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Glossary of Terms

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



The symbol for 3-A Sanitary Standards Inc. The standard, collaboratively developed by a group of processors, suppliers, regulatory officials, and sanitation specialists, is accepted by federal, state, and local regulatory authorities. Dixon products have earned the 3-A symbol through third-party verification.

3-A Finish

Product surface finish equivalent to 150 grit or better O.D., and 180 grit or better I.D. A minimum of Ra 32 micro inch (0.8 microns) is indicated.


Absolute Pressure

The sum of atmospheric and gauge pressure.


Alternating current is an electric current that periodically reverses direction and changes its magnitude continuously with time.

Accidental Disconnection

Disconnection of a coupling while in operation due to failure of the coupling mechanism.


An energy storing device.

Acme Thread

An American screw thread having a section that is a mean between the V threads and square threads. This thread typically has a 29° included angle.


A device that connects equipment, hose, etc. that cannot be connected directly.


Introduction of air into a material.

Affinity Laws

Also known as 'pump laws' they are used to predict how capacity, head, and horsepower are affected by changes in the centrifugal pump impeller diameter or impeller speed.

Air Inclusion

The air forced into the system during the connection of a quick disconnect coupling.

Air Receiver Manifold

A tank that is connected to a compressor via a bull hose. It has multiple outlets so several pneumatic tools can operate simultaneously. An air receiver manifold must have an ASME build certification plate attached to comply with OSHA regulations.

Ambient Temperature

The temperature at a point or area expressed as an average of the surrounding areas or materials. Ambient surface temperature is generally given to be 70°F to 80°F (21°C to 27°C) – an average of daily and seasonal variations.


Stress relief of stainless steel, a heat treatment to remove the stresses generated in forming and welding operations. This is best done under a controlled atmosphere or vacuum to maintain the mill finish. The fittings are not quenched, as in solution annealing as this would reintroduce residual stresses.


A process for aluminum in which the part is electrically charged then dipped in various chemicals to produce various colors and/or surface hardness.


American National Standards Institute, Inc.


American Petroleum Institute.

Armored Hose

A protective covering, applied as a braid or helix, that protects the hose from physical abuse.


A reference to a hose having couplings installed in one or both ends.

Assembly Pressure Rating

The pressure rating (in PSI) of the lowest-rated component whether it be the hose or couplings.


American Society for Testing and Materials.

Atmospheric Pressure

Force per unit area exerted against a surface by the weight of the air above that surface. At sea level, atmospheric pressure is 14.7 PSI.


The method or process of securing a coupling to a hose, for example banding, clamping, swaging, or crimping.


A pressure vessel used for vulcanizing rubber products by means of steam.

Automatic Welding

Welding with equipment that performs the welding operation without adjustment of the controls by a welding operator.



The resistance or force opposing the desired flow of fluid through pipes, leading to friction loss and pressure drop.

Best Efficiency Point (BEP)

The flow at which the pump operates at the highest or optimum efficiency for a given impeller diameter.

Bevel Seat Ferrules

A set of plain (male) and externally threaded (female) bushings with matching bevel angles that produce a leak-proof seal when connected with a hex union nut. The threads used are Acme form.


The process of creating a product utilizing complete living cells.

Bioprocessing Equipment

Equipment, systems or facilities used in the creation of products utilizing living organisms.

Blind Mate Connector

Designed with self-aligning features that automatically guide themselves into the correct mating position without wrenches or other tools.


A raised area or separation between hose layers that creates a void or air-filled space that is visible on the hose cover or hose tube.

Bolt Hole Circle

A circle on the flange face around which the center of the bolt holes is distributed.


The exterior shell of an expansion ring type coupling.


A continuous sleeve of interwoven single or multiple strands of material. In hose construction, these strands are usually textile or metal.

Braid Angle

The angle at the intersection of a braid strand and a line parallel to the axis of a hose.

Brake Horsepower (BHP)

The actual horsepower of an engine as measured on a brake attached to the drive shaft or recorded on a dynamometer. This is not the horsepower used by the motor or driver.

Break Away

Automatic disconnection of a coupling when an axial separation force is applied.

Bright Annealed Finish

A silvery satin surface, approximately the mill finish of stainless steel.

Bright Annealing

Heating and cooling metal in an inert atmosphere to inhibit oxidation; surface remains relatively bright.


Permanent indentation of a hard surface named after the Brinell scale of hardness, in which a small ball is pushed against a hard surface at a preset level of force, and the depth and diameter of the mark indicates the Brinell hardness of the surface.


British Standard Pipe Parallel thread.


British Standard Pipe Taper thread.


Grinding or removing surface material to obtain dimensional conformance.

Bull Hose

Typically, a large diameter air hose that connects a compressor to an air receiver manifold.

