Air Inlet check valve
The purpose of the Air Inlet Check Valve is to permit a high flow air intake into the pipe, in order to prevent negative pressure, the result of which would be damage to the sealing joints and a risk of the pipe being crushed. It provides a normal flow during pipe draining.
Generally speaking, the choice of the ND of the air inlet check valve is based on an admissible negative pressure in the pipe of 2 meters water column. We then apply a ratio between the air flow in L/s and the cross section of the passage of the air inlet check valve, in dcm2 equal to 1900.
This figure is constant whatever the ND for the air inlet check valve, since it is given by the maximum velocity of air input which is 1900 dcm/s, that is 190m/sec.
We obtain maxi. air input flow rates for a negative pressure of 2m/wc. to:
When the negative pressure reaches 3, 4 or 5 m/wc, see table below:
|DN||Air speed in Subsonic mode||Air speed in Sonic mode|
|mm||118,4m/s||157,5 m/s||179,9 m/s||191,5 m/s||195 m/s|
|ELIGIBLE LOW BAR PRESSURE RELATING TO THE NATURE OF PIPE MATERIALS|
|80||595 L/s||792 L/s||894 L/s||962 L/s||980 L/s|
|100||929 L/s||1236 L/s||1412 L/s||1503 L/s||1530 L/s|
|150||2091 L/s||2782 L/s||3177 L/s||3382 L/s||3444 L/s|
|200||3718 L/s||4945 L/s||5648 L/s||6013 L/s||6123 L/s|
|250||5809 L/s||7727 L/s||8826 L/s||9395 L/s||9567 L/s|
|300||8364 L/s||1127 L/s||12710 L/s||13529 L/s||13776 L/s|
|350||11385 L/s||15145 L/s||17300 L/s||18415 L/s||18751 L/s|
|400||14871 L/s||19782 L/s||22595 L/s||24052 L/s||24492 L/s|
|500||23236 L/s||30909 L/s||35305 L/s||37581 L/s||38268 L/s|
The air speed does not exceed 195m / s (speed of sound), this is due to a blockage of the mass flow at the level of the passage of the valve section. Note that the active section of the air passage is equal to the DN of the SNH valve, for example on a flanged valve DN 200 the air inlet section at the level of the valve seal marked N ° 3 is equal to 200mm.
Choice of diameter
Abacus enabling the choice of the ND of the air inlet check valve
For a 500mm pipe, with a tolerated negative pressure of 4m/wc, the maximum slopes on each side of the point in consideration being 8 cm/m, we choose the ND100. For a 500mm pipe, with a tolerated negative pressure of 2 m/wc, the maximum slopes on each side of the point in consideration being 8 cm/m, we choose the ND150.
Material and coatings
Protection Epoxy 200 microns oven baked 200¢ªC - RAL 5015 Blue
|Protection Epoxy 200 microns oven baked 200¢ªC - RAL 5015 Blue|
316L St. Steel
|7||Inlet cone||S235 Steel||Protection Epoxy 200 microns oven baked 200¢ªC - RAL 5015 Blue|
* Deflection cone (4) present from DN200
Compliance with standards
The Air Inlet check valve conforms to standard EN 1074 -1 & 4.
Minimum and maximum operating temperature: 0 to 70° C.
Minimum sealing pressure: 0.1 bar.
Permissible operating pressure (PFA) 10/16/25/40 bars depending on model.
Certificate of sanitary Conformity (ACS).
The air inlet check valve is installed in a valve chamber (see diagram) sufficiently ventilated by an upper grill cover.
It is recommended to fit a stop valve, which allows an eventual dismantling of the appliance, without having to close down the operation of the circuit.
It must be placed in a vertical position, at a height well above the pipe (see diagram) in order to prevent the sucking in of foreign matter into the pipe.
E x E
1000 x 1000
1000 x 1000
1200 x 1200
|200||1500 x 1500||2200|
|250||2000 x 2000||2500|
|300||2150 x 2100||2580|
|350||2200 x 2150||2600|