What are the technical requirements for galvanized pipes?
In order to increase the service life of
smls pipes or welded pipes, steel pipe manufacturers often choose galvanized pipes. There are two types of galvanized pipes: hot-dip galvanizing and electro-galvanizing. Hot-dip galvanizing has a thick galvanizing layer and has the advantages of uniform coating, strong adhesion, and long service life. The cost of electro-galvanized pipes is low, the surface is not very smooth, and its corrosion resistance is much worse than that of hot-dip galvanized pipes.
Galvanized pipe technical requirements
1. Brand and chemical composition
The grade and chemical composition of the steel used for galvanized steel pipes should comply with the chemical composition of the steel used for black pipes.
2. Manufacturing method
The method of manufacturing the clarinet (furnace welding or electric welding) is chosen by the manufacturer. Galvanizing adopts hot dip galvanizing method.
3. Threads and pipe joints
(1) Galvanized steel pipes delivered with threads should be threaded after galvanizing.
(2) Steel pipe joints shall comply with the requirements of YB 238; malleable iron pipe joints shall comply with the requirements of YB 230.
4. Uniformity of galvanized layer Galvanized steel pipes should be tested for uniformity of galvanized layer. The steel pipe sample should not turn red (copper-plated color) after being soaked in copper sulfate solution for 5 consecutive times.
5. Cold bending test Galvanized steel pipes with a nominal diameter not larger than 50mm should be subjected to cold bending test. The bending angle is 90°, and the bending radius is 8 times the outer diameter. No filler is used during the test, and the weld of the sample should be placed on the outside or upper part of the bending direction. After the test, there should be no cracks or peeling of the zinc layer on the specimen.
6. Hydraulic pressure test The hydraulic pressure test should be carried out on the black pipe, and eddy current flaw detection can also be used instead of the hydraulic pressure test. The test pressure of eddy current flaw detection or the size of the comparison sample should comply with relevant regulations.
Technical requirements for galvanized welded steel pipes for low-pressure fluid transportation
1. Uniformity of galvanized layer: the steel pipe sample should not turn red (copper-plated color) after being immersed in copper sulfate solution for 5 consecutive times.
2. Surface quality: The surface of galvanized steel pipes should have a complete zinc coating, and there should be no uncoated black spots and bubbles. Small rough surfaces and local zinc tumors are allowed.
3. Galvanized layer weight: According to the requirements of the buyer, galvanized steel pipes can be used to determine the galvanized layer weight. The average value should not be less than 500g/square meter, and any sample should not be less than 480g/square meter.
Process characteristics of galvanized pipes
1. Optimization of sulfate galvanizing process
2. Sulfate galvanizing transformation
3. Fast deposition rate and excellent protective performance
4. Unique clean production
5. Particularity of electroplating equipment