Classification of boiler tubes

Definition of boiler tubes:

Boiler tubes are an important part of boilers and the main component of boiler heating surfaces. They are used to transfer heat, withstand pressure and temperature in boilers. Simply put, boiler tubes are pipes installed in boilers for heating water, generating steam or superheated steam.

The main functions of boiler tubes include:

Heat transfer: Boiler tubes transfer the heat generated by fuel combustion to water, causing it to heat, evaporate and overheat.
Pressure bearing: Boiler tubes need to withstand the pressure of the medium inside the boiler to ensure the safe operation of the boiler.

High temperature resistance: Boiler tubes work in high temperature environments and need to have good heat resistance.

Classification of boiler tubes:

Boiler tubes can be classified according to different standards. The following are several common classification methods:

1. Classification by pressure level

General boiler tubes: Suitable for medium and low pressure boilers, with low pressure.
High-pressure boiler tubes: Used for high-pressure and ultra-high-pressure boilers, and can withstand higher pressure and temperature.

2. Classification by material

Carbon steel boiler tube: For example, 20G, carbon steel tube has good processing performance and welding performance, low price, and is used for medium and low pressure boilers.
Alloy boiler steel tube: For example, 15CrMoG, 12Cr1MoVG, has higher heat resistance and strength, and is used for high pressure and ultra-high pressure boilers.
Stainless boiler steel tube: For example, TP304H, TP347H, has excellent corrosion resistance and high temperature resistance, and is used for boilers under special working conditions.

3. Classification by manufacturing process

Seamless steel pipe: Produced by hot rolling or cold drawing process, without welds, good integrity, high strength, used for high pressure and ultra-high pressure boilers.
Welded steel pipe: Made of steel plate rolled and welded, with high production efficiency and low cost, used for medium and low pressure boilers.

4. Classification by purpose and transmission medium

Superheater tube: Used to heat saturated steam into superheated steam, withstand high temperature and high pressure, usually made of heat-resistant alloy steel.
Reheater tube: used to reheat the steam discharged from the high-pressure cylinder of the steam turbine to improve thermal efficiency. The working environment is similar to that of the superheater tube.

Economizer tube: used to preheat boiler feed water, reduce exhaust gas temperature, and improve boiler efficiency. It is usually made of carbon steel or low-alloy steel.
Water-cooled wall tube: arranged in the furnace, absorbs radiant heat, heats water into saturated steam, withstands high temperature and corrosion, and is usually made of heat-resistant alloy steel.

Boiling water tube: used to produce boiling water or steam.
Air preheater tube: used to preheat the air entering the furnace and improve combustion efficiency. It is usually made of steel resistant to low-temperature corrosion.

Air guide tube: used to transport steam or flue gas.
Main steam pipe: used to transport steam generated by the boiler to the user end or turbine.

5. Classification by shape

Smooth pipe: smooth surface, used for boilers under general working conditions.
Threaded pipe: with threads on the inner or outer wall, used to enhance heat transfer or increase strength.
Finned tube: The outer wall has fins to increase the heat exchange area and improve the heat exchange efficiency.

6. Other categories

Classification by size: such as outer diameter, wall thickness, length, etc.
Classification by standard: such as GB, ASME, DIN, etc.

What factors should be considered when choosing a suitable boiler tube?

The following factors should be considered when choosing a suitable boiler tube:

1. Working conditions
Working pressure: The boiler tube needs to withstand the pressure of the medium inside the boiler. The higher the pressure, the higher the strength requirement of the boiler tube.
Working temperature: The boiler tube needs to withstand high temperature. The higher the temperature, the higher the heat resistance requirement of the boiler tube.
Medium properties: The medium flowing in the boiler tube may be water, steam, flue gas, etc. Different media have different corrosiveness to the boiler tube, and corresponding corrosion-resistant materials need to be selected.

2. Boiler type

Boiler structure: Boilers of different structures have different requirements for the shape, size, and layout of boiler tubes.
Boiler capacity: The larger the boiler capacity, the more boiler tubes are required, and there are also different requirements for the specifications and models of boiler tubes.

3. Material properties

Strength: Boiler tubes need to withstand a certain amount of pressure, so it is necessary to select materials with sufficient strength.
Heat resistance: Boiler tubes work at high temperatures, so it is necessary to select materials with good heat resistance to ensure their long-term stable operation.
Corrosion resistance: Boiler tubes need to withstand the corrosion of the medium, so it is necessary to select materials with good corrosion resistance to extend their service life.
Processing performance: Boiler tubes need to be bent, welded and other processes, so it is necessary to select materials with good processing performance.

4. Economic efficiency

Material cost: The prices of boiler tubes made of different materials vary greatly. It is necessary to select materials with high cost performance while meeting the use requirements.
Processing cost: The costs of different processing processes are different, so it is necessary to select processes with low processing costs.
Maintenance cost: The maintenance cost of boiler tubes also needs to be considered, such as replacement frequency, maintenance difficulty, etc.

5. Other factors

Standard specifications: The selection of boiler tubes needs to comply with relevant national standards, industry standards, etc.
Supplier qualifications: Select qualified and reputable suppliers to ensure the quality and after-sales service of boiler tubes.

In short, choosing a suitable boiler tube requires comprehensive consideration of the above factors, and a technical and economic comparison, and ultimately choosing the most suitable boiler tube.

Read more: Boiler tube materials and standards or Carbon steel ERW boiler tube & air heater tube specification