Need to confirm standard system

There are two main international flange standard systems. One is the European flange standard system represented by the European Union EN standard (nominal pressure rating represented by PN), and the other is the American flange standard system represented by the American ASME standard (nominal pressure rating represented by Class). In addition, there is also Japan's JIS standard system (nominal pressure rating expressed in K). But JIS is not commonly used, so today we will mainly discuss the European and American flange standard systems.

The EN flange standard system consists of two systems: EN1092-1 based on the original DIN (German Standard), NF (French Standard), and BS (British Standard), and EN1759-1 based on ASMEB16.5. EN1092-1 is the most commonly used. EN1092-1 includes 7 grades with nominal pressures of PN2.5, PN6, PN10, PN16, PN25, PN40, and PN100, and nominal sizes of DN10-DN4000.

The American standard ASME flange standard system mainly consists of two standards, ASMEB16.5 and ASMEB16.47. The diameter range of ASMEB16.5 is DN600 and below, and ASMEB16.47 includes two series A and B, which are used in situations above DN600. ASMEB16.47A was developed based on MSS SP-44. ASMEB16.47B was developed based on API605. It should be noted that the A and B series of ASMEB16.47 distinguish between paired dimensions and other external dimensions, and are two different concepts from the English and metric outer diameters of flange connection ends.

Need to confirm flange matching size and pipe size

The matching size of a flange refers to the number of bolts, bolt diameter, sealing surface width, sealing surface height, and other dimensions of the flange. Only when these dimensions of two flanges are completely consistent can the accurate connection and reliable sealing of the flange be maintained. It is obvious that flanges of different standard series and pressure levels cannot be paired.

Need to confirm nominal pressure level

The nominal pressure rating is a grouping of flange strength. The maximum allowable non impact working pressure at a specific temperature varies for flanges of different materials and nominal pressure levels, which is the concept of temperature pressure rating. (know more about it: Standard pressure rating of flanges)

Regarding the correspondence between European and American standard flanges

Actually, this question is very common and many people may have doubts about it. Firstly, the matching sizes are different, and secondly, the outer diameter of the connecting pipe may be the same or different. More importantly, can the flange of CL150 be used in situations with PN2.5, PN6, PN10, and PN16? Then you need to check the corresponding flange standards to see if the specific temperature and pressure rating (the maximum allowable working pressure of a flange made of a specific material at working temperature) can meet the requirements. However, pairing flanges with PN2.5, PN6, PN10, and PN16 is likely not possible. Please refer to the specific standards.

How to mark the flange

At least, you should indicate the following information: pressure rating, material, sealing surface type, outer diameter and wall thickness of the connecting pipe.

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