Pipes production glossary

Actual Size / Actual Pipe Size

The real measured inside or outside diameter of a pipe, as opposed to its nominal size.

Adapter

A fitting that joins pipes of different materials or joining methods, e.g. a threaded pipe to an unthreaded tube.

Air Hardening

Hardening a high-hardenability steel by heating above the critical temperature and then cooling in air.

Air Testing

Subjecting a pipe or component to air pressure to check for leaks.

Alloy

A metal combined with one or more other elements, metallic or not, to give a material with new properties.

Annealing

Heating and then cooling a metal, usually slowly, to soften it, relieve stresses, refine grain or improve machinability.

Atmospheric Corrosion

Rusting of unprotected steel exposed to air containing moisture.

Bales

Banded lifts (bundles) of pipe.

Bar Mill

A rolling mill where blooms or billets are rolled into bars.

Bark

The decarburized layer just beneath the scale, caused by heating steel in an oxidizing atmosphere.

BDLS / Bundles

Pipe packaged in bundles for shipping; the number of pieces per bundle depends on pipe size.

B.E. / Beveled End

A pipe end cut at an angle (typically 30°) to prepare it for butt welding.

Beading

Forming a raised or depressed ridge of specified shape on a section of tube.

Bearing Load

A compressive load carried by a tube or collar along the line where it contacts a pin, rivet, axle or shaft.

Bearing Strength

Maximum bearing load at failure divided by the effective bearing area (hole diameter × thickness of the bearing member).

Bend Test

A test in which a specimen is bent to a specified radius and angle to check ductility and the absence of cracking.

Bevel

The angle between the prepared end edge of a pipe and a plane perpendicular to its surface; 30° is standard for line pipe.

Billet

A semi-finished solid steel bar, round or square, which is pierced to make seamless pipe or rolled further.

Black Steel Pipe / Blk. St.

Uncoated, ungalvanized steel pipe, usually treated with a rust preventative for shipping and storage.

Bloom

A semi-finished hot-rolled product, square or nearly square in section, made on a blooming mill.

BOF (Basic Oxygen Furnace) / BOP (Basic Oxygen Process)

Steelmaking in which oxygen is blown through molten pig iron and scrap to remove carbon and impurities.

Borescope

An optical instrument for visually inspecting the inside surface of tubes.

Box Annealing / Pot Annealing

Annealing metal in a closed container to minimize oxidation, with slow heating and slow cooling.

Brittleness

The tendency to fracture without appreciable plastic deformation.

Burr

A rough or sharp edge left on metal by a cutting tool.

Burst Test

A destructive hydraulic test that pressurizes a pipe until it fails, to find its actual yield and ultimate strength.

Butt Weld

A joint made by welding together two beveled pipe ends, or a pipe and a fitting, of the same diameter and wall thickness.

Camber

A deviation from edge straightness: the greatest gap between a side edge and a straight line.

Cap

A fitting placed on the end of a pipe to close it.

Casing

Pipe used to line the walls of oil, gas or water wells.

Chamfer

A beveled surface that removes a sharp corner; also a finishing operation before threading.

CL / Cut Length

Pipe or tube cut to a specific ordered length, usually with the tolerance on the plus side only.

Cladded Racks

Storage racks for stainless steel made of iron with strips of stainless steel running across them, to avoid contamination.

Cladding

Covering one metal with another and forming a metallurgical bond between them.

Coated Tubing

Tubing made from pre-coated strip, or coated in-line after welding (e.g. galvanized or aluminized), for extra corrosion protection.

Coating

Covering steel with another material, mainly to resist corrosion.

Dry (coating type)

No oil coating at all; the tubes rust quickly in transit and storage.

No Oil (coating type)

No intentional oil application; a light film of processing oil gives limited rust protection.

Coefficient of Thermal Expansion

The change in length (or area or volume) per unit, per degree of temperature increase.

Cold Drawing / Cold Drawn (CD)

Pulling a tube through a die, with or without a mandrel, to reduce diameter and wall and to get closer tolerances, a better finish and higher strength.

Cold Reduction

Reducing the cross-sectional dimensions of a tube or sheet by cold-working operations.

Cold Rolled Sheet

Hot-rolled sheet that has been cold reduced to get thinner gauges and a better surface finish.

Collapsing Pressure

The external pressure that makes a tube cave in, bend or buckle inwards.

Compression Test / Crush Test

A test in which a tube section is compressed across its diameter, or crushed endwise, to check ductility.

Concentricity

How well the center of the inside diameter matches the center of the outside diameter; related to wall thickness variation.

Conditioning

Removing surface defects (seams, laps, pits) from semi-finished steel such as blooms, billets and slabs.

Constant-Load Test

A stress-corrosion-cracking or mechanical test in which the specimen is loaded with a dead weight.

Continuous Casting / Con Cast / Strand Casting

Casting molten steel directly into slabs, blooms or billets that solidify continuously as they are poured, instead of into ingots.

Strand

The product of the continuous casting process.