Burst Pressure

The maximum pressure a device is able to withstand before failure.



The National Electrical Manufacturers Association (NEMA) standard for motor mounting dimensions.

C360 Brass

C36000 Brass is copper, alloyed with lead and zinc. C360 is also known as Free-Cutting and Free-Machining brass because it has a 100% machinability rating, and is the standard against which all other copper alloys are compared. CDA 360 brass is also strong, with a strength similar to that of leaded steel.


Flow rate normally measured in gallons per minute (GPM).


A common mechanical seal face material chemically inert to most fluids with the exception of oxidizers, bleaches, halogens and a few other fluids.


The fabric, cord and/or metal reinforcing section of a hose as distinguished from the hose tube or cover.

Case Hardening

Hardening the entire surface of a low carbon steel to a specific depth.


When the NPSH required by the pump is greater than the NPSH available by the system, cavitation occurs. Vapor is formed and moves along with the stream. These vapor bubbles or "cavities" collapse when they reach regions of higher pressure on their way through the pump cavities. When these cavities form at the suction of the pump, several things happen all at once:

  • We experience a loss in capacity.
  • We can no longer build the same head (pressure).
  • The efficiency drops.
  • The cavities or bubbles will collapse when they pass into the higher regions of pressure causing noise, vibration, and damage to many of the components.


Counter clockwise.


The metric unit of dynamic viscosity.


The kinematic unit of viscosity. Viscosity in centipoise divided by the liquid density at the same temperature gives kinematic viscosity in centistokes.

Centrifugal Pump

A pump that uses an impeller to move water or other fluids. The rotational energy typically comes from an engine or electric motor.


A hard, chemically inert seal face material that has very high compressive resistance.


To cut an angle on the hose tube to aid in stem insertion and to prevent the hose end from flaring when a stem is inserted.

Charge Pressure

The pressure at which replenishing fluid is forced into the hydraulic system (above atmospheric pressure).

Check Valve

A valve that permits the flow of media in one direction only.


A device used to join mechanical parts, fittings, ensuring a quick leak-proof connection and enabling easy take down.

Clean-In-Place (CIP)

Internally cleaning a piece of equipment without relocation or disassembly. The equipment is cleaned but not necessarily sterilized. The cleaning is normally done by acid, caustic or a combination of both with water-for-injection (WFI) rinse.

Close Coupled

The pump impeller is mounted directly to the motor shaft or stub shaft that is mounted directly on the motor shaft. There is no separate bearing case.

Cold Flow

Continued deformation or movement of rubber or PTFE under stress.

Compression Set

The deformation that remains in rubber or PTFE after it has been subjected to and released from stress such as a clamp. The longer the stress is maintained the more definitive the deformation.

Connect Under Pressure

The ability to connect coupling halves with internal line pressure applied to either both sides or one side.


Any material foreign to a media that has a harmful effect on its performance in a system.

Controlled Sulfur

The sulfur content must be between .005% and .017% to ensure better orbital welding in the 316L stainless steel weld ends used in bioprocessing equipment (BPE) installations.


A chemical or electrochemical interaction between a metal and its environment, which results in changes in the property of the metal. This may lead to impairment of the function of the metal, the environment and/or the technical system involved.

Corrugated Hose

Hose with an exterior that is radially or helically grooved to enhance flexibility and/or reduce weight.


A device at the end or ends of a length of hose that allows a connection to be made.

Coupling, Female Half

Also known as a coupler, socket, or receiver.

Coupling, Male Half

Also known as a nipple, plug, adapter.


The outermost part of the hose. The main purpose for the hose cover is to protect the hose reinforcement form physical and environmental abuse. Covers can have materials (rubber compounds) that are blended to produce characteristics such as ozone resistance, abrasion resistance or oil resistance.


A sharp break or fissure in the hose surface. Usually caused by stress, flexing and/or environmental conditions.


A surface effect on hose characterized by multi-directional minute cracks.

Crimp Diameter

The finished dimension that a ferrule or sleeve is reduced.


The act of forming the metal sleeve or ferrule of a hose fitting with a surrounding series of die segments to compress the hose within the fitting. The crimping process changes the shape of the entire circumference and length simultaneously. Often interchanged with the term "swaged".


The flow rate (in U.S. GPM) of pure water at 60°F passing through a valve when the valve is fully opened and the pressure differential between the two ends of the valve is 1 PSI.




Cold Working Pressure.



Double acting.

Date Code

Any combination of letters, numbers, or symbols to identify time and/or location of manufacture.


Direct current. The movement of electrical charge is only in one direction.

Dead Head

The condition of a centrifugal pump running with a closed discharge line.


The effect of crimping that produces a change in the shape or size of the stem.


Acetal homopolymer (Polyoxymethylene POM) is the ideal material in parts designed to replace metal. Registered trademark of E.I. DuPont de Nemours.

