Pipe connection

It is safe to say that pipe connections are an essential part of pipelines all around the world. They ensure that whatever substance is travelling through the pipe has a continuous smooth flow.

Pipe connection is varied, the commonly used have Butt weld, Flanged, Threaded, Socket weld, Glued, Brazed and Grooved end.

Pipe connections have many uses; Among other things they help pipelines to be many miles long, help to change the direction of the flow, allow for maintenance to be carried out and for valves to be changed.

You assign connection types in the Connector Properties dialog box as you build fittings content using the Content Builder (see Adding Connectors to a Parametric Fitting). Assigned connection types are then displayed on the Connection Assignments tab of the Pipe Layout Preferences dialog box.

Unthreaded Connections are not threaded, must be either welded or bolted together. The following table shows the different orientations of pipe connection types:

Butt weld:
A butt weld is two pipes lined up with one another and welded along the contact edge to create a seal.

Fittings and pipe segments connect directly to each other.

Butt weld
No extra objects are added.

Flanged All types
A flange is a plate or ring that is attached to a pipe. Two flanged pipe then create a tight seal by being bolted together.
  • Fitting to pipe: Flanges are typically included on fittings. A separate flange is added to the pipe segment.
  • Pipe to pipe: A separate flange is added to each pipe end to create the connection.
  • Fitting to fitting: Fittings with inherent flanges connect directly to each other. No separate flanges are added to the connection.

Flange connections are very important in the petroleum and chemical industries, and bolts and nuts are an essential part of them.

The most common flange connections are:

  • ANSI which is an American standard
  • PN / DIN which is a European standard
  • JIS/KS which is a Japanese / Korean standard
  • In the UK you will find both ANSI and PN in use

In order to clamp two flanges to together, nuts and bolts are vital. The quantity required will be determined by the number of bolt holes in a flange, while the diameter and length of bolts is dependent of flange type and Pressure Class of flange.

In the petro and chemical industries Stud Bolts and Hex Bolts are most frequently used for flange connections. The Stud Bolt features a threaded rod with two robust hexagon nuts, while the Hex Bolt has a head with just one nut.

Stud Bolts:

  • Stud Bolt length is defined in ASME B16.5 standard.
  • The material qualities for studs are defined in the different ASTM standards, and are indicated by Grade.
  • ASTM A193 covers alloy and stainless steel bolting material for pressure vessels, valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications.
  • ASTM A194 covers a variety of carbon, alloy, and martensitic and austenitic stainless steel nuts. These nuts are intended for high-pressure or high-temperature service, or both.

Hex Nuts:

  • Hex nuts are defined in ASME B18.2.2
  • Depending on a customer specification, nuts must be both sites chamfered or with one side a washer-face.


Threaded, Socket weld, Glued, Brazed
The pipe is the male fitting and the socket is equivalent to a female fitting. To provide a tight seal it is best to line the outside of the pipe and the inside of the socket with a sealant.
  • Fitting to pipe: Pipe segments typically have inherent male ends, and fittings are typically female. The pipe inserts directly into the fitting.
  • Pipe to pipe: A female coupling is inserted between the pipe segments.
  • Fitting to fitting: Fittings connect directly to each other.

Threaded – or screwed – connectors are used regularly to connect pipes when water, steam and other various fluids and gases need to be transferred from one place to another. A risk with threaded connectors is if they are over-tightened which means then they can be damaged and thus be very difficult to separate.

The most common threaded connections are BSP & NPT:

– BSP stands for ‘British Standard Pipe’ and is a British standard. There are two types of BSP threaded connectors – parallel (BSPP) and taper (BSPT). BSPP is mainly used in the UK, Europe, Asia, Australia, New Zealand and South Africa. BSPT is mainly used in China and Japan. Both of these threads feature the same pitch, the same angle (55 degrees) and the same shape (rounded peaks and valleys).

– NPT stands for ‘National Pipe Thread’ which is an American standard. NPT threads are typically tapered. Both threads have the same pitch, shape (flat peaks and valleys) and angle (60 degrees). These threaded connectors can be used without sealant due to the taper itself, but this also depends upon the material it is made from.

Socket welds require a pipe and socket connection.

Grooved end
A grooved end fitting has a groove or shoulder along the edge. This fittings groove allows for a seal without the need for welding.
  • Fitting to pipe: Fittings and pipe segments are considered to have grooved ends that are ready to accept a coupling. A coupling is added to connect the fitting and pipe.
  • Pipe to pipe: A coupling is added to connect the pipe segments.
  • Fitting to fitting: A coupling is added to connect fittings.



The Piping domain includes a connection type called Same Connection. When Same Connection is configured for a pipe object that is attached to a hub, connector 1 inherits the connection type of the connection type on connector 2 of the attached hub.

Weled steel pipe specification, Standard and identification

Welded steel pipe (steel pipe manufactured with a weld) is a tubular product made out of flat plates, known as skelp, that are formed, bent and prepared for welding.