The topic of the day is seams and welds. There are many of them, so people understandably wonder: what makes them different, and which one should I choose? One crucial point to remember is that welding can eliminate seams, therefore it’s definitely worth it if you want to get rid of those annoying seaming problems sticking out.
What is a Seamless pipe?
Round steel billets are used to make seamless pipes (a strong tube-shaped hunk of steel that is projected from crude steel). Once heated, this billet is stretched out and either pulled or pushed over a structure. With a bite of the dust and a mandrel, it is then pierced through the middle, expanding internally while contracting externally. Despite the fact that uniform lines are produced in a range of sizes, the cost of production rises as pipe diameter increases. The lack of a seam is where the term “seamless” originates. Shipbuilding, power transmission, pressure vessel manufacturing, compounding, and other industries frequently use seamless pipes.
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What is a Welded Pipe?
By using a roller or plate twisting machine to cold form flat strips, sheets, or plates into a rounded or roundabout shape, the welded pipe is created. The line is then joined using a high-energy source, either with filler material or without. With no size restriction, welded lines can be produced in enormous sizes. Huge volumes of water, oil, or gases are frequently transported via welded pipes.
Seamless vs Welded Pipe
It is clear from the aforementioned paragraphs that the production processes for seamless and welded pipes are different. The table that is attached below lists the further differences.
| Sr. No | Parameter | Seamless Pipe | Welded Pipe |
| 1 | Strength | Able to withstand more pressure and load as there is no weak seam. | Due to welding, they are believed to withstand 20% less pressure and load as compared to the seamless pipe. |
| 2 | Length | Relatively shorter in length due to manufacturing difficulties. | Can be manufactured in long continuous lengths. |
| 3 | Size | Manufactured for nominal size 24 inches or less. | No such size restriction on production. |
| 4 | Corrosion Resistance | Less prone to corrosion means more corrosion resistance. | Weld areas are more prone to corrosion attacks, which means less corrosion resistance. |
| 5 | Surface Quality | Rough due to extrusion process | Smooth high-quality surface as compared to the seamless pipe. |
| 6 | Economy | Costlier | More economic |
| 7 | Production Process | Complex, long procurement lead time | Simpler, short procurement lead time. |
| 8 | Tests | Seamless pipes do not require testing for weld integrity. | Must be tested before use. |
| 9 | Application | Suitable for high-pressure temperature and corrosive environment | Normally used for less corrosive and low-pressure environments. |
| 10 | Availability | Less available, limited material types, longer delivery time | Readily available for various different materials; shorter delivery time |
| 11 | Wall Thickness | Inconsistent wall thickness across the length, thicker so heavier | Wall thickness is more consistent than seamless ones, thinner |
| 12 | Ovality | Better ovality, roundness | Poor ovality and roundness as compared to seamless counterpart. |
| 13 | Internal surface check | Checking not possible | The internal surface can be checked before manufacturing |
Manufacturing welded pipe
The welded pipe initially appears as a skelp, a long, coil-like ribbon of steel. The skelp is cut into the perfect length slices, resulting in a rectangular sheet that is level. The line’s exterior periphery, which can be used to calculate its potential external distance across, will be equal to the width of that sheet’s more constrained finishes.
The rectangular sheets are handled by a moving device that twists the more angular exteriors up toward one another to form a chamber. High-recurrence electrical flow is transferred between the edges during the ERW cycle, causing them to soften and merge.
The fact that no combination metals are used and the weld crease cannot be seen or felt are two advantages of ERW pipe. This contrasts with double-lowered bend welding (DSAW), which leaves a noticeable weld dab that must later be removed depending on the application.
Production techniques for welded pipes have been under long-term development. The switch to high-recurrence electric flows for welding may be the biggest advancement. A low-recurrence current was used before the 1970s. Low-recurrence ERW-produced weld creases were more susceptible to erosion and crease disappointment.
The majority of welded pipe types need to be heated after production.
Manufacturing seamless pipe
A sturdy, hollow, round piece of steel known as a billet serves as the initial step in the manufacturing of a seamless pipe. The middle of the billets is pierced with a mandrel while they are still hot. Rolling and expanding the empty billet is the next step. The billet is precisely expanded and rolled until it reaches the desired length, breadth, and divider thickness.
Some forms of continuous lines solidify during production, negating the requirement for heat treatment after assembly. Others do need to be heated. Consult the manufacturer of the sort of continuous line you’re considering to determine whether heat treatment is necessary.
Pipe Selection, Welded or Seamless?
Even though continuously improved manufacturing techniques may produce welded pipes that are on par with seamless pipes, seamless pipes are still preferable in the majority of situations. In any event, welded pipes are typically used due to their lower cost for large-scale channeling applications (> 24-inch NPS). For pipe selection, factors other than price include accessibility, erosion resistance, measurement to thickness ratio, and so on.
Products at Sumer Metal Industries
From our specialized inventory, choose the quality welded and seamless pipes that meet your needs. To get the most out of our resources, contact us for further technical details.