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Pipe Sizing — by Pressure Loss and Velocity
The smallest standard size that satisfies both the allowable pressure loss and the velocity limit, and which criterion governs.
Unit system
Inputs
Recommended nominal size (DN)
80
Governing criterion
PRESSURE LOSS governs — the velocity limit would allow a smaller size
Details
| Inch equivalent | 3" |
| Inside diameter | 77.92 mm |
| Pressure loss at this size | 0.3067 bar a |
| Velocity at this size | 22.64 m/s |
| If pressure loss alone governed | 80 |
| If velocity alone governed | 65 |
| Density | 5.145 kg/m³ |
Assumptions
- The size is picked from a DISCRETE list; no intermediate value is produced. There is no pipe between DN 65 and DN 80.
- Only STRAIGHT pipe friction is counted. Leave margin for bends and valves: adding 10–30 % to the equivalent length is common practice depending on how many fittings the line carries.
- Velocity limits are field practice, not a standard. Where noise matters, 25 m/s can be the better choice for steam.
Continue with this result
Calculation report
A PDF carrying the inputs, results, assumptions and the source. A one-time code is sent to your address.
Source
- Darcy–Weisbach · Sürtünme kaybı
- Swamee–Jain · Colebrook–White’in açık çözümü
- ASME B36.10M · Standart boru kademeleri
Results are for engineering pre-assessment and are not a product selection commitment. Final responsibility rests with the user.
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