Glossary of Common Piping Terms



Adapter: A fitting for changing from one end type to another.
AGA: American Gas Association.
AISI: American Iron and Steel Institute.
API: American Petroleum Institute.
Ambient Temperature: The air temperature of an object or environment where equipment or appliances are stored.
ANSI: American National Standards Institute. A private organization that administers the US voluntary standards and conformity assessment system.
ASME: American Society of Mechanical Engineers. A certification for products, providing they are reliable and perform consistently, comply with government regulations, and are easily shipped domestically and internationally.
Aqueous: Contains water.
ASTM: American Society for Testing and Materials. A standard important to evaluating material, chemical, mechanical and metallurgical properties of metals.
AWWA: American Water Works Association. 


Bales: Term associated with banded lifts of pipe.
Ball Valve
: A device that controls flow using a hollow ball. It is open then the ball’s hole is in-line with the inlet and closes by pivoting an attached handle 90-degrees, blocking the flow.
Barlow's Formula: An equation which shows the relationship of internal pressure to allowable stress, nominal thickness and diameter.
Bevel: The angle formed between the prepared edge of the end of the pipe and a plane perpendicular to the surface of the member. The standard bevel for line pipe is 30o to facilitate welding.
Billet: A solid semi-finished round or square product that has been hot worked by forging, rolling or extrusion. For seamless tubular products, the billet is heated and pierced to form a tube hollow.
Black Bare: Term associated with pipe surface whereby the pipe will not be coated with mill spray oil and grease spots and cutting oil will not be removed.
Black Dry: Term associated with pipe surface whereby the pipe will not only be coated with mill spray oil and all grease spots and cutting oil will be removed by washing.
BSP: British Standard Pipe. A piping specification based on trade size rather than the actual diameter. Commonly used in Australia and commonwealth countries.
Black Oiled: Term associated with pipe surface whereby material ordered in this manner is protected with a varnish-type oil on the O.D. for temporary corrosion protection during transit and in short-term storage.
Bundles: Term associated with practice of packaging NPS 1-1/2" and smaller pipe. Pieces per bundle vary depending upon size.
Bushing: A pipe fitting, threaded on both the inside and outside, used for connecting pipes with different diameters.
Burst Test: A destructive hydraulic test employed to determine actual yield strength and ultimate strength of both seamless and welded pipe.
Bulkhead Fitting: A fitting made to allow piping connections and drainage through a hole in a tank.
Buttweld Pipe: See Continuous Weld.


Chamfer: A beveled surface to eliminate an otherwise sharp corner.
Chemical Properties: Normally associated with a limited number of chemical elements; however, depending upon the specification, practically a full analysis may be required. Minimum or maximum limits are established in standards.
Cold Work: Deforming metal plastically at a temperature lower than the recrystallization temperature. Mechanical or hydraulic expansion employed to achieve higher mechanical properties.
Conduit: Pipe serving as a duct for electrical wiring.
Continuous Weld: In common usage, a phrase for continuous butt weld. Furnace-welded pipe produced in continuous lengths from coiled skelp and subsequently cut into individual lengths, having its longitudinal butt joint forge welded by the mechanical pressure developed in rolling the hot-formed skelp through a series of round pass welding rolls.
A fitting joining two pieces of pipe.
Compression Fitting: A type of fitting used in plumbing and electrical systems, joining two tubes together with a water-tight seal.
Cross: A type of fitting with one inlet and three outlets. Also called a cross branch line or four-way fitting.
Cut Lengths: Pipe cut to a specific length as ordered.


Die Stamping:  Permanent marking placed on pipe as required by some specifications.
Double Extra Strong: Standard pipe weight designation (XXS). Sometimes described as XXH (double extra heavy).
DRL: Double Random Length (35' minimum average or as defined in specifications).
DSAW: Double Submerged Arc Weld.
Ductility: The ability of a material to deform plastically without fracturing, being measured by elongation or reduction of area in a tensile test or by other means.


Eddy-Current Testing: Non-destructive testing method in which eddy-current flow is induced in the test object. Changes in the flow caused by variations in the object are reflected into a nearby coil or coils for subsequent analysis by suitable instrumentation and techniques.
 A type of fitting that changes the direction of piping. Elbows are commonly used to reroute pipe or turn corners in without a pipe-bender.
ERW: Electric Resistance Weld. See High Frequency Welding.
EW: Electric Weld. See High Frequency Weld.
Elongation: In tensile testing, the increase in the gage length, measured after fracture of the specimen within the gage length, usually expressed as a percentage of the original gage length.
Expanded Pipe: Pipe which has been enlarged circumferentially by mechanical or hydraulic pressure.
Extra Strong: Standard pipe weight designation (XS). Sometimes described as XH (extra heavy).


Ferrule: The sealing component of compression fittings.
Female Thread: A fitting with grooves or threads on the inside.
Flange: A type of fitting used for connecting pipes, valves and other piping equipment, usually screwed or bolted together with a gasket in between, creating a tight seal.
Flattening Test: A quality test for pipe in which a specimen is flattened between parallel plates that are closed to a specified height.


