First, high pressure seamless pipe quality problems
Boilers with high pressure seamless pipe is an important material for manufacturing boiler pipe, the quality of how it will be directly related to the the boiler manufacture of quality so that the quality of the installation and use of quality. High pressure seamless steel quality should by steel pipe factory to make a guarantee, but in the case of short supply, the use of high-pressure supplied to the boiler manufacturers seamless steel pipe always found some quality problems, it made boiler pressure components such as water wall tubes, convection tubes, superheater tubes, heat exchanger tubes leaking or burst pipes phenomenon have occurred, has become a big problem that plagued boiler product quality, this boiler manufacturers and users are opinions. In the case of a seller's market, the boiler manufacturer almost assume full responsibility for the material supply side, including; how to control the quality of the boiler tube is now a boiler manufacturers are increasingly concerned about the problem, the solution is no more than two : a root-by high pressure seamless steel pressure test; another high pressure seamless implementation of 100% eddy current testing.
Second, high pressure seamless pipe defects and injuries
Excellent metal materials in accordance with the point of view of materials science, chemical composition, physical properties, geometry should be continuous, pure and uniform. If these three are deficient or damaged by a metal material, it is considered defective. If the metallic material is a discontinuity exists in geometry (i.e. does not close or not dense or non-dense), for example, cracking, shrinkage, from the skin, the dimple, layered, pinholes, slag, etc. Scar (referred to as the injury) exists that the metal material, it does not include the discontinuous chemical composition or physical properties of discontinuous. As can be seen from here, defects contains wounded. The boiler steel smelting and rolling process in the same possible defects and injuries. According to Steel Pipe Plant, boiler tube defects (here mainly refers to the injury), mainly in the surface, more than the inner surface and the outer surface. Raw material (billets), about 70% of these defects from billet enough oxygen blowing in the slag material, shrinkage and other remnants of folders, use it rolling steel pipe there may be transverse cracks, mezzanine, folding, heavy leather defects longitudinal cracks are mostly the strain caused by the rolling. If these defects or wounds in the high pressure seamless, it appears that the material is not continuous, the compactness of the material inside the damage in the hydrostatic test, there may be leaks, made of boiler pressure parts running is likely to leak or burst pipe. Because of this, in order to ensure the quality of boiler tube, whether Chinese or foreign boiler seamless steel tubes for standard defined as a process performance guarantee, the pipe should be out by the root for hydrostatic testing.
Third, the hydrostatic test of the boiler tube density test
Is generally believed that the purpose of hydrostatic testing two types: one is the hydrostatic testing of the craft, its purpose is to test materials (or components) for leaks, the sealing performance of the test material; another confirmatory hydrostatic test, the aim is to test the strength of the material (or member) whether sufficient. From here we can see, the hydrostatic test of the boiler tube is the process of hydrostatic test, material density test, the test material is continuous and whether dense; it is not to verify the strength test. Seen from the strength of the material mechanics theory, seamless steel tubes are thin and long component, its small diameter, thin tube wall thickness thinner under a lot of pressure.