A fitting is a weldable pipe fitting that allows for change of direction of flow, to branch off, reduce pipe size or attach auxiliary equipment. Pipe fitting is the occupation of installing or repairing piping or tubing systems that convey liquid, gas, and occasionally solid materials.

Butt weld pipe fittings

Butt weld pipe fittings allow for changing the direction of flow, reducing pipe sizes and attaching auxiliary equipment.

Pipe flanges

Pipe flanges are basically plates or rings used to connect pipes, valves and other piping equipment to form a piping system.

General standard of fittings

Pipe fitting is work that involves the installation or repair of pipes or tubes.


Even welding and smooth weld line, can be substitute for seamless tube after drawing and cold rolling.

ASME B16.9

This Standard covers overall dimensions, tolerances, ratings, testing, and markings for wrought factory-made buttwelding fittings in sizes NPS 1 ⁄ 2 through 48 (DN 15 through 1200).

Fittings may be made to special dimensions, sizes, shapes, and tolerances by agreement between the manufacturer and the purchaser.

ASTM A234/ SA234M

ASTM A234/ SA234M Standard specification for pipe fittings of wrought carbon steel and alloy steel for moderate and high temperature service.

These fittings are for use in pressure piping and in pressure vessel fabrication for service at moderate and elevated temperatures.

Carbon steel pipe fittings production process

Buttweld Fittings manufacturing process includes a series of steps like Annealing, Straightening, Pickling & Passivation and Polishing.

How a Butt Weld Fitting is Made?

A butt weld pipe fitting is made by the process of hot forming that includes bending and forming to shape. The starting material of butt weld fitting is a pipe that is cut to length, heated and molded into specific shapes by means of dyes. Heat treatment is also done to remove residual stresses and obtain desired mechanical properties.

These fittings are produced using latest technology, ensuring excellent strength and long service life. The process needs a lesser amount of heat treatments to ensure better physical properties.

The series of steps involved in the manufacturing Process of Buttweld Fittings are given in a detailed view below:

Annealing :

Annealing is also known as heat treatment, which plays an active role in the production. In this step, the tubes are carried out in fully automated and conveyor to heat them at certain temperature. Once the tubes get heated, they immediately quench in water.

Straightening :

The tubes are straightened with the help of straightening machine to provide a high degree of straightness in this step.

Pickling :

The process of Pickling refers to the removal of high temperature scale and adjacent low chromium layer of metal from the surface of stainless steel.

Passivation :

Passivation is the process of treating the surface of stainless steels in order to eliminate the contaminants from the metal. The process also helps in promoting the formation of a continuous passive film on a freshly created surface.

Polishing :

The final step, is named as Polishing that reflects the wonderful quality, high aesthetic & hygienic value and high durability of buttweld fittings. Polishing is a essential step to gain excellent features for meeting the varied demands of clients.

Pipe Fitting sizes and dimensions

Pipe fitting dimensions are in either metric or Standard English. Because pipe fitting covers Pipe Fitting Dimensions several aspects, only the most common pipe fitting sizes can be given here.

How are pipe fittings measured?

Pipe fittings are measured by their diameter, wall thickness (known as “schedule”), and shape or configuration. (Fittings are also defined by their material grade and whether they are welded or seamless.)

Diameter refers to outside diameter of a pipe or fitting.

The North American standard is known as Nominal Pipe Size (NPS). The International Standard is known as Diameter Nominal (DN). Pipes and fittings are actually made in similar sizes around the world: they are just labeled differently.

From ½ in to 12 inch “Nominal Pipe Size”, outside diameters are slightly larger than indicated size; inside diameters get smaller as schedules grow.

From 14 in and larger “Nominal Pipe Size”, outside diameters are exactly as indicated size; inside diameters get smaller as schedules grow.
As with other North American standards (inch, foot, yard, mile, …), many pipe standards (diameters up to 12 inch and wall thickness) are based on historical precedents (a toolmaker’s dies during US Civil War) rather than a “scientific” method.

Schedule Numbers

The schedule numbers are used by the ANSI (American National Standards Institute) to denote wall thickness. The schedule numbers encompass all pipe dimensions beginning at NPS 1/8” up NPS 36”. Note that this configuration is only for fittings that match with a particular ANSI schedule number.

Nominal Pipe Size (NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures.

