Issues regarding the selection of specifications for nuts and fasteners used in pipe flanges
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This post was last edited by zjq1962 on 2018-5-2 08:16. In the HG/T20613 standard, the standard for fine-threaded nuts used in specialized applications is GB/T6176, with the largest size being M56. However, according to the GB/T6176 standard, the maximum size for nuts is M36. To avoid this issue, the standard for nuts in container flanges does not use GB/T6176 but instead NB/T47027. As shown in Figure 1, 1 represents the standard for pipe flanges, 2 represents the standard for nuts, and 3 represents the standard for container flanges. What do fellow maritime professionals think about this issue? Is it a negligence on the part of the standard compilers for pipe flanges?
It must have been an oversight; there can be no other explanation.
The key question is, what if it can’t be purchased?
There is an issue with the specifications in the table. For sizes below M36, GB/T6175 and GB/T6176 are applied; for sizes from M39 and above up to M56, the nut size specifications in standard HG/T20613-2009 are used. In HG/T20592-2009, the maximum size for flange bolts is M56. It basically meets the requirements. If it exceeds the M56 specifications, the HG/T20634-2009 standard or high-pressure standards can be referred to.
That’s right; nuts larger than M36 are selected in accordance with Table 3.0.5-1 of the standards, as Table 5.0.4 of the standards does not provide clear guidance on this matter.
I wonder if fellow sailors have noticed this: the specification M33 is not included in GB/T6175. So how is this standard formulated then?
This post was last edited by Baoji ChaoSheng Titanium Industry on 2018-5-4 at 11:07. This is the old standard, right? It is specified on page 190 of HG/T20613-2009. I can’t upload pictures. You can look it up by yourself. The new standards also include M56
You are absolutely right; in HG/T20613, it refers to studs, while the standards for nuts only list GB/T6170, 6171, 6175, and 6176.
Yes, this is a flaw in the standard formulation; American standards do include nuts specifically designed for pipe flanges.