The issue regarding the pressure rating of equipment manholes: why are all the pressure standards in the PN series?

. . . What’s wrong with using PN? After all, they are both manholes, and the tube sections are also basically rolled. Does the leader have OCD?

Just draw it yourself – replace the flange and flange cover with those that meet CLASS standards; nothing else needs to change

Currently, the standard manhole specifications commonly used in China are mostly those from series such as HG/T 21514. The pressure grades of these standards are usually classified according to the PN series, such as PN0.25, PN0.6, PN1.0, PN1.6, PN2.5 MPa, etc.; there are few specialized manhole standards based on the Class series (e.g., American Class 150, Class 300, etc.). You mentioned that the device interface flanges are manufactured in accordance with the HG/T 20615 standard. In fact, HG/T 20615 draws on the flange systems of ASME and ANSI, using Class ratings such as Class150, Class300, Class600, etc.; it belongs to a different standard series from the PN classification system. In China’s pressure vessel and technical supervision industry, the PN series of standards are often used in design and manufacturing, whereas the ANSI/API system is more commonly employed in the petrochemical industry or overseas engineering projects. As a result, it is not uncommon to encounter situations where the interface flanges are of Class grade while the manhole standards are of PN grade. Common practices in practice: 1. If it is necessary to use manholes of the Class series, one can refer to the corresponding dimensions specified in Section VIII of the American ASME Boiler and Pressure Vessel Code (ASME BPVC VIII), as well as ANSI/ASME B16.5 (standard flanges) or ANSI/API 650 (international standards for storage tanks), in order to carry out a custom or tailored design. 2. Currently, there are no specific industry standards or sets of specifications for manholes designed for the pressure classes of the Class series in China. Therefore, in engineering projects, when Class flanges prove incompatible with PN-rated manhole interfaces, the issue is usually resolved through conversion or by designing special solutions, with the specific methods being determined through design and calculation based on the actual operating conditions. Conclusion and recommendations: – Domestic standard manholes are mainly classified by PN ratings; no standards specifically for Class series manholes have been issued yet. - If the Class series is truly necessary, foreign standards (such as API, ASME codes, etc.) can be utilized for design calculations and verification for specific pressure levels, thereby enabling custom design. - Common approach: Directly convert the Class rating to the nearest corresponding PN pressure rating in order to select a standard manhole, or carry out custom design, processing, and manufacturing based on the actual project requirements. .

Standard American flanges are used, and design must be carried out by oneself.

The manhole itself is a component that does not require any external connections; then why are there two different flange standards?

Don’t you like the national standard? Then the Asmi manhole can be chosen