  • Schedule, often shortened as sch, is a North American standard that refers to wall thickness of a pipe or pipe fitting. Higher schedules mean thicker walls that can resist higher pressures.
  • Pipe standards define these wall thicknesses: SCH 5, 5S, 10, 10S, 20, 30, 40, 40S, 60, 80, 80S, 100, 120, 140, 160, STD, XS and XXS. (S following a number is for stainless steel. Sizes without an S are for carbon steel.)
  • Higher schedules are heavier, require more material and are therefore more costly to make and install.

What does “schedule” mean for pipe fittings?

Schedule, often shortened as SCH, is a North American standard that refers to wall thickness of a pipe or pipe fitting.

What is schedule 40, SCH80?

Higher schedules mean thicker walls that can resist higher pressures.

Pipe standards define these wall thicknesses: SCH 5, 5S, 10, 10S, 20, 30, 40, 40S, 60, 80, 80S, 100, 120, 140, 160, STD, XS and XXS.
(S following a number is for stainless steel. Sizes without an S are for carbon steel.)

Higher schedules are heavier, require more material and are therefore more costly to make and install.

Why are fittings sometimes thicker and heavier than pipes to which they are connected?

Fittings are sometimes thicker than their connecting pipes to meet performance requirements or due to manufacturing reasons.
Due to fitting geometry, stress is very different when compared to a pipe. Using extra material is often necessary to compensate for such additional stress, especially for tees and tight curve elbows.
Fitting manufacturers may not always stock plates or pipes for all metal grades or sizes. When responding to an order, manufacturers always use the right metal or alloy, but sometimes made with next-higher available plate or pipe size while still respecting specified inside diameters.

Fitting standards and certifications

In pipe fittings as well, standards play a vital role. The manufacture and installation of pipe fittings is tightly regulated by various standards and codes.

Who decides on standards and specifications for butt weld fittings ?

Manufacturers of butt weld pipe fittings have to meet specifications and requirements of many organizations, to assure quality, compatibility and performance of their products.

Key national and international standards organizations focus on materials and end-user industries, including American Society for Testing and Materials (ASTM), American Society of Mechanical Engineers (ASME), International Organization for Standardization (ISO), Norway’s NORSOK, …

Some international organizations also focus on quality standards across all industries, such as International Organization for Standardization (ISO).
Large industrial end-users also have their own programs to certify individual manufacturing plants as meeting their criteria to be listed on their Approved Manufacturers List (AML).

All these certifications and approvals are valid for a specific period, and must be renewed regularly.

Types of pipe fitting standards:

Some widely used pipe fitting standards are as follows:

ANSI: The American National Standards Institute

ANSI is a private, non-profit organization. Its main function is to administer and coordinate the U.S. voluntary standardization and conformity assessment system. It provides a forum for development of American national standards. ANSI assigns "schedule numbers". These numbers classify wall thicknesses for different pressure uses.

ASME: American Society for Mechanical Engineers

This is one of the reputed organizations in the world developing codes and standards. The schedule number for pipe fitting starts from ASME/ANSI B16.

The various classifications of ASME/ANSI B16 standards for different pipe fittings are as follows:

ASTM International: American Society for Testing and Materials

This is one of the largest voluntary standards development organizations in the world. It was originally known as the American Society for Testing and Materials (ASTM). This is a reputed scientific and technical organization that develops and publishes voluntary standards on the basis of materials, products, systems and services. This is a trusted name for standards. The standards covered by this organization covers various types of pipes, tubes and fittings, especially made of metal, for high-temperature service, ordinary use and special applications like fire protection. The ASTM standards are published in 16 sections consisting of 67 volumes.

AN: Here, "A" stands for Army and "N" stands for Navy

The AN standard was originally designed for the U.S. Military. Whenever, a pipe fitting is AN fittings, it means that the fittings are measured on the outside diameter of the fittings, that is, in 1/16 inch increments. For example, an AN 4 fitting means a fitting with an external diameter of approximately 4/16" or ¼". It is to be noted that approximation is important because AN external diameter is not a direct fit with an equivalent NPT thread.

BSP: British Standard Pipe

BSP is the U.K. standard for pipe fittings. This refers to a family of standard screw thread types for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread. This has been adopted internationally. It is also known as British Standard Pipe Taper threads (BSPT )or British Standard Pipe Parallel (Straight) threads (BSPP ). While the BSPT achieves pressure tight joints by the threads alone, the BSPP requires a sealing ring.

