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Flow Regulators
SECOND STAGE:
Design features:
Given that a tired diver uses 70% of inhaled oxygen to supply respiration muscles, the flow regulator, and in particular the second stage, are the key to the system.
The delivery system is made up of a first stage, a hose and a second stage. It controls and regulates the flow of air from the tank to be then used in respiration.
Ideally this system should not cause problems of fatigue. To simplify, if the mechanism is not perfect, the whole system makes respiration tiring. The more tiring respiration is, the more air is consumed and the more air is required.
Given the above, it is easy to understand the need for a perfect system allowing either low or abundant air delivery as necessary. A good distribution system must spontaneously supply the necessary amount of air under all diving conditions.
The market offers three different types of second stage mechanisms:
- A simple valve mechanism with mechanical opening.
- A servo-assisted valve mechanism with mechanical opening.
- A balanced servo-assisted valve mechanism with pneumatic opening.
To simplify, the main features are as follows:
- In the first case distribution is inhibited by a "plug" pushed by a steel spring. The force contrasts with the air pressure and/or push coming from the first stage. If the respiration system is to remain open and/or in distribution, it requires a force greater than that exerted by the spring which is further compressed. It is the most widely used and economical flow regulator available on the market.
- In the second case, given that the steel spring offers the main resistance to inhalation, the valve uses a special "piston" pushed by a "spring" which is approximately 50% weaker than the previous one. This spring is "servo-assisted" (when closed) by the pressure coming from the first stage. The air passes through the piston and exerts a force on the piston which when added to that of the spring shuts OFF the air supply. If the respiration system is to remain open it requires a force greater than that exerted by the spring alone which as we have seen is weaker in this case. This system is known as servo-assisted and is even used by professional divers during deep and/or extreme dives. (Octopus OW).
In the third case the valve does not use steel springs but an "elastic lung". This uses the pressure from the first stage to dilate and/or elongate itself. This action closes the air passage.
As pressure decreases due to the effect of inhalation, the "elastic lung" returns to its normal and/or natural size. If the respiration system is to remain open it only requires the force needed to control the "elastic lung".
This "balanced and servo-assisted" system belongs to the group of flow regulators offering the best performance. It is much appreciated for delivery flow and sensitivity during deep and/or extreme dives (2nd stage WIND and OW).
There is more market diversification when considering the system used to expel exhaled air. Remember that the larger the exhaust valve membrane the less tiring exhalation is.
The two most common systems are as follows:
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The most widely used system sees the exhaust valve positioned on the second stage box and protected by special "whiskers".
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The exhaust valve is at the front and is integrated in the inhale membrane to enable a larger size to be used. It is usually protected by a rubber cap.
The advantages offered by the two systems can be attributed to the different positions.
The main technical features of the WIND and OW910 second stages are as follows:
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Balanced servo-assisted piston valve, pneumatic movement with silicon lung (patented).
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Venturi effect controlled by a deflector with humidifying effect.
- · Dive+ and predive- command.
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Body mechanism in special carbon fibre reinforced polymer.
- Special mechanism components in self-lubricating waterproof Delrin.
- Second stage body in special glass reinforced polymer.
- Inhale and exhaust membrane in special medicine-safe silicone.
Membrane lever and disk in stainless steel.
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Viton and/or polyurethane o-rings for mixtures (on request).
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Mouthpiece in shaped silicon.
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Hose with large internal diameter, length 800 mm, tested to 35 bar.
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Working pressure from 3 to 16 bar, standard 10-11.5 bar (hp 250-50 bar).
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Air flow 1.2 to 2.8 litres depending on first stage calibration.
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