The integrity of the Brazed weld seam to be inspected before the installation of the Brazed plate

Source: 　 Time: 2025-07-30 10:44:57　Hit:

Before installing the Brazed plate heat exchanger, the integrity of the brazed weld seam needs to be inspected to ensure that it can meet the usage requirements and safety standards of the equipment.

I. Visual Inspection

1. Wettability of the brazing surface and the brazing Angle

The brazing surface should have good wettability and the brazing Angle range should be less than 90°. For the brazed joint under force, the optimal brazing Angle range is 15° to 45°. For the brazed joint that is not subjected to force, the brazing Angle should be as small as possible.

2. Surface quality of weld seams

The weld seams should be continuous, uniform and smooth, and should not have burrs, pores or particles that affect usage. In addition, the area where the brazing filler metal flows over the base metal of the brazed joint should not exceed 3 mm around the weld seam.

3. Weld defects

Cracks, incomplete brazing and other defects are not allowed at the weld seams and joints. The surface of the weld seam should be free of defects such as cracks, pores, arc pits and slag inclusions.

4. Weld undercut and excess height

The undercut depth of the weld seam should not exceed 0.5mm, the continuous length of the undercut should not exceed 100mm, and the total length of the undercut on both sides of the weld seam should not exceed 10% of the length of the weld seam. The excess height of the weld seam should not exceed 1.5mm.

5. Weld cleaning

The slag on the weld seam and the spatter on both sides should be thoroughly removed to ensure the cleanliness and aesthetic appearance of the weld seam.

Ii. Internal Quality Inspection

1. Metallographic structure examination

By observing the microstructure of the brazing seam through metallographic specimens, it should be ensured that the brazing seam is fine and uniform, with all phases diffusing evenly. Cracks and overburned structures are not allowed. After the sample is etched, it is observed under a microscope at a magnification of 100 to 1,500 times.

2. Non-destructive testing

For important welds, non-destructive testing should be carried out, including radiographic testing, ultrasonic testing, magnetic particle testing and penetrant testing, etc., to ensure that there are no cracks, incomplete penetration and other defects inside the welds.

3. Air tightness test

After brazing, a gas tightness test should be conducted. Compressed air at a pressure of 2 atmospheres should be introduced into the assembled heat exchanger and placed in water for 5 to 7 minutes to observe if any bubbles are produced. If there are bubbles, brazing should be redone.

Iii. Other Matters needing Attention

1. The use of flux and solder

Excessive flux may cause corrosion, so flux must not be allowed into the Brazed plate heat exchanger. At the same time, the use of solder should comply with the specifications to ensure the uniformity and integrity of the weld seam.

2. Repair of weld seams

Brazing rework should not exceed once, and other welding reworks should not exceed twice. The rework process should comply with the relevant standards, and the number of rework times, parts and test results should be recorded in the quality certificate.

3. Assembly and fixation of weld seams

During the assembly process, it is necessary to ensure the correct alignment and fixation of the weld seams to avoid weld deformation or incomplete welding due to improper assembly.

Iv. Summary

Before installing the Brazed plate heat exchanger, a comprehensive inspection of the integrity of the brazed weld seam must be carried out, including visual inspection, internal quality inspection, non-destructive testing and air tightness test, etc. These inspection steps help ensure the uniformity, continuity and defect-free nature of the welds, thereby enhancing the overall performance and service life of the heat exchanger. At the same time, operations should be carried out strictly in accordance with relevant standards and norms to ensure that the quality of the weld seam meets the design and usage requirements.

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