Standard flange

As long as the applicable conditions of the flange standards are met.

Generally, the HG and JB standards are adopted, but more importance should be given to the user’s piping* practices.

No, equipment designers generally determine which standard should be used for the flanges based on the requirements specified in the manufacturing process; it’s not a matter of choosing arbitrarily, unless the customer has no specific requirements

According to Article 54 of the regulatory standards, the design of fasteners for gaskets on pipe flanges of steel pressure vessels shall comply with the provisions of the industry standards HG20592-20635. Therefore, the HG standard is given priority. But if there are valves or similar on the container, there is nothing to do; in some cases, the JB standard must be adopted. Because the valves are all manufactured in accordance with JB standards. The outer diameters of the flanges vary, and the diameter of the bolt holes also differs in some cases. When selecting them, it is essential that all dimensions match; otherwise, it is better to choose those of type JB, as this will avoid any problems. The new HG standard has been released; factors unrelated to valves have been taken into consideration and adjustments have been made. I haven’t seen the new standard yet. I just have this impression. In short, be very careful when selecting a flange that matches the valve.

According to the process-specific requirements; if none are available, the standards set by the Ministry of Chemical Industry are generally adopted.

As a supplementary note, JB is still more commonly used for steam distribution cylinders.

The HG20615 HG20615 flange standard is the one that gives priority to tolerance specifications

According to Article 54 of the relevant regulations, the design of fasteners for gaskets on pipe flanges of steel pressure vessels should follow the provisions of the industry standards HG20592-20635; therefore, flanges specified by the Ministry of Chemical Industry are generally used in vessel design； However, JB flanges are mostly used on boilers; therefore, I believe that for container design, chemical industry flanges should be preferred first, followed by mechanical industry flanges.

Generally, for newly designed chemical processing equipment, we adopt the HG flange standard; if it is equipment replacement, then we follow the standard of the flanges used for pipeline connections by the customer. If the flange standards are provided on the user condition chart, it’s simple.

As long as the applicable conditions and usage conditions of the flange standards are met

According to the regulatory requirements, the HG flange standard should be used; however, design institutes and users generally prefer the GB and JB standards. I have compared GB flanges with those specified by the Ministry of Chemical Industry, and they are basically the same. There are a few differences in the specifications outlined by the Ministry of Machinery (I recall that the DN80 specification is different). Therefore, when choosing a flange standard, it is not possible to use them interchangeably – it is necessary to check the dimensions carefully.

The designer generally determines which standard should be used for the flange based on the requirements specified in the manufacturing process; it is not chosen arbitrarily, unless the customer has no specific requirements

In fact, the difference between flanges of the same specification under mechanical industry standards and chemical industry standards lies in two aspects: first, the outer diameter of the flanges is different, with those under the mechanical industry standards being smaller； Secondly, since flanged pipes are divided into Series A and Series B, the neck dimensions of flanges for certain specifications differ; for example, DN100 pipes have outer diameters of 114 and 108, while DN150 pipes have outer diameters of 159 and 168. As a result, connection problems often arise due to inconsistent use of standards.

The national standard flange standards are consistent with the chemical industry standards (divided into European and American series), but they differ from the standards set by the Ministry of Machinery. The flanges of the mechanical department are compatible with B-series pipes, while the flanges according to chemical industry standards are compatible with A-series pipes.

It should be selected according to the flange standards of the relevant industry

According to the capacity regulations, HG20592-635 is generally used

For pressure vessel flanges, JB/T4700-2000 is applied; for pipe flanges, HG, GB, SH, and JB/T standards can be used according to the requirements of the project.