PN16 vs Class 150 Valves and Flanges: Buyer Guide
Technical guide · Supreme Valves India · Updated 2026-10-28
Direct answer: PN16 (often written 1.6 MPa) is an EN pressure designation with EN 1092 flanges. Class 150 is an ASME designation with ASME B16.5 flanges. Similar cold pressure capability does not make the flanges interchangeable. Specify the flange standard on every valve RFQ or you will get the wrong drilling.
Our RFQ archive is full of both languages: “CL150 RF” on process packages and “PN16 / 1.6MPA” on water, HVAC and large-bore strainer lines. Mixing them on one isometric is a common site problem.
Two flange systems, two drawings
| Item | PN16 world | Class 150 world |
|---|---|---|
| Pressure label | PN16 / 1.6 MPa | ASME Class 150 |
| Flange standard | EN 1092-1 / -2 | ASME B16.5 (B16.47 large dia.) |
| Size language | DN (mm) | NPS (inch) |
| Facing | Type A/B raised face common | RF (raised face) common; FF on some DI |
| Typical BOQ examples | Y-strainer DN700 1.6 MPa; butterfly DN600 PN16 | Gate WCB CL150 RF; ball CL150 RF RPTFE |
Pressure rating vs flange geometry
Engineers sometimes treat PN16 ≈ Class 150 for rough pressure screening at ambient temperature. That is only a starting point. Allowable pressure falls with temperature per the material group in ASME B16.34 or the EN rating system. More importantly for procurement: bolt circle diameter, number of bolts, bolt size and gasket OD/ID differ. A PN16 valve will not land on a Class 150 flange.
When BOQs say 1.6 MPa
Metric project documents (India solar/water, Chinese EPC packages, some Gulf civil works) write diameter as DN and pressure as 1.6 MPa. That almost always means PN16 flanges unless the datasheet explicitly says ASME. Large fabricated Y-strainers (DN500–DN700) in our archive are almost all PN16 / 1.6 MPa.
Butterfly, gate, ball — what to write
- Water / building / metric process: DN, PN10 or PN16, EN flange facing, wafer/lug/flanged.
- Oil & gas / ASME process: NPS, Class 150/300/600, RF or RTJ, API design standard.
- Gunmetal / bronze building valves: often PN16 screwed BSPP rather than flanged Class 150.
Face-to-face is a separate decision
Even when flanges match, face-to-face must match the piping gap (ASME B16.10, EN 558, API 609 short pattern, etc.). Replacing a PN16 EN 558 butterfly with a Class 150 API 609 wafer of “the same DN” can still leave a gap or clash.
RFQ checklist
- Pipe flange standard: EN 1092 PN16 or ASME B16.5 Class 150 (state explicitly)
- Size as DN or NPS — do not mix on one line without conversion
- Facing (RF / FF / RTJ) and gasket standard
- Design standard (API 600/608/609, EN 593, BS 5154, etc.)
If your line list mixes PN and Class tags, send it as-is — we will flag conflicts before production. Related RFQs: PN16 Y-strainer, WCB Class 150 gate.
Frequently asked questions
Is PN16 the same working pressure as Class 150?
They sit in a similar cold-working-pressure band for many carbon-steel services, but they are not interchangeable. Flange dimensions, bolt circles, bolt counts and gasket standards differ between EN 1092 and ASME B16.5. Match the valve flange to the pipe flange standard on the isometric.
Why do Chinese and Indian BOQs write 1.6 MPa?
1.6 MPa is the metric way of stating PN16. Large Y-strainers and butterflies on water and utility projects are often specified DN + 1.6 MPa rather than NPS + Class 150.
Can I bolt a Class 150 valve to a PN16 flange?
Not safely as a general practice. Bolt holes will not align except in rare coincidental sizes, and gasket geometry differs. Order the valve drilled to the same standard as the mating flanges.