum or most severe temperature expected during normal operation caused by equipment failure.

Dial Indicator
A measuring device, equipped with a readout dial, used most often to determine end motion or irregularities/runout.

Die Cut
Shaped articles cut with a die from a sheet of material.

Die Forming
A manufacturing process in which braid or graphite foil is compressed in a mold to form a ring.

Dielectric Strength
The measure of a product’s ability to resist passage of a disruptive discharge produced by an electric stress described in volts/mil (1 mil = 0.001").

Dirty Power
The term used to describe any type of abnormality in the electricity that runs a facility. Could be a surge, a spike, a transient, a fluctuation, an interruption, or noise.

Discharge Pressure
The fluid pressure measured on the discharge (or outlet) side of the pump where the fluid exits the volute.

Drawn Cup Needle Roller Bearing
A needle roller radial bearing with a thin, pressed steel outer ring (drawn cup). It is usually employed without an inner ring. Available in caged and full complement designs. Drawn cup bearings are normally supplied with both ends open, but most sizes are also available with one end closed. A drawn cup bearing can only carry a radial load.

Drill Pattern
The systematic location of bolt holes on the mating and expansion joint flange through which the expansion joint will be attached.

The ability to be drawn. Example: The stretching of metal wire to a smaller cross-section.

Dynamic Runout
Twice the distance the center of the shaft is displaced from the center of rotation and expressed in TIR. That runout to which the seal lip is subjected due to the outside diameter of the shaft not rotating in a true circle. Synonym: Shaft Runout.

Dynamic Seal
A seal required to prevent leakage past parts which are in relative motion. The opposite of static seal.

EDI stands for Electronic Data Interchange. It’s a generic term that refers to the systems and processes that retailers have in place for sending orders and receiving stock.

Elastic Limit
The limiting extent to which a body may be deformed and yet return to its initial shape after removal of the deforming force.

Elastohydrodynamic Lubrication (EHD)
A lubricant regime characterized by high-unit loads and high speeds where the mating parts, usually in roller bearings, deform elastically, causing an increase in lubricant viscosity and load-carrying capacity.

An elastic rubber-like material which, in the vulcanized state and at room temperature, can be stretched repeatedly to at least twice its original length. Upon release of the stress, this material will immediately return to approximately its original length.

The increase in length expressed numerically as a fraction or percentage of the initial length.

Gaseous or liquid leakage given off by a piece of equipment. This usually refers to volatile organic hydrocarbons monitored by government agencies. It is typically expressed in parts per million volumetric (ppmv, or simply ppm).

End Play
A measure of axial movement encountered or allowed, usually in reference to the shaft on which the seal lip contacts.

Abbreviation for "Environmental Protection Agency", the US government agency responsible for enforcing the regulations imposed by the Clean Air Act Amendment.

EPA Method 21
A method established by the EPA for performing emissions measurements on equipment such as valves, pumps, and flanges.

ethylene propylene diene monomer. A unique rubber construction that provides improved performance and heat resistance.

Rusting with pitting and corrosion from moisture and water exposure.

Evaporation Loss
The portion of a lubricant that evaporates under the effects of temperature, pressure and time.

Exclusion Device
A device capable of excluding contaminating particles and fluids that would otherwise be dragged back into the primary sealing area of the equipment.

The increase in any linear dimension or volume.

External Arch Corner
An expansion joint corner with the arch formed outwardly that is designed primarily for pressure service, generally used in conjunction with a rectangular or square expansion joint.

Extraction Test
A test involving the separation of certain components from a solid by dissolving them in a liquid solvent under suitable conditions.

Failure Frequency Reduction
An application where the supplier provides product that lasts longer.

False Brinelling
Wear caused by vibration or relative axial movement between the rollers and races.

The weakening or deterioration of a material occuring when a repetition or continuous application of stress causes strain.

Fatigue Life
The number of cycles of stress that a metal component can sustain prior to failure under a stated test condition.