Differential Pressure (DP)

The difference in pressure between any two points of a system or a component, also known as Delta-P or pressure drop.

Dilatent Fluid

Liquids whose viscosity increases with the application of stress.

Discharge Head

The outlet pressure of a pump.

Double Acting

Any pneumatic actuator, which uses air to drive the actuator, output shaft in both the clockwise and counterclockwise directions. The air supply is piped to one side of a piston-drive or a diaphragm while the air contained on the opposing side is exhausted.

Double Pole Double Throw (DPDT)

A type of limit switch.

Double-Acting Sleeve

Permits push-to-connect and pull-to-connect convenience when female half is mounted on the sleeve.

Dovetail Extension

The "fingers" on the sides of a clamp that interlock to prevent straight line leaks.

Dry Running

Occurs when a pump is running with insufficient or no fluid in the pump.

Drybreak Coupling

A coupling that allows connection and disconnection without spillage or air inclusion (also known as flush face, flat face, no-spill)


An instrument for measuring the hardness of rubber.

Durometer Hardness

A numerical value, which indicates the resistance to indentation of the blunt indentor of the durometer.

Dust Cap

Dust or dirt repelling enclosure for the nipple.

Dust Plug

Dust or dirt repelling enclosure for the coupler.


The amount of time the crimp dies are held in the closed position to eliminate the metal sleeve or ferrule attempting to return to its original diameter.

Dynamic Head (System Head)

A moving fluid exerts a pressure higher than the static pressure due to the kinetic energy of the fluid.

Dynamic Pressure

Pressure that, once it is released, is able to be immediately replenished.


Eccentric Wall

In hose or tubing, a wall of varying thickness.


In hose, tubing or cylindrical articles, the condition resulting from the inside and outside diameters not having a common center.


Power out of the pump divided by power into the pump.

Efficiency Formula

A measure of how much work or energy is conserved in a process. The efficiency is the energy output, divided by the energy input, and expressed as a percentage. A perfect process would have an efficiency of 100%.


An elastic substance occurring naturally, as natural rubber, or produced synthetically, as butyl rubber or neoprene.

Elastometric Material

A material that can be stretched or compressed repeatedly and, upon immediate release of stress, will return to its approximate original size.

Electric Actuator

An electro-mechanical device used to open and close or modulate a valve. The actuator (which is mounted and coupled to the valve in a similar fashion as the pneumatic actuator), operates the valve using an electric motor driving a gear train. While the basic function of the electric actuator is similar to the pneumatic, there are distinct differences in the application and flexibility of the two types.

Electric Failsafe Actuator

Electrically driven actuator that contains an internal spring to close the valve on loss of power.


A controlled electrochemical process utilizing acid electrolyte, DC current, anode, and cathode to smooth the surface by removal of metal.


The enclosing of material by an encapsulant for protective purposes. In a ball valve, the ball is encased in PTFE, preventing the material flowing through the valve from getting behind the ball causing contamination problems.


Ethylene propylene diene monomer, a synthetic rubber.

Expansion Ring

Typically referring to a type of fire hose coupling that is attached by expanding a sleeve (usually brass) outward to compress the hose against the wall of the bowl of the coupling.

External Swage (Swaging)

A ferrule is passed through a reducing die to bring the ferrule O.D. down to a pre-determined size for proper coupling retention by forcing the hose tube down into the stem serrations.

Eye of the Impeller

The center of the impeller where the fluid enters.


Fail-Closed Spring

Return pneumatic actuator is applied to the valve such that the spring will drive the valve to the close position upon loss of air (may be termed air-to-open).

Fail-Open Spring

Return pneumatic actuator is applied to the valve such that the spring will drive the valve to the open position upon loss of air (may be termed air-to-close).


Food and Drug Administration.


A ferrule is generally used for fastening, joining, sealing, or reinforcement. They are often narrow circular rings made from metal.


A fluoroelastomer widely used as a sealing product. FKM is the generic equivalent of the material originally developed by DuPont.

Flex Cracking

Surface condition directly related to repeated bending and straightening.

Flooded Suction

Liquid flows to a pump inlet from an elevated source by means of gravity.


See Capacity.

Flow Checking

Occurs when a valve closes during flow conditions, such as when quickly lowering a heavy implement (a.k.a. check off, backchecking, lock-up).

Flow Coefficient (Cv)

The flow in U.S. gallons of water (at 60°F) that will pass through the valve in one minute with a differential pressure across the valve of 1 PSI.

Fluid End

The portion of the pump that comes in contact with the fluid being pumped.


Various chemically inert compounds containing carbon and fluorine used mainly as lubricants, refrigerants, nonstick coatings, and in manufacturing resins and plastics. Known as FKM.


