Steel Pipes

What is steel pipe called?

The two most common types of pipes are welded pipe and seamless pipe. Both are available in carbon steel and stainless steel. Welded pipe is also called ERW (Electric Resistance Welded) pipe. Most common specification for welded carbon steel pipe is A53.

How Pipe is Measured?

Pipe is generally identified by "Nominal Pipe Size" (NPS), with the wall thickness defined by "Schedule" (SCH). NPS is dimensionless designator and is an indication of a size but not an actual size. This is confusing for many people new to the piping industry. NPS 1/8 through NPS 12 has an outside diameter that is defined by the ansi pipe sizes. Generally speaking, a schedule 40 pipe dimension for up to 12 NPS is roughly equal to the ID of the pipe. Pipe sizes 14 and above are less confusing as a 14 NPS is equal to 14" OD (outer diameter).

Pipe Size Chart

ASME B 36.10 has more details of pipe sizes. The industry norm for pipe size also varies between different types of pipe. For a standard pipe, a 4.5" OD pipe will be referred to as 4" NPS however for line pipe and OCTG, it will be referred to as 4.5" only. Wall thickness is also mentioned differently. For standard pipe, pipe schedule is used to designate wall thickness. However line pipe is almost always referred by wall thickness whereas OCTG is referred by weight per foot.

Weight of Pipe

Weight of pipe is measured in pounds per foot or kilograms per meter. One should remember that weight of pipe in the ansi pipe size chart is "theoretical" weight and not an actual weight. Actual weight will vary based on the tolerance of pipe size.

Formula to calculate weight of steel pipe is;

W = [{OD-WT} x WT] x 10.69

W = Weight per lineal foot

OD = Outer Diameter

WT = Wall Thickness

Pipe Manufacturing

Steel pipe is grouped in two main categories;

Welded Pipe

Seamless Pipe

There are four main methods of producing metal pipe:

Furnace Weld (FW). Also called Continuous Weld

Electric Resistance Weld (ERW)

Submerged Arc Weld (SAW), also DSAW

Seamless (SMLS) method

Steel Pipe Material

Metal Pipes are available in following material grades;

A106B/A53B/API 5L-X42/API 5L B

Stainless Steel  304

Stainless Steel 316

Super Stainless A20

Duplex Stainless D2205

Nickel Alloy A200

Nickel Alloy A400

Nickel Alloy A600

Stainless Steel Pipe

Stainless steel is iron based alloy containing a minimum of 16% chromium. Nickel is another important alloying element in stainless steel pipe. Stainless Steel pipes are highly resistant to corrosive media and to oxidation at almost any temperature.

Stainless steel welded and seamless pipes are used for variety of reason such as to resist corrosion, preform at high temperature, for clean look and low maintenance cost. The most important aspect for stainless steel pipe is its inherent material characteristics that allows much thinner walls to be created such as sch 5, sch 10 without compromising the structural integrity of the pipe. The use of fusion welding to join pipe also eliminates the need for threading.

Type 304 stainless steel pipe is mostly used for general corrosive resistant application. it is used in chemical plants, refineries, paper mills and food industries. 304SS pipe has maximum carbon content of 0.08%. It is not recommended for use in the temperature range between 800 deg F and 1650 deg F due to carbide precipitation at the grain boundaries. Type 304L is the same as 304 except that it has a 0.035% maximum carbon content.

Type 316SS pipe is much more resistant to pitting than other chromium nickel alloys due to the addition of 2-3% molybdenum. It is useful in applications with acids, brines, sulphur water, sea water and with hologen salts. 316L stainless steel pipe, like 304L,  has a max carbon content of 0.035%.

Welded Stainless Steel Pipe is made to specification ASTM A312 and A358. A312 is the most common spec for stainless steel pipe. Welded stainless pipe is made from 1/8" to 24" NPS.

Seamless Stainless Steel Pipe is made to specification ASTM A312 and A376. A312 is also the most common spec for seamless stainless steel pipe. Seamless stainless pipe is made from size 1/8 to 14" nominal

Steel Pipe Country of Origin

Steel pipe is made by mills all around the world and traded in different countries. Some of the big names in the pipe industry are US Steel, ArcelorMittal, Nippon Steel, Nucor Corp, Hyundai Steel, ThyssenKrup, Vallourec, Hebei Iron and Steel Group, Posco, Jiangsu Shagang, Ulma Piping, Shultz USA and Webco etc.

Q&A Steel Pipe

Trupply sells a large variety of welded and seamless pipe. Based on our years of experience, the following are main questions or key points customers inquire about;

Steel pipe is sold by nominal pipe size and schedule. It is important to mention both

A106 B is the most common seamless pipe specification. Most customers just know they want A106B pipe and it simply implies they want carbon steel seamless pipe as per A106B. A106 is NOT a specification for stainless steel pipe

Pipe sizes 10 inch and above do NOT correlate directly with schedule number. Such as SCH 40 and SCH 80 does NOT always mean Standard and Extra Heavy respectively. Refer to pipe chart to make sure you are ordering the correct wall thickness

A53 grade B is the most common specification of welded pipe. It just means a pipe that has been produced by ERW process.

Welded pipe does NOT have a weld seam inside or outside. Welded pipe is produced by electric resistance welding and the seam has been taken out during manufacturing process

Pipe sizes smaller than 2" are available in continuous weld pipe, also know as A53 grade A.

Stainless Steel pipe is available in both welded and seamless configuration and in 316 and 304 material grade. Other stainless grades are also available but are less common

Stainless steel pipe is also very common in schedule 10 which is a thin wall.

Stainless steel pipe schedules are specified by "s" after the schedule number such as Sch 10s, Sch 40s, Sch 80s.

Stainless steel pipe schedules do NOT always correlate with carbon steel pipe schedules. Check ansi pipe chart for proper determination of schedule number and wall thickness

Pipes are mostly sold by SRL (single random length) or Double Random Length (DRL). SRL means pipe will be usually between 17 ft and 24 ft. DRL usually means pipe will be 37 ft to 44 ft.

Majority of pipe sold have lacquer finish. If you want bare pipe, please specify at the time of ordering

Epoxy coating of pipe can be done upon request.

Most common pipe end type is plain end or beveled end. Threaded ends are also available upon request