Fractional horse power

Fillet Radius
Shaft or housing corner dimension that bearing corner must clear.

Fixed Bearing
Bearing which positions shaft against axial movement in both directions.

Rim or edge projecting at right angles to provide strength, or a means of attachment to another part.

Flange Joint
A joint formed by two abutting flanges.

Flex Life
The relative ability of a rubber article to withstand cyclical bending stresses.

Floating Bearing
Bearing so designed or mounted as to permit axial displacement between shaft and housing.

Flow Direction
Direction of media (fluid, gas, air, etc.) movement through the system.

Flow Liner (Baffle)
A metal shield that is designed to protect the abrasive media in the stream and to reduce flutter caused by the air turbulence in the gas stream. Flow Liner/Baffles may be welded or bolted into position.

Flow Meter
A device used to measure the flow rate of a fluid through a pipe. In packing applications a flow meter may be used to measure the amount of flushing fluid that is entering and/or leaving the stuffing box.

Flush Port
A hole in the side of a stuffing box through which a cleansing or lubricating fluid is injected.

Flushing Fluid
A clean liquid (usually water) which is injected through a flush port to exclude solid particles from the stuffing box area and minimize abrasive wear. A flushing fluid might also be used to cool the packing in a high temperature application, or to keep air from being drawn into a pump in a suction application.

A series of small axial burns caused by an electric current passing through the bearing while it is rotating.

A push or a pull acting on an object.

Force Pounds
The total load required to deflect an expansion joint a distance equal to the maximum rated movement of the product.

Foreign Material
Any extraneous material such as dirt, sand or metal that should not normally be present in or on a product.

Abbreviation for "Feet per Minute", a measure of the surface speed of a rotating shaft.

Wear characterized by the removal of fine particles from mating surfaces. Fretting is caused by vibratory or oscillatory motion of limited amplitude between contacting surfaces.

Resistance to motion due to the contact of surfaces which normally generates heat.

Friction Break-Out
Friction developed during initial or starting motion.

Fluid Sealing Association, an American-based trade association for the mechanical packing industry.

Full Service Integration. Programs that allow BDI to take over and manage all of the MRO-related processes and activities at a customer site. BDI manages all of the supply channel elements, and the end result is an annual cost savings for the customer.

Fugitive Emissions
An unintentional gaseous or liquid leakage given off by a piece of equipment.

Full Complement Bearing
A bearing without a cage that contains the maximum number of rollers and has maximum load carrying ability. The rollers are mechanically retained by the cup in most full complement drawn cup bearings.

Full-Face Gasket
A gasket covering the entire flange surface and including bolt holes.

Functional Lip Diameter
The apparent inner diameter of the seal when the seal case is concentric with the outer diameter of the sizing mandrel in an air gage, light box, or similar inspection equipment.

A form of wear in which seizing or tearing of the gear or bearing surface occurs.

Galvanic Corrosion
An electrochemical reaction that may occur between a metal and a more chemically noble material such as another metal, carbon, or graphite. When both materials are immersed in an electrically conductive media called an electrolyte, a galvanic cell is formed and current flows between the two materials. The least noble material (called the anode) will corrode, while the more noble material (the cathode) will not.

A deformable material, which, when clamped between essentially stationary faces, prevents the passage of matter through an opening or joint.

Gasket Spacer
A gasket material cut to fit in a stuffing box between braided packing rings. Gasket spacers may be used to provide protection against abrasive particles, to increase the pressure resistance of some packing sets, or to reduce the flow of fluid through the body of the braid.

The thickness of a material; also the device used to measure material thickness.

A set of gears in a casing which converts speed and torque from a rotating power source to another device.

Geometric Stress Concentration
Spalling from misalignment, deflections or heavy loading.

Hand Wheel
A wheel located at the top of a manually operated valve that is used to actuate the valve stem.

The resistance to indentation. This is measured by the relative resistance of the material to an indentor point of any one of a number of standard hardness testing instruments.

