Class 150 vs PN16
ASME Class 150 and EN PN16 are pressure ratings from different standards systems (ASME B16.5 and EN 1092-1, respectively). They are often treated as equivalents on international projects, but they are not identical in pressure capacity, dimensions, or bolt patterns.
Comparison Table
| Feature | ASME Class 150 | EN PN16 |
|---|---|---|
| Standard | ASME B16.5 | EN 1092-1 |
| Max pressure at ambient (CS) | 19.6 barg (285 psig) | 16 barg (232 psig) |
| Max pressure at 200°C (CS) | 15.8 barg (229 psig) | 14.2 barg (206 psig) |
| Nominal size system | NPS (inches) | DN (mm) |
| Flange OD (6”/DN150) | 279.4 mm | 285 mm |
| Bolt circle (6”/DN150) | 241.3 mm | 241.0 mm |
| Number of bolts (6”/DN150) | 8 | 8 |
| Bolt size (6”/DN150) | 3/4” (M20) | M20 |
| Raised face height | 1.6 mm (1/16”) | 2 mm |
| Face finish | Serrated (3.2-6.3 Ra) | Serrated (3.2-12.5 Ra) |
| Gasket | Spiral wound per ASME B16.20 | Spiral wound per EN 1514-2 |
| Material designation | ASTM (e.g., A105) | EN (e.g., P250GH per EN 10222-2) |
Key Differences
Pressure capacity. Class 150 is rated higher than PN16 at all temperatures. At ambient, Class 150 provides 19.6 barg vs. 16 barg for PN16. This means a PN16 flange can operate in a Class 150 system only if the design pressure stays below 16 barg, but a Class 150 flange has margin above the PN16 limit.
Dimensions. For many sizes, the outer diameter and bolt circle of Class 150 and PN16 are close but not identical. In some sizes (NPS 2/DN50, NPS 4/DN100), the bolt holes align well enough for field mating. In other sizes, the holes do not match, making them physically incompatible.
Gasket compatibility. Spiral wound gaskets for ASME and EN flanges have different inner and outer diameters due to the dimensional differences. ASME gaskets per B16.20 and EN gaskets per EN 1514-2 are not interchangeable.
Material traceability. ASME flanges reference ASTM material specifications; EN flanges reference EN 10222 (forgings) or EN 10213 (castings). Although the chemical compositions are similar, the test requirements, certification formats (EN 10204 3.1 vs. ASME MTR), and marking differ.
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