Understanding pipelines (3): Seamless Steel Pipe: Types and Applications
Seamless steel pipe is the pipe with the largest consumption and the most varieties and specifications in industrial pipelines.
Basically, seamless steel pipes can be divided into:
- Seamless steel pipe for fluid transportation
- Seamless steel pipe with special features - This includes boiler special steel pipe, cracking furnace tube, and heat exchanger steel pipe.
According to the material, seamless steel pipes can be classified into:
- Carbon seamless steel pipe
- Chromium-molybdenum seamless steel pipe
- Stainless and acid-resistant seamless steel pipe
According to the nominal pressure, seamless steel pipes can be classified into three categories:
- Low pressure: 0 ≤ 1.0 MPa
- Medium pressure: 1.0 < 10 MPa
- High pressure: ≥ 10 MPa
Below is a detailed classification of seamless steel pipes for fluid transportation in process pipelines:
1. Carbon Seamless Steel Pipe
The commonly used manufacturing materials are No. 10, No. 20, and 16Mn steel.
Specifications:
- Hot-rolled outer diameter: φ32 ～ 630mm
- Cold-drawn outer diameter: φ6 ～ 200mm
- Single pipe length: 4 ～ 12m
- Allowable operating temperature: -40 ～ 450℃
This type of pipe is widely used for transporting various non-corrosive media, such as steam, oxygen, compressed air, oil products, and oil and gas.
2. Low Alloy Steel Seamless Steel Pipe
Low alloy steel pipes contain a certain proportion of alloy elements and can be divided into two types:
- Ordinary low alloy steel pipes, such as 16Mn, 15MnV, etc.
- Chrome-molybdenum steel pipes, containing chromium, molybdenum, and other elements, such as 12CrMo, 15CrMo, 12Cr2Mo, etc.
Specifications:
- Outer diameter: φ10 to φ273mm
- Single tube length: 4 to 12m
- Applicable temperature range (chrome-molybdenum steel): -40 to 550℃
Low alloy seamless steel pipes are commonly used for transporting high-temperature oils, non-corrosive salt water, low concentration organic acids, and more.
3. Stainless and Acid-Resistant Seamless Steel Pipe
Stainless and acid-resistant seamless steel pipes are made of various materials, including Cr13, 00Cr17Ni14Mo2, 1Cr18Ni9Ti, and others.
Specifications:
- Most used steel grade: 1Cr18Ni9Ti (often referred to as 18-8 on construction drawings)
- Applicable temperature range: -196 ～ 700℃
This type of steel pipe is used in chemical production for transporting highly corrosive media, such as nitric acid, acetic acid, and urea.
4. High-Pressure Seamless Steel Pipe
High-pressure seamless steel pipes are similar to the other types of seamless steel pipes mentioned above, but with thicker pipe walls. The thickest pipe wall is 40mm.
Specifications:
- Size range: φ14 × 4(mm) to φ273 × 40(mm)
- Single pipe length: 4 ～ 12m
- Applicable pressure range: 10 ～ 32 MPa
- Working temperature range: -40 ～ 400℃
High-pressure seamless steel pipes are used in petrochemical plants for transporting raw gas, hydrogen, nitrogen, synthesis gas, high-pressure condensed water, and other media.
5. Low-Temperature Steel Pipe
Low-temperature steel pipes are often used in cold regions for imported engineering projects. Their material grades are STPL-39 and STPL-46, with an operating temperature range down to -105℃.
Specifications:
- Seamless low-temperature steel pipes: φ15 ～ 400mm
- Seamed low-temperature steel pipes: φ400 ～ 1100mm
- Wall thickness for seamed pipes: 6 ～ 10mm
- Standard pipe length: 6m
These pipes are suitable for transporting various non-corrosive low-temperature media. Currently, there is no mass production of steel pipes meeting this standard in China.
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