Heat Exchanger
A piece of equipment designed to transfer thermal energy from one media to another. The unit is typically a long cylindrical body with multiple tubes passing within the body. Media of one temperature flows within the body but external to the tubes, while media of another temperature flows within the tubes, thus allowing thermal energy to exchange without cross-contamination of the products.

Heavy-Duty Needle Roller Bearings
A needle roller radial bearing with a machined and ground channel-shaped outer ring with a complement of needle rollers, retained and guided by a cage. A heavy-duty needle roller bearing can only carry a radial load.

Helical Motion
The circular, screw-like, up and/or down motion of a rod or valve stem.

Helicoflex® Seal
Metal seal composed of a helical, wound spring with a single or double jacket wrapped around the spring. Cross-section of the seal is circular and various shapes and sizes can be created using different jacket wrappings.

Helium Seal
A sealing level that does not exceed 1.0 x 10-9 atm cc/sec of Helium.

Of uniform composition throughout.

Horsepower (HP)
The standard unit of power in the imperial system. HP = (T in lbs) (RPM) / 63025

Housing Fit
Amount of interference or clearance between bearing outside surface and housing bearing seat.

Hub Bearing Assembly
A packaged wheel-end unit that contains bearings, seals and all components necessary for easy installation. It is pre-sealed, pre-lubricated and pre-set for precise performance.

Hub Grease Cap/Dust Cover
A metal cap that fits over the outer end of the hub to keep grease in and dirt out of the bearing assembly.

HVAC (heating, ventilating, and air conditioning; also heating, ventilation, and air conditioning) is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality.

Hydrodynamic (Fluid-Film) Lubrication
That state of lubrication in which the shape and relative motion of the sliding surfaces cause the formation of a continuous fluid film under sufficient pressure to prevent any contact between the surfaces. It is commonly called fluid-film lubrication.

Hydrodynamic Seal
A dynamic sealing device which utilizes the viscous shear and inertia forces of the fluid; imparted by a helically grooved or ribbed seal lip, to generate a pressure differential that opposes fluid flow.

Abbreviation for "Inside Diameter"

1) A non-powered pulley, sheave, sprocket or wheel around which a belt travels. 2) A non-powered roll or rolls supporting a belt.

The part of a centrifugal pump that, when rotated, will generate pressure and cause flow.

Inner Ring Race
The surfaces on the cup and cone where the rolling elements make contact.

Substitution of product to a suitable alternative

Internal Clearance
Is known as the radial internal clearance or end play.

Abbreviation for: Integrated Supply Agreement. Includes value-added services such as consignment inventory, standardization, technical support, OEM Interchange, and repair & inspection.

Abbreviation for: International Standards Organization

Jacketed Gasket
Type of gasket with a metallic cover either partially or completely surrounding a filler material to improve temperature, pressure, chemical and crush resistance.

Abbreviation for: Japanese Industrial Standards

Kaizen is a Lean term. Of Japanese origin, it simply means “improvement” (improve for the better). A Kaizen event is a focused improvement project that can accomplish breakthrough improvements in a short amount of time. The goal is to deliver a rapid breakthrough improvement within a common time frame of 4-5 days. A well designed Kaizen event will have the right team, will be focused on the right targets, and will use the right tools and techniques.

Abbreviation for: Local Area Network

Lateral Deflection or Lateral Movement
The relating displacement of the two ends of the expansion joint perpendicular to its longitudinal axis. Lateral movement is usually caused by the thermal expansion of the ducting system and measured in inches or millimeters.

Lateral Offset
The offset distance between two adjacent flanges or faces. Can be due to misalignment, equipment settling, or by design to compensate for excessive displacement in the opposite direction during cycle.

Life Test
A laboratory procedure that is used to determine the amount and duration of resistance of an article to a specific set of destructive forces or conditions.

Line Spalling
Roller spaced spalling from bearings operating after etching damage.

Linear Bearing
Mechanical component that bears loads while ensuring stable and accurate linear motion.

