Pipes & Tubes

A pipe or tube is a term used to designate a hollow, tubular body which is used to transport any fluid possessing flow characteristics such as those found in liquids, gases, vapors, liquefied solid, and fine powders. The pipe can be categorized as seamless pipe and welded pipe. Welded pipes can be further classified as butt-welded pipe and spiral-welded pipe. There 3 important parameters to specify a pipe: outside diameter(O.D), inside diameter(I.D), and wall thickness(W.T). Metals-Piping supplies pipes & tubes manufactured from cast iron, carbon steel, low alloy steel, alloy steel, stainless steel, nickel & nickel alloy, titanium, aluminum, zirconium, copper and copper alloy, and cladding metals.

End Connection/Joint Types

Butt welding(BW), Threaded(Screwed), Socket Welding.

Dimension & Weight

The dimension & weight specification shall be in accordance with ASME B36.10, ASME B36.19.

Typical Standards for Pipes & Tubes

  • Carbon & Alloy Steel: ASTM A106, ASTM A53, API 5L, ASTM A134, ASTM A135, ASTM A178, ASTM A179, ASTM A210, ASTM A214, ASTM A334, ASTM A691, ASTM A211, ASTM A252, ASTM A335, ASTM A213, ASTM A209, ASTM A249, ASTM A250, ASTM A333, ASTM A358, ASTM A369, ASTM A376, ASTM A381, ASTM A405, ASTM A409, ASTM A423, ASTM A426, ASTM A450, ASTM A691, ASTM A430, ASTM A451, ASTM A452, ASTM A530, ASTM A587, ASTM A589, ASTM A660, ASTM A671, ASTM A672, ASTM A795, ASTM A714.
  • Stainless Steel: ASTM A312, ASTM A213, ASTM A731, ASTM A790, ASTM A733, ASTM A778, ASTM A813, ASTM A814, ASTM A872.
  • Nickel & Nickel Alloy: ASTM B161, ASTM B163, ASTM B165, ASTM B167, ASTM B369, ASTM B407, ASTM B423, ASTM B444, ASTM B464, ASTM B466, ASTM B467, ASTM B468, ASTM B514, ASTM B515, ASTM B516, ASTM B517, ASTM B535, ASTM B619, ASTM B622, ASTM B626, ASTM B668, ASTM B672, ASTM B673, ASTM B674, ASTM B675, ASTM B676, ASTM B677, ASTM B690, ASTM B704, ASTM B705, ASTM B710, ASTM B729, ASTM B751, ASTM B775, ASTM B804, ASTM B829,
  • Copper & Copper Alloy: ASTM B251, ASTM B315, ASTM B359, ASTM B369, ASTM B395, ASTM B466, ASTM B467, ASTM B543, ASTM B956, ASTM B42, ASTM B43, ASTM B75, ASTM B111, ASTM B135.
  • Titanium & Titanium Alloy: ASTM B338, ASTM B861, ASTM B862.
  • Aluminum & Aluminum Alloy: ASTM B210, ASTM B221, ASTM B234, ASTM B241.
  • Zirconium & Zirconium Alloy: ASTM B523, ASTM B658.

What is the difference between Pipe and Tube

People use the words pipe and tube interchangeably, and they think that both are the same. However, there are significant differences between pipe and tube.

The short answer is.. A PIPE is a round tubular to distribute fluids and gases, designated by a nominal pipe size (NPS or DN) that represents a rough indication of the pipe conveyance capacity; a TUBE is a round, rectangular, squared or oval hollow section measured by outside diameter (OD) and wall thickness (WT), expressed in inches or millimeters.

What is Pipe..

Pipe is a hollow section with round cross section for the conveyance of products. The products include fluids, gas, pellets, powders and more.

The most important dimensions for a pipe is the outer diameter (OD) together with the wall thickness (WT). OD minus 2 times WT (schedule) determine the inside diameter (ID) of a pipe, which determines the liquid capacity of the pipe.

ASTM A335 Seamless Pipes

Examples of actual O.D. and I.D.

Actual outside diameters

  • NPS 1 actual O.D. = 1.5/16″ (33.4 mm)
  • NPS 2 actual O.D. = 2.3/8″ (60.3 mm)
  • NPS 3 actual O.D. = 3.1/2″ (88.9 mm)
  • NPS 4 actual O.D. = 4.1/2″ (114.3 mm)
  • NPS 12 actual O.D. = 12.3/4″ (323.9 mm)
  • NPS 14 actual O.D. = 14″ (355.6 mm)

Actual inside diameters of a 1 inch pipe.