Polymer material having a carbon chain either partially or completely bonded to fluorine atoms. FKM and PTFE are examples of this material type.

Flush Position

A no-spill valve that allows connection and disconnection without spillage or air inclusion (also known as flush face or dry break).

Foot Valve

A type of check valve used at the point of the liquid intake to retain liquid in the system and prevent the loss of prime when the liquid source is lower than the pump.

Force to Connect

Axial and/or rotational force required to make a complete connection.

Force to Disconnect

The reverse of the above.

Free O.D.

Hose outside diameter before the stem is inserted.

Friction Head

The pressure needed to overcome the resistance to the flow in the pipe and fittings.

Friction Loss

The loss of pressure or that occurs in pipe or duct flow due to the effect of the fluid's viscosity near the surface of the pipe or duct.


Gas Tungsten-Arc Welding (GTAW)

An arc welding process that produces coalescence of metals by heating them with an arc between a tungsten (non-consumable) electrode and the work. Shielding is obtained from a gas or gas mixture. (This process is sometimes called TIG welding, a non-preferred term.) GTAW may be performed by adding filler material to the weld or by a fusion process in which no filler is added.


A seal used between matched machine parts to prevent escape of a gas or fluid. Special seals fit between the ferrules on the fittings, which are then clamped together, compressing the seal and making a leak-proof joint.


Gallons Per Minute, a measure of flow.

Gripping Finger

The part of the clamp that goes over and behind the stem collar to aid in clamp retention.

Grooved Fittings

Typically refers to fittings that have grooves or shoulders that enable a faster installation.


Hard Face

A seal face either rotating or stationary. The most common materials are silicon carbide, ceramic and tungsten carbide.

Hardcoat Anodize

An electrochemical process that applies a corrosion-resistant coating that is chemically bonded to the surfaces of aluminum and aluminum alloy parts. 


The pressure which is measured by the height to which fluid that is being pumped can be raised by the pressure.

Heat Number

An identification number of a stated tonnage of metal obtained from continuous melting in a furnace.

Heat-Affected Zone

In welding the portion of the base metal that has not been melted, but whose mechanical properties have been altered by the heat of welding or cutting operations.


A wire or other reinforcement material spiraled around the cylindrical body of a hose.


Frequency (cycles per seconds).

Hex Union Nut

An internally Acme-threaded, six-sided connector used to assemble bevel seat fittings.

Hold Test

Subjecting a hose to a specific hydrostatic pressure for a specific duration.


Unit of measurement of power or the rate at which work is done equal to 550 foot-pounds per second (745.7 watts) for mechanical horsepower.


A flexible conduit consisting of a tube, reinforcement, and usually an outer cover.

Hose Assembly

A length of hose with a coupling attached to one or both ends.

Hygienic Clamp Joint

A tube outside diameter union consisting of two neutered ferrules having flat faces with a concentric groove and mating gasket secured with a clamp and providing a non-protruding, recessless contact surface.



Inside Diameter.


To strike with a mallet or hammer.


A rotor or rotor blade attached to the end of the stub shaft imparting energy from the motor to the fluid being pumped.


An application of force in a manner that produces sudden strain or motion such as pressure spikes.

Induction Hardening

A type of surface hardening in which a metal part is induction-heated and then quenched which increases the hardness and brittleness of the part.

Internal Expansion

The process in which: (1) A plug (aka bullet) is pulled through a stem to increase the stem I.D. to the plug O.D.  or, (2) A finger expander increases the I.D. to a predetermined size or pressure setting. Either process creates a "full flow" effect. Also referred to as IX.

Investment Cast

Also known as the "lost wax" process. A wax mold that is an exact replica of the part to be produced is dipped in a ceramic slurry. When dry, the part is placed in an oven to harden the ceramic and melt out the wax. From there the metal is poured to produce the desired part.


Iron Pipe Thread, also known as NPT or National Pipe Taper thread.


International Standardization Organization.

ISO 5211

The international standard for valve and actuator interface.



Joint Industrial Committee.

JIC Thread

Typically refers to the threads on hydraulic fittings having 37° conical sealing surfaces.


Kalrez ®

A perfluoroelastomeric compound containing a higher amount of fluorine than FKM fluoroelastomers. A registered trademark of DuPont the generic term is FFKM.


Another name for cam & groove couplings.

Kinetic Energy

Created by a centrifugal pump when the velocity of the fluid is accelerated to the outer rim of the impeller. The amount of kinetic energy given to the fluid corresponds to the velocity at the impeller vane tip. The faster the impeller revolves or the bigger the impeller, the greater the energy given to the fluid. This kinetic energy is then harnessed and slowed by the resistance created by the pump volute.


A temporary or permanent distortion of a hose caused by bending or twisting the hose beyond the minimum bend radius.


