what the gasket used for the nozzle during the pressure test

17.1.3 of HG/T 20584-2020 "Technical Specifications for the Manufacturing of Steel Chemical Containers" requires that the gasket used for the nozzle during the pressure test should be equivalent to the equipment product gasket.

This provision did not exist in the previous edition (2011 edition), but the standard used the vague word "equivalent", and did not distinguish between standard flanges and non-standard flanges (as we all know, in fact, standard flanges have passed the Long-term practical test, its sealing is guaranteed, in fact, there is no need to test it again with the pressure test), which leaves room for all parties to pull.

ASME VIII.1-2021 version also added relevant requirements, but the regulations are more specific, see the new provisions of the standard UG-99 (l) and UG-100 (g), which are respectively applicable to hydraulic test and pneumatic test.

As shown in the figure below, UG-99 (l) stipulates that: for non-standard flanges, the same gaskets as those used in the operation of the equipment should be used during the hydraulic test, or the same size (inner diameter, outer diameter, thickness) and m, y-value shims, but at the same time allow the user to request a waiver due to cost considerations. However, the standard recognizes that the use of gaskets or fasteners that differ from design calculations may not necessarily adequately verify the integrity of flanged joints. 

Finally, by the way, in general, in addition to metal ring gaskets, spare gaskets supplied by suppliers or gaskets that need to be installed on site cannot be used for the manufacturer's withstand voltage test.

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