Understanding Pipelines: A Comprehensive Guide to Metal and Non-Metal Pipes
A pipeline refers to a system of pipes, pipe connectors, and valves used for conveying gas, liquids, or fluids containing solid particles. Typically, the fluid is pressurized by a blower, compressor, pump, or boiler. It flows from the high-pressure part of the pipeline to the low-pressure part. Alternatively, the fluid can be conveyed by its own pressure or gravity.
Pipelines are widely used in various industries, including water supply, drainage, heating, gas supply, long-distance transportation of oil and natural gas, agricultural irrigation, hydraulic engineering, and various industrial devices.
Classification of Pipelines
Pipelines are classified into different categories based on their material, purpose, design pressure, temperature, and medium. Here are some of the common classifications:
Classification by Material
- Metal Pipes: Made of materials like steel or copper, metal pipes are known for their high strength and resistance to pressure.
- Non-Metal Pipes: These pipes are made from materials like plastics and fiberglass, which are lightweight and have excellent corrosion resistance.
Classification by Design Pressure
- Vacuum Pipes: Designed for low-pressure or vacuum environments.
- Low Pressure Pipes: Suitable for transporting fluids at lower pressures.
- High Pressure Pipes: Suitable for transporting fluids at higher pressures.
- Ultra-High Pressure Pipes: These pipes are used for fluid transportation at extremely high pressures.
Classification by Temperature
- Low Temperature Pipes: Designed for fluid transportation in low-temperature environments.
- Normal Temperature Pipes: Used for fluid transportation at standard temperatures.
- Medium and High Temperature Pipes: Used for fluid transportation in medium to high-temperature environments.
Classification by Transportation Medium
- Water Supply and Drainage Pipes: Used for transporting water and wastewater.
- Compressed Air Pipes: For the transportation of compressed air.
- Hydrogen, Oxygen, and Acetylene Pipelines: For transporting gases like hydrogen, oxygen, and acetylene.
- Heat, Gas, and Fuel Pipelines: Used to transport heat, gas, and fuel.
- Highly Toxic Fluid Pipelines: Designed for transporting hazardous fluids, such as acids and alkalis.
- Boiler, Refrigeration, and Pure Gas Pipelines: For transporting fluids used in boilers, refrigeration, and pure gas systems.
Introduction to Metal Pipes
Now, let's focus on metal pipes, particularly welded steel pipes. These pipes are commonly referred to as seam steel pipes and are typically made by rolling and welding steel plates or strips.
Surface Treatment
Welded steel pipes can be divided into two main types based on their surface treatment:
- Galvanized Welded Steel Pipes: These pipes have a white, galvanized coating and are used in pipelines requiring relatively clean media, such as domestic water, purified air, and instrument air.
- Non-Galvanized Welded Steel Pipes: These pipes, also known as black iron pipes, do not have the galvanized coating and are commonly used for transporting steam, gas, compressed air, and condensed water.
Types Based on User Requirements
Welded steel pipes are available in two types when leaving the factory, depending on the user's requirements:
- With Threads: These pipes have threads at the ends and are usually between 4 to 9 meters in length.
- Without Threads: These pipes do not have threads at the ends and generally range from 4 to 12 meters in length.
Classification by Pipe Wall Thickness
Welded steel pipes are further categorized based on the thickness of the pipe wall:
- Thin-Walled Steel Pipes
- Thickened Steel Pipes
- Ordinary Steel Pipes: The most commonly used pipes in process pipelines. Their test pressure is typically 2.0 MPa, while thickened steel pipes have a test pressure of 3.0 MPa.
Connection Methods
Welded steel pipes can be connected in several ways, depending on the specific application:
- Threaded Connection
- Flange Connection: This can be a threaded or welded flange connection.
- Welding: Various welding methods, including gas welding and arc welding, can be used to join the pipes.
Commonly Used Specifications
The nominal diameter of commonly used welded steel pipes ranges from 6 to 150 mm.