Linear Motor
An electric motor that produces linear motion directly, making the mechanical conversion of rotary to linear motion unnecessary.

An oil or grease placed between two surfaces in relative motion that reduces friction and wear between them.

Lubricant Starvation
Lack of proper lubrication at the seal interface which may cause premature wear and early failure.

The reduction of friction and wear between two surfaces in relative motion by application of a lubricant.

A term used to describe the ability of a lubricant to reduce friction between rubbing surfaces. There are no generally accepted test methods available to evaluate this property. Lubricity is important mostly in conditions of boundary lubrication and probably represents some relationship to the ability of the oil to wet the bearing surfaces and to resist being rubbed off. Lubricity has no known direct relationship to oil viscosity. It is also referred to as oiliness.

Matte Finish
A dull surface, as opposed to a smooth plate finish.

Maximum Capacity Bearing
A bearing with filling notches to allow the loading of the maximum number of balls.

Market Development Adjustment "Rebate"

The incorrect arrangement or position of something in relation to something else.

Molded Notch Belts
Often referred to as cogged, notched or cut notch belts. Notches reduce bending stress.

Abbreviation for "Motor Operated Valve", a motor-actuated control valve.

Abbreviation for: Maintenance, Repair and Operation

Abbreviation for "Manufacturers Standardization Society of the Valves and Fittings Industry".

Abbreviation for Material Technology Institute of the Chemical Process Industry.

Needle Roller Bearing
A bearing which uses small cylindrical rollers.

Non-Metallic Expansion Joint
Expansion joint which utilizes flexible non-metallic material to accommodate joint movements.

Any deviation from specified requirements.

An elastomeric seal of homogeneous composition molded in one piece to the configuration of a torus with circular cross section; more simply, a round ring with a round cross section.

Abbreviation for: Open Catalog Interface. It’s the standard format used by SAP when connecting to external punch-out catalogs.

An abbreviation for "Outside Diameter".

Abbreviation for: Original Equipment Manufacturer

Oil Seal
A seal designed primarily for the retention of oil.

Oil Swell
The change in volume of a gasketing product resulting from contact with oil.

Open-End Bearing
A drawn cup bearing that does not have a closed end. This allows a shaft to extend through the bearing.

Operating Pressure/Vacuum
The temperature at which the system generally will operate during normal conditions.

Overall Bearing Width
The overall dimension when the cup and cone are mated, including rollers and cage.

This occurs when oxygen attacks petroleum fluids. The process is accelerated by heat, light, metal catalysts and the presence of water, acids, or solid contaminants. It leads to increased viscosity and deposit formation.

Oxidation Inhibitor
A substance (chemical additive) added in small quantities to a petroleum product to increase its oxidation resistance, thereby lengthening its service or storage life.

Oxidation Stability
The resistance of a petroleum product to oxidation and, therefore, a measure of its potential service or storage life.

Ozone Cracking
Surface cracking or cracks caused by exposure to an atmosphere containing ozone.

P X T Value
A numerical value resulting from the multiplication of the internal pressure and the temperature of the fluid involved. In English system, usually psi x °F = PTValue.

Pan-Based Carbon
A carbon fiber derived from the carbonization process of a poly acrylonitrile fiber in an inert gas.

The quality or condition of allowing passage of fluid/gases/air through a material such as rubber.

The measure of the strength of an acid or base. On the pH scale, a neutral solution (neither acidic or basic) has a pH of 7. Solutions with a pH below 7 are acidic; the smaller the pH value, the more acidic the solution. Solutions with a pH above 7 are basic.

A cylindrically-shaped part which fits within a cylinder and transmits or receives motion by means of a connecting rod (Cylinder Rod).

Surface cavities that occur on a metal as a result of galvanic corrosion or mechanical erosion.

A compounding ingredient which can change the hardness, flexibility or plasticity of an elastomer.

Plate Finish
A commercially smooth surface, resulting from vulcanization between press plates (platens).

