Welding & Joining Technology: Pipe Welding

Technical Piping 

Video playlist on technical piping fundamentals for welders and mechanical engineering industries

Pipe Welding Videos 

Playlist of pipe welding videos from weld.com

Pipe fabrication Institute 

The Pipe Fabrication Institute's promotes the Standard of Excellence in the Pipe Fabrication Industry worldwide

Pipe Welding

Pipe welding or pipe fabrication is a method where two pipes are joined together. This process is achievable through different welding methods like Arc Welding, MIG Welding, TIG welding, and several other welding techniques.

Categories of Piping

Low-pressure or light structural piping: considered noncritical may be used to carry water, noncorrosive or noncombustible chemicals, and other nonhazardous materials used in industry. 

Medium-pressure piping is used for low-pressure steam heat, corrosive or flammable chemicals, waste disposal, ship plumbing, and mediumservice to heavy-service structural items such as highway signs, railings or light posts, trailer axles, and equipment frames or stands.

High-pressure piping systems are used for critical applications such as high-pressure steam, radioactive materials, the Alaskan pipeline, fired or unfired boilers, and refinery reactor lines.

Pipe welding is performed with either E6010 or E6011 electrodes for the complete weld, or these electrodes are used for the root pass, and E7018 electrodes are used to complete the joint. Pipe welding can also be done using the E7018 electrode for the entire weld

Preparation: 

• preparation of the pipes begins with ensuring that the edges to be joined are smooth and uniform. This can be done through a surface grinding procedure to get the edges right
• clean any form of lubricants, oils or other contaminants present on the pipe surface

Alignment:

• Align parts to the right position before welding. hold the two pipes togethre with clamps if need be.

 Horizontal rolled 1G—The pipe is rolled either continuously or intermittently so that the weld is performed within 0° to 15° of the top of the pipe

  Horizontal fixed 5G—The pipe is parallel to the horizon, and the weld is made vertically around the pipe

● Vertical 2G—The pipe is vertical to the horizon, and the weld is made horizontally around the pipe

● Inclined 6G—The pipe is fixed in a 45° inclined angle, and the weld is made around the pipe
  Inclined with a restriction ring 6GR—The pipe is fixed in a 45° inclined angle, and there is a restricting ring placed around the pipe below the weld groove

Pipe welding has a higher level of standards compared to other welding processes. Weld quality is of high priority, however the surface of the pipe on both sides of the weld is also important. No arc strikes should be made on this surface. Arc strikes outside of the weld groove are considered to be defects by much of the pipe welding industry

Root weld pass: A root weld is the first weld in a joint. It is part of a series of welds that make up a multiple pass weld. The root weld is used to establish the contour and depth of penetration.

• The root face is the part of this weld pass that must be smooth and uniform
• Weld face does not have to be smooth or uniform. Can be fixed by grinding out.

Hot weld pass: Used to quickly burn out small amounts of slag trapped along the edge of the root pass. This is slag that cannot be removed easily by chipping or wire brushing. The hot pass can also be used to reshape the root pass by using high current settings and a faster-than-normal travel speed. 

Filler weld pass(es): The filler pass(es) may be either a series of stringer beads or a weave bead. Stringer beads require less welder skill because of the small amount of metal that is molten at one time. 

Cover weld pass(es): The final covering on a weld is referred to as the cover pass or cap. It may be a weave or stringer bead.