Seamless steel pipe for fluid transportation

Fluid seamless steel pipe is a kind of steel pipe used for fluid transportation. Seamless steel pipes (SMLS) for fluid transport are the most common and widely used type of steel pipe in the industrial sector. As the name suggests, they are designed and manufactured specifically for the safe and reliable transport of fluids. They are primarily used for piping in engineering projects and large-scale equipment.

What is a fluid pipe?

Fluid pipe is a general engineering term referring specifically to pipes used to transport fluid media. "Fluid" here includes liquids (such as water, oil, and chemicals), gases (such as steam, air, and natural gas), and gas-solid and liquid-solid mixtures.

Common Materials:
Carbon steel: Most commonly used, such as A106 and A53. Used for transporting general media such as water, steam, air, and oil.
Stainless steel: Such as 304 and 316L. Used in applications requiring corrosion resistance or hygiene, such as food, pharmaceuticals, and chemicals.

Alloy steel: Such as 15CrMoG. Used in high-temperature and high-pressure environments, such as superheated steam pipes in power plant boilers.

Manufacturing Process for Seamless Steel Pipes for Fluids:

1. Hot-Rolled (Extruded) Seamless Steel Pipe

Process: Round billet → Heating → Piercing → Three-roll cross-rolling, continuous rolling, or extrusion → Drawing → Sizing (or reducing) → Cooling → Straightening → Hydrostatic Testing (or NDT) → Marking → Warehousing.

Features: Covers medium and large diameters, has thicker walls, high production efficiency, and relatively low costs, making it the primary production method for fluid pipes.
Outer Diameter (OD): Φ32mm to Φ630mm (or even larger, but welded pipe is generally more economical for extra-large diameters).

2. Cold-Drawn (Cold-Rolled) Seamless Steel Pipe:

Process: Cold-drawn or cold-rolled after hot-rolling.

Features: High dimensional accuracy, excellent surface finish, and superior mechanical properties. However, production costs are high, and it is typically used for applications requiring more precise dimensions or thinner walls. Typically small diameters with a wide range of ODs are common in applications requiring precise dimensions. 

Outer Diameter (OD): Φ6mm ~ Φ168mm

Features and Advantages of Seamless Fluid Pipes:

1. Seamless Structure: Formed in one go from round steel billets through piercing and rolling processes, the entire pipe body is free of welds, ensuring structural integrity and continuity.
2. High Pressure Capacity: Its uniform wall thickness and dense material allow it to withstand significantly higher pressures than comparable welded pipes. It is the only choice for high-pressure steam systems, high-pressure hydraulic systems, boiler piping, and other applications.

3. Excellent Corrosion Resistance: While corrosion resistance depends primarily on the material (e.g., stainless steel), the dense and uniform inner and outer surfaces of seamless steel pipes are less susceptible to corrosion pitting and more easily accept uniform anti-corrosion coatings, extending their service life.

4. Strict Quality Control Standards: This includes individual hydrostatic testing, non-destructive testing (eddy current, ultrasonic), and rigorous chemical composition and mechanical property testing. 

5. Long Service Life: Combining high strength, corrosion resistance, and reliability, seamless steel pipes for fluid transportation, with proper selection and maintenance, can significantly extend the service life of welded pipes, resulting in lower overall lifecycle costs.

6. Wide Range of Applications
Media: Safely transport water, steam, air, oil, various chemicals, and even radioactive media.
Operating Conditions: Suitable for demanding operating conditions such as high temperature, high pressure, low temperature, and corrosion. For example, ASTM A106 Gr.B steel pipe is specifically designed for high-temperature service.

Applications of Seamless Steel Pipes for Fluid Transportation:

Fluid pipes are ubiquitous and fundamental to the operation of modern industry and society. Seamless pipes for fluid transportation are suitable for a variety of high-pressure and high-risk fluid transportation scenarios:

1. Oil and Gas Industry: Used in long-distance pipelines transporting crude oil, natural gas, refined oil, and other products, capable of withstanding high pressure and corrosive media within the pipeline.
2. Chemical Industry: Process piping for transporting various chemical raw materials, finished products, and catalysts. The chemicals involved in chemical production are often highly corrosive and flammable, placing extremely high demands on the material selection of pipelines.

3. Power Industry: Seamless pipes for high-pressure boilers transport high-temperature, high-pressure steam, ensuring the thermal cycle of generator sets, such as steam pipes and water pipelines in power plants.
4. Urban Utilities: Water supply pipes, city gas pipelines, and central heating pipelines, especially in high-pressure main pipeline networks.

5. Mechanical Equipment: High-pressure oil pipes in hydraulic systems and air pipes in air compressor systems.
6. Metallurgical Industry: Used to transport cooling water, hydraulic oil, and other equipment, adapting to complex workshop conditions.
7. Aerospace and Shipbuilding: Used in fuel, hydraulic, and cooling systems. Their seamless nature reduces the risk of leakage and ensures safe and stable fluid transportation in high-pressure, high-temperature, or corrosive environments.

Fluid seamless steel pipes are widely used in modern fluid transportation due to their seamless structure, high strength, and corrosion resistance. Surface anti-corrosion and thermal insulation treatments can also be applied to fluid seamless pipes, depending on the application and actual construction conditions.

The length of fluid seamless pipes can be customized to meet customer requirements, typically ranging from 6 to 12 meters, with export lengths of less than 6 meters. The seamless steel pipe for fluid at the outlet also needs to be grooved, painted and sealed.

Difference between structural seamless steel pipe and fluid seamless steel pipe:

Structural seamless steel pipe is applicable to seamless steel pipe for general structure and mechanical structure, and fluid seamless steel pipe standard is applicable to general seamless steel pipe for conveying fluid. The main difference between it and the structural seamless steel pipe is that the fluid seamless steel pipe is subjected to hydraulic test one by one or ultrasonic, eddy current and magnetic flux leakage inspection. Therefore, in the standard selection of pressure pipeline steel pipes, fluid seamless steel pipes should be used.

Manufacturing method:
① Generally, the temperature of boiler tubes is below 450 °C, and domestic tubes are mainly made of No. 10 and No. 20 carbon steel hot-rolled tubes or cold-drawn tubes.
② High-pressure boiler tubes are often used in high temperature and high pressure conditions, and the tubes will be oxidized and corroded under the action of high-temperature flue gas and water vapor. The steel pipe is required to have high lasting strength, high oxidation corrosion resistance, and good organizational stability.

Application:
①General boiler tubes are mainly used to manufacture water wall tubes, boiling water tubes, superheated steam tubes, superheated steam tubes for locomotive boilers, large and small smoke tubes and arch brick tubes, etc.

②High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, gas guide tubes, main steam tubes, etc. of high-pressure and ultra-high-pressure boilers.

Read more: Types of Seamless Carbon Steel Pipes or Seamless vs Welded pipe