This section provides an overview for seamless pipes as well as their applications and principles. Also, please take a look at the list of 10 seamless pipe manufacturers and their company rankings.
Table of Contents
A seamless pipe is a pipe without joints.
Steel pipes are generally manufactured by rounding steel plates into a cylindrical shape and welding them together. However, the presence of these joints can lead to major strength problems (e.g., crude oil leaking from the pipe) depending on the intended use.
Seamless pipes are manufactured using a process (e.g., Mannesmann method) that does not produce joints, which are the cause of strength reduction. Therefore, seamless pipes are used when high strength and reliability are required.
Seamless pipes are widely used to transport fluids such as gas, oil, and water.
There are also many types of seamless steel pipes, as there are also pipes for construction applications.
The materials and standards differ depending on the application, so it is necessary to select the seamless pipe that best suits the application.
Examples of specific applications include oil and natural gas facilities, boiler tubes in thermal power plants, and high-pressure piping for industrial machinery.
The "Mannesmann method" is a typical method for manufacturing seamless pipes, which will be explained in this section.
Simply put, the Mannesmann method forms pipes from round bars, not steel plates. Therefore, no joints are created.
In the manufacturing process, the material for the round bar shaped pipe, called billet, is heated at a high temperature to the point where it becomes bright red (about 1,300°C). When the billet is ready to be rolled, a tool called a plug (for seamless pipe inner diameter forming) is pressed against the center of the billet to form it into a pipe.
If the plug is pressed against the billet as it is, excess meat (billet that has lost its place) is pushed out of the billet and it will not be formed into a pipe shape, so a roll (cone or barrel type) is used to hold the outer circumference while forming. By doing so, excess meat is pushed forward and the outside shape can be formed while the inside diameter is formed.
The Mannesmann method is the most productive method for manufacturing seamless pipes. Other methods are extremely unproductive.
In general, the surface properties of the billet may be inferior due to the harsh rolling process on the hot billet. Similarly, it is relatively easy to produce thick-walled products, where the load on the rolling process is lighter. In this context, there are companies that specialize in thin-wall processing despite their seamless piping. Keep in mind that there are small-diameter seamless pipes with ultra-thin thicknesses such as 0.08 mm, as well as large-diameter seamless pipes in the 426.0 mm diameter size.
The difference between seamless and welded pipes is the use of welding in the pipe manufacturing process. The reason why seamless pipe is needed in the first place is because of grooved corrosion.
This groove corrosion is a V-shaped corrosion that occurs at the welds (inside) of pipes. Because of the high temperatures at the welds of piping, the composition of the material changes. The difference in microstructure between the weld and the original base metal causes a potential difference, resulting in corrosion. Once corrosion occurs, grooves are formed and corrosion progresses at an accelerated rate, eventually reaching the surface of the pipe or leading to fluid leakage and pipe damage due to insufficient strength.
While seamless pipes are sometimes used to prevent groove corrosion, there are also welded pipes called groove corrosion-resistant steel pipes. This involves adjusting the molecular composition of the base metal (reducing sulfur content) and adding special elements to the weldment. In this way, groove corrosion is made less likely to occur. Although more expensive than ordinary piping, it is not as expensive as seamless pipe, and is widely used as piping for liquids (such as water) where there is no danger of leakage.
This section describes the price difference between seamless pipes and welded pipes (ERW steel pipes are used here as an example). As an example, the material used here is SUS304. The price of a seamless pipe is about 1.5~2 times higher than that of an ERW pipe. The price difference is small when the pipe diameter is small, but the larger the diameter, the larger the price difference. In addition, the price of materials such as stainless steel, which is used for piping, also increases or decreases. Therefore, the price variation occurs depending on the time of the year. When purchasing, it is important to have a firm grasp of the most recent material price estimates, as well as past results.
The cost of piping alone is 1.5~2 times higher than the cost of a new pipe, so the price difference will not be that great when replacing part of the piping, but when constructing a new plant, the overall cost will vary greatly. Therefore, it is important to select appropriate piping according to the fluid to be handled to reduce costs.
*Including some distributors, etc.
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Ranking as of March 2023 in United States of AmericaDerivation Method
Derivation MethodThe ranking is calculated based on the click share within the seamless pipe page as of March 2023. Click share is defined as the total number of clicks for all companies during the period divided by the number of clicks for each company.
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