Summary: DIN flanges are commonly specified by DN size and PN pressure designation. For pressure gauges and diaphragm seals, the standard, facing, material, bolt pattern, diaphragm diameter and process conditions must all match—not only the nominal pipe size.
Many plants still use the term “DIN flange” for European PN-designated flanges. In current projects, steel flanges are generally checked against EN 1092-1 or the applicable project specification, while older drawings may refer to standards such as DIN 2527. Always verify the exact standard and edition stated on the piping drawing or purchase specification.
What Does a DIN Flange Standard Describe?
A flange standard defines the geometry and identification needed for compatible assembly. Depending on the document, it may cover flange types, facing, dimensions, tolerances, materials, bolt-hole arrangement, marking and testing requirements.
- DN: nominal size used to identify the piping connection.
- PN: a pressure designation used for a standardized flange series; it is not a universal allowable-pressure value for every material and temperature.
- D: flange outside diameter.
- K: bolt-circle diameter.
- d2: bolt-hole diameter.
- b: flange thickness.
- Facing: the gasket-contact surface, such as flat face or raised face, as required by the mating flange and gasket.
How to Read DN and PN
DN identifies the nominal connection size, while PN identifies the standardized pressure series. A marking such as DN 50 PN 16 therefore indicates a nominal DN 50 connection in the PN 16 flange series. It does not by itself confirm the allowable working pressure at the actual operating temperature.
Before ordering, check the pressure-temperature limits for the selected material, the required facing and gasket, corrosion allowance, bolt material and the current governing standard. For an instrument flange, also confirm whether the sensing diaphragm has enough effective area for the requested measuring range.
Archived SJ Gauge Diaphragm-Flange Reference
The following values were recovered from SJ Gauge’s 2025 article. They are an application reference for selected diaphragm-seal configurations, not a substitute for the complete EN 1092-1 dimensional standard or an approved product drawing. Dimensions are in millimetres; confirm the final drawing with SJ Gauge before procurement.
| DN | PN | Effective diaphragm diameter Mb | Outside diameter D | Thickness b | Bolt-hole diameter d2 | Bolt circle K | Seat height F | Inside diameter d4 | Number of holes |
|---|---|---|---|---|---|---|---|---|---|
| 25 | 10/40 | 32 | 115 | 22 | 14 | 85 | 2 | 68 | 4 |
| 25 | 63/100 | 25 | 140 | 24 | 18 | 100 | 2 | 68 | 4 |
| 40 | 10/40 | 45 | 150 | 18 | 18 | 110 | 2 | 88 | 4 |
| 40 | 63/100 | 45 | 170 | 26 | 22 | 125 | 2 | 88 | 4 |
| 40 | 160 | 45 | 170 | 28 | 22 | 125 | 2 | 88 | 4 |
| 40 | 250 | 45 | 185 | 34 | 26 | 135 | 2 | 88 | 4 |
| 50 | 10/40 | 59 | 165 | 20 | 18 | 125 | 2 | 102 | 4 |
| 50 | 63 | 59 | 180 | 26 | 22 | 135 | 2 | 102 | 4 |
| 50 | 100 | 59 | 195 | 28 | 26 | 145 | 2 | 102 | 4 |
| 50 | 160 | 59 | 195 | 30 | 26 | 145 | 2 | 102 | 4 |
| 50 | 250 | 59 | 200 | 38 | 26 | 150 | 2 | 102 | 8 |
| 80 | 10/16 | 89 | 200 | 20 | 18 | 160 | 2 | 138 | 8 |
| 80 | 25/40 | 89 | 200 | 24 | 18 | 160 | 2 | 138 | 8 |
| 80 | 63 | 89 | 215 | 28 | 22 | 170 | 2 | 138 | 8 |
| 80 | 100 | 89 | 230 | 32 | 26 | 180 | 2 | 138 | 8 |
| 80 | 160 | 89 | 230 | 36 | 26 | 180 | 2 | 138 | 8 |
| 80 | 250 | 89 | 255 | 46 | 30 | 200 | 2 | 138 | 8 |
| 100 | 10/16 | 89 | 220 | 20 | 18 | 180 | 2 | 158 | 8 |
| 100 | 25/40 | 89 | 235 | 24 | 22 | 190 | 2 | 162 | 8 |
| 100 | 63 | 89 | 250 | 30 | 26 | 200 | 2 | 162 | 8 |
| 100 | 100 | 89 | 265 | 36 | 30 | 210 | 2 | 162 | 8 |
| 100 | 160 | 89 | 265 | 40 | 30 | 210 | 2 | 162 | 8 |
| 100 | 250 | 89 | 300 | 54 | 33 | 235 | 2 | 162 | 8 |
How to Select a DIN/EN Flanged Pressure Instrument
- Identify the exact flange standard, DN, PN and facing from the piping specification.
- Confirm process pressure, design pressure, temperature and pressure spikes.
- Select wetted materials and gasket materials compatible with the process fluid.
- Check the diaphragm’s effective diameter against the measuring range and required accuracy.
- Approve the dimensional drawing, bolt pattern, capillary arrangement and installation orientation before manufacture.
DIN/EN, JIS and ASME Are Not Automatically Interchangeable
DIN/EN flanges use PN designations, JIS flanges commonly use K classes, and ASME flanges use pressure classes such as Class 150 or Class 300. Flanges with similar nominal sizes can still differ in outside diameter, bolt circle, hole count, facing and pressure-temperature rating. Do not connect them solely because the pipe size appears similar.
Frequently Asked Questions
Is PN 16 exactly equal to 16 bar?
No. PN identifies a standardized flange series. The actual allowable pressure depends on the flange material, temperature and governing standard. Use the standard’s pressure-temperature rules and the project design basis.
Can an old DIN 2527 flange be replaced directly with an EN 1092-1 flange?
Not without checking. Compare the exact type, facing, dimensions, material, bolt pattern and service conditions. Have the final match reviewed by the responsible piping engineer or instrument supplier.
Why does a low-pressure diaphragm seal need a larger diaphragm?
A larger effective diaphragm area can improve sensitivity and reduce measurement error caused by diaphragm stiffness. The required size also depends on fill fluid, capillary length, temperature and the instrument’s measuring range.
Conclusion
For reliable pressure measurement, specify the complete DIN/EN flange connection and the instrument application—not DN and PN alone. SJ Gauge can review flange dimensions, diaphragm size, wetted materials, coating or lining, flushing connections and remote-seal arrangements for your process.
Need a flange drawing review or a pressure-gauge selection proposal? Contact SJ Gauge with the standard, DN, PN, process fluid, temperature, pressure range and installation drawing.
Standards reference
Refer to the current edition of DIN EN 1092-1 and the project specification. Standards are copyrighted; purchase the official document when complete requirements or dimensional tables are needed.
