Issues regarding weld quality. (I II III? ）
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We are waste heat boilers for gas-steam combined cycles, with main steam parameters of 3.82 MPa/450°C. The welding design specified by the design institute for the main steam pipes is actually: only 10% of the pipes to be inspected! ! ! The weld quality grade meets Level III requirements! ! Damn it, what an amateurish design firm! The first question can be found in Table 5 of DL/T 869-2012. 50% sampling should be sufficient, but as the owners, we require it to be increased to 100%. Second question: Are there any specifications that specify what the acceptable quality grade is for welds in steam pipes under certain pressure and temperature conditions? Is it Grade I, Grade II, Grade III, or Grade IV? It seems there are no regulations on this in NB/T 47013, nor in DL/T 869. . . DL/T 869 only provides a brief description of levels I, II, and III; there is no relevant information indicating what quality level is considered acceptable for welds in steam pipes operating under certain pressure and temperature conditions Also, is RT generally used for the non-destructive testing of pipe butt welds? I hope all the sea friends can give me some advice. Thank you everyone.
The quality grade of the boiler welding joints shall be no lower than Grade II, and the inspection technology grade shall be no lower than Grade AB.
Firstly, the main steam pipeline falls under the category of pipelines associated with boilers, and the primary standard for acceptance is the \"Regulations on Safety Supervision of Boilers\"; other standards serve as supplementary guidelines. For the non-destructive testing of pipe butt welds, RT is generally used in manufacturing and installation, while PT is typically employed during inspection. Your boilers are classified as Class A boilers; you just need to follow the relevant regulations, and it’s not as complicated as you think.
The pipes from the boiler outlet to ahead of the main steam valve are considered part of the boiler’s system and fall under the boiler’s jurisdiction； Is the area behind the valve the pipeline outside the boiler range? ? ?
It depends on what you plan to use it for. If it is used for power generation, then all the pipes up to the turbine fall under the category of boiler pipes； If it is not for power generation, the main steam valve is connected directly to the heat-consuming equipment after exiting; generally, within a range of 200 meters, the inspection standards for pipes in the boiler area can also be applied.
Is there any standard that specifies what quality grade (I/II/III, etc.) the welds of pipes at certain pressure and temperature levels must have? If you know which standard it is, let me know.
“For the non-destructive testing of pipe butt welds, RT is generally used in manufacturing and installation, while PT is typically employed for inspection – why is PT used for inspection? I don’t understand what it means. Can’t RT be used for testing?
The qualified grade for pressure boilers is the one I mentioned; as long as a boiler complies with the \"Regulations on Safety Supervision of Boilers,\" there is no difference in its qualified grade
RT is used less often for regular inspections, mainly because it is cumbersome; moreover, RT is already employed during installation and manufacturing. The severity of defects that are buried is lower than that of surface defects. Unless there are special requirements, PT inspection is sufficient for pipelines in general
May I ask which standard specifies this 200-meter limit? Thank you.
GB50184 specifies the classification of inspection grades for pipe welds