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Technical

Apeks Technical - FST Balanced First Stage Operation

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Picture Map
 

As the air is turned on, it flows through the first stage (shown by the arrows) and through the hose to the second stage. When the pressure builds to 9.5 bar, it exerts sufficient load on the primary diaphragm to compress the large spring. This allows the smaller spring to push the high pressure (H.P.) Valve onto its seat.The valve is then in a balanced state with the medium pressure pushing on the diaphragm, holding the large spring compressed, while the H.P. valve is being held onto the seat by the smaller spring, preventing the H.P. air flowing.
Inhale Phase
 
As the diver inhales, the medium pressure air (9.5 bar) acting on the primary diaphragm drops, allowing the large spring to push the diaphragm, which in turn pushes the H.P. valve off its seat. This allows more air to flow from the high pressure side until the diver stops inhaling. The medium pressure then builds up again to 9.5 bar and the first stage returns to its balanced state.
 
Exhale Phase
 
The first stage is protected from freezing and contamination by a secondary diaphragm. This second diaphragm also maintains hydrostatic balance by transmitting the pressure of the water via the load transmitter to the primary diaphragm. By this method medium pressure of 9.5 bar is always maintained above the water pressure, ensuring that second stage supply is always sufficient regardless of depth.