Laminar Flow

The flow of a fluid where each particle follows a smooth path that never interferes with another path.


The media unintentionally released from a coupling due to component failure or retention weakness.


A crack or hole in a tube which allows media to escape; or a hose assembly which allows the media to escape at the couplings.


Liquified Petroleum Gas.


Liters Per Minute, a measure of flow.


Any fluid that maintains a film thickness of one micron or more at its operating temperature and load.


Machine Welding

Welding with equipment that performs the welding operation under the constant observation and control of a welding operator. The equipment may or may not perform loading and unloading. 

Manual Override

Any mechanical device by which an automated valve is manually operated. On smaller actuators, this may simply be wrench flats on the output shaft. Larger actuators may require a more sophisticated system, such as declutchable hand wheels, or manual gears.

Manual Welding

Welding in which the entire welding operation is performed and controlled by hand.


Maximum Allowable Working Pressure.

Maximum Shut-Off

The pressure of the media flowing into the valve against which the valve will have to close.


In the middle or average.


Of or pertaining to a weld bead that deviates from side to side across the weld joint rather than tracking the joint precisely.

Mechanical Seal

A positive sealing device used to seal fluids. It consists of two parts, a rotating element attached to the pump shaft and a stationary element attached to the pump casing. Each of these elements has a highly polished sealing surface. The polished faces of the rotating and stationary elements come into contact with each other to form a seal that prevents leakage along the shaft.


The material flowing through the system.

Minimum Burst Pressure

The lowest pressure at which rupture occurs under prescribed conditions.

Modulating Service

Proportional positioning of a valve between the open and closed positions, used for flow control processes.


Mine Safety and Health Administration.


Material Test Report.



Fire Hose thread, also known as NST.


User Association of Automation Technology in Process Industries, established in 1949 in Germany.

Necking Down

A localized decrease in the cross-sectional area of a hose, also known as "goose necking".


Weather-proof enclosure suitable for indoor/outdoor applications to protect from windblown dust, rain or hose-directed water.


Offers the same protection as Nema 4 with the addition of corrosion resistance.


Enclosure that may be submerged up to six feet for 30 minutes.


Enclosure for hazardous locations must be capable of withstanding an internal explosion of gases so as not to ignite an external gas-air mixture.

NEMA Rating

 National Electrical Manufacturers Association code ratings for electrical component enclosures.


Synthetic rubber, chemically and structurally similar to natural rubber.

Net Positive Suction Head

Amount of energy in the liquid at the pump datum. It must be defined as either available or required NPSH.


A surface void anomaly caused by material removal or compression from the surface, whose bottom surface is usually irregular.


The section of the fitting that is inserted into the hose, also known as the shank of a coupling.

Nitrile Rubber

A brand of synthetic rubber made by polymerizing or copolymerizing butadiene with another material such as acrylonitrile or styrene.


A dimensional value assigned for the purpose of convenient designation, or average measurement.

Nominal Size

A dimensional value assigned for the purpose of convenient designation, used for pipes.


National Pipe Straight thread, same as NPSM.


The net positive suction head available is the amount of fluid pressure at the suction side of the pump due to atmospheric pressure, a pressurized tank, or other means.


The net positive suction head required is the amount of fluid pressure required at the suction to prevent cavitation. This is found on pump curves produced by each pump manufacturer.


National Pipe Straight Mechanical thread.


National Standard Thread, also known as fire hose thread.



Outer Diameter.


Open Drip Proof motor enclosure.

On-Off Service

When a valve is used to cycle to a full-open or full-closed position.

Operating Pressure

The pressure at which a system functions, also known as working pressure.

Orbital Cracking

The surface cracks, checks, or crazing caused by exposure to an environment containing ozone.

Orbital Welding

The in-place automatic or machine welding of tubes or pipe with the electrode rotating (or orbiting) around the work. Orbital welding can be done with the addition of filler material or as a fusion process without the addition of filler.


Oil Suction and Discharge.



Removal of iron from the surface of stainless steel and higher alloys by means of a chemical dissolution, typically by a treatment with an acid solution that removes surface contamination and enhances the formation of the passive layer.

Peak Pressure

Maximum momentary pressure encountered in the operation of a component, also known as pressure spike or surge pressure.

Permanent Fitting

The type of fitting which, after it is applied, cannot be removed for reuse.

Permanent Set

The amount by which an elastic material fails to return to its original form after deformation.

Phonograph Finish

A series of small grooves cut into the shank surface to aid in the coupling retention for hoses having hard tubes such as cross-linked polyethylene (XLPE) or ultra-high molecular weight (UHMW). The grooves resemble those on a phonograph record.


An object forced, usually via air pressure, through the length of an assembly to clean out any residual product.


