The DF piping system should be cleaned periodically and checked for corrosion, wear and deformation. If necessary, the double headed bolts and forged valves shall be subjected to magnetic powder, coloring or ultrasonic testing.
On one of the following circumstances, when necessary, take a cut (to include weld) destructive test, test content including chemical composition, mechanical properties, impact toughness (wall thickness greater than 12 mm), and can continue to use is determined according to the inspection results:
A may affect the strength of metallic materials and structures in the case of over temperature, over pressure and over cooling during use;
B, control the service life with creep rate, the service life is close to the service life;
C a pipe that is likely to cause high temperature hydrogen corrosion. The results of external tests shall be recorded in the piping file in detail.
Magnetic or penetrant inspection shall be applied to the pipe and weld surface. A longer pipe that cannot be assembled can be tested only on suspected parts.
Conduct 20% ultrasonic or radiographic inspection of pipe welds. For pipe sections connected with the containers in welded form, 40% ultrasonic or radiographic inspection shall be carried out. Random inspection found excessive defects, it should be expanded inspection, such as the continuous detection of excessive defects, should be all remaining weld inspection.
Check the erosion of the inner and outer surfaces of the pipe, check the inner surface of the straight pipe, the bent pipe, the three pass and so on.
The tube end screw, sealing surface and sealing surface of flange for macroscopic examination. The pipeline corrosion and serious vibration, the pipe end thread parts should be colored or magnetic particle examination.
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