Are national standard flanges different from American and European standard flanges?

The so-called national standards refer to the flanges specified by the Ministry of Machinery, or GB flanges such as HG20592~~HG20635. The flanges specified by the Ministry of Chemical Industry are revised with reference to ISO7005, ANSI B16.5, and DIN standards; they are not directly based on those standards, and some of their dimensions differ

Are national standard flanges different from American and European standard flanges? Many of them are the same. I just asked the manufacturer, and they said that national standards are different from American and European standards. But don’t the specifications for pipe flanges HG20592~HG20635 reference those European and American systems? I agree with what was said above regarding this issue

HG flanges follow European standards, while SH and SY flanges adhere to American standards. The key is to check the dimensions of the flanges when using them; as long as they fit together, they can be connected

At present, there are four types of flange standards in use in our country: **national standards (GB/T9112~9124-2000), chemical industry standards (HG20592~20635-1997), petrochemical industry standards (SH3406-1996), and machinery industry standards (JB/T74~86.2-1994). Although the four types of flanges mentioned above differ in terms of standard grades and industries to which they are applied, the standards they follow are all ISO 7005-1, DIN flange standards, and ANSI B16.5 (petroleum industry standards include ANSI 16.47). Only the mechanical flanges use the former Soviet Union’s ГОСТ flange standards, yet these also belong to the European flange system. Therefore, the substitutability between these standards and the interchangeability of standard flanges is quite evident. The GB/T9112~9124-2000 series of standards for **steel pipe flanges are based on the use of the HG20592~20626-1997 standards in the chemical industry, which deal with steel pipe flanges, gaskets, and fasteners. The advantages of those standards have been incorporated into these new standards, whose overall structure has been improved to be consistent with or equivalent to that of the standards used in the chemical industry. Interchangeability of flange dimensions between petrochemical industry standards and national standards for flanges belonging to the American system. Flange sizes belonging to the European system (Series II) in mechanical industry standards and national standards are interchangeable, but there are three flanges in mechanical industry flange standards that cannot be interchanged with national standards: PN0.25MPa–DN500, PN0.6MPa–DN500, and PN1.0MPa–DN80, due to differences in the number of bolts. It can be seen that the standard levels and dimensions of chemical industry standards are basically consistent with those of national standards, allowing for interchangeability of dimensions. Therefore, it is entirely feasible to manufacture valves according to national standard flanges and to use flanges specific to the chemical industry during installation.

I have compared the dimensions of national standard flanges and those according to the Ministry of Chemicals’ standards, and they are exactly the same; it’s just the standard numbers that differ

Internationally, there are mainly two systems for pipe flange standards: the European pipe flange system represented by German DIN (including the former Soviet Union), and the American pipe flange system represented by American ANSI. In addition, there are Japanese JIS pipe flanges, but they are generally used only for utility systems in petrochemical plants, and have little influence internationally.

National standard flanges are similar to European standard flanges, but quite different from American standard flanges.

It should be different; to know what’s best to do, it’s necessary to have specific standard specifications and drawings, as this will prevent mistakes. For example, national standards and American standards differ in terms of dimensions. When it comes to manufacturing pipe fittings such as elbows and flanges, it’s best to provide the manufacturer with the entire pipeline system, so that they know what kind of pipes to use and can work more easily.

What was said on the 5th floor is correct – the valves follow the JB standard. Then are the two flanges on the valves themselves also flanges that meet the JB standard?

In my opinion, national standard flanges refer to Series B of the European system specified in the Ministry of Chemical Industry’s flange standards. The difference from the A series is only the inner diameter of the connection tube ； National standard flanges and those from the American system certainly cannot be matched.

It’s different from the US standard. Same as EU standards

PN European standard, class American standard

We have many flange standards; some are similar to the American standards, while others are similar to the European standards. For example, HG20615 is similar to the American standards, whereas HG20592 belongs to the European system. There are also standards such as JB and GB, which are different from the others.

HG20592 is similar to European standards and also to the so-called national standards, so it can be used as a substitute; however, it differs from American standards, which are more similar to HG20615.