What exactly is steel pipe?

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Steel pipe has been manufactured in the United States since the early 1800s. Pipe is a hollow piece having a circular cross-section that is used to convey items such as fluids, gas, pellets, powders, and more. Steel pipes, on the other hand, are employed in a number of applications. They are used to transmit water and gas underground across cities and villages. They are also used in building to safeguard electrical wiring. Steel pipes may be both robust and light. As a result, they are ideal for bicycle frames. They are also utilized in the manufacture of vehicle components, refrigeration equipment, heating and plumbing systems, flagpoles, and street lighting, to mention a few.

The outer diameter (OD) and wall thickness are the two most essential dimensions for a pipe (WT). The internal diameter (ID) of a pipe is determined by OD minus 2 times WT (schedule), which defines the pipe’s liquid capacity. When we speak about pipe in our profession, we usually refer to it by its (ID) and schedule, such as 2-inch schedule 40 or 14 inch extra heavy. Sch. 40, Sch. 80, Sch. Standard (STD), Sch. XS/XH, and Sch. XXS are examples of walls or schedules. The majority of pipe is offered in lengths of 21 or 42 feet.

What exactly is Steel Tube?

The term tube refers to hollow portions that are round, square, rectangular, or oval and are utilized for pressure apparatus, mechanical applications, and instrumentation systems.

Steel tube may be manufactured using a variety of basic ingredients, including iron, carbon, manganese, vanadium, and zirconium. Tubing, like pipe, may be made as either seamless or welded. Seamless tubing is made from a solid piece of steel that is rolled into a circular form before being perforated and stretched to its full length. Consider a wad of play dough and shaping it into a cylinder. Then, using the leftover dough, press your finger into the center and lengthen it. That’s how it’s made, but it’s hot and whirling and all automated. Welded steel tube, on the other hand, is produced from coil. The coil is sliced and rolled into a circular form before the ends are soldered together. From then, the tubing may be cut to a certain length as round tubing or further distorted into different forms such as square, rectangular, oval, and so on.

Tubes are labeled with their outer diameter (OD) and wall thickness (WT), both in inches and millimeters. Buyers in our business often refer to the item they seek as a (OD) and a wall thickness (WT). Wall thicknesses such as 11 gauge, 1/4″, 3/8″ and 5/8″ are examples. Tubing is often available in lengths of 20, 24, 40, and 48 feet, although bespoke lengths are readily made.

Is it a tube or a pipe?

Although the names are often used interchangeably, there is one significant distinction between tube and pipe, notably in how the material is arranged and toleranced. Because tubing is utilized in structural applications, the outer diameter is the most essential dimension. Tubes are often used in applications requiring exact outer diameters, such as medical equipment. The outer diameter is significant because it indicates how much weight it can support as a stability element. Pipes, on the other hand, are often used to carry gases or liquids, therefore knowing the capacity is critical. Knowing how much water can flow through the pipe is critical. The pipe’s round form makes it effective at managing pressure from the liquid running through it.


Pipes are classified according to their schedule and nominal diameter. Pipe is normally ordered in accordance with the Nominal Pipe Size (NPS) standard, with a nominal diameter (pipe size) and schedule number specified (wall thickness). The schedule number on various sizes of pipe may be the same, but the actual wall thickness will vary.

Tubes are usually ordered by outer diameter and wall thickness, but they may also be ordered by OD & ID or ID and Wall Thickness. The wall thickness of a tube determines its strength. A gauge number specifies the thickness of a tube. Larger outer diameters are indicated by smaller gauge numbers. The interior diameter (ID) is a theoretical measurement. Tubes may be square, rectangular, or cylindrical in form, while pipe is always round. The circular form of the pipe distributes the pressure load equally. Pipes are used for bigger purposes and come in diameters ranging from 12 inch to several feet. Tubing is often utilized in applications that demand lower sizes.

Purchasing Tubing or Pipe

Tubing is usually ordered by outer diameter and wall thickness, but it may also be ordered by OD & ID or ID and Wall Thickness. Although tubing contains three dimensions (O.D., I.D., and wall thickness), only two of them may be defined with tolerances, while the third is purely theoretical. Tubing is often ordered and kept to stricter tolerances and requirements than pipe. Pipe is normally ordered in accordance with the Nominal Pipe Size (NPS) standard, with a nominal diameter (pipe size) and schedule number specified (wall thickness). Tubes and pipes may both be cut, bent, flared, and constructed – see our top 10 ordering advice for tubing and piping.


There are a few fundamental differences between tubes and pipes:

  • Shape

Pipe is usually circular in shape. Tubes come in square, rectangular, and circular shapes.

  • Measurement

Outside diameter and wall thickness are frequently selected when ordering tubes. Tubing is often held to stricter tolerances and requirements than pipe. Pipe is commonly ordered using the nominal pipe size (NPS) standard, with the nominal diameter (pipe size) and schedule number specified (wall thickness)

  • Capabilities for Telescoping

Telescopes may be used on tubes. Telescoping tubes are ideal for applications that need many pieces of material to be sleeved or expanded within one another.

  • Rigidity

Pipe is unyielding and cannot be shaped without the use of specialized tools. Tubes can be shaped with considerable effort, with the exception of copper and brass. Tubing can be bent and coiled without causing severe deformation, wrinkling, or breaking.

