Flange standards define the dimensions, bolt patterns and pressure ratings of pipe flanges, so that valves, instruments and pipes from different suppliers fit together. The most common flange standards in industry are JIS (Japan), DIN / EN 1092-1 (Germany / Europe), ANSI / ASME B16.5 (USA) and BS 4504 (UK). This guide summarises each standard and its pressure classes.
JIS flange standard – 5K, 10K, 16K, 20K
JIS stands for Japanese Industrial Standards. JIS flanges (JIS B2220) are widely used in Japan and across Asia, including Vietnam. Classes are expressed in “K” (kgf/cm²):
| Class | Working pressure |
|---|---|
| JIS 5K | Up to about 5 bar |
| JIS 10K | Up to about 10 bar |
| JIS 16K | Up to about 16 bar |
| JIS 20K | Up to about 20 bar |
The Japanese standards system began in 1921 as JES and was renamed JIS; current flange dimensions follow JIS B2220.
DIN / EN flange standard – PN6, PN10, PN16, PN25, PN40
DIN stands for Deutsches Institut für Normung (German Institute for Standardisation). DIN flanges have been superseded by the European standard EN 1092-1, but the PN designation remains the same and is used throughout Europe. PN is the nominal pressure in bar:
| Class | Working pressure / typical use |
|---|---|
| PN6 | Up to 6 bar – flat-face slip-on flanges |
| PN10 | Up to 10 bar |
| PN16 | Up to 16 bar – the most common class for water and steam |
| PN25 | Up to 25 bar |
| PN40 | Up to 40 bar – boiler and high-pressure lines |
ANSI / ASME flange standard – Class 150, 300 and above
ANSI (American National Standards Institute) flanges are now specified by ASME B16.5 and used worldwide, especially in oil & gas and petrochemicals. Classes include 150, 300, 600, 900, 1500 and 2500. At ambient temperature, Class 150 carbon steel is rated about 20 bar and Class 300 about 50 bar; ratings fall as temperature rises.
BS 4504 flange standard – PN2.5 to PN40
BS (British Standards, by the BSI) flanges to BS 4504 use PN classes like DIN: PN2.5, PN6, PN10, PN16, PN25 and PN40. PN6 suits low-pressure valves and pumps; PN10 is common in fire-fighting and water lines; PN16 is one of the most used classes; PN40 flanges are made in carbon steel (SS400, A105) or stainless steel (SUS304, SUS316).
How to choose the right flange standard
- Match the flange of the existing pipe or equipment – standard and pressure class must both match.
- Check pressure–temperature rating, not just nominal pressure.
- When ordering instruments (flow meters, level gauges, transmitters), always state the flange standard, e.g. “DN50 PN16 EN 1092-1” or “2” Class 150 ASME B16.5″.
Related products
Where to buy flanged instruments and fittings?
EQUIPMENT INDUSTRIAL SOLUTION CO., LTD (ISE) – Ho Chi Minh City, Vietnam – supplies genuine flanged instruments and fittings with technical consulting, fast quotation and on-site commissioning support across Vietnam and Southeast Asia.
Contact us: Sales +84 909 617 185 – Technical +84 979 117 185 – Email: [email protected]
