20
February
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As industrial applications become increasingly complex, piping products and systems must evolve to meet these demands.
Among the various pipe manufacturing methods, the debate between electric resistance welded (ERW) and seamless (SMLS) steel pipe is a prominent one. Both methods have been in use for decades, with continuous advancements in their production processes. So, which one is the better choice?
A seamless steel pipe has no seams, as the name indicates and produced via hot rolling and cold rolling. A seamless pipe is formed by piercing a solid, near-molten, steel rod, called a billet, with a mandrel to produce a pipe that has no seams or joints. A welded pipe, on the other hand, is made by rolling of a steel coil to the required gauge thickness, a manufacturing procedure that leaves a seam on the pipe's body. Cutting the seams to the width that corresponds to the size of the pipe to be constructed is the next phase.
Seamless pipe starts as a solid steel cylinder known as a billet. While still hot, the billet is pierced through the center using a mandrel. The next step involves rolling and stretching the hollowed billet to the desired length, diameter, and wall thickness as specified by the customer.
Certain types of seamless pipes harden during the manufacturing process, eliminating the need for post-production heat treatment. However, others may still require heat treatment. It's important to consult the specifications of the specific seamless pipe type to determine whether heat treatment is necessary.
Welded pipe begins as a long, coiled steel ribbon known as a skelp. The skelp is cut to the desired length, forming a flat rectangular sheet. The shorter ends of the sheet will become the pipe's outer circumference, which can then be used to calculate the final outside diameter.
The rectangular sheets are passed through a rolling machine that curls the longer sides towards each other, forming a cylinder. In the ERW process, a high-frequency electrical current is passed between the edges, causing them to melt and fuse.
One advantage of ERW pipe is that it requires no fusion metals, and the weld seam is smooth and seamless, making it invisible to the touch. This contrasts with double submerged arc welding (DSAW), which leaves a visible weld bead that must be removed depending on the application.
Welded pipe manufacturing techniques have evolved significantly, with one key advancement being the shift to high-frequency electric currents for welding. Before the 1970s, low-frequency currents were used, but weld seams created with low-frequency currents were more prone to corrosion and failure.
Most welded pipe types require heat treatment after production to ensure strength and durability.
The distinction between ERW and seamless steel piping exists largely due to historical perceptions.
Welded pipe was traditionally considered weaker due to the presence of a seam, while seamless pipe, lacking this feature, was viewed as structurally superior and safer. While the weld seam does introduce a potential weak point, advancements in manufacturing and quality control have significantly improved welded pipe performance, ensuring reliability within specified tolerances. Conversely, a drawback of seamless pipe is the variability in wall thickness resulting from the rolling and stretching process, whereas welded pipe offers more consistent thickness due to its fabrication from uniform steel sheets.
Industry standards still reflect these historical views. Seamless piping remains a requirement for many high-pressure, high-temperature applications, such as those in the oil & gas, power generation, and pharmaceutical industries. Meanwhile, welded piping, which is more cost-effective and widely available, is specified for various applications as long as temperature, pressure, and service conditions remain within standard limits.
For structural applications, there is no performance difference between ERW and seamless steel pipe. In such cases, specifying seamless pipe when welded pipe meets the requirements would be an unnecessary expense.
Increased Strength and Durability: Seamless pipes are generally stronger and more durable than welded pipes, as they lack a seam that could become a weak point. This makes them particularly well-suited for high-strength and high-durability applications, such as oil and gas pipelines.
Smooth Interior Surface: The interior surface of seamless pipes is smoother compared to welded pipes, reducing the risk of contamination and making them easier to clean. This quality makes them ideal for applications requiring high levels of cleanliness, such as in food processing and pharmaceutical manufacturing.
No Welding Defects: Unlike welded pipes, seamless pipes are free from welding defects, which can weaken the pipe over time. This makes them a reliable choice for critical applications that require maximum reliability, such as in nuclear power plants.
Higher Cost: Seamless pipes are more expensive than welded pipes, making them less suitable for budget-conscious applications.
Limited Size Range: Seamless pipes are limited in their size range, making them less suitable for applications that require larger pipe sizes.
Longer Lead Times: Seamless pipes have longer lead times than welded pipes, as they require more time and effort to manufacture.
Both seamless and welded steel pipes offer unique advantages, depending on the specific needs of your project. Seamless pipes typically have a higher pressure rating, but that may not be the most important factor for your application.
Welded pipes, on the other hand, are generally more cost-effective and can come in larger sizes, making them a better choice for projects like bridge construction that require large quantities of pilings.
Whether you’re building a tall structure or a large bridge, steel pipe piles provide the deep, strong foundation necessary to bear heavy loads. While seamless pipes can handle higher pressure, they come at a higher cost and offer less flexibility. Welded pipes are often more suitable for large-scale construction projects, as they allow for precise dimensions at a lower cost.
If you have any questions about the steel pipes you need for your construction project, don’t hesitate to reach out to our team.
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