PN 16 operating pressures and sizing from DN 15 to DN 108
Permissible pressures by application and medium temperature, the difference between test and operating pressure, sizing by flow rate and pressure loss.
Operating pressures of the TAVINOX PRESS system
The TAVINOX PRESS system is designed and operated at a nominal pressure of PN 16. We hold no certification for PN 40 — do not state it in designs or in quotations.
The permissible operating pressure is not a single figure for the whole range: it depends on the application and on the temperature of the medium. The values for the individual applications:
- Drinking water, cold: 16 bar / max. 25 °C
- Drinking water, hot (DHW): 10 bar / max. 95 °C
- Heating (EN 12828): 16 bar / max. 110 °C
- Service water, industrial: 16 bar / max. 110 °C
- Service water, rainwater: 6 bar / max. 40 °C
- Compressed air: 10 bar / max. 60 °C (vacuum down to −0.8 bar, non-medical)
- Cooling: 6 bar / from −10 °C
- Solar thermal systems and heat pumps: 6 bar / −35 °C to +110 °C
- Fire protection pipework: 16 bar (DN20–DN80 / Ø22–88.9 mm), 12.5 bar (DN100 / Ø108 mm)
In fire protection pipework, stricter pressing requirements apply on top of the pressure — see the article on fire protection.
Test pressure is not operating pressure
TAVINOX PRESS fittings were tested at PAVUS at four times the nominal pressure (4 × PN). That is the TEST pressure, which verifies the strength of the press joint — not the permissible operating pressure.
The sizing calculation and the design documentation always take the value for the given application from the table above, not the result of the test. The test pressure does not entitle anyone to operate the system above PN 16.
The pressure test of the finished installation follows a separate procedure — first with air up to 3 bar (this reveals unpressed joints), and only then with water.
Sizing by flow rate
Correct sizing starts from the required flow rate and the maximum permitted velocity of the medium:
- Drinking water (cold): max. 2.0 m/s
- Drinking water (hot): max. 1.5 m/s
- Heating: max. 1.0 m/s
- Cooling: max. 1.5 m/s
Recommended sizes for apartment buildings:
- Connection to a flat: OD 15–18 mm
- Riser (up to 10 flats): OD 28–35 mm
- Main distribution: OD 42–54 mm
- Main run: OD 76.1–108 mm
Pressure loss
Pressure loss in stainless steel pipework is lower than in plastic systems thanks to the smooth inner surface (roughness Ra < 0.8 um). Friction factor for the Darcy-Weisbach calculation:
- Stainless steel: lambda = 0.015–0.020
- Plastic (PE-X): lambda = 0.020–0.030
- Copper: lambda = 0.015–0.022
Local resistances of fittings (zeta coefficients):
- Elbow 90°: 0.5–1.2 (depending on OD)
- Tee, straight run: 0.3–0.5
- Tee, branch: 1.0–1.8
- Threaded adaptor: 0.2–0.4
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