Quality inspection method for low-pressure boiler tubes

Low-pressure boiler tubes refer to medium delivery pipelines with a pressure not exceeding 2.5MPa, which are mainly used to transport heat medium and water vapor. During the operation of the boiler, heat energy needs to be transported to various parts of the boiler through pipelines, such as kettles, drums, superheaters, etc., so as to achieve boiler heating and steam generation.

According to its material and purpose, it can be divided into various types such as ordinary carbon steel pipes, alloy steel pipes, stainless steel pipes, etc. For low-pressure boiler tubes, seamless pipes (SMLS) can be selected for production to improve efficiency and durability. Usually, water pressure, curling, flaring, flattening and other tests are required to ensure product quality and performance.

The methods for detecting the quality of low-pressure boiler tubes mainly include the following aspects:

1. Appearance inspection
The appearance of the low-pressure boiler tube is inspected by naked eyes, including the gloss of the outer surface, the flatness of the surface, and the presence of scratches, cracks and other defects. Attention should be paid to check whether there are problems such as desoldering and corner bending at both ends of the tube, and check whether there are abnormal conditions such as depressions and bulges on the tube wall.

2. Dimensional inspection
Measure the diameter, wall thickness, length and other dimensions of the low-pressure boiler tube. Use measuring tools such as calipers and micrometers to measure and compare with the manufacturing standards to check whether it meets the specified size range.

3. Internal inspection
Evaluate the internal quality of the low-pressure boiler tube through fluid or optical inspection methods. Fluid inspection usually includes testing the flow performance of the liquid or gas in the pipeline to detect leaks, blockages and other problems. Optical inspection can use equipment such as endoscopes to observe the welds, edges and corners inside the tube.

4. Chemical composition analysis
By analyzing the physical and chemical composition of the low-pressure boiler tube, it can be detected whether its material meets the standard requirements. Commonly used chemical analysis methods include spectral analysis, electron probe analysis, etc.

5. Stress test
By applying a certain stress on the low-pressure boiler tube, it is detected whether the pipeline can withstand pressure and maintain the stability of shape. Commonly used mechanical property testing methods include pressure test, impact test, hardness test, etc., to test the mechanical properties of the pipe such as strength and toughness.

6. Non-destructive testing
Such as ultrasonic testing, X-ray testing, magnetic particle testing, etc., to detect whether there are defects inside the pipe.

7. Metallographic analysis
The microstructure of the tube is observed under a microscope to evaluate its quality and performance.

In summary, the quality of low-pressure boiler tubes can be effectively evaluated through the comprehensive testing of the above aspects. When conducting the test, the relevant standards should be strictly followed, and accurate and reliable testing equipment and methods should be used to ensure the accuracy and reliability of the test results.

Read more: Which material is used for boiler tubes?