Location of the equipment ellipticity inspection and measurement
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According to GB50461-2008 \"Code for Acceptance of Construction Quality of Installation of Petrochemical Static Equipment\", 5.3.13 stipulates that the difference between the maximum and minimum internal diameters of the shell after the spherical tank is assembled should be less than 3‰ of the designed internal diameter of the spherical tank, and shall not exceed 50 mm. For other equipment, after assembly, the difference between the maximum and minimum diameters of the shell shall comply with the following requirements: 1 The difference between the maximum and minimum inner diameters at the same cross-section of the shell shall not exceed 1% of the inner diameter at that cross-section (1‰ for forged-welded containers), and shall not be greater than 25 mm. 2 When the section under inspection is located within a range equal to one time the inner diameter of the opening at its center, the difference between the maximum and minimum inner diameters of that section shall not exceed the sum of 1% of the inner diameter of that section (1‰ for forged-welded containers) and 2% of the inner diameter of the opening, and shall not be greater than 25 mm. I’m not quite sure about the meaning of point 2: is the measured end face located on the hole itself, or at a distance equal to one diameter from the hole? If the center of the hole lies on the measured end face, then is the maximum inner diameter equal to the diameter of the circular cross-section, and the minimum inner diameter equal to the diameter at the point where the circle of the hole intersects the circle of the end face?
This post was last edited by bluishice on 2019-10-8 at 16:26. The range within one diameter of the center of the opening, expressed in numerical terms: the opening diameter D, which refers to the area enclosed by a circle with the center of the opening as its center and D as its diameter; this circle is calculated along the arc length of the cylinder. Since it is a curved surface, describing it is rather cumbersome. Note: The opening diameter D is not necessarily equal to the outer diameter of the fitting.
Can the “content of Article 2” be understood as follows: when measuring at the opening on a cylindrical shell with an opening, the maximum diameter is the actually measured diameter, and the minimum diameter is the diameter at the edge of the notch; the difference between these two diameters shall not exceed 1% of the sum of the inner diameter of the cylinder and 2% of the inner diameter of the opening.
It is still the size of a cylindrical shell. I guess it’s probably because the opening weakening and welding deformation have caused the roundness in that area to be slightly relaxed.
Take a look at GBT150, this standard!
Due to the effects of welding, the area where the hole is made will certainly experience some deformation. When measuring the roundness in the vicinity of the hole, an additional 2% of the inner diameter of the hole can be taken into account as a criterion for controlling the roundness of that area
For areas without openings, the ellipticity is controlled such that 1% ≯ 25 mm; for areas with openings, it is controlled according to the formula 1% + 2% of the opening size ≯ 25 mm. Since welding and other processes at the openings can cause deformation, the size of these openings is set to be larger. In other words, the requirements are slightly relaxed for cylinders smaller than DN2500mm, while the requirements remain the same for cylinders larger than DN2500mm, as the upper limit is 25mm.
For areas without openings, the ellipticity is controlled such that 1% ≯ 25 mm; for areas with openings, it is controlled according to the formula 1% + 2% of the opening size ≯ 25 mm. Since welding and other processes at the openings can cause deformation, the size of these openings is set to be larger. In other words, the requirements are slightly relaxed for cylinders smaller than DN2500mm, while the requirements remain the same for cylinders larger than DN2500mm, as the upper limit is 25mm.
Thank you, I watched it again recently and now I understand a bit better