  • NPS 1-SCH 40 = O.D.33,4 mm – WT. 3,38 mm – I.D. 26,64 mm
  • NPS 1-SCH 80 = O.D.33,4 mm – WT. 4,55 mm – I.D. 24,30 mm
  • NPS 1-SCH 160 = O.D.33,4 mm – WT. 6,35 mm – I.D. 20,70 mm

Such as above defined, the inside diameter is determined by the oudside diameter (OD) and wall thickness (WT).

The most important mechanical parameters for pipes are the pressure rating, the yield strength, and the ductility.

The standard combinations of pipe Nominal Pipe Size and Wall Thickness (schedule) are covered by the ASME B36.10 and ASME B36.19 specifications (respectively, carbon and alloy pipes, and stainless steel pipes).

pipe vs tube

What is Tube..

The name TUBE refers to round, square, rectangular and oval hollow sections that are used for pressure equipment, for mechanical applications, and for instrumentation systems.

engine steel tubes 04

Tubes are indicated with outer diameter and wall thickness, in inches or in millimeters.

Steel tubing is used throughout industrial applications, particularly for transportation of water, gasses and liquid wastes. Steel tubes are a common component of industrial machines, used in conveyor belts, hydraulic lifts, mills and many other machines.

Pipe vs Tube, 10 basic differences

Key Dimensions (Pipe and Tube Size Chart) The most important dimensions for a pipe is the outer diameter (OD) together with the wall thickness (WT). OD minus 2 times WT (SCHEDULE) determine the inside diameter (ID) of a pipe, which determines the liquid capacity of the pipe. The NPS does not match the true diameter, it is a rough indication The most important dimensions for a steel tube are the outside diameter (OD) and the wall thickness (WT). These parameters are expressed in inches or millimeters and express the true dimensional value of the hollow section.
Wall Thickness The thickness of a steel pipe is designated with a "Schedule" value (the most common are Sch. 40, Sch. STD., Sch. XS, Sch. XXS). Two pipes of different NPS and same schedule have different wall thicknesses in inches or millimeters. The wall thickness of a steel tube is expressed in inches or millimeters. For tubing, the wall thickness is measured also with a gage nomenclature.
Types of Pipes and Tubes (Shapes) Round only Round, rectangular, square, oval
Production range Extensive (up to 80 inches and above) A narrower range for tubing (up to 5 inches), larger for steel tubes for mechanical applications
Tolerances (straightness, dimensions, roundness, etc) and Pipe vs. Tube strength Tolerances are set, but rather loose. Strength is not the major concern. Steel tubes are produced to very strict tolerances. Tubulars undergo several dimensional quality checks, such as straightness, roundness, wall thickness, surface, during the manufacturing process. Mechanical strength is a major concern for tubes.
Production Process Pipes are generally made to stock with highly automated and efficient processes, i.e. pipe mills produce on a continuous basis and feed distributors stock around the world. Tubes manufacturing is more lengthy and laborious
Delivery time Can be short Generally longer
Market price Relatively lower price per ton than steel tubes Higher due to lower mills productivity per hour, and due to the stricter requirements in terms of tolerances and inspections
Materials A wide range of materials is available Tubing is available in carbon steel, low alloy, stainless steel, and nickel-alloys; steel tubes for mechanical applications are mostly of carbon steel
End Connections The most common are beveled, plain and screwed ends Threaded and grooved ends are available for quicker connections on site


Pipes are usually made of carbon steel or low alloy steel.

Tubes instead are made of mild steel, aluminum, brass, copper, chrome, stainless steel, etc.

The difference in materials is also a reason for the difference in the cost and applications. [4]

Some widely used steel pipe standards or piping classes are:

  •  The API range – now ISO 3183. E.g.: API 5L Grade B – now ISO L245 where the number indicates yield strength in MPa

  •  ASME SA106 Grade B (Seamless carbon steel pipe for high temperature service)

  •  ASTM A312 (Seamless and welded austenitic stainless steel pipe)

  •  ASTM A36 (Carbon steel pipe for structural or low pressure use)

  •  ASTM A795 (Steel pipe specifically for fire sprinkler systems)