Pipes are classified based on several factors, including their manufacturing process, the materials they are made from, their application, and their size/dimensions.
Here's a breakdown of common pipe classifications:
1. By Manufacturing Process:
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Seamless Pipes: These pipes are made from a solid steel billet that is heated and pushed or pulled over a mandrel to create a hollow tube. This process results in a pipe with no welded seams, offering high strength and pressure resistance. They are commonly used in high-pressure applications like oil and gas pipelines and in critical structural applications.
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Welded Pipes: These pipes are manufactured by rolling steel plates or strips and welding the edges together. There are several types of welded pipes, each with its own specific manufacturing process:
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SAW (Submerged Arc Welding): Uses an arc welding process where the arc and weld zone are submerged under a granular flux. These are often used for larger diameter pipes. Welded pipes made by SAW can be further subdivided into:
- Straight SAW: The weld runs straight along the length of the pipe.
- Helical/Spiral SAW: The weld follows a spiral path along the length of the pipe, which allows for the production of pipes from narrower steel strips.
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ERW/EFW/HFW (Electric Resistance Welding/Electric Fusion Welding/High-Frequency Welding): Uses electrical resistance to heat the edges of the steel strip, which are then pressed together to form a weld. This method is efficient and produces high-quality welds, commonly used for water and gas pipelines. EFW is very similar but includes the addition of filler metal.
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2. By Material:
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Steel Pipes: A common choice due to their strength, durability, and ability to withstand high temperatures and pressures. Different grades of steel are used depending on the application, including carbon steel, alloy steel (e.g., stainless steel, chrome-moly steel), and cast iron.
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Plastic Pipes: Commonly used for plumbing, irrigation, and drainage due to their corrosion resistance, flexibility, and ease of installation. Common types include:
- PVC (Polyvinyl Chloride): Rigid and cost-effective, suitable for cold water applications.
- CPVC (Chlorinated Polyvinyl Chloride): Similar to PVC but can withstand higher temperatures, making it suitable for hot water applications.
- PEX (Cross-linked Polyethylene): Flexible and durable, often used for potable water supply and radiant heating systems.
- HDPE (High-Density Polyethylene): Strong and resistant to chemicals, commonly used for sewer lines and gas distribution.
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Copper Pipes: Known for their excellent corrosion resistance and thermal conductivity, often used for plumbing and HVAC systems.
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Concrete Pipes: Typically used for drainage and sewer systems, offering high strength and durability.
3. By Application:
- Water Pipes: Designed for transporting potable water, often made from copper, PVC, CPVC, or PEX.
- Gas Pipes: Used for transporting natural gas or propane, typically made from steel or polyethylene.
- Sewer Pipes: Designed for carrying wastewater, often made from PVC, concrete, or cast iron.
- Oil and Gas Pipelines: Used for transporting crude oil or natural gas over long distances, typically made from high-strength steel.
- Structural Pipes: Designed for structural support in buildings, bridges, and other structures, often made from steel.
- Drainage Pipes: Used to remove surface or subsurface water.
4. By Size and Dimensions:
- Pipes are also classified by their diameter (both inside and outside diameter) and wall thickness. These dimensions are crucial for determining the pipe's flow capacity, pressure rating, and structural integrity. Standards like ASME/ANSI B36.10M and B36.19M define pipe dimensions, schedules, and tolerances. Pipes sizes are normally referred to by their NPS (Nominal Pipe Size) which is a dimensionless number.
