IP shim Conshelf XIV?

[northernone]

Good evening.

I'm looking for someone willing to fill in the gaps in my knowledge. I am able to overbreathe my conshelf XIVs (exceptional circumstances) and would like to sacrifice cracking pressure for increased air flow. Am already at the point where gas density is the limiting factor and increasing the IP would be ineffective?

I've already adjusted my xiv regs to 155psi (mistakenly thinking this was the supreme recommended ip) on a full tank IP which I found has helped on my deeper dives. The next step in my logic would be to shim the spring to allow for further exceeding the recommended IP. It seems straight forward. What is wrong with my logic? Any concerns I should be aware of?

Thank you in advance,
Cameron

Ps. Since those reading my post might be interested: Recently 'o2 cleaned' a conshelf, last serviced in 1987, appeared clean under black light and didn't need rebuilt yet. Cleaned it anyway and reassembled. Breathes beautifully and no kaboom on 100% o2 yet. Yes, it's overkill for a deco reg, but it gives me an excuse to bring yet another along with me.

 

[halocline]

How high are you currently able to adjust the IP? I would try a new spring before adding shims. I had a problem with keeping stable IP on a DA aquamaster several years ago. A new spring completely solved it.

I seriously doubt that you are at a depth where viscosity is your limiting factor if you're breathing air; its quite toxic at those depths so you would be breathing trimix or some other deep gas.

You might try a very high performance balanced 2nd stage that is less sensitive to greater IP drop and has a very high flow rate. Try a pilot or at least a D series just for laughs.

 

[Bryan@Vintage Double Hose]

 

[northernone]

How high are you currently able to adjust the IP? I would try a new spring before adding shims. I had a problem with keeping stable IP on a DA aquamaster several years ago. A new spring completely solved it.

I seriously doubt that you are at a depth where viscosity is your limiting factor if you're breathing air; its quite toxic at those depths so you would be breathing trimix or some other deep gas.

You might try a very high performance balanced 2nd stage that is less sensitive to greater IP drop and has a very high flow rate. Try a pilot or at least a D series just for laughs.

Thank you for your reply.

It's at 155 psi (set on a full tank). I dug out the manual and discovered already I've gone rogue. Xiv is 140-+ and the supreme is recommended 15psi LOWER, not higher as I wrongly recalled. Reading on the DH forum I'm seeing IP set has been discussed in depth and perhaps I'm barking up the wrong tree with creating yet another thread.

Thanks for pointing me to the second stage, once I scrounge up a lp hose I have a rebuilt Scubapro 109 I have yet to put into service.

Realizing my ignore on my own,
Cameron

 

[Fishpie]

I would look for other potential problems in your reg before doing this.
Replace springs as suggested by Halocline.
Check the length of pin.
Check if center hole in seat is too long.....essentially making the pin shorter.
How indented is the seat? Some seats from the 80's were different from the typical ones seen and could take quite a set (particularly the white/yellowish ones).
Check there's nothing blocking full movement in balance chamber.

Supreme IP ?........I would have thought that it would be set lower than a regular Conshelf.

 

[oldschoolto]

I would talk to Herman... Man knows his stuff...

Jim...

 

[Blue Quaker]

Check your lever height + check the inhale diaphragm. They originally came with a black or grey rubber diaphragm that was replaced in later models with a much more flexible silicone one that improved breathing resistance, and made for a better reg.

 

[northernone]

How high are you currently able to adjust the IP? I would try a new spring before adding shims. I had a problem with keeping stable IP on a DA aquamaster several years ago. A new spring completely solved it.

I seriously doubt that you are at a depth where viscosity is your limiting factor if you're breathing air; its quite toxic at those depths so you would be breathing trimix or some other deep gas.

You might try a very high performance balanced 2nd stage that is less sensitive to greater IP drop and has a very high flow rate. Try a pilot or at least a D series just for laughs.

Following up with a thanks, I followed the recommendations. My conshelf first stages were fine. Holding a respectable IP fairly stable and performing nicely. I was looking at the wrong end of the hose.

Thanks to some of you lovely folks I have a small fleet of d300s for my deep dives. The result is marked improvement in flow and the resulting clarity from reduced co2 retention I suspect will be welcomed if I'm headed deeper again.

In clarification, the dives in question were deep enough viscosity became significant factor. I'm staying shallower this year as my camera rig is only good to 200'.

Happy new year,
Cameron

 

[2airishuman]

Good evening.

I'm looking for someone willing to fill in the gaps in my knowledge. I am able to overbreathe my conshelf XIVs (exceptional circumstances) and would like to sacrifice cracking pressure for increased air flow. Am already at the point where gas density is the limiting factor and increasing the IP would be ineffective?

A question to ponder is whether the flow restriction is at the 1st or 2nd or in combination. I would suspect mainly the 2nd, but it's hard to say. To the extent that the 1st is limiting flow, turning up the IP won't do anything because the 1st stage will already be fully open.

I've already adjusted my xiv regs to 155psi (mistakenly thinking this was the supreme recommended ip) on a full tank IP which I found has helped on my deeper dives. The next step in my logic would be to shim the spring to allow for further exceeding the recommended IP. It seems straight forward. What is wrong with my logic? Any concerns I should be aware of?

The limits are the elastic limit for the spring and the maximum stress the diaphragm can handle. I would guess that the spring would be the weaker point. Ideally you would switch to a spring made from slightly heavier wire, rather than shimming a stock spring. I am not sure that the relatively slight IP pressure increases you are likely to achieve will help. Flow rate goes by the square root of the absolute pressure so another 50 PSI will give you about a 10% flow increase (doing the math in my head).

Ps. Since those reading my post might be interested: Recently 'o2 cleaned' a conshelf, last serviced in 1987, appeared clean under black light and didn't need rebuilt yet. Cleaned it anyway and reassembled. Breathes beautifully and no kaboom on 100% o2 yet. Yes, it's overkill for a deco reg, but it gives me an excuse to bring yet another along with me.

Hmm.