DIN: Deutsches Institut für Normung
This refers to the industrial pipe, tube and fittings standards and specifications from the DIN, Deutsches Institut für Normung which in English means the German Institute for Standardization. DIN is the German national organization for standardization and is ISO member body for that country.

DIN standard designation
The designation of a DIN standard shows its origin where # symbolizes a number:

Dash (-) size

Dash size is the standard used to refer to the inside diameter of a hose. This indicates the size by a two digit number which represents the relative ID in sixteenths of an inch. This is also used interchangeably with AN fittings. For example, a Dash "8" fitting means an AN 8 fitting.
A standard hose guide is given below:

Hose Size In Nominal ID Inch Dash Size Standard Dash Size
1/4 3/16 -04
3/8 5/16 -06
1/2 13/32 -08
3/4 5/8 -12
1 7/8 -16
1 ½ - -
1 ¼ 1 1/8 -20

ISO: International Organization for Standardization
ISO is the industrial pipe, tube and fittings standards and specifications from the International Organization for Standardization. ISO standards are numbered. They have format as follows:

“ISO[/IEC] [IS] nnnnn[:yyyy] Title" where

JIS: Japanese Industrial Standards

This is the Japanese industrial standards or the standards used for industrial activities in Japan for pipe, tube and fittings and published through Japanese Standards Associations.

NPT: National Pipe Thread

National Pipe Thread is a U.S. standard straight (NPS) threads or for tapered (NPT) threads. This is the most popular US standard for pipe fittings. NPT fittings are based on the internal diameter (ID) of the pipe fitting.

What is an MTR ?

Material Test Reports (MTRs) are provided by manufacturers to certify physical properties and metal grade or alloy for each fitting, flange, pipe, or valve. This MTR is essential for demanding applications (pressure, temperature, corrosion, abrasion,…)

