Should Steam Pipelines Use Seamless or Welded Pipes?

Steam pipelines are pipeline systems specifically designed for transporting steam and are one of the most common and important types of pipelines in the industrial field. They are widely used in power plants, chemical plants, heating systems, food processing, papermaking, textiles, and various other industries. Steam pipelines can use either seamless pipes or welded steel pipes, depending on the working pressure, temperature, and laying method.

Main selection principles:

● High-pressure, high-temperature conditions (e.g., pressure > 1.6 MPa or temperature > 200℃): Seamless steel pipes must be used due to their lack of welds, high strength, and good sealing performance, effectively preventing leakage.
● Low-pressure, low-temperature conditions (e.g., pressure ≤ 1.6 MPa and temperature ≤ 200℃): Welded steel pipes can be used, but seamless steel pipes remain the safer and more reliable choice.
● Direct burial (regardless of pressure): Seamless steel pipes are recommended or required to ensure long-term operational safety and sealing. Aerial or Trench Laying: Both seamless and welded steel pipes can be used, provided the pressure and temperature conditions are met.

Material Selection for Different Scenarios:

1. High-Temperature and High-Pressure Steam Pipelines
For critical components such as superheaters, reheaters, and main steam pipelines, due to high operating pressures (typically ≥9.8MPa) and high temperatures (450℃-650℃), seamless steel pipes conforming to the following standards must be used.
Material: ASME SA-213/SA-335 (e.g., T11/T22/P91, etc.)

2. Medium and Low-Pressure Steam Pipelines
For steam pipelines with pressures <1.6MPa and temperatures <200℃, welded steel pipes can be used.

3. Buried or Special Laying Requirements
When steam pipelines are laid in inaccessible trenches or directly buried, seamless steel pipes should be used regardless of the parameters. This is to minimize the risk of failure in situations where maintenance is impossible or difficult.

International Standards:

1. American Standards (ASME/ASTM)

According to US federal regulations and ASME B31.1 "Power Piping":
Seamless pipe: Suitable for high-temperature and high-pressure conditions, such as A106 Gr.B (carbon steel), A335 (alloy steel)
Welded pipe: Suitable for medium- and low-pressure conditions, such as A53 Gr.B (resistance welded pipe)

2. European Standards (EN)

According to EN 10217 series-7:
EN 10217-2: High-temperature welded pipe, suitable for steam piping ≤500℃
EN 10217-5: Submerged arc welded pipe, suitable for high-temperature large-diameter piping

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