Introdução
There are various processes for manufacturing pipes across industries. The two most popular pipe manufacturing techniques are sem emendas e electric resistance welded (ERW). Construction, water transportation, and oil and gas are among the businesses that employ these pipes. There are similarities between these pipes, including their shapes and functions. But there are certain differences, like strength, cost, and applications, that make these pipes different.
Understanding these distinctions is crucial for both manufacturers and users. You can make an informed choice once you understand the difference between seamless and ERW pipes. Many factors can determine the choice of a specific pipe type. Such as:
- Pressure rating
- Mechanical strength
- Custo
- Resistência à corrosão
This article describes the main distinctions between seamless and ERW pipes.
Processo de fabricação
To manufacture ERW and seamless pipes, different manufacturing processes are used. The pipe’s manufacturing process will determine its appropriate application.
Seamless Pipe Manufacturing
Some pipes have high strength and lack weld seams. These pipes are seamless. In the manufacturing process, the solid stainless steel billets are heated. The rod (mandrel) is inserted into the billet at the center. Subsequently, the billet is converted into a hollow rod under pressure.
To maintain the rod’s diameter to the required specifications, the hollow rod is formed by stretching. The pipe has no weld seam, which is why it has a smooth circumference along its length.
There are two categories for the seamless pipes:
- Hot finished
- Cold drawn
ERW Pipe Manufacturing
The steel coils and strips are welded to form pipes. There is a clear welding seam on these pipes. The strip is first twisted into a cylindrical form. A high-frequency electrical current is used to weld the pipes. The welding seam is visible on the longitudinal side of the pipe.
The difference between the ERW and the traditional welding is that ERW does not use filler metal. The high pressure generated by the electrical resistance will bind the edges together. In the end, the pipe undergoes heat treatment, strengthening, and sizing.
Physical and Mechanical Differences
ERW and seamless steel pipes differ in their mechanical and physical properties. The manufacturing process will decide it.
The specific distinctions between these two types of steel pipes are as follows:
| Properties | Tubos sem costura | Tubos ERW |
| Presence of seam | There are no weld seams on these pipes. | A longitudinal weld seam is visible on the surface. |
| Strength distribution | There is no welded seam on the pipe. So, the user can get the uniform strength along the length. | The weld point reduces the pipe’s strength. The distribution of strength along the pipe length differs. |
| Espessura da parede | The process that determines the wall thickness is the extrusion and rolling. These processes will cause thickness variations. | These ERW pipes are made by rolling the sheets. Steel sheets have uniform thickness, so ERW has a consistent wall thickness. |
| Resistance to Temperature and Pressure | Seamless steel pipes have high strength. It means they have high-pressure resistance. Similarly, it can withstand higher temperatures. | The grades and standards of ERW pipes make them ideal for low-temperature and low-pressure applications. |
| Acabamento da superfície
|
Better dimensional precision and surface finish are features of the seamless pipes. | Pipes made by the ERW process have a smooth outer surface. At the same time, the inner surface requires additional processing. |
Advantages and Disadvantages
The use of seamless and ERW pipes has many advantages. However, there are certain disadvantages to the process. The benefits and drawbacks of employing seamless and ERW steel pipes are detailed below.
Tubo sem costura
| Vantagens | Desvantagens |
| There is no weld seam present on the surface. | Because of the production process’s perfection, the price is slightly higher. |
| Have applications in high-temperature, high-pressure environments. | The production process is a bit time-consuming. |
| The use of seamless pipes is very common for gas and oil drilling. | These pipes have a very limited range for larger diameter pipes. |
| There are no gaps at the weld site. It will provide greater stress and rust resistance. | The pipe may have slightly different wall thickness along its length. |
Tubo ERW
| Vantagens | Desvantagens |
| It is a cost-effective decision to use ERW pipes. | The major drawback of ERW pipes is their longitudinal seam. |
| ERW pipes have consistent wall thickness. | These pipes cannot withstand the very high temperatures and pressures. |
| The manufacturing process is quite efficient. | The welding site is susceptible to corrosion. |
| There is a large selection of pipe diameters. | Absence of uniform distribution of pressure resistance. |
| The manufacturing process is very short. |
Standards and Specifications
The manufacturing of ERW and seamless steel pipes is based on international standards. The most common standards are:
- ASTM A53: both seamless and ERW fall in the standard.
- For seamless carbon steel pipes intended for high-temperature applications, ASTM A106is the standard.
- API 5L: approved pipes are available for gas and oil transport.
- ASME B36.10 / B36.19: wall thickness and pipe dimensions schedules
Seamless pipes are typically made in pressure classes such as Schedule 40, 80, and 160. These pipes have a pressure-bearing capacity that is often 15-25 times that of ERW pipes. The diameters of ERW pipes range from 1/2 inch to 24 inches. Seamless pipes are available up to 20 inches, with sizes larger than 20 inches at a premium.
Both types of API grades exist: X42, X52, X65, and X70. Smooth-bore pipes are sometimes used in critical high-pressure work above 5000 psi. It all depends on wall thickness and material grade.
Aplicativos
ERW or seamless pipes are selected based on operating pressure, temperature, and service conditions.
Applications of seamless pipes are popular in:
- Oil and gas exploration and drilling
- High-pressure boilers (more than 450 degrees)
- Usinas de energia
- Hydraulic systems
- Petrochemical processing units.
Seamless pipes are also suitable for high-stress, high-temperature, and cyclic loading due to the absence of a weld seam.
ERW Pipes are generally applicable in:
- Water pipelines
- Aplicações estruturais
- Medium and low-pressure oil and gas transportation
- Fencing and scaffolding
- Tubing is used in automobile and mechanical applications.
ERW pipes are cheaper and more reliable for applications at temperatures below 350 °C and moderate pressure.
Custo
The price difference between seamless and ERW pipes is among the most significant. The prices of seamless pipes are normally 20-40 percent higher than those of ERW pipes. It is due to complications in billet piercing and rolling.
High-frequency welding is used to produce ERW steel pipe coils. This minimizes time and material waste in production.
ERW pipes are 25–35% less expensive than seamless pipes. This makes ERW pipes a viable option for large-scale infrastructure and construction projects where ultra-high-pressure resistance is not required.
Conclusão
The key distinction between ERW and seamless pipes lies in their production methods and structural quality. The main benefits of seamless pipes are their higher strength, greater pressure rating, and improved performance as they do not have weld joints. Conversely, ERW pipes are economical, dimensionally stable, and can be produced more quickly. They are suitable for structural and general industrial applications.
The selection of ERW and seamless pipes will be influenced by:
- Pressure
- Operating temperature
- Project cost
- Application requirements
UNISEN provides professional advice and high-quality piping solutions. The company is always happy to receive calls.