Seamless vs welded pipe in petrochemical industry

Seamless vs welded pipe in petrochemical industry

Seamless steel pipes and welded pipes are two important steel products, they have many unique production processes and a wide range of application fields, especially play an important role in the petroleum industry.

Production process of seamless steel pipe and welded pipe

Seamless steel pipe:

1. Raw material preparation The raw material of seamless steel pipe is mainly steel billet, and high-quality carbon structural steel or alloy steel is usually used as raw material. The steel billet is processed into a seamless steel pipe blank by hot rolling, forging or cold drawing.
2. Hot rolling heats the billet to a certain temperature, and then passes through multiple passes of rolling to form the billet into the shape of a seamless pipe. During this process, the steel billet will undergo various deformation methods such as stretching, compression and rotation to ensure the accuracy of the size and shape of the steel pipe.
3. Heat treatment Heat treatment is to improve the mechanical properties and physical properties of steel pipes. Common heat treatment methods include annealing, normalizing, quenching and tempering. Through different heat treatment methods, steel pipes can have different hardness, strength and toughness.
4. Inspection and trimming The appearance quality inspection and dimensional inspection are carried out on the produced seamless steel pipes to ensure that the quality of the steel pipes meets the standard requirements. Trim or reject some unqualified steel pipes.
5. Chemical composition analysis The chemical composition of the steel pipe is analyzed to ensure that the chemical composition of the steel pipe meets the requirements. Commonly used analytical methods include spectral analysis, chemical analysis, and mass analysis.

Welded pipe:

The manufacturing process of welded pipe starts with rolling the steel coil to the required thickness to form flat strip or plate. It is then rolled up, and then the seams of the resulting pipe need to be welded. There are two main welding methods. details as follows:

1. Resistance welding (ERW) process
In the electric resistance welding (ERW) process, welded pipes are manufactured by cold forming flat sheet steel into a cylindrical shape. An electric current is then passed through the sides of the steel cylinder, heating the edges to a temperature that forces them to form a bond together. This process means that no welding filler material is required.
2. Submerged arc welding (SAW) process
The submerged arc welding (SAW) process is commonly used in industries involving thick steel plates or where long welds are required. It involves forming an arc between a continuously fed electrode and a workpiece. Flux is used to generate shielding gas and slag, and to add alloying elements to the weld pool. The arc moves along the seam line, during which excess flux is recycled through a hopper. Because the arc is completely covered by the flux layer, the arc is usually invisible during welding and heat loss is extremely low.
3. Welded pipe finishing
Welded tubes can be processed in many different ways depending on customer requirements and the desired end application. These finishes include threaded and coupled ends, threaded ends for uncoupled ends of different diameter wires, and plain or cut square ends for more general use. Pipes with pre-grooved or beveled ends are also available for structural applications. For added corrosion protection, different metal coatings such as galvanized, aluminized and clad are available. For protection during storage and transportation, non-metallic coatings such as oils, paints, plastic coatings, coal tar, etc. can also be used. Welded pipe can also go through a process called "pickling and passivation," which means dipping the pipe in an acid bath to remove the first layer of metal, before passing it through a water bath. This produces a smoother, more uniform surface finish that helps reduce the risk of corrosion.

Application of seamless steel pipe and welded pipe in petroleum industry

Seamless steel pipe:

1. Oil exploitation Seamless steel pipes are widely used in the field of oil exploitation. In oil wells, seamless steel pipes are used as oil pipes to transport oil from the well to the surface. Because seamless steel pipe has good corrosion resistance and high strength, and can withstand high pressure and high temperature environments, it plays an important role in the process of oil extraction.
2. Oil storage and transportation Seamless steel pipes are also widely used in the field of oil storage and transportation. In the petroleum pipeline system, seamless steel pipes are used as oil pipelines, gas pipelines and water pipelines. Seamless steel pipe has good sealing performance and pressure resistance, which can ensure the safe transportation and storage of oil.
3. Petrochemical seamless steel pipes are also used in the petrochemical industry. In petrochemical processes, seamless steel pipes are used as pipes for equipment such as reactors, heat exchangers, and separators. Seamless steel pipe has excellent high temperature resistance, corrosion resistance and pressure resistance, and can withstand complex chemical environments and high temperature and high pressure working conditions.
4. Petroleum equipment manufacturing Seamless steel pipes are also widely used in the field of petroleum equipment manufacturing. For example, seamless steel pipes are used as structural materials for oil drilling rigs, oil pumps, and oil pipeline equipment. Seamless steel pipe has good strength and toughness, which can meet the requirements of petroleum equipment for material properties.

Welded pipe:

1. One of the main advantages of LSAW pipe is its durability. Longitudinal welded pipe is manufactured by welding together a series of pipe sections joined end-to-end. This joining process makes the pipes more resistant to pressure, corrosion and temperature stresses than conventional pipes. LSAW pipe also has a smooth inner wall and is corrosion resistant, making it ideal for transporting oil and gas. Additionally, LSAW pipe is often made from higher quality steel than standard pipe, making it more durable.
2. Another advantage of the LSAW pipeline is its flexibility. LSAW pipes can bend, allowing them to navigate around obstacles in their route, such as trees or rocks. This flexibility makes the pipes easier to install as they can be bent to fit in the most convenient way. The flexibility of LSAW piping also makes it ideal for piping through difficult terrain. In addition, individual pipe segments can be moved and adjusted to accommodate changes in pipe routing or elevation, which helps reduce construction time and costs.
3. The cost-effectiveness of LSAW piping is another big advantage. Longitudinally welded pipe is generally less expensive than other types of pipe because they have fewer parts and are easier to assemble. Additionally, LSAW pipes require less maintenance than other types of pipes because they are more resistant to corrosion and wear. Therefore, Longitudinal Welded Pipes can provide significant cost savings in the long run.

Both seamless steel pipes and welded pipes have their own advantages, and their production processes are processed and processed through multiple procedures to ensure the quality and performance of steel pipes. In the petroleum industry, seamless steel pipes and welded pipes are widely used in fields such as petroleum exploration, petroleum storage and transportation, petrochemical industry and petroleum equipment manufacturing, and play an important role. With the continuous development of the oil industry, the demand for seamless steel pipes and welded pipes will continue to grow, which will promote the further development of the steel industry.