Cressi MC7 Manuel D'instruction page 45

44 SECOND STAGES
The XS2 orifice consists of a new modular plastic and chrome-
plated brass poppet (22K). It is perfectly interchangeable with all
the previous models of the XS range (5). On one side, the pop-
pet is connected to the small lever, while on the other side it
houses, in a special housing, a newly designed and thicker rub-
ber seat. This seat closes the new adjustable orifice, through
which air flows at a pressure by 9.0÷10 (128÷146 psi) bar higher
than ambient pressure.
The air flowing through the orifice (21K) pushes the seat which is
counteracted by the poppet spring (7).
Therefore the new poppet sort of "floats" under the push of the
incoming air and the spring. However, since the spring force is
greater, the orifice will be kept tightly closed.
The adjustable orifice is housed inside the housing. When the
mechanism is open, the air is pushed through the injector (10)
and directly sent into the mouthpiece. When a significant
amount of air is flowing through the injector into the mouthpiece,
a vacuum is formed inside the regulator case due to increased
air speed. This is called Venturi effect, which keeps the
diaphragm down and significantly reduces the inhalation effort.
When breathing stops, the Venturi effect is immediately discon-
tinued; the diaphragm resumes its original position, the lever,
pushed by its spring, is raised and the orifice is closed by the
poppet.
In order to maximize this Venturi effect, XS2 CE is fitted with a
flow control vane (12K) with two operating positions, as clearly
indicated in the graduated scale on the regulator case :
pre-dive "-" and dive "+". When the device is set on the first posi-
tion, a flow limiter inside the mouthpiece hose is actuated which
limits the Venturi effect, and prevents free-flowing. When in "+"
position, the Venturi effect is maximized, and the air flow to the
regulator is increased to the highest level.
Warning: the small lever of the flow control vane must
always be kept in pre-dive (-) position when you are not using
the regulator. Otherwise in case of accidental impact, when
the regulator is placed in water, when pressure is exerted on
the manual air supply button and the regulator is not in the
mouth, or even when suddenly taking the regulator out of your
mouth, the regulator may even violently start to free flow with
significant air consumption.
The dive (+) position must exclusively be used for diving at
depth and only when the mouthpiece is in the mouth.
DIVE
When the diver exhales, the pressure inside the regulator case is
raised and the exhaust valve opened (18). This is a new tapered
angled design valve with a greater diameter to let the air out. The
exhaust tie (14K) conveys the air at the side of the head protect-
ing the valve against water turbulence which could open it when
the valve body is not under pressure, flooding it.
The 2nd stage is connected to one of the 3/8" seats of the 1st
stage through a flexible medium pressure and high capacity
hose.
All Cressi-sub second -stage regulators feature a down-stream
type valve so that in case the 1st stage calibration is lost or there
is a sudden intermediate pressure peak, the valve will open
automatically.
This means that any excessive pressure flowing to the 2 nd
stage may cause the regulator to free flow but never to get
stuck.
XS2 CE case is manufactured with new technopolymer materi-
PRE-DIVE
fig. 21