Galvanizing: Covering of iron or steel surfaces with a protective layer of zinc (weight defined in specifications).
Gate Valve:
 A type of valve that opens by lifting a gate out of the way of the flow.
Globe Valve: A type of valve used for regulating the flow with a movable plug or disc and a ring seat with spherical design.


Hex Plug: A fitting, threaded in the end with the top of the plug in a hexagon shape.
High Frequency Welding: A technique employed in the manufacture of electric resistance weld pipe. Typical radio frequency power for welding is supplied at 450,000 cycles/sec.
Hollow Plug: A fitting used to restrict flow of a liquid or gas through a pipe.
Hot Stamp: Permanent marking placed on pipe as employed by manufacturer or as established by specification.
Hydrostatic Test: Normal mill test as required by specifications. The pipe ends are sealed and high pressure water is introduced to predetermined pressures as required by specifications.


I.D.: Inside diameter. The measurement from inner wall to inner wall of a pipe. Inside diameter is dependent on the outside diameter, as well as its wall thickness.
Impact Test: A test performed at a specified temperature (usually lower than ambient) to determine the behavior of materials when subjected to high rates of loading, usually in bending, tension or torsion. The quantity measured is the energy absorbed in breaking the specimen by a single blow, as in a Charpy Test.
Ink Mark: Continuous printing identification associated with NPS 1-1/2 and smaller pipe. Detail is normally limited to the trademark and "Made in USA". 


Kip: A unit of weight equal to 1,000 pounds used to express dead weight.


Joint Thread: A connection at the ends of pipe, where the internal and external fittings are threaded so they can be screwed together.


Lap Joint Flange: A type of flange that is not welded and its lip does not extend past the edge of the pipe.
Lifts: Term associated with separated segments of pipe (banded or unbanded for ease of handling).


Magnetic Particle: One of several methods of non-destructive testing. A non-destructive method of inspection for determining the existence and extent of possible defects in ferromagnetic materials. Finely divided magnetic particles, applied to the magnetized part, are attracted to and outline the pattern of and magnetic-leakage fields created by discontinuities.
Magnetic Properties: The properties of a material that reveal its elastic and inelastic behavior where force is applied, thereby indicating its suitability for mechanical application; for example, tensile strength, elongation, hardness and fatigue limit.
Male Thread:
 A fitting with grooves or threads on the outside.


Nipple: A fitting, usually a short piece of pipe with male threaded ends on each side, used to connect to other fittings.
NPS: A dimensionless designator for such traditional terms as "nominal diameter", "size", and "nominal size". Corresponds to actual outside diameter only in sizes 14 inches and over.
Normalizing: Heating a ferrous material to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range.


O.D.: Outside diameter. The measurement from outer wall to outer wall of a pipe.
Oiled: See Black Oiled.
Orifice Flange: A flange used to measure the rate of flow through a pipe system.


PE: Plain End. 
Pickling: Pipe immersed into acid bath for removal of scale, oil, dirt, etc.
 A fitting used to close the end of a pipe.
PSI: Pounds per square inch.
PSIG: Pounds per square inch gage.


R & D: Reamed and Drifted. Pipe commonly used in water wells which has a special, heavy-duty coupling and a guaranteed I.D. clearance.
 A fitting used to connect different sizes of pipe, usually from a larger inner diameter to a smaller inner diameter.
Rigid Coupling: A fitting used to make a solid connection between two shafts, without movement.


Sanitary Fitting: Specialized fittings, primarily used in hygienic applications.
SC: Square cut plain end pipe.
Skelp: A piece or strip of metal produced to a suitable thickness, width and edge configuration, from which welded pipe is made.
Sleeve: A larger piece of pipe used to protect the smaller inner pipe.
SMLS: Seamless.
SRL: Single Random Length (16-22 ft. for standard weight ASTM pipe or as defined in specifications).
Stencil: Paint spray identification placed on pipe. Specification size, wall, grade, test pressure, method of manufacture and normal mill characters and mill identification are usually included; however, detail varies by specification. "Country of Origin" is included. 
Stretch Reduction: A technique employed in the manufacture of continuous weld pipe and in certain instances in the manufacture of seamless and electric resistance weld pipe. It involves one or several "master" sizes which are stretch-reduced or rolled under tension through a number of stands to achieve a variety of standard pipe diameters and walls.
Strip - A sheet of metal in which the length is many times the width.
Stop Valve: A valve used to turn off the flow of liquid through the pipe system.


TBE: Threaded Both Ends.|
T & C: Threaded and Coupled. 
Tee: A fitting with a T-shape and three openings. Tees are used to connect pipes of different diameters and change the direction of the run of pipe.
Tensile Strength: In tensile testing, the ratio of maximum load to original cross-sectional area. Also, called ultimate strength. Usually expressed in pounds per square inch.
TO: Threads Only. 
Tube Round: See Billet.


Ultrasonic: An electronic method of non-destructive testing utilizing sound waves.
 A three-piece fitting that is used to join two pipes, allowing the pipes to be disconnected easily without having to cut the pipe.


Wye: A Y-shaped fitting with three openings used join pipes at an angle.


Yield Strength: The stress at which a material exhibits a specified deviation from proportionality of stress and strain. An offset of 0.2% is used for many metals including steels.