Automatic Welding Systems

Automatic welding systems enable various degrees of automation
of the girth welding process. The method combines well with others, such as manual and semi–automatic welding.

The degree of automation that is economically efficient depends
on the specifics of the project:

• its length, construction deadlines,
• diameter and wall thickness of pipe,
• the availability of qualified personnel, and other considerations.

CRC–Evans Automatic Welding Systems have been used
world–wide for about 30 years.

1. It is a well known fact that the first and most important factor
in providing for stable weld joint quality during automatic welding
is proper pipe end preparation.

In most CRC–Evans automatic welding systems this is achieved
by mechanically beveling the pipe ends with the aid
of a pipe facing machine.

Skilful end beveling has a direct relationship to weld quality and repeatability. Likewise it boosts productivity and cuts the amount
of weld metal required (at the same time cutting arc time and consumables consumption).

2. The second factor is to perform the root weld pass using
one of the technologies recommended by CRC–Evans:

• internal, using an internal welder
  (IWM — Internal Welding Machine);
• external, using an internal line–up clamp with built–in copper shoes;
• external, using a standard internal line–up clamp
  and STT Technology developed by Lincoln Electric.

3. The next step is the use of external welding heads to perform hot, fill and cap passes.

These heads are mounted on guide belts which surround the pipe.

When using the STT process for welding the root pass, no hot pass is required.

CRC–Evans has developed a wide range of external welders
for performing root, hot, fill, and cap passes.

The highest degree of automation of the welding process is achieved by using

• an internal line–up clamp, which has an onboard welding system to perform the root pass,
• and external welders, which make the fill and cap passes.

All welding is performed using the MIG process.

The advantages of organizing automatic welding as shown above are obvious especially in fairly large projects with distances of 50 km or more to weld
and with pipeline diameters of 22" (558mm) or more.

Tens of thousands of kilometres of pipelines have been welded onshore and offshore literally from the Arctic to Antarctica using this technology. Welding records that have been set, for example 15 joints per hour on a 48" (1220 mm) land pipeline, do not truly push the limits of the possibilities of this system.

If an internal welder cannot be used or is impractical (for example for smaller diameters), a completely external automatic method may be employed.

High quality automatic welding of the root externally became possible
with the advent of STT technology.

By virtue of the combined efforts of CRC–Evans, the VNIIST Institute
in Moscow, Lincoln Electric, and Argus Limited, the technology has been developed, tested, and found a superb application in automatic welding systems.

Welding the root pass with STT technology gives a quality that matches TIG welding, and a significant improvement in welding speed.

MIG is far from being the only method that can be used for fill and cap passes.

Given wall thickness of 10 mm or less, a complete STT approach for the entire weld is recommended. This achieves technical uniformity of the process, and reduces the types of materials and equipment required, most importantly the welding machines.

As in semi–automatic welding, in the automatic process a combination of STT and Outershield processes may be employed. This combination provides a high weld deposition rate and, therefore, rapid closing of the weld joint with the required high mechanical characteristics.

CRC–Evans Automatic Welding systems lead the world
and feature the following advantages:

• Uniformly high quality welds from joint to joint over the entire length of pipeline construction;
• High weld deposition rates;
• Reduction in volume of wasted weld metal;
• Quality and stable mechanical properties in the weld joint;
• Assured stable weld quality despite minor errors by the welder;

• Unique possibilities to customize the equipment for each specific project given technical, cost and work organization requirements;
• No physical strain on the operator;
• Quick and easy to train and learn;
• Significant reduction of equipment and staff needed to weld large diameter, heavy walled pipe;
• Support and service anywhere in the world.