The distance from one point on a helix to the corresponding point on the next turn of the helix, measured parallel to the axis.

Pneumatic Actuator

An air operated mechanical device used to open, close, or modulate a valve. The actuator, which is mounted to the valve by a bracket and coupled to the stem, is designed to convert air pressure into mechanical force sufficient to operate the valve.

Pock Marks

Uneven blister-like elevations, depressions, or nicks on a surface.


To make smooth and shiny by rubbing. Fittings may be machine polished to a 180 grit finish. Polish can be I.D., O.D., or both.


A macromolecular material formed by the chemical combination of monomers having the same or different chemical composition.


A lightweight thermoplastic polymer used in a wide variety of applications.


Small eruptions within the tube rip or tear-away material leaving cavities in the tube. This is a common occurrence in steam hose.

Positive Displacement Pump

A pump that causes a fluid to move by trapping a fixed amount of it then forcing (displacing) that trapped volume into the discharge pipe.

Powder Coat

A process in which electrically charged dry plastic powder paint is applied to a metal surface or part. The part is then baked in an oven resulting in a uniform and durable finish. The only way to remove a powder coat finish is by sandblasting or burning.


The force per unit area applied on a surface in a direction perpendicular to that surface.

Pressure Cap

A cap that incorporates a seal capable of withstanding the rated pressures on the male half.

Pressure Head

In fluid mechanics, the pressure head is the height of a liquid column corresponding to a particular pressure exerted by the liquid column on the base of its container. It is also known as static pressure head or static head. 

Pressure Impulse Test

Subjecting a component to a specified pressure at a specific rate of increase or decrease for a specified time and cycle.

Pressure Rating

The pressure at which a system is designed to operate, allowing for applicable safety factors.

Prick Mark

Perforations of the hose cover that allow pressure buildup between the sections of a hose to escape before damaging the hose. Commonly found in steam hose.


The charge of liquid required to create enough pressure to begin the pumping action of a pump when it has been turned off for an extended period of time.


An instrument for the measurement of the degree of surface roughness.

Proof Pressure

The nondestructive test pressure in excess of the maximum rated operating pressure, generally 1.5 times the standard.


Pounds per square inch.


Pounds per square inch gauge.


Tetrafluoroethylene, a high-performance thermoplastic polymer that has excellent dielectric strength, chemical, and temperature resistance.

Push to Connect

Locking arrangement which permits one-handed, or automatic, connection by pushing the nipple into the coupler.



Log of the arithmetic average of a surface profile.


The center part of a hose that gives it strength. The hose working pressure is dependent upon the type and amount of reinforcement used in the hose construction. Types of reinforcement include wire braid, helical wire, textile braid, wire spiral, or textile spiral.

Reusable Fitting

A type of fitting designed to be removed from a hose and re-coupled on another hose.


Rubber Manufacturers Association rebranded as the U.S. Tire Manufacturers Association in 2017.


The act of spinning the coupler and nipple in opposite directions in a continuous manner beyond 360°.


Revolutions per minute.



Society of Automotive Engineers.

SAE Threads

Similar to JIC thread except for 45° conical sealing surfaces.

Safety Factor

A ratio used to establish the working pressure of a hose based upon the burst pressure. Typical safety factors include:

  1. Water hose up to 150 PSI working pressure: 3 to 1.
  2. Hose for all other liquids, solid materials suspended in liquids or air and water hose over 150 PSI working pressure: 4 to 1.
  3. Hose for compressed air and other gases: 4 to 1.
  4. Hose for liquid media that immediately changes into gas under standard atmospheric conditions: 5 to 1.
  5. Steam hose: 10 to 1 also known as "Design Factor".

Sanitary (hygienic) Weld

Generally considered to be a groove weld in a square butt joint made by the gas tungsten arc welding (GTAW) process as a fusion weld without the addition of filler material. A sanitary weld must be completely penetrated on the weld I.D., with little or no discoloration due to oxidation and be otherwise without defects that would interfere with maintenance in a clean and sterile condition.


A thermoplastic elastomer, a rubber-like material, that complies with FDA requirements.


Standard Cubic Feet per Minute. Typically refers to the amount of compressed air a compressor can produce.


Dimensional standard for pipe as defined by ASTM.

Screw-Together Reusable Fitting

A type of hose fitting where the socket and nipple along with the hose are screwed together.

Seal Face

Surface point on which a seal is achieved.


The part of the shank (stem) that grips the hose tube.

Serration Crest

The top of the serration.

Serration Root

The bottom of the serration.

Service Temperature

The maximum and minimum temperature of the media.

Service Test

Test in which the product is used under actual service conditions.


The amount of deformation remaining after the stress has been relieved.


The section of the fitting or coupling that is inserted into the hose.


To break or cut off.

Shelf Storage Life

The period of time prior to use during which a product retains its intended performance capability.

