7
GENERAL WORKING PRINCIPLE
Regulators reduce cylinder pressure, referred to as inlet pressure, to a pressure suitable for breathing. Modern regulators do this in two
stages connected by a hose. The first stage provides pressure to the second stage; this reduced pressure remains constant despite the
sizeable changes undergone by the cylinder inlet pressure during the dive (dropping from 3000/4350 to few hundred psi). The second
stage brings pressure down to ambient pressure and delivers air only when the diver inhales. Each stage of the regulator contains an
internal valve. When the diver inhales, the pressure inside the case is lowered and a pressure differential (imbalance) is created across the
diaphragm (beginning of inhalation). The response of the diaphragm is to bend inward, contact the lever and open the second stage valve.
Air continues to flow into the case until the pressure balance is regained (end of inhalation).
FIRST STAGE
For the second stage to work properly, the 1st stage must deliver air at a correct and - most importantly - constant intermediate pressure.
This characteristic, provided by all MARES first stages, is essential for obtaining optimal adjustment of the second stage and ensuring top
performance for the entire duration of the dive, regardless of tank pressure.
All MARES first stages are available with the following types of tank valve fittings: DIN 477/13 screw (max pressure 200 bar), DIN 477/50
screw (max pressure 300 bar), international YOKE CGA 850 adapter (max pressure 232 bar), in accordance with the EN 250: 2000
standard.
SECOND STAGE
The purpose of the second stage is to deliver air at ambient pressure, only during the inhalation phase. The diagram of a 2nd stage shown in
Fig. 4 illustrates its operation.When the diver inhales, the pressure inside the second stage decreases, creating a pressure difference (imbalance)
between the two sides of the diaphragm. This pulls the flexible diaphragm inward, pressing the demand lever and unseating the second stage
valve. This opening allows air to flow in through the second stage and to the diver, until the diver stops inhaling. At this point the internal 2nd stage
pressure increases, pushing the diaphragm back in the opposite direction, causing the valve to return to its seat and shutting off the airflow.
Abyss (MR22) First Stage (Fig. 2)
The Abyss (MR22) diaphragm first stage features the DFC system and a replaceable HP seat connector.
The high pressure poppet was designed for a "2 year or 200 dives" service interval; double the high pressure seat life standard!
Compact body, in a modern and smart style, it is made of hot-forged nickel-plated and chromed brass.
It is fitted with a preferential intermediate pressure port for connection to the primary second stage, plus 3 other LP ports and 2 HP ports
with 7/16" UNF thread.
The latter are inclined at a 45° angle to allow a more rational layout of hoses.
DFC System
The exclusive MARES DFC system featured on the Abyss (MR22) first stage minimizes the intermediate pressure drop which occurs in all
regulators during the inhalation phase (Fig. 3). This phenomenon is all the more marked when higher airflow is demanded of the regulator.
The DFC system substantially reduces breathing effort and inhalation resistance, especially during deep dives and under demanding
conditions. The Abyss (MR22) first stage incorporates the DFC system on the preferential LP port for the primary second stage, whereas
the operation of the other low pressure ports (for octopus, inflator, etc.) is standard.
CWD Kit
For particularly demanding conditions, such as professional use in cold or contaminated water, the Abyss (MR22) first stage can be retrofitted
with the CWD kit which completely seals off all first stage internal components from contact with the water. The CWD kit should only be
installed by an authorized MARES service centre.
Abyss second stage
Abyss second stage, with its V.A.D. system, is made of nickel and chrome-plated brass. This material offers a number of benefits:
absolute ruggedness and thinner walls, hence compact dimensions obtained without using smaller-diameter diaphragms; this results in
reduced water drag.
Anti-freeze function, which is enhanced by the "radiator action" of the metal.
The second stage coverplate features the new "turbo flow" system for water inflow and outflow, which provides a further performance
improvement. Furthermore, the compact and ergonomic exhaust tee ensures superior hydrodynamic performance and reduced exhalation
resistance.
The mouthpiece is made of soft hypoallergenic silicone: limiting jaw fatigue and offering a secure fit even after very long dives.
!!
WARNING
For safety reasons, the submersible pressure gauge / high pressure safety device that is assembled on the regulator must
comply with the EN 250: 2000 standard. According to this regulation, with an upstream pressure of 100 bar the maximum
permitted airflow through the connector toward the first stage must not exceed 100 liters/min. If you have a submersible
pressure gauge / high pressure safety device that complies with the EN 250:1993 standard or a different specification,
check whether the instruction manual indicates the value of the maximum airflow.
The use of submersible pressure gauges / safety devices that do not comply with the EN 250: 2000 standard, or which do
not have an indication of the maximum permitted airflow through the first stage connector may result in serious accidents.
!!
WARNING
For safety reasons, it is not advisable to use an Octopus second stage that is not a certified MARES Octopus. The
manufacturer declines responsibility for damages to persons or property resulting from the use of different Octopus
second stages. The Mares Octopus second stages have been designed and tested for use on first stage low pressure ports
OTHER than the preferential port used for the primary second stage. An Octopus second stage MAY NOT be substituted
for a primary second stage, and must in no circumstances be connected to the preferential low pressure port intended for
the primary second stage.
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