Chemical Analysis(%) For Part Standard
Standard Grade C Si Mn P S V Nb Ti Cr Mo Ni Al Nb N Others
max max max max max max max max max max max max max max max
0.04–0.09 W 1.5–2.00 B
ASTM A420/A420M
Steel No. Type Chemical composition
C Si S P Mn Cr Ni Mo Other ób ós δ5 HB
WPL6 0.3 0.15-0.3 0.04 0.035 0.6-1.35 0.3 0.4 0.12 Cb:0.02;V:0.08 415-585 240 22
WPL9 0.2 0.03 0.03 0.4-1.06 1.6-2.24 435-610 315 20
WPL3 0.2 0.13-0.37 0.05 0.05 0.31-0.64 3.2-3.8 450-620 240 22
WPL8 0.13 0.13-0.37 0.03 0.03 0.9 8.4-9.6 690-865 515 16
ASTM A815/A815M
Steel No. Standard No. Type Chemical composition
C Si S P Mn Cr Ni Mo Other ób ós δ5 HB
UNS S31803 ASTM A815/A815M 0.03 0.1 0.02 0.03 2 21-23 4.5-6.5 2.5-3.5 N:0.08-0.2 620-795 450 25 290
ASTM A105/A105M
Steel No. Type Chemical composition
C Si S P Mn Cr Ni Mo Other ób ós δ5 HB
A105 0.35 0.1-0.35 0.04 0.035 0.6-1.05 0.3 0.4 0.12 V:0.05;Nb:0.02 485 250 22 187 ψ%:30
ASTM A182/A182M
Steel No. Type Chemical composition
C Si S P Mn Cr Ni Mo Other ób ós δ5 HB
F11 CL1 0.05-0.15 0.5-1 0.03 0.03 0.3-0.6 1-1.5 0.44-0.65 415 205 20 121-174 ψ%:45
F11 CL2 0.1-0.2 0.5-1 0.04 0.04 0.3-0.8 1-1.5 0.44-0.65 485 275 20 143-207 ψ%:30
F11 CL3 0.1-0.2 0.5-1 0.04 0.04 0.3-0.8 1-1.5 0.44-0.65 515 310 20 156-207 ψ%:30
F12 CL1 0.05-0.15 0.5 0.045 0.045 0.3-0.6 0.8-1.25 0.44-0.65 415 205 20 121-174 ψ%:45
F12 CL2 0.1-0.2 0.1-0.6 0.04 0.04 0.3-0.8 0.8-1.25 0.44-0.65 485 275 20 143-207 ψ%:30
F304 0.08 1 0.03 0.045 2 18-20 8-11 N:0.1 515 205 30 ψ%:50
F304H 0.04-0.1 1 0.03 0.045 2 18-20 8-11 515 205 30 ψ%:50
F304L 0.035 1 0.03 0.045 2 18-20 8-13 N:0.1 485 170 30 ψ%:50
F316L 0.035 1 0.03 0.045 2 16-18 10-15 2-3 N:0.1 485 170 30 ψ%:50
F317 0.08 1 0.03 0.045 2 18-20 11-15 3-4 515 205 30 ψ%:50
F321 0.08 1 0.03 0.045 2 17-19 9-12 Ti:5C%-0.7 515 205 30 ψ%:50
F347 0.08 1 0.03 0.045 2 17-20 9-13 Ti:10C%-1.1 515 205 30 ψ%:50
Steel No. Standard No. Type Chemical composition
C Si S P Mn Cr Ni Mo Other ób ós δ5 HB
B ASTM A53/A53M 0.3 0.045 0.05 1.2 0.4 0.4 0.15 V:0.08 415 240 See sdandard
Steel No. Type Chemical composition
C Si S P Mn Cr Ni Mo Other ób ós δ5 HB
B 0.3 0.1min 0.035 0.035 0.29-1.06 0.4 0.4 0.15 V:0.08 415 240 22
C 0.35 0.1min 0.035 0.035 0.29-1.06 0.4 0.4 0.15 V:0.08 485 270 20
ASTM A312/A312M
Steel No. Type Chemical composition
C Si S P Mn Cr Ni Mo Other ób ós δ5 HB
TP304 0.08 0.75 0.03 0.04 2 18-20 8-11 515 205 35
TP304H 0.04-0.1 0.75 0.03 0.04 2 18-20 8-11 515 205 35
TP304L 0.035 0.75 0.03 0.04 2 18-20 8-13 485 170 35
TP316L 0.035 0.75 0.03 0.04 2 16-18 10-15 2-3 485 170 35
TP321 0.08 0.75 0.03 0.04 2 17-20 9-13 Ti:5C%-0.7 515 205 35
ASTM A515/A515M
Steel No. Type Chemical composition
C Si S P Mn Cr Ni Mo Other ób ós δ5 HB
60 0.24 0.13-0.45 0.035 0.035 0.98 415-550 220 25
65 0.28 0.13-0.45 0.035 0.035 0.98 450-585 240 23
70 0.31 0.13-0.45 0.035 0.035 1.3 485-620 260 21

Tensile Property For Part Standard
StandardGradeYield Strengh(Mpa)Tensile Strengh(Mpa)Hardness

Important Points for selecting best carbon steel fittings

If you have a new industrial project which includes pipe installation, you would want to select best material for laying down the pipes, elbows, flanges etc. In this context it would be useful to keep in mind a few of the following points:

  • Evaluate the magnitude of the project
  • Understand the scale of the implementation
  • Enumerate the liquids or gases the pipes are going to carry
  • The desired age or longevity of the structure

These pointers will help u decide which metal to choose to lay down the pipes. Usually, steel is a popular choice, considering its characteristics. Additionally, in order to enhance the characteristics of steel, carbon or chrome is used. So, the carbon steel fittings become the perfect choice for industrial projects. The major benefits of using these carbon steel pipe fittings are:

  • Robustness to the product.
  • More the carbon, more the durability.
  • Improve the strength without losing the shape.
  • The proportion of carbon to steel can be morphed.
  • Rust resistant.

Also with carbon steel pipe fittings,There is a wide variety of flanges available in the market today. However, making the right choice of flange to the right project becomes critical ss per the project requirements.weld neck flanges are good choices, If the project demands high temperatures or sub zero temperatures.

This flange provides extra reinforcement.The flange fits perfectly into the internal diameter of the pipe and this helps to avoid all hitches in the flow of desired substances through the pipes.