Shut-Off Head

The maximum head that a pump can generate.

Silicon Carbide

Synthetic mineral of silicon and carbide. It is used in abrasives, refractories, ceramics, and numerous high-performance applications.


Dimethyl silicone, a synthetic rubber.

Single Acting Sleeve

A connection that requires manually pulling the female sleeve back and inserting the male tip (also known as semi-auto sleeve, or manual sleeve).

Single Pole Double Throw (SPDT)

A type of limit switch.

Single Pole Single Throw (SPST)

A type of limit switch.


Process in which powdered metal is formed in a mold under extreme pressure to form a finished part.


Heat process in which powdered metal particles are heated to near the melting point, fusing the metal granules together.


To remove or cut away part of the hose cover exposing the reinforcement to permit the attachment of a coupling directly over the reinforcement.

Sleeve Lock

A coupling that provides an additional lock that must be actuated before the locking sleeve can be retracted (also known as pin-lock, or locking sleeve).


Stem Mean Outside Diameter. The average diameter between the crest of the stem serrations and the root of the stem serrations.

Smooth Bore Hose

A wire reinforced hose in which the wire is not exposed on the inner surface of the tube.

Smooth Cover

A hose cover having an even and uninterrupted surface.


The external portion of a hose fitting on a screw-together reusable fitting.

Soft End

A hose end in which the reinforcement, usually wire, is omitted.

Specific Gravity

A measure of the weight of a liquid in relation to that of water. If the liquid in question will float on water then the specific gravity will be less than one and if the liquid will sink when mixed with water the specific gravity will be greater than one.


A rapid rise of internal pressure followed by a rapid decrease of internal pressure.


The fluid released from the system due to the disconnection of a quick disconnect coupling. This is the fluid trapped between the mating seal and the valve seal of the coupling halves.

Spring Back

The attempt of a metal sleeve or ferrule to return to its original diameter.

Spring Return

Any pneumatic actuator which contains a single coil spring or group of coil springs to oppose the pneumatic actuator movement of a piston. As air moves the piston or diaphragm, the spring is compressed. When the air supply is discontinued and exhausted, the spring extends and drives the piston in the opposite direction. This type of actuator is normally used for applications where it is necessary for the valve to move to the open or close position upon loss of air supply, whether by design or by system failure.

Standard Temperature and Pressure (STP)

In physical sciences standard sets of conditions are for experimental measurements to allow comparisons between sets of data. The standard temperature is 273 K (32°F or 0°C) and the standard pressure is 1 atm pressure.

Static Discharge Head

The vertical distance in feet between the pump centerline and the point of free discharge, or the surface, of the liquid in the discharge tank.

Static Head

The pressure at any point in a liquid can be thought of as being caused by a vertical column of the liquid which, due to its weight, exerts a pressure equal to the pressure at the point in question. The height of this column is called the static head and is expressed in terms of feet of liquid.

Stem Torque

The force required at the valve stem to open or close the valve. Torque is expressed in inch pounds or foot pounds.

Suction Head

Exists when the source of supply is above the centerline of the pump. The static suction head is the vertical distance in feet from the centerline of the pump to the free level of the liquid to be pumped.

Suction Lift

Exists when the source of supply is below the centerline of the pump. Thus the static suction lift is the vertical distance in feet from the centerline of the pump to the free level of the liquid to be pumped.

Supply Pressure

The plant air supply pressure available to operate a pneumatic actuator.

Surface Finish

All surfaced as defined by Part SF of the current ASME BPE Standard and/or the owner/user or manufacturer and referred in Ra µin. or µm.


Rapid rise or decrease of internal pressure. Surge conditions typically occur, but are not limited to, start and stop sequences. Also known as water hammer.

Surge Flow

A rapid increase in fluid flow.


Often interchanged with the term "crimp".


The act of spinning the coupler and nipple in opposite directions to a degree that is less than 360°.

System Curve

A description of what the pump is required to perform. The pump will pump where the system curve intersects the pump curve.

System Head

The head caused by friction in the piping valves and fittings.


Thermal Build-Up

Pressure caused by the expansion of a media due to heat from an external source such as sunlight (also known as thermal expansion).

Thixotropic Fluid

A fluid where viscosity thins with shear.


Twisting or turning force usually measured in inch-pounds (in. lbs.) or foot-pounds (ft. lbs.).

Total Dynamic Discharge Head

The static discharge head plus the velocity head at the pump discharge flange plus the total friction head in the discharge line. The total dynamic discharge head, as determined on the pump test, is the reading of a gauge at the discharge flange, converted to feet of liquid and corrected to the pump centerline, plus the velocity head at the point of gauge attachment.

