Boiler Tube Welding Gap Standard

Importance of boiler tube butt welding gap

Control of boiler tube butt welding gap is an important part of boiler tube welding process. Reasonable welding gap can ensure the uniformity and density of weld, improve the strength and sealing of welded joint, and ensure the safe operation of boiler. Therefore, it is very important to follow the standard specification of boiler tube butt welding gap.

Standard specification of boiler tube butt welding gap

1. Allowable misalignment value

During butt welding, the misalignment value of boiler tube should be controlled within a certain range.

According to the specification requirements, the local misalignment value of butt welding should not exceed 10% of the wall thickness, and the minimum should not be less than 1mm; the local misalignment value of butt welding should not exceed 10% of the thickness of weldment, and the maximum should not exceed 3mm.

This standard helps to ensure the flatness and strength of weld.

2. Butt centerline deviation

The butt centerline deviation is also an important indicator to measure whether the welding gap is qualified. Depending on the diameter of the pipe, the allowable deviation of the butt centerline also varies.

When the nominal diameter of the pipe is DN<100mm, the allowable deviation of the center line of the butt joint α should be ≤2mm; when the nominal diameter of the pipe is DN≥100mm, α should be ≤3mm. Controlling the deviation of the center line of the butt joint helps to ensure the symmetry and aesthetics of the weld.

3. Weld joint layout regulations

In order to ensure the quality of welding and facilitate welding and post-weld heat treatment, the layout of the weld joints of boiler tubes also needs to follow certain specifications.

The weld joints should avoid stress concentration areas to reduce the stress effects during welding.

The center line of the butt weld of the heating surface pipe should be at least 70mm away from the starting point of the pipe bending or the outer wall of the header and the edge of the support bracket to prevent the weld from being deformed by heat or damaged by external forces.

The distance between two butt welds on the same pipe shall not be less than 150mm to ensure that there is enough spacing between the welds to avoid overlapping of the heat-affected zones.

Precautions in actual operation

When performing boiler tube butt welding, in addition to following the above standards and specifications, the following points should also be noted:

1. Before welding, make sure to clean the boiler tubes, remove rust, oil and other impurities.

2. Select appropriate welding methods and welding materials to ensure the quality and performance of the weld.

3. During the welding process, parameters such as welding speed and temperature must be strictly controlled to avoid welding defects.

Summary

In summary, the gap standard for boiler tube butt welding is a key link to ensure the safe operation of the boiler. Only by strictly following the standard specifications can the quality and performance of the weld meet the expected requirements. Therefore, in actual operation, it is necessary to strictly abide by the relevant regulations and pay attention to detail processing.