Bellow Counterlungs...

[Danny D]

I was wondering if somebody could explain to me the workings of the Bellow counter lungs of the Halcyon and other bellows rebreathers .

I understand how the exhaled air gets into the small bellow and that there is a oneway valve at the top of the small bellows allowing air only to enter. In all the pictures that I have seen such as on the http://www.golemgear.com/scr/SCRteardown.htm
web page the small inner bellow has a exhaust valve at the bottom. It looks to me like all the exhaled air would go into the inner bellow and out the axhaust valve.
so how does the air get from the inner bellow to the larger outer bellow ?

 

[caveseeker7]

The RB80 is a semi-closed circuit rebreather. The valve on the bottom of the inner counterlung makes it so. Both inner and outer bellows get filled during the divers exhalation. The gas in the inner bellows gets dumped over board, the gas in the larger, outer bellows goes through the scrubber and gets rebreathed. When the gas in the inner bellows passes through the exhaust valve, so does any water that may entered.

By bottoming out, the levers are pushed in for gas addition. If there is a leak from the inner to the outer counterlung less gas will added, which can reduce the amount of oxygen in the loop to dangerously low levels (hypoxia).

As gas addition is audible the diver must pay close attention that it is working properly. A ppO2 meter can be added to monitor the gas in the loop.

 

[Danny D]

Thank you very much for the explanation...I thought that is how it worked , but I just wanted to make sure. Thanks