Return Valve; Minimum Pressure - Biral A 12 Instrucciones De Instalación Y Funcionamiento

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The arrow on the pump
housing indicates
the direction of flow.
The shaft must always be
horizontal, never vertical.
english

4.5 Return valve

If a return valve has been fitted, the pump must be set up
(see 7.2) so that the minimum delivery pressure of the pump
can exceed the closing pressure of the valve at any time.
Install the sluice gate before and after the pump.
This prevents the fluid from being drained and refilled
when the pump is exchanged.

4.6 Minimum pressure

The minimum pressure in the pump connection at –10 °C ... +75 °C
to ensure lubrication of the friction bearings:
at
The values apply up to 500 m above sea level.
Additions for higher altitudes:
0.01 bar per 100 m of altitude
< 75 °C
< 90 °C
<110 °C
0,10 bar
0,55 bar
1,20 bar