72
38
32
21
15
9
Sizes that help you order the right part.
DN, NPS, outside diameter, PN and SDR describe different things. Include these references, the standard and material in your list.
- Reference
- Designation, standard and material
- Confirmation
- Part drawing and datasheet
DN and NPS: two nominal size designations.
DN 50 corresponds to NPS 2 as a nominal designation. Neither alone gives the actual outside or inside diameter. For HDPE and PVC, specify outside diameter in millimetres.
Nominal correspondence. Check actual dimensions on the drawing.
Check PN and Class against the standard.
An ASME Class does not convert directly to PN. Allowable pressure depends on the standard, material group and temperature. Quote the complete designation.
| System | How to specify |
|---|---|
| PN | EN 1092-1 · PN 10 / PN 16 |
| ASME | ASME B16.5 · Class 150 / 300 |
| JIS | JIS · 10K / 20K |
Designation examples; rows are not equivalent ratings.
Matching bolt holes is only the start.
Confirm standard, nominal size, rating, facing and material. Check bolt circle, holes and facing on the drawings of both parts.
| Reference | Designation | Check |
|---|---|---|
| EN 1092-1 | DN + PN | Steel, flange type and facing |
| ASME B16.5 | NPS + Class | Material, temperature and facing |
Request outside diameter, bolt circle, hole count and diameter, and face-to-face length where applicable.
SDR relates diameter to wall thickness.
SDR = nominal outside diameter / nominal wall thickness. For the same material class, a lower SDR means a thicker relative wall. Check temperature and service conditions before selection.
| Material | SDR | PN |
|---|---|---|
| PE100 | 17 | 10 |
| PE100 | 13.6 | 12.5 |
| PE100 | 11 | 16 |
| PE100 | 9 | 20 |
| PE100 | 7.4 | 25 |
Reference for water at 20 °C and coefficient C = 1.25. Confirm the manufacturer datasheet and applicable standard; other conditions need review.
Select for service, material and installation.
Use these guides to prepare the technical discussion. Confirm valve, seat and connection against your project conditions.
Butterfly or gate: which suits drinking water
A butterfly valve takes less space between flanges, weighs less and operates with a quarter turn; it suits medium and large sizes and pumping stations. A resilient-seated gate valve leaves a full bore and is the usual choice for buried distribution networks, operated rarely and needing tight shut-off.
DN, PN and class: the quick equivalence guide
DN is the European nominal size and NPS inches its North American counterpart: DN 200 equals 8". PN states nominal pressure in bar; ASME class is not a direct conversion because it depends on material and temperature. When quoting, always state the flange standard as well as the number.
HDPE PE100: what SDR means
SDR is the ratio between outside diameter and wall thickness. The lower the SDR, the thicker the wall and the higher the pressure: in PE100, SDR 17 works at PN 10 and SDR 11 at PN 16. For electrofusion, the fitting should match the pipe SDR or be thicker.
Request the datasheet for the part you will buy.
Drawings, dimensional sheets and reports are requested by product reference. Send the product and documents required; availability and scope are confirmed with the factory.
- DN / NPS
- Nominal size
- OD / Ø
- Outside diameter
- PN / Class
- Pressure designation
- SDR
- Diameter / thickness ratio