Abbreviation for: Programmable Logic Controller

Acronym for Partner Managed Inventory (also known as Vendor Managed Inventory), PMI is a streamlined approach to inventory management and order fulfillment. VMI involves collaboration between suppliers and their customers that changes the traditional ordering process. In BDI terms, Sourcing does not control, but influences, the inventory levels on PMI brands at D99. Check with Sourcing for active suppliers.

Point Surface Origin
Spalling from debris or raised metal exceeding the lubricant film thickness.

A synthetic elastomeric material made by chemically reacting a polyol and a diisocyanate in such a manner that a high molecular weight polymer is formed.

Press Cure
A method of vulcanizing rubber by the use of heated platens, which can be brought together and separated by hydraulic pressure or mechanical action, to cure rubber sheet under pressure.

Press Length
The length of a product that can be vulcanized at one time in a press, limited by the length measurement of the press.

Pressure Absolute
The pressure above zero absolute. (i.e the sum of atmospheric and gage pressure)

Pressure Cycling
The variation of pressure in a system.

Pressure, Absolute (PSIA)
The pressure above zero absolute, i.e., the sum of atmospheric and gage pressure.

Pressure, Atmospheric
Pressure exerted by the atmosphere at any specific location. Sea level pressure is approximately 14.7 lbs./ absolute.

Pressure, Gauge (PSIG)
Pressure differential above or below atmospheric pressure, expressed as lbs./ or psig.

Abbreviation for "Pounds per Square Inch", a unit of pressure.

A wheel, usually cylindrical, but polygonal in cross-section with its center bored for mounting on a shaft.

In the papermaking industry, pulp is the primary raw material from which paper is made. It is a cellulose fiber product produced by the mechanical and/or chemical processing of wood.

Pump Shaft
The metal rod connecting the impeller of a pump to the motor.

Purge Fluid
A clean liquid (usually water) which is injected through a flush port to flush solid particles from the stuffing box area to minimize abrasive wear.

Purge Port
A hole in the side of a stuffing box through which a flushing fluid is injected.

Abbreviation for: Pulse Width Modulated

Abbreviation for Qualified Products List (associated with U.S. Government specifications).

Quarter Turn Valve
A valve that will fully open or close with a 90-degree rotation of the stem.

In the direction perpendicular to a shaft axis.

Radial Deviation
The amount of deviation from the true circular form.

Radial Internal Clearance
Also called radial clearance. It is the total distance the inner ring (or shaft) may be displaced relative to the outer ring of an assembled, installed bearing.

Reciprocating Motion
An oscillating, back and forth motion as it normally pertains to a piston rod or valve stem.

Reciprocating Pump
A type of pump that relies on the reciprocating motion of a plunger, or series of plungers, to generate pressure and cause flow.

Lubrication types that define the relationship of the contacting surfaces in an operating condition. Hydrodynamic, Elastohydrodynamic, and Boundary.

Remote Handling
Handling without direct individual contact, usually done with robotic arms.

Able to recover rapidly, i.e. elastic.

Rising Stem Valve
A valve in which the movement of the stem is simply reciprocating, with no rotation.

Rising/Rotating Stem Valve
A valve in which the movement of the stem is both reciprocating and rotating at the same time, usually following a helical path.

Rodless Mechanical Actuators
Linear actuators whose load is attached to a fully supported carriage. Rodless mechanical actuators provide linear motion via a motor-driven ball screw, acme screw, or belt drive assembly.

Roller End Scoring
Metal-to-metal contact resulting from the breakdown of lubricant film.

Roller Nicking/Denting
Damage from rough handling or installation damage.

Roller Space Nicking
Raised metal on races from contact with roller edges.

The motion of a body turning on an axis.

Acronym for Revolutions Per Minute

A material that is capable of recovering from large deformations quickly and forcibly and can be or already is, modified to a state in which it is essentially insoluble (but can swell) in boiling solvent such as benzene, methyl ethyl keytone, and ethanoltoluene azeotrope.

