I emailed you about it, I'd like to find a way to incorporate it on the site for future reference. It's a subject that comes up quite a bit.slonda828 wrote:That's really good Russ. I may borrow that video, if you don't mind, for my class. There's a certain level of detail that most people need to know for everyday use,and this explains it really well. I liken this to the idea that you don't need to understand how Dell creates CPUs in order to use a home computer.
captain wrote:A good demonstration however there is one point that is not made in that the J seat is not constantly held open by the high pressure, it cycles open and closed with each breath until tank pressure can no longer overcome J spring pressure which coincides with the reserve pressure. At that point air flow will stop or be restricted until the lever is moved down to release tension on the J spring.
You can see this quite well of you use a reg set with an SPG. This happened to me with my boat tank and I had to put the valve in fill position to maintain my sanity. It is disconcerting to see a pressure gauge drop sharply on the air you are breathing no matter if you understand the reason. I have been meaning to try the SPG on a J-valve with an SPG port to see what happens, I assume it would not have the same effect however, its on my to do list.
I know the video is a little wonky and yes the reserve valve should reset after each breath, but in general, the video gets the point across. I might re-visit it and fix that, as well as inform the audience that the reserve valve works through a reduction of back pressure behind the valve when the diver takes a breath.captain wrote:Maybe I am not on the same page understanding the how the operation is described in the video.
The only time the J valve is off the seat is during inhalation. As soon as inhalation stops the J valve returns to closed. Tank pressure of any amount can not hold the J valve off the seat at any time unless inhalation is taking place. A reverse way to visualize it is that the diver sucks the J valve open with every inhalation. Just like the regulator operation is based on diver demand during inhalation so is the J valve.
The video does not show the J valve returning to completely closed after each inhalation or when the the valve is initially opened and the regulator is pressurized. At that point once the whole system is equalized the J valve returns to the closed position.
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