1987 Bauer Capitano - Questions

[Bloody Knuckles]

Mine has a NRV on both sides of the filter housing plus a PMV on the discharge side which functions as an NRV. My housing will maintain pressure for as long as I've had occasion to leave it sitting.

@grantmac, thanks for the reply, would you have a picture of your setup?

 

[oldairdude]

Mike, sorry for the delayed response on this, I have been out of the country again...
The fact that your pressure in the P-0 filtration leaks down after shutting down is really not a big concern. In fact most of them do eventually. If you have noticed it coming out of your intake, this is most likely from the stages having pressure in them and it leaks past the rings into your crankcase. Once there, it goes out the return tube to your air inlet. Very common. After shutting down, be sure to drain the first and second stages of all pressure. If you still have a slight pressure discharge into our air intake, it would be your P-0 pressure going back thru your final 3rd stage discharge valve. Once there it goes past the final piston into the crankcase. As you know the valve is sealed to the head with a metal to metal seal. The valve internally is also metal to metal for durability but not necessarily bubble tight. In some rare cases some people my have a perfect seal and never have a loss around these seals. But that is rare and most likely going to change with time and future valve changes. Most of these (90%) will leak slowly, it is no big deal. By the way, the O-ring is not the issue. If it were to fail or leak, it would leak out to the atmosphere, not internally. You can hear it after shutting the unit off. If you keep your filtration attached to a filling hose and have it shut off when not in use, you will be fine as far as the Molecular Sieve life. That's a whole another discussion, but in short the Sieve is not an active desiccant that "searches" for humidity, but rather requires airflow to pass it so it can trap the specific molecules it is designed to entrap. Lastly, as others have stated, the PMV is not really a check valve. It kind of works like one in some cases but you should also have a check valve to insure that any downstream air does not try to re-enter the filtration if left open or connected to a storage bank, etc.
I hope that helps you see that you are OK as is.

 

[grantmac]

@grantmac, thanks for the reply, would you have a picture of your setup?

I'm away from it for a few months unfortunately.

 

[Bloody Knuckles]

The discharge valve is not an NRV. It can be slightly leaky because it has to close every rotation of the compressor only for a very short time, so about 15 times per second. In order for it not to wear out too quickly, the contact pressure metal to metal must not be too high. These are therefore different conditions than the NRV between the separator and the filter, where the airflow is already much more uniform.
But a picture shows that you have the combi filter, so no NRV is possible between the separator and the filter.
This is not the best construction for a dive shop that fills tanks every day, but Bauer considers it sufficient for a recreational diver who fills tanks approximately once a week. I share this opinion, so for me, it is fine as it i

Mike, sorry for the delayed response on this, I have been out of the country again...
The fact that your pressure in the P-0 filtration leaks down after shutting down is really not a big concern. In fact most of them do eventually. If you have noticed it coming out of your intake, this is most likely from the stages having pressure in them and it leaks past the rings into your crankcase. Once there, it goes out the return tube to your air inlet. Very common. After shutting down, be sure to drain the first and second stages of all pressure. If you still have a slight pressure discharge into our air intake, it would be your P-0 pressure going back thru your final 3rd stage discharge valve. Once there it goes past the final piston into the crankcase. As you know the valve is sealed to the head with a metal to metal seal. The valve internally is also metal to metal for durability but not necessarily bubble tight. In some rare cases some people my have a perfect seal and never have a loss around these seals. But that is rare and most likely going to change with time and future valve changes. Most of these (90%) will leak slowly, it is no big deal. By the way, the O-ring is not the issue. If it were to fail or leak, it would leak out to the atmosphere, not internally. You can hear it after shutting the unit off. If you keep your filtration attached to a filling hose and have it shut off when not in use, you will be fine as far as the Molecular Sieve life. That's a whole another discussion, but in short the Sieve is not an active desiccant that "searches" for humidity, but rather requires airflow to pass it so it can trap the specific molecules it is designed to entrap. Lastly, as others have stated, the PMV is not really a check valve. It kind of works like one in some cases but you should also have a check valve to insure that any downstream air does not try to re-enter the filtration if left open or connected to a storage bank, etc.
I hope that helps you see that you are OK as is.

Ok, I got it, chasing my tail again... Thanks for the reply and insight. I'll just continue to dive, fill, repeat
Hope you enjoyed your trip, and I hope it included water sports. Thanks again, Mike

 

[oldairdude]

Ok, I got it, chasing my tail again... Thanks for the reply and insight. I'll just continue to dive, fill, repeat
Hope you enjoyed your trip, and I hope it included water sports. Thanks again, Mike

Exactly!