National standards, American standards, European standards, German standards – it’s a bit confusing,,,

Chemical standards are more appropriate for the chemical industry

Just take it literally: GB national standard, **the minimum standard. HG Chemical Industry Department standards, industry standards. Industry standards are higher than **standards.

HG/T20592-2009 corresponds to European standard flanges, while HG/T20615-2009 corresponds to American standard flanges; HG/T20615-2009 is identical to ASME B16.5. In the petrochemical industry, either HG/T20592-2009 or HG/T20615-2009 is generally used. GB/T19115-2010 is rarely used.

HG flanged piping is available in metric, European, and British standards, while GB flanged piping uses American and British standard pipes.

It is recommended to use American standard flanges, ASME B16.5, and for larger diameters, the B16.47 A series. Using domestic flange standards, there are many of them, which makes selection and application quite challenging. Replacing them later is even more troublesome. Specifically: 1. After the standards are updated, the dimensions change. For example, using a flange according to a certain standard from the 2009 model year – the 2010 version – will have slightly different dimensions in some cases. If ordered this way again, it won’t be able to connect. 2. Scattering within the standard range: For example, this system uses a certain flange standard, and people choose that standard assuming it’s the right one; later on, it turns out that there are no specifications available for sizes above DN400, nor is it indicated which standard should be used. 3. After selecting a certain standard, sometimes there are no corresponding accessories for pressure levels above a certain threshold, such as 8-shaped blind flanges. 4. Even with standard sizes, individual items can be defective, which can also lead to failure in connection. 5. Some standards become obsolete quite quickly as they are updated; for example, a certain standard used ten years ago is now rarely used, and engineers new to this field have never even heard of it. 6. Replacement is troublesome; for example, if equipment needs to be replaced later, it is difficult to ensure that the new equipment can be connected properly without knowing the exact flange standard and model year, as different versions may have different dimensions. Moreover, if only the domestic standard is known, the equipment manufacturer cannot determine whether it is based on JB, GB, HG, or SH standards It’s difficult; there’s only surveying and mapping, and even that doesn’t guarantee anything, which is problematic. In short, there are too many standards, they lack coherence, and it’s troublesome. Using American standards, in the simplest case, it is sufficient to inform the manufacturer of the length according to American standards; a raised-face flange along with the valve provided will suffice.

If you look closely, actually the two are the same. Both HG and GB are based on the American and European standards, merely combining the two into one.

HG and GB are now basically consistent.

GB flanges are probably used more in the municipal industry

This post was last edited by longziyun on 2018-9-10 at 12:51. For security reasons, the design standards for process media in the petrochemical industry should follow American standards, as they are more reliable.