Abbreviation for: Society of Automotive Engineers

Uneven localized wear resulting from excessive endplay.

Scoop Trim
A trimmed surface which is concave.

Gouges on the surface of a shaft, stem, or bore due to mechanical wear.

Abbreviation for: Silicon Controlled Rectifier

Abnormal wear due to localized welding and fracture. It can be prevented through the use of anti-wear, extreme-pressure and friction-modifier additives.

Any device designed to prevent or control the movement of fluid from one chamber to another to exclude contaminants.

Seal Assembly
A group of parts, which includes sealing surfaces, provisions for initial loading, and a secondary sealing mechanism which accommodates the radial movement necessary for installation and operation.

Seal Case
A rigid member to which the seal lip is attached

Seal Gasket
A gasket that is placed between two adjacent metal parts to make a gas tight connection.

Seal Outer Diameter
The external diameter of a lip-seal assembly, which normally corresponds to the outer diameter of the outer seal case.

Shaft Eccentricity
The radial distance which the geometric center of a shaft is displaced from the axis of shaft rotation.

Shaft Fit
Amount of interference or clearance between bearing inside diameter and shaft bearing seat outside diameter.

Shaft Hardness
The resistance to indentation. At minimum, it should be Rockwell C45.

Shaft Lead
Spiral grooves on a shaft surface caused by relative axial movement of grinding wheel to shaft.

Shaft Lobing
Uniform radial deviation of the shaft surface. An oval shaft is said to have two lobes. Faulty centerless grinding usually causes an odd number of lobes to occur. Higher order lobing is also referred to as chatter.

Shaft Out-of-Round
The deviation of the shaft cross section from a true click. Out-of-round is measured as the radial distance, on a polar chart recording, between concentric, circumscribed and inscribed circles that contain the trace and are centered to minimize the radial distance.

Shaft Surface Texture
A term used to describe the quality, appearance, or characteristics of the shaft surface resulting from operations, such as grinding, polishing, burnishing, etc.

Shaft Tolerance
This is the allowable variation in the shaft diameter.

Metal products with “V” shaped grooves specially designed for various types of V-belts.

Size, Actual
Actual dimensions of the part, including tolerance limits.

Size, Nominal
Approximate size of part in fractional dimensions.

A thick sheet.

A fluid mixed with solid particles.

Metal flaking (off) of the race or roller caused by inclusions in bearing steel, misalignment, deflection or heavy loading.

Specific Gravity
The ratio of the weight of a given substance to the weight of an equal volume of water at a specified temperature.

A short tapered axle that supports a free rolling wheel. Also referred to as a stub axle.

Spindle Nut
A nut threaded on the end of the spindle for adjusting the wheel bearing endplay or preload.

Procedure for making endless boot or bellows from open-ended material. Splicing may be accomplished by one or more of the following: cementing, bonding, heat sealing, stitching, vulcanizing, or mechanical fasteners.

External or internal slots or grooves cut in a shaft/gear/hub or yoke used so that two different components must rotate together.

Spring Rate
The force in pounds required to deflect an expansion joint one inch in compression and elongation or in a lateral direction.

Metal products for high-torque synchronous power transmission systems. Sprockets are specifically designed to transmit power with only the corresponding belt product line.

An event that causes inventory to be exhausted.

Straight Housing
A housing that is through bored. The machining passes all the way through the housing forming a through hole.

Straight Mineral Oil
A petroleum oil not containing compounds, animal or vegetable oils or chemical additives.

The unit change, due to force (stress), in the size or shape of a body compared to its original size or shape—it is non-dimensional quantity, but is frequently expressed in inches per inch, centimeters per centimeter, etc.

The intensity at a point in a body of the internal forces or components of force that act on a given plane through the point (Lbs./sq. inch).

Maximum amount of travel from one end to the other.

Superior Length Stability
Assures V-belts require less re-tensioning and take-up during their service.

Surface Finish
A measure of the roughness of a surface, usually expressed in microinches or micrometers.