Total Dynamic Head (TDH)

A combination of the suction head and the head being produced by the pump. Discharge reservoir pressure head + static discharge head + velocity head at pump discharge + total friction head in the discharge line.

Total Dynamic Suction Head

The static suction head plus the velocity head at the pump suction flange minus the total friction head in the suction line. The total dynamic suction head, as determined on the pump test, is the reading of the gauge on the suction flange, converted to feet of liquid and corrected to the pump centerline, plus the velocity head at the point of gauge attachment.

Total Dynamic Suction Lift

The static suction lift minus the velocity head at the pump suction flange plus the total friction head in the suction line. The total dynamic suction lift, as determined on pump tests, is the reading of a gauge on the suction flange, converted to feet of liquid and corrected to the pump centerline, minus the velocity head at the point of gauge attachment.

Total Head or Total Dynamic Head

The total dynamic discharge head minus the total dynamic suction head or plus the total dynamic suction lift. TDH = HD + HS (with suction lift) TDH = HD - HS (with a suction head).

Total Static Head

The vertical distance in feet between the free level of the source of supply and the point of free discharge or the free surface of the discharge liquid.

Totally Enclosed Fan Cooled (TEFC)

A motor enclosure.

Totally Enclosed Non Ventilated (TENV)

A motor enclosure.

Trapped Pressure

Pressurized fluid trapped behind a closed coupling valve.


A hollow cylinder especially one that conveys a fluid. For sanitary applications, a thin wall is implied.

Tube Fitting

A length of tubing formed into a usable shape either welded to an apparatus or welded to ferrules for use in an apparatus.


A piece or length of tube.

Tumble Polish Surface

A uniform finish applied by vibratory equipment to stainless steel, varying from matte grey to bright, depending on media used. This process may cause work hardening on the surfaces.

Tungsten Carbide

A common hard face seal material available in several grades depending upon hardness and corrosion resistance. Cobalt and nickel are the two most common binders.


The condition where the media does not move smoothly parallel to the flow direction. Turbulent flow is caused by abrupt changes in direction, changes of cross-section, or high velocity. The result is increased friction, which generates heat, decreases operating pressure, and wastes power.

Twist Lock

A locking arrangement which requires a rotational actuation to unlock the mating halves.



Unified National (constant pitch) thread.

Ultra High Molecular Weight (UHMW)

Thin tube liner made from extremely dense material having excellent chemical resistance properties.


Unified National Coarse thread.


Unified National Fine thread.



Partially or completely exhausted of air, gas or other media to create a negative pressure. Theoretically, a perfect vacuum would be measured as 30 inches of mercury, but that is unattainable. The true perfect vacuum is 29.7 inches of mercury.

Vapor Pressure

Below this pressure the liquid being pumped will vaporize.


When a fluid passes from a liquid to a gaseous state.

Variable Frequency Drive (VFD)

Used to vary the frequency going into a motor, thus varying the speed at which the motor runs.


A measurement of the speed of the liquid in the system; Velocity = distance/time.

Velocity Head

The energy of a liquid as a result of its motion at some velocity. It is the equivalent head in feet through which the water would have to fall to acquire the same velocity, or in other words, the head necessary to accelerate the water. Velocity head can be calculated from the following formula: H = V2 / 2g where g = 32.2 ft/second-2 V = liquid velocity in feet per second.

Victaulic Groove

A style of coupling that has a groove cut near the end of the stem where threads would typically be. The couplings are attached using a "C" shaped clamp that fits into the grooves on the stem.


Internal friction of a liquid tending to reduce flow.


Casing surrounding the pump impeller. The volute converts velocity energy to pressure energy.


Washdown Duty

Motor enclosure that is suitable for a liquid washdown atmosphere.

Water Horsepower (WHP)

The calculated horsepower coming out of the pump. WHP = head x GPM / 3960.

Water, Oil, Gas (WOG)

Pressure rating for valves handling these products. This does not include steam.


Undulations or rippling of the surfaces.


Joining two (or more) pieces of material by applying heat to produce a localized union through fusion across the interface. For sanitary fittings, a ferrule is attached to the ends of a tube fitting by tungsten inert gas (TIG) welding without the addition of filler metal. Tube fittings can then be joined with clamps and gaskets to form parts of a system.


Water, Oil, Gas. Pressure rating for valves handling these products. This does not include steam.


An increase in hardness and strength caused by plastic deformation at temperatures below the annealing ranges. Work hardening will increase the cost of polishing because of increased hardness and can also increase the chance of corrosion in stainless steel.

Working Pressure (WP)

The maximum pressure to which a hose assembly will be subjected to including pressure surges.



Cross-Linked Polyethylene tube material that has good chemical resistance properties.



A registered trademark of DuPont used for a number of high strength, abrasion, and impact resistant thermoplastic polyamide formulations of the family more commonly known as nylon.

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