User manual

18
3.7 FULL-FACE MASK AND BREATHING VALVE
The mask has an inner mask with separate inhalation and exhalation channels that match corresponding
channels in the breathing valve. This ensures that inhalation and exhalation air is never mixed. During
inhalation, air ows from the breathing valve up through the mist protection openings, over the inside of
the visor and continues through the check valves in the inner mask. During exhalation, the exhaled air exits
into the surrounding water via the exhalation valve.
1 Diaphragm assembly 8 Exhalation valve
2 Lever arm 9 Cover
3 Sealing spring 10 Sealing disc
4 Sealing cone 11 Overpressure valve piston
5 Connection nipple 12 Overpressure valve spring
6 Check valve (two) 13 Balance diaphragm
7 Exhalation channel
The following text describes usage of the breathing valve. See gure above.
When the diver inhales, the diaphragm unit (1) is drawn inwards and presses against the lever arm (2). The
lever arm lifts the sealing cone (4) from the valve seat on the connection nipple (5). Then air ows through
the inhalation channel into the inner mask through the check valves (6). When the diver stops inhaling,
the diaphragm unit (1), the lever arm (2) and the sealing cone (4) return to their starting positions and the
inow is closed by the sealing spring (3). When the diver exhales, exhalation air ows from the inner mask
through the exhalation channel (7) and the exhalation valve (8), and lifts the sealing disc (10). Then the
exhalation air ows out into the surrounding water through the gaps in the cover (9). The overpressure
valve mechanism functions as a safety valve for the rst-stage regulator by automatically opening the
sealing cone if the secondary pressure increases to between 14 and 20 bar (203-290 psi). For example, this
can happen when the regulator is leaking. When this happens, the overpressure valve spring (12) can no
longer withstand the pressure against the central section of the balance diaphragm (13). The back-pressure
piston is then pressed inwards so that the valve mechanism is lifted and pulls the sealing cone off the valve
seating. Air then ows out until the pressure drops to approximately 10 bar (145 psi). The breathing valve
has a check valve in the inhalation channel (not shown in the gure) that prevents water penetration, thereby
minimizing the risk of freezing.
Regulations specify that breathing valves and face masks must regularly be cleaned and disinfected. In
addition, breathing valves and face masks used by several persons must be cleaned and disinfected after
each use. Interspiro recommends personal breathing valves and face masks as the most hygienic solution.