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VALVE SIZING
What Do DN and PN Mean on a Valve?
DN is the nominal size of the valve and pipeline, while PN is the nominal pressure class assigned to the connection and body. PN is not the allowable working pressure at every temperature; it must be verified against material pressure-temperature ratings.
Direct answer
DN is the nominal size of the valve and pipeline, while PN is the nominal pressure class assigned to the connection and body. PN is not the allowable working pressure at every temperature; it must be verified against material pressure-temperature ratings.
Technical review: MDES Engineering Technical TeamUpdated: 2026-08-05
How is DN selected?
DN often matches pipeline nominal size, but copying pipe size is not enough where velocity, cavitation or control is important. Flow and pressure-drop calculations are required.
How is PN verified?
The pressure class must be compatible across body, flange, gasket and fasteners. Allowable pressure may change as material temperature rises.
Connection and face-to-face length
Valves with the same DN and PN may have different flange standards and face-to-face dimensions. Applicable EN 1092 and EN 558 requirements should be checked before ordering.
Basic selection data
| Value | Meaning |
|---|---|
| DN | Nominal size |
| PN | Nominal pressure class |
| Flow | Required capacity |
| ΔP | Pressure drop across valve |
Key points
- Do not copy pipe size blindly.
- Verify PN with temperature and material.
- Check flange and face-to-face dimensions.
- Fluid compatibility is mandatory.
Frequently asked technical questions
Can a PN16 valve operate at 16 bar at every temperature?
No. Allowable pressure depends on material and temperature; consult the manufacturer's rating.
Is a DN100 valve exactly 100 mm inside?
DN is nominal; the actual bore depends on valve type and standard.
Are valves with the same DN and PN interchangeable?
Not always. Face-to-face length, flange drilling, actuator and flow characteristics must also match.
Which information is required for an industrial valve quotation?
Provide the fluid, DN, PN, operating temperature and pressure, connection standard, body and sealing materials, actuation type, quantity and delivery location. Chemical compatibility and pressure-temperature limits must be confirmed before ordering.
Technical references
- EN 1092 flange connections
- EN 558 valve face-to-face dimensions
- EN 12266-1 pressure tests
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