Moisture in my first stage?

[HeatCker]

jim .. so your saying that you would lower the IP (for cold water diving) instead of upping the cracking pressure.
if its not to involved can you explain why so that i understand
is adjusting the cracking pressure harder / easier than adjusting the IP
thanks

 

[LeadTurn_SD]

thanks for the info, i'm not reg savy so i probably got things backwards.
i'm not sure what the shop owner meant but he did say he would have to adjust the 1st stage or i may hear noises when i breathed.
i had the cracking pressure adjusted to help with cold water free flows, water temps are 56 F and dropping fast, soon to be in the low 40's, our dive season is almost over for this year.
i had a free flow earlier this year (spring time) and the owner said he would adjust the cracking pressure from 1 to 1.4 to try and help with a possible free flow.
does that make sense ??????

Raising the cracking effort makes the 2nd stage less "sensitive" and less likely to free flow. Most high performance 2nd stages will free flow vigorously if mishandled, for example removing the 2nd stage from you mouth and quickly turning the regulator mouthpiece up will do it on most any 2nd stage (unless it is seriously de-tuned), and this is normal. If it freeflows while in your mouth (i.e., with back pressure) then it needs to be adjusted.

Like Jim mentions, for cold water it is common to reduce the IP to help prevent "freeze" flows. The reason is that the higher the IP, the more adiabatic cooling occurs. If you've ever used compressed air hand tools, or felt your first stage after purging the 2nd stage for a few moments, you'll understand the cooling effect that rapidly released HP air has on the metal parts it flows past.

Best wishes.

 

[HeatCker]

ok, lets see if i have this right with an example.
tank pressure 3000 psi, IP at 2nd stage is say 140 psi.
the cooling is caused by the pressure dropping from 3000 to 140 psi.
so to reduce the pressure drop, and therefore the cooling effect, the IP at the 2nd stage would have to go up, say to 170 (just an arbitrary number).
that would be a smaller pressure drop from 3000 psi.
so when you "reduce the IP" you are actually increasing the pressure at the 2nd stage to reduce the pressure drop from the 1st stage.
do i have this right or am i confused.

 

[halocline]

Like Jim mentions, for cold water it is common to reduce the IP to help prevent "freeze" flows. The reason is that the higher the IP, the more adiabatic cooling occurs.

Actually, with equal air flow higher IP means less adiabatic cooling because the vast majority of the cooling takes place in the first stage, and the higher the IP, the less of a pressure gradient at the HP seat. (3000PSI to 150PSI is a smaller drop than 3000 to 125) But, the differences are so slight that I can't imagine there would be any real-world effect on freezing.

The reason old school reg techs used to lower IP for cold water use was to slow down flow rates. I guess this is most important in the sense of lowering venturi assist in the 2nd stage which can cause a free flow, which then can easily contribute to a freeze up. I also guess cracking effort adjustment could accomplish sort-of the same thing.

---------- Post added October 15th, 2014 at 08:36 PM ----------

ok, lets see if i have this right with an example.
tank pressure 3000 psi, IP at 2nd stage is say 140 psi.
the cooling is caused by the pressure dropping from 3000 to 140 psi.
so to reduce the pressure drop, and therefore the cooling effect, the IP at the 2nd stage would have to go up, say to 170 (just an arbitrary number).
that would be a smaller pressure drop from 3000 psi.
so when you "reduce the IP" you are actually increasing the pressure at the 2nd stage to reduce the pressure drop from the 1st stage.
do i have this right or am i confused.

You have it right, but increasing the IP also increases the flow rate, sometimes dramatically, which contributes to more free flows.

 

[Super Noob 1258]

It's an Edge EXP, which is a diaphragm reg.

Thanks for the reassurance re: salt water. I'll give the shop that serviced it a call tomorrow. I knew it wasn't a leak since there wasn't any bubbling underwater.

My XTX 50 had a similar problem when I got the 5th port upgrades installed. It whistled like a train whenever I breathed or ran my bc inflator. Turns out they forgot to lube an o ring on the hp seat, causing the whistling. It was a 5 minute fix.


Sent from my iPhone using Tapatalk

 

[HeatCker]

ppatin .. i apologize for side tracking your thread


jim, leadturn, halocline .. thanks for the info

 

[ppatin]

Hi ppatin,

If the tech finds the problem, let us know... it may help someone else, and I'm interested to know the cause. I'm not familiar with the Edge EXP, but there are only a few internal parts that can produce a "hiss" during inhalation.

I hope you get it sorted out quickly.

Best wishes.

I called the shop today and they said that if I'm not seeing bubbles and the reg breathes fine underwater they couldn't really think of what could be causing a sound from the first stage. The shop is an hour+ drive away from my house so I'm going to hold off on bringing it in since it sounds like the chances of a catastrophic underwater failure because of this are pretty much nil.

 

[redacted]

I called the shop today and they said that if I'm not seeing bubbles and the reg breathes fine underwater they couldn't really think of what could be causing a sound from the first stage. The shop is an hour+ drive away from my house so I'm going to hold off on bringing it in since it sounds like the chances of a catastrophic underwater failure because of this are pretty much nil.

Your reg has a symptom of a problem and they are not competent enough to troubleshoot it??? Perhaps you should look for a shop 2 hours away.

While such noises are not usually an urgent problem, they should not exist UW. It can be fixed.

 

[ppatin]

Awap:

FWIW I didn't actually notice the noise underwater, it was on the surface that it was noticeable. I plan on bringing the reg in the next time I'm in the area of the shop but since it sounds like the original theory of it being moisture was debunked it's not an urgent problem that will cause further damage if I wait.