Surface Speed
The linear speed of a point on the surface of a rotating shaft, usually expressed in FPM or m/sec.

Surge Pressure
Operating pressure plus the increment above operating pressure that the expansion joint will be subjected to for a very short time period. Surge Pressure is typically due to pump starts, valve closing, etc.

The increase in volume or linear dimension of a specimen immersed in liquid or exposed to a vapor.

Generic term used for power transmission drive systems utilizing toothed belts in mesh with grooved pulleys or sprockets. These systems are also referred to as Gilmer or timing.

Tapered Roller Bearing
A friction reducing bearing that is made up of a cup, cone and tapered rollers, which rotate around the raceway of the bearing.

Tensile Member
Capable of being stretched or extended

Tensile Strength
The amount of tensile stress that causes a specimen to rupture; measured in psi.

Thermal Barrier
A layer of insulating material designed to reduce the surface temperature at the gas sealing layer to a level compatible with its heat resistance capability.

Thermal Conductivity
A measure of the rate at which thermal energy is transferred through a substance.

Thermal Cycling
The repeated heating and cooling of a tank, vessel or piping system. The duration of the cycle can vary tremendously.

Thermal Expansion
Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.

Thermal Movements
Movements created within a system caused by a thermal change. Can be axial, lateral, or torsional.

The continuous pressure of one object against another, parallel to the center of the axis.

Thrust Load
A load applied parallel to the center line of rotation.

Thrust Needle Bearing
A needle roller thrust bearing contains a cage that holds needle rollers in a spoke-like configuration. A thrust needle roller bearing can only carry a thrust load.

The upper and lower limits between which a dimension must be held.

Tooth Facing
Specially woven and treated nylon fabric that reduces friction of the belt in the sprocket and resists abrasion and other tooth damage.

Tooth Pitch
The distance between two corresponding points on adjacent screw threads or gear teeth.

The tendency of a body to rotate as a result of a force being applied at some distance away from the center of rotation.

Torque Wrench
A torque wrench measures the amount of turning force being applied to a fastener (nut or bolt). Scales usually read in foot-pounds or Newton-meters.

True Brinelling
Damage from shock or impact.

Truncated Rib
Construction profile that provides improved crack resistance, higher load-carrying capacity and improved flex fatigue resistance.

Ultimate Elongation
The maximum elongation prior to rupture.

Abbreviation for "Volatile Hazardous Air Pollutant".

A manifestation of internal friction opposed to mobility. The property of fluids and plastic solids by which they resist an instantaneous change of shape, i.e., resistant to flow.

Abbreviation for "Volatile Organic Compound".

Volume Swell
Increase in physical size caused by the swelling action of a liquid.

The internal area (housing) of a centrifugal pump where the fluid comes in contact with the impeller.

An irreversible process during which a rubber compound, through a change in its chemical structure becomes: 1) less plastic, and 2) more resistant to swelling by organic liquids; and elastic properties are conferred, improved or extended over a greater range of temperature.

To improve the strength, resiliency, and freedom from stickiness and odor of a material (e.g. rubber) by combining with sulfur or other additives in the presence of heat and pressure.

Vulcanized Splice
A splice that is bonded with heat and pressure.

Damage resulting from the removal of materials from surfaces in relative motion. Wear is generally described as: Abrasive: Removal of materials from surfaces in relative motion by a cutting or abrasive action of a hard particle, which is usually a contaminant. Adhesive: Removal of materials from surfaces in relative motion as a result of surface contact. Galling and scuffing are the extreme cases. Corrosive: Removal of materials by chemical action.

Wear Sleeve
A replaceable metal ring generally used in assemblies to eliminate expensive shaft replacement caused by grooving that may occur at the seal-shaft interface.

A product containing wire(s) to give added strength, increased dimensional stability or crush resistance.


Work Pressure
The maximum operating pressure encountered during normal service.

Yield Strength
The amount of stress which causes a material to permanently lose its elasticity.

Zero Clearance
No clearance between the roller and races.