Table of Contents
Introduction of Pipeline Welding:
Joining of unifom pipes by welding process is known as pipeline welding. Diameter and material of all the pipes in a pipeline are same. Pipeline welding is a critical job and should be performed by skilled workers.
Pipe welding and pipeline welding are two different things. Pipe welding refer to uniform or non-uniform diameter pipes welding together for small distance. While, Pipeline welding is a process in which lots of same diameter and same material pipes joined together to make a pipeline.
Pipelines are very important in modern industry where fluid transported from one place to another via pipelines. Pipelines are used to transfer various types of fluids such as hydrocarbons, water, and sewage.
Pipeline welding should be performed as per various ASME welding codes such as B 31.4, B 31.8, ASME BPVC, etc.
Pipeline Welding Methods:
- Shielded Metal Arc Welding
- Gas Metal Arc Welding
- Flux-Cored Arc Welding
- Submerged Arc Welding
- Gas Tungsten Arc welding
Let’s know more about above mentioned pipeline welding methods.
1. Shielded Metal Arc Welding
This type of welding also called as Stovepipe welding. In this type of welding, the pipelines are welded by melting the electrodes with the heat generated by an electric arc. No of welding passes depend on the pipe thickness, electrode size,
welding position, and the current used for pipeline welding. The basic thumb rule for pipeline welding by Shielded Metal Arc Welding is to consider one pass for each 1/8 inch(3.2 mm) of pipe thickness. Electrode diameters for Shielded Metal Arc Welding pipeline welding normally vary from 1/8 inch to 3.16 inches (3.2 mm to 4.8 mm).
The key benefit of shielded metal arc welding is that the welding equipment is simple and portable. There is no flux or shielding gases are needed during welding. However, the productivity by this method is less due to lower travel speed.
2. Gas Metal Arc Welding
Gas metal arc welding is fas compare to shielded metal arc welding. Welding variable must be controlled properly for high efficiency and quality work. Fuke generation should be low to achieve high efficiency. Gas metal arc welding cost is little higher.
3. Flux-Cored Arc Welding
Flux-cored arc welding is very popular in pipeline welding process. Semi-automated machine is used to perform welding. It does not required any external gas to perform the welding. Its efficiency also very high.
4. Submerged Arc Welding
on the modern pipeline industry, semi-automatic Submerged arc welding is used. The main advantage is arc is not visible and it provides the highest deposition efficiencies as compared to all other pipeline welding
techniques. Submerged arc welding provides best quality finished welding surface.
5. Gas Tungsten Arc Welding
Gas Tungsten Arc Welding also known as Tungsten Inert Gas Welding. In short form it is known as TIG welding. This type of welding is highly expansive. Tungsten electrode are used to produce high quality weld. TIG welding is very popular in piping industry. It gives high quality final finished surface. Critical joints also welded by TIG welding.
How to Do Pipeline Welding?
It is very important to know the correct procedure of pipeline welding. If you don’t have proper knowledge of pipeline welding then you can not perform the job in correct way.
Here is the step by step procedure of pipeline welding:
- Prepare the joint as per guidelines mentioned in the API 1104.
- End of both pipes should be cleaned . There should not be Undesirable moisture, paint, primer, rust, oil, varnish, and other coatings must be removed by cleaning the pipeline ends.
- Collect all the necessary information of welding given in the project welding specifications.
- Now, weld the root pass.
- Then, weld the hot pass.
- In the final stage, weld the cap passes.
- Check and repair defects.
How to Choose Correct Pipeline Welding Method?
It is very crucial to select right type of pipeline welding method. Pipes used in hydrocarbon pipelines may be very expensive. Various factors are considered while selecting welding method. They are:
- Material of pipes.
- Diameter of pipe.
- Thickness of pipe.
- Welding location.
- Welding cost.
- Difficulty of the process.
- Workers safety.
Conclusion
I hope you got some idea about pipeline welding. You should read various ASME welding codes such as B 31.4, B 31.8, ASME BPVC and API 1104. These codes contains all the specification and procedure related to welding.