Selection and welding process of boiler tubes

What is a boiler tube?

A boiler tube is a metal tube located inside a boiler that is used to heat water to produce steam. There are two main types of boiler tubes: water tube boilers and fire tube boilers. According to the production method, it can be divided into seamless boiler tubes and welded boiler tubes.

In a water tube boiler, water circulates inside the tube and is heated outside by hot air generated in the furnace. In a fire tube boiler, hot air passes through one or more pipes and heats the surrounding water by heat conduction.

How to choose a suitable boiler tube?

Choosing a suitable boiler tube is an important step to ensure the safe operation of the boiler.

1. Tube diameter and wall thickness: When purchasing a boiler tube, the appropriate tube diameter and wall thickness should be selected according to the use conditions of the boiler. If the tube diameter is too small or the wall thickness is insufficient, it will cause safety problems such as excessive boiler pressure and water leakage.

2. Material: The boiler tube material is also very important. Different boiler uses require boiler tubes of different materials. Generally, ordinary carbon steel tubes are used for low-pressure boilers, alloy steel tubes or stainless steel tubes are used for medium and high-pressure boilers; special materials are required for ultra-high-pressure boilers.

3. Corrosion resistance and heat resistance: Different boiler use environments will also affect the selection of boiler tubes. For example, in acid, alkali, high temperature and other environments, corrosion-resistant and heat-resistant boiler tubes need to be selected.

Boiler tube welding process:

When repairing or installing boiler tubes, boiler tubes need to be welded. The connection of boiler tubes can be seamless or welded. Welding is divided into manual welding and automatic welding. Manual welding is suitable for small and single product production, and automatic welding is suitable for large and batch production.

Welding method:

According to the model and requirements of the boiler tube, the commonly used welding methods include argon arc welding, submerged arc welding, manual arc welding, etc.
The automatic welding process is easy to control and stable, and the weld quality is relatively high, but it is suitable for production with high quality requirements. Manual welding is relatively flexible, but it requires the welder to have a high technical level, and the weld quality will be greatly affected.

Welding materials:

The selection of welding materials is directly related to the compliance of performance indicators such as impact resistance, heat resistance, and corrosion resistance. Depending on the material of the boiler tube, the selected welding materials are also different.

For carbon steel boiler tubes, E4315, E5015 and other welding rods are generally used, which are suitable for submerged arc welding and manual welding. If the welding quality requirements are high, low-hydrogen welding rods E5016 or E5516 can be used. For special materials such as alloy steel and stainless steel, select the corresponding E70 welding material for welding.

Precautions for welding boiler tubes:

1. Welding position and angle: When welding boiler tubes, you need to pay attention to the welding position and angle. Before welding, you should carefully clean the welding surface to ensure that it is clean, bright and beautiful. During the welding process, the weld should be neat and firm to avoid cracks, pores and other problems, and prevent foreign debris from falling in.
2. Types of welding rods: Different types of welding rods are required for welding boiler tubes of different materials. Generally speaking, carbon steel boiler tubes can use E43 series welding rods, and alloy steel boiler tubes need E70 series welding rods.
3. Welding temperature and time: The temperature and time should be strictly controlled during welding. The welding temperature should meet the requirements of the welding materials, and the welding environment should be kept clean and hygienic to avoid affecting the welding quality.
4. After welding, the weld should be inspected to ensure that its quality meets the standards.

Conclusion:
Welding is an indispensable part of the production process of boiler tubes. Correct selection of welding materials and methods, attention to welding details, and quality inspection can effectively improve the service life and safety performance of boiler tubes.

Read more: What are seamless boiler tubes and how are they made?