Controlled Cooling

Cooling from an elevated temperature in a pre-determined way to avoid cracking or to obtain a desired microstructure.

Cooling Stresses

Stresses that develop from uneven contraction or localized plastic deformation during cooling.

Corrosion

Gradual chemical or electrochemical attack on a metal by atmosphere, moisture or other agents.

Corrosion Fatigue

Cracking and loss of properties of a metal under repeated stress in a corrosive environment, faster than from either cause alone.

Coupling (CPLG)

A short sleeve, usually internally threaded, used to connect two pipes or fittings in a straight line.

Creep

Slow, long-term deformation of metal under constant load or stress, usually at elevated temperature.

Creep Strength

The constant stress that produces a specified amount of creep in a given time at constant temperature.

Crop

The end of a pipe containing defects, which is cut off and discarded.

Cut Off

Cutting tube to the customer's length or cutting samples for testing.

Dia / Diameter

The distance across a circle measured through its center.

Die Stamping

Permanent marking pressed into pipe, as required by some specifications.

Drifted

Checked for minimum inside clearance by passing a mandrel (drift) through the pipe.

Dye Penetrant Inspection

A non-destructive test using dye or fluorescent liquid to reveal surface defects.

Eddy Current Testing

A non-destructive method using induced electrical currents to detect discontinuities in a piece.

Elastic Deformation

Temporary change in dimensions caused by stress; the material returns to its original size when the stress is removed.

Elastic Limit

The maximum stress a material can take without permanent deformation after the stress is released.

Electric Furnace (EF) / Electric Arc Furnace (EAF)

A furnace that makes steel by melting mainly scrap metal with electric arcs.

Elongation

The permanent extension at fracture in a tensile test, expressed as a percentage of the original gauge length.

Endurance Limit

The maximum stress a metal can withstand for a specified number of stress cycles without failing.

Erosion

Wearing away of metal by liquid or gas flow, made worse by suspended solid particles and sometimes by corrosion.

Etch Tests

Tests that dip a sample in acid to reveal inclusions and other structural features of steel.

Expanded Pipe

Pipe whose diameter has been enlarged mechanically or hydraulically.

Extrusion

Forcing steel through a die, and over a mandrel for tubes, to form solid or hollow shapes.

Fatigue

The tendency of a metal to break under repeated cyclic stress well below its ultimate tensile strength.

Fatigue Limit

The maximum stress a metal can withstand without failure for a specified number of cycles.

Fitting

A part of a pipeline other than straight pipe or valves, used to join, redirect, reduce or close off pipe.

Flat Rolled Products

Mill term for hot-rolled bands and sheets, cold-rolled sheets and plates, in coil or flat form.

Fracture Test

Breaking a piece of metal to examine the fracture surface for structure, carbon content or internal defects.

Free Machining

Steel with added elements (e.g. sulphur or lead) that make short chips, lower cutting power and give a better finish.

Gage Length / Gauge Length

The length between reference marks on a tensile test piece, used to calculate percentage elongation.

Gal. St. / Galv / Galvanized Steel Pipe

Steel pipe with a hot-dip zinc coating that protects it from corrosion and abrasion.

Galvanizing (GALV)

Applying a coating of zinc to steel, by hot dipping or electrolytic deposition.

Grade

A class of steel defined by chemistry and mechanical properties such as yield and tensile strength.

Heat Treatment

Controlled heating and cooling of a solid metal to obtain desired properties.

HR-P&O

Hot-rolled, pickled and oiled sheet.

ID / Inside Diameter

The distance across the inside of a pipe, measured through its center.

Inclusions

Non-metallic impurities (oxides, sulfides, silicates) trapped in steel during and after solidification.

Joint

A point where pipes, fittings or valves are connected; also a single length of pipe.

Large OD Pipe

Pipe of large outside diameter, with a typical cutoff at NPS 14 and above.

Leaded Resulphurized Steels

Resulphurized steels with added lead for even better machining speed and surface finish.

Lifts

Bundles of small-diameter pipe as shipped.

Line Pipe

Steel pipe used to carry gas, oil and other fluids in pipelines.

Machining

Cutting away metal with power-driven machinery.

Malleability

The ability of a metal to be deformed by rolling or hammering without breaking.

Mandrel

A rod that keeps the cavity open in hollow products during working, or a bar around which metal is shaped.

Mandrel Drawn

Drawn over a mandrel to get closer ID, OD and wall tolerances and better properties (also called DOM).

Mechanical Properties

Properties that describe how a material reacts to force, e.g. tensile strength, yield strength, elongation and hardness.

Destructive Testing / Mechanical Testing

Tests that damage or break the sample to measure properties such as strength, ductility and toughness.

NOM (Nominal)

The theoretical or stated value of a dimension; also the standard size designation, which is not the actual measurement.

Nominal Pipe Size (NPS)

A North American size designation roughly equal to inside diameter for small pipe; for NPS 14 and above it equals the OD.

Non-Destructive Testing (NDT)

Methods that find defects without damaging the material, e.g. ultrasonic, eddy current, magnetic particle, penetrant, X-ray.