Unsealed Conshelf Supreme IP spec

[Six2Life]

I just finished rebuilding my Conshelf Supreme that is missing the outer environmental seal. I understand this pretty much makes it functionally identical to a Conshelf XIV. The repair manual calls out an IP of 120-130psi for the Supreme and 135-145psi for the XIV.

Which IP spec should I use?

Why is there even a difference between the two?

 

[halocline]

Assuming you're using a single adjustment downstream 2nd (is that what the conshelf is?) I'd set the IP at whatever makes that work best, maybe starting at 130 or so and moving up as needed.

 

[herman]

Whatever you want in the 130-145 range. The exact IP is not critical, it being stable is. I have a lot of different regs and to make things simple, I picked one IP to adjust everything to. That way I can mix and match first and second stages as I need/want without having to worry about need to readjust them.

 

[Luis H]

The Supreme with the environmental seal was intended for cold water and ice diving. Therefore it makes sense that it might have been recommended to be somewhat detuned for that purpose. It makes somewhat less of a chance for it to go into a free flow.

If you are not using it for ice diving or very cold water, I would tune it for best performance with the higher IP as mentioned above.

 

[Six2Life]

I got it tuned fairly well with an IP just below 140. Luis, your explanation on the difference in spec's sounds pretty good to me. I was also thinking that since the XIV is/was a military item that maybe they had a requirement for a specific IP.

Halo, yes the 2nd is a single adjustment reg....sorta. It has a fixed orifice so the only airflow adjustment in the 2nd is the nyloc nut but there is also a slack adjustment screw on the backside of the purge button. For me it was definitely a little more tricky to get adjusted then a SP piston reg with a 109.

 

[halocline]

With those second stages if you adjust the lever height via the nyloc nut but cannot adjust the orifice, the only other 'adjustment' you have is the IP. These are 2nds that really do best with a balanced 1st stage.

 

[herman]

With those second stages if you adjust the lever height via the nyloc nut but cannot adjust the orifice, the only other 'adjustment' you have is the IP. These are 2nds that really do best with a balanced 1st stage.

The Conshelf is balanced..

 

[Six2Life]

But every time you adjust the IP it changes the downstream force on the LP poppet which affects lever height. So for the most part every IP adjustment also requires a lever height adjustment. At least that how it looks to me.

 

[halocline]

The Conshelf is balanced..

I know....

 

[halocline]

But every time you adjust the IP it changes the downstream force on the LP poppet which affects lever height. So for the most part every IP adjustment also requires a lever height adjustment. At least that how it looks to me.

I think you basically want the IP high enough to allow you easiest possible breathing with the lever at the correct height. I don't see how raising the IP would drop the lever at all unless it was also free-flowing. I could see how getting the IP too high would cause the 2nd stage to flow a little, and you'd have to adjust that out by tightening the nyloc nut, which would then lower the lever.

What determines the lever height is the position of the orifice (fixed in this case) the thickness of the seat (also I assume fixed, but it is an interesting idea to use seat thickness as a possible adjustment in this type of 2nd stage) and the position of the nyloc nut, which also compresses the spring.

Or am I missing something?