Thus, having a good knowledge of pipes as well as flanges that suit the requirements of a particular project, help you to select better material. This choice is critical for the perfect implementation of the project and durability, effectiveness and longevity of the implementation.Additionally, using the right kind of pipes and flanges during project implementation helps the project to pass the quality, efficiency as well as safety parameters.

How a Butt Weld Fitting is Made?

There are numerous processes for manufacturing butt weld fittings, several examples listed as follows.

Extrusion method (Hot Forming)

The hot-extrusion process consists of enclosing a piece of metal, heated to forging temperature, in a chamber called a "container" having a die at one end with an opening of the shape of the desired finished section, and applying pressure to the metal through the opposite end of the container.

Mandrel method (Hot Forming)

One of the most common manufacturing methods for manufacturing Elbows from pipes. After heating the raw material, it is pushed over a die called "mandrel" which allows the pipe to expand and bend simultaneously.

Deep Drawing method

One of the most common manufacturing methods for caps, where plate is cut out in a circle and formed by deep drawing.

End connections

There are four different type of connections that are used for fittings:

  • Butt Weld Fittings – Probably the most common type of fitting. They are easily manufactured and are easily installed. Butt weld fittings can be connected directly to each other. This is called fitting make up.
  • Flanged Fittings – Flanged fittings are piping components where the flange is an integral component of the fitting. These are most often used in water treatment applications or lined piping where welding would be destructive to the liner.
  • Socket Weld Fittings – These fittings have a socket weld connection on each end. They might be used for smaller diameter piping. These fittings utilize a single fillet weld to join the piping with the fitting.
  • Threaded Fittings – Threaded fittings are generally four inches and smaller. The reason for this size constraint is the pipe end needs to be threaded with a male type connection and die sizes are unobtainable in the larger diameters.
Fitting Weights
ASME buttweld fitting specifications do not specify weights for fittings.

Weights quoted in the tables on this page are based on manufacturers information and should be considered as approximate and provided as a guide only (fitting weights can vary considerably between manufacturers due to differences in construction).

Three groups:

Fittings are divided into three groups:

  • Buttweld (BW) fittings whose dimensions, dimensional tolerances et cetera are defined in the ASME B16.9 standards. Light-weight corrosion resistant fittings are made to MSS SP43.
  • Socket Weld (SW) fittings Class 3000, 6000, 9000 are defined in the ASME B16.11 standards.
  • Threaded (THD), screwed fittings Class 2000, 3000, 6000 are defined in the ASME B16.11 standards.

Fittings applications and markets

Pipe and pipe fittings go hand-in hand. Just as pipes are used for a variety of residential, public and industrial applications, so also the pipe fittings. No pipes can be connected without the use of proper fittings and flanges. Pipe fittings allow pipes to be installed and connected or joined where necessary and terminated in the right place.

Such as Oil and gas industries, Midstream, Shipbuilding, Power plants, Food plants, Pharmaceuticals, etc.

Pipe fittings include a wide range of products in various shapes, sizes and materials. With rapid developments in the field of industrial fittings and continuous research work in this industry, various new products are manufactured. Some fittings have certain special features so that they can be fabricated on different principles like hydraulics, pneumatic depending on the end usage. Fittings include a comprehensive range of products depending on various applications in which they are applied.

Fittings are used wherever liquids, gases, chemicals and other fluids are created, processed, transported, or used.

There is no end to applications of pipe fittings so long there is no end to the applications of pipes . While the list of piping applications continues to expand, its strength, flexibility, very good flow rates and high chemical resistance are qualities which are uniquely suited for the movement or transfer of liquids, steam, solids and air from one point to another.

With piping, pipe fittings have many other uses like as follows:

  • The transfer of extremely hazardous materials such as chemical and waste.
  • Protection of sensitive equipment from high pressures.
  • Protection from corrosion and other extreme weather conditions.
  • Resistance to household and industrial chemicals.
Considering the various purposes of pipe fittings, these pipe fittings are used in various industries like:
  • Chemical / Petrochemical
  • Municipal
  • Food, Beverage, and Dairy
  • Oil and Gas
  • Power
  • Process Instrumentation
  • Pulp and Paper
  • Semiconductor
  • Marine & dredging
  • Sanitation

The regular fittings of A234 WPB pipe fittings are elbows, tees, reducers, caps, cross.

Fitting specification, Standard and identification

There are different varieties of pipe fittings made of various materials and available in various shapes and sizes.