How to choose seamless pipe or ERW pipe for oil and gas pipelines?

Depending on the specific requirements and usage scenarios of oil and gas pipelines, both seamless pipes and welded pipes can be used, but in some cases, it is recommended to use seamless pipes.

There are two benefits to using seamless pipes. First, the working pressure capacity of seamless pipe is 20% higher than that of ERW pipe. Unlike ERW pipe, the application of higher pressure levels with seamless pipe will not cause the pipe to fail or burst. Another more common reason for choosing seamless pipes is that they are less susceptible to intergranular corrosion. Unlike seamless pipes, the seam lines of welded pipes, especially the heat-affected zone or heat-affected weld zone, are affected at the grain boundaries due to sensitization. This promotes intergranular corrosion, which weakens the ERW pipe.

Difference between seamless pipe and ERW welded pipe:
The difference between seamless pipe and ERW welded pipe lies in the different manufacturing processes. Seamless pipe is made by hot rolling or cold drawing of steel billet, so its surface is smooth, without seams, and has high strength and good pressure resistance; while ERW welded pipe is welded by steel plates, and the welding joints will affect its strength and pressure resistance during the manufacturing process.

Advantages and disadvantages of seamless pipe and welded pipe:

1. Advantages of seamless pipe
Since seamless pipe has no seams, it has high strength and good pressure resistance, which is suitable for high pressure, high temperature and high quality requirements of pipelines. In addition, the inner wall of seamless pipe is smooth, which can improve the fluid transmission effect and is conducive to the transportation of high energy consumption media.

2. Disadvantages of seamless pipe
The manufacturing process of seamless pipe is long and there are more processes, so the cost of seamless pipe is always higher than that of welded pipe. Because the seamless pipe node is used to connect the pipe for too long, and it is difficult to detect the quality defects of seamless pipe, there are certain safety hazards in its use.

3. Advantages of ERW welded pipes
The manufacturing process of ERW welded pipes is relatively simple, with low cost, and can produce long lengths of pipes, which has obvious economic advantages. At the same time, the manufacturing process of welded pipes has less environmental pollution, and welded pipes can also be used in occasions where some medium and low temperature media are transported.

4. Disadvantages of ERW welded pipes
The weld joints of ERW welded pipes will affect their strength and pressure resistance, so caution should be exercised when used in certain high-demand occasions, such as gas pipelines that transport high-temperature and high-pressure gas sources. At the same time, the weld joints of welded pipes are also susceptible to corrosion and have certain flammability hazards.

Why does the oil and gas industry choose seamless pipes?
The use of seamless pipes is suitable for all high-pressure operations. In the oil and gas industry, the flow of media through the system exerts a strong force on the pipeline, especially at high temperatures. This strong force coupled with the increase in temperature will cause high stress on the pipeline. In the case of seamless pipes, their pressure bearing capacity is almost 20% higher, which makes them very suitable for use in the oil and gas industry.

Which pipeline is more suitable for natural gas pipelines?

For natural gas transportation, safety is the most important consideration. Considering the advantages and disadvantages of seamless pipes and welded pipes, the safety of seamless pipes is significantly higher than that of welded pipes. Therefore, it is recommended to use high-quality seamless pipes in key pipe sections, such as natural gas import pipelines, pipeline strings, branch pipelines, etc. In relatively flat pipe sections or some low-pressure transmission pipelines, such as city gas pipelines, welded pipes are also a viable option.

Read more: Seamless Steel Pipe Raw Material or ERW Pipe Grades and Specifications