  • Applications

Tubes are employed in applications that need a precise outer diameter, such as medical equipment. The outer diameter is significant because it indicates how much weight it can support as a stability element. Pipes are used to transfer gases or liquids, therefore knowing their capacity is critical. The pipe’s round form makes it effective at managing pressure from the liquid running through it.

  • Metal Forms

Tubes may be cold or hot rolled. Only hot rolled pipe is available. They may both be galvanized.

  • Sizing

Larger applications may be accommodated by size pipes. Tubing is often utilized in applications requiring tiny diameters.

  • Strength

Tubes are more durable than pipe. Tubes outperform other materials in situations requiring durability and strength.

Types of steel pipe fittings

Pipe fittings are constructed from a variety of steels, including:

  • Galvanized Steel: Galvanized steel is coated with layers of zinc by a chemical process to protect it against rust and corrosion. Galvanized steel is resistant to rust and corrosion and is widely used in the manufacture of pipe fittings and pipe. Galvanized steel also extends the life of pipe fittings. Galvanized steel fittings are offered in conventional diameters ranging from 8mm to 150mm. Galvanized pipe fittings are often made from seamless tube, forgings, rolling bar, or welded tube in accordance with particular specifications. Galvanized steel pipe fittings are used for all sorts of pipes inside a structure. They are also used in water distribution lines, but not in gas pipes.
  • Carbon Steel: Carbon steel is far more durable and stronger than other types of steel, making it ideal for the manufacture of pipe fittings. Carbon steel, often known as simple carbon steel, is a malleable iron-based metal that contains mostly carbon and trace quantities of manganese and other metals. Steel may be cast to shape or worked into different mill forms from which final products are made, forged, stamped, machined, or otherwise shaped. Carbon is the primary hardening and strengthening ingredient in steel, providing maximum hardness and strength but decreasing ductility and weldability. Carbon steel pipe fittings are available in a variety of sizes and forms. Again, there are certain butt-weld carbon fittings with beveled edges that produce a shallower channel for the bead of weld that holds the component together. Butt-weld fittings are primarily utilized to link pipe sections when permanent and welded connections are needed. Butt-weld steel fittings are used to make elbows, reducers, tees, and other similar items. Carbon steel fittings are used in pipe systems that transport liquids or gases such as oil, water, natural gas, or steam. Aside from that, carbon steel fittings are in great demand in residential construction, commercial construction, electric power generation, petroleum refining, shipbuilding, and other industrial-use industries.
  • Stainless steel: Because it is extremely resistant to oxidation and corrosion in a variety of natural and man-made settings, stainless steel is frequently utilized in the manufacture of pipe fittings. Stainless steel is a ferrous alloy that contains at least 10% chromium. It is critical to choose the correct grade of stainless steel for a certain application. Stainless steel is used in a variety of pipe fittings such as tees, unions, elbows, and so on. Household pipes are often fitted with stainless steel fittings.

Common Pipe Fittings

  • Bushings

Pipe bushings are used to connect pipes of varying diameters, often by decreasing a larger pipe fitting to a smaller pipe. Bushings are often threaded on both the inside and exterior. They take up extremely little space as compared to a coupling or union, both of which serve the same purpose of lowering downsizes. Use with a wrench and has a hexagonal head for enhanced leverage.

  • Elbows

If you need to alter the direction of flow, threaded or socket weld pipe elbows are typically employed. Elbows with 90- and 45-degree angles are the most prevalent. Elbows are a kind of fitting that is often used in plumbing. Street elbows include male and female threaded ends that make it simple to connect different pipes or fittings. Side outlet elbows with a bend serve like a tee. There are additional 22-1/2-degree elbows available.

  • Caps

Caps are available with female National Pipe Taper (NPT) threads in stainless steel 304 or 316 cast pipe fittings. To seal the termination of a male pipe. To halt flow, the cap fits over the end of a male pipe. They are also available with hex and square heads for enhanced leverage and use with a wrench during construction and disassembly.

  • Crosses

Cross pipe fittings are four-way fittings that are basically simply two tees combined. Many people will choose to wear two shirts instead.

  • Flanges

Pipes are joined using flanges. The pipe is threaded or welded to the flanges before being bolted together. Flanged connectors are often employed in high-pressure industrial applications.

  • Reducers/Reducing Couplings

Pipe couplings are used to extend the length of a pipe or to adjust the size of a pipe. When reduced, this is referred to as a bell reducer. Female threads or a socket weld are also options.

  • Nipples

A pipe nipple is a small length of pipe with a male pipe thread on one or both ends. It is used to join two other fittings. Pipe, hoses, and valves are all connected using nipples. Pipe nipples are often seen in low-pressure pipe systems.

  • Tees

Pipe Tees are T-shaped with two outputs at 90° to the main line connection. It’s a small section of pipe having a lateral exit. Pipe tees are used to join pipelines with a pipe that is at a right angle to the line. Tees are sized based on their run*. When the run of a tee is shorter than the side outlet*, the fitting is referred to as a “bull head.”

Run* refers to the horizontal or straight-through dimension of the fitting and the side outlet.

Side outlet* – the fitting’s “top,” 90 degrees off the run

  • Unions

Unions are a better option than couplings. Unions depend on their own nut to lock the pipe ends together. As a result, they are ideal for joining two permanent pipes that cannot be screwed into a standard connection. Unions also make future repairs simpler.

  • Valves

Valves are used to regulate flow pressures and rates.