Seamless Tubing and Welded Tubing: Choosing the Right One
When a project involves the selection of an appropriate stainless steel piping material, then it is the project manager who has to make the final choice. There are a couple of choices such as welded and seamless tubing and he really needs to make sure that he is choosing the right option.
For almost a decade, the stainless steel pipes were seamless. But, with the latest inventions in metal purifications and welding technologies, welded tubing has become popular than ever before. So, the question is whether you should choose seamless steel tubing or welded tubing for your project.
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Let us help you select the right tubing material by taking a look at the important aspects of the two materials.
Seamless Tubing and its Benefits
The type of tubing doesn’t have a longitudinal weld joint (seam). Manufacturing of the seamless piping (tubing) is done through a mechanism that makes a hole in the billet. Today, rotary rolling and piercing is a highly adapted method for the production of seamless piping.
The procedure begins with a round conditioned steel bar, that is heat-treated, sliced, and worked. The bar forms the hollow billet by flowing around the piercer point. The tube interior gets the support of a plug or a mandrel and billet roller gets stretched. Additional rolling is done on the outside diameter to achieve sizing of steel tube.
The ASME working pressure of seamless tubing is 20% higher than the same size and material welded tubing. This is because the seamless stainless tubing doesn’t have a welded seam (joint). The drawn and welded tubing may also incorporate a visible joint that should be a concern for the end-users.
Key Benefits
The key advantage that comes with this type of tubing is that it is stronger and has higher pressure resistance. Another benefit that comes with the seamless stainless tubing is that it provides better corrosion resistance than the other options. This type of tubing helps you encounter all potential differences and defects in the malleability that might be linked with welded areas in the welded tubes.
Unlike a welded tube, a seamless tube doesn’t need any testing for weld integrity. So, the seamless stainless tubing is usually a more adapted type of tubing for the critical applications.
Application Areas
The seamless steel tubing is used in the following industries and/or areas:
- Gas and oil control lines
- Safety valves (below sea)
- Chemical injection lines
- Gas and fluid transfer
Seamless steel tubing is also a popular tubing choice used in the chemical processing plants and the heat trace bundles.
Welded Tubing and its Benefits
The production process of welded tubing starts with steel coil rolling to the required gauge thickness. The process result produces flat strip coil. In the next stage, the strip is pierced to a size according to the tube that is to be shaped. A sequence of rollers is used to move cut coil for the formation of the tube. The tube seam is welded in an environment that is chemically neutral. A rolling program forges welded seam and heat treatment is carried out to complete the welded steel tube.
To smooth a welded joint and make it almost invisible to the bare eye, the welded tubes are drawn over the mandrels and the ground. Less annealing and drawing is required to manufacture drawn and welded tube. Therefore, the drawn and welded seam cost is less than the seamless steel tubing. Typically, the procuring time of the welded and drawn joint is also less than the seamless tubing.
Key Benefits
One of the key benefits of the welded steel tubing is that it is a cost-efficient tubing option, when compared to the other available types. It is also readily available in the long lengths. The welded tubes also have the fast lead times.
Application Areas
Different areas where the welded stainless steel tubing can be used are as follows:
- Automotive industry
- Marine industry
- Architectural applications
- Pharmaceutical industry
Apart from the above listed industries and areas, the welded steel tubing is also used in beverage and food industry.
Cost of Seamless vs. Welded Tubing
The cost of both welded and seamless steel tubing depends on a few important factors, such as durability and strength. The manufacturing process of welded tubing is easy so the tubing of large diameter with the thinner walls will cost less. These are the properties that are not easy to produce with seamless steel tubing.
When it comes to seamless tubing, achieving heavy walls is comparatively easier. Therefore, seamless stainless steel tubing is an idea choice for applications with heavy wall tubing that needs to tolerate high pressure. It is also the preferred option in extreme environments.
Pressure Standards
The standard specification for the seamless and welded tubing is known as ‘ASTM A269’ that is recognized globally. The standard depends on the conformation of the chemical structure specifications and specifies hardness requirements for diverse tube grades. Both tubing types must meet the pressure standards.
ASTM A269 needs a hydrostatic or nondestructive electric test to perform pressure testing for all welding and seamless steel tubing. ASTM A269 includes limitations of tensile strength for tubing (piping) of variable wall thicknesses and outside diameters. Apart from that, there are more ASTM standards available that are applied to the welded/drawn or seamless steel tubing.
Choosing the Right Tubing
When it is the time to choose between the seamless and welded tubing you must make sure that the selected type meets your specific project specifications. If the project specifications are not available, then you should choose the tubing type according to the environment. So, keep in mind that the environment in which you are going to use the tubing is also important. This will help you decide whether you need to opt for the welded tubing or the seamless tubing for your project.
You should know this fact that the seamless can be a perfect alternative to the welded tubing, but the welded tubing cannot substitute seamlessly. Why? This is because of the weld seam. Look at the following chart. It will help you choose the most appropriate tubing type according to your project specifications and/or environment.
Comparison Table
| Seamless | Welded/Drawn | |
| Tolerances | X | |
| Lead Time | X | X |
| High Pressure | X | |
| Concentricity | X | |
| ID Surface | X | |
| Substitution | X | |
| Heavy Wall | X | |
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There are several differences between welded/drawn and seamless tubing. Manufacturing process complexities, finished product cost, defect opportunities, and the pressure rating is just a few to name.
It is the responsibility of the engineer who is in charge of equipment design to choose between the available types of tubing. He must make the most appropriate selection according to the application type. The project engineer must determine if the process failure would be disastrous.
If the tubing is to be used in the critical applications, then the most highly preferred type would be seamless tubing. This is because the seamless steel tubing has the least defect opportunity when compared with the welded tubing. Seamless steel tubing can also tolerate higher pressures. However, there are a number of non-critical application areas where welded/drawn tubing is effectively utilized.
If you are still confused and not sure about which type of tubing to choose for your project, then you can also get help from the material suppliers.
Look for a highly credible and reputable supplier who can guide you about what material is suitable in accordance with your overall project specifications and environment. They will go through your project details and specifications, and then help you choose the most suitable material.
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