freeflowing??

[JahJahwarrior]

So, I got int he pool this morning with my new Scubapro R390, then switched it out for my old Conshelf (only 2 LP ports so I had to get out and switch them over, soon one will be octo and one will be main reg). The conshelf is nice and I think it breathes just as easily as the scubapro if not better.....but, when I am upside down or even looking down (well, if I'ms wimming horizontal and bent my head to look at my fins or something, not when I'm looking straight out, which when horizontal is down...) it seems to "freeflow" out of the exhaust port. If I breathe in, it seems to stop, but whenever I'm not breathing it "freeflows" out of the exhaust port. It's not just air trapped I'm pretty sure, otherwise why would it stop as soon as I breathe? If the purge was being hit then I'd be able to feel it, but I don't feel any air being forced into my mouth. ???

 

[jamiep3]

If you are talking about switching the 2nd stages, the conshelf 2nd might need to be adjusted for the IP of the Scubapro 1st.

 

[JahJahwarrior]

both are on a Conshelf XII first stage. both conshelfs were sent in and worked on at the same time just recently, only one day of diving/two dives on them. The scubapro I just got in the mail last night

 

[DA Aquamaster]

There are two issues leading to your problem.

1. Any second stage should ideally be atached to and then tuned to the first stage as first stage intermediate pressure will vary within a range of 120-145 psi. If the spring pressure or orifice is adjusted so that there is too little pressure holding the seat against the orifice, the result is a wonderfully low cracking (inhalation) effort. However...

2. All conventional second stage designs have "Case Geometry Fault" issues. The difference in height in the water column between the center of the diaphragm and the top of the exhaust valve varies depending on what direction you are looking. If you are looking straight down or even aft toward you feet you are in the worst case position as the difference in height between the two is at a maximum. This can be over an inch in some models. This means that air will slip past the exhaust valve and as it does so, the greater pressure outside the diaphragm will force it upward into the case and depress the demand lever - just like when you inhale. If the force required to initiate air flow is strong enough, the diaphragm will stop moving inward when the pressure inside the case equalizes with the water pressure outside the exhaust valve. However if the force required is too light, the valve will open and a produce a slight freeflow which continues to supply air that then continues to leak out the exhaust valve.

Based on your description, the inhalation effort on your Conshelf second stage is too light and it needs to be properly tuned to your first stage in order to avoid the freeflow in downward looking positions.

It is possible that it was properly tuned when it was serviced. However over time a seating groove develops in the seat in the second stage that in effect reduces the force required to initiate air flow. When a non adjustabel secodn stage is serviced the tech anticipates this effect and sets the reg to breathe slightly harder than optimum so that it is set optimally when the seating groove develops. If you don't do that, or if you do not compensate enough, a freeflow can occur.

 

[JahJahwarrior]

Should I take it back to the place I had it serviced and ask for that to be adjusted again? I would assume both Conshelfs (1st and 2nd stage) were tuned together, since they were connected when I sent them off

Do you have to get 2nd stages rebuilt each year or just have them looked at? This Scubapro has been serviced around a year ago and seems to work fine, I'd hate to rebuild it just because, but I wouldn't mind having a tech make sure all the settings are correct. You know, what I'd really like is something that explains how these things work for dummies: I'd love to know what IP pressure is and why it's important and all that stuff. Is there any website you know of that has a really good guide for the complete idiot yet is in enough detail that I could actually learn something from reading it?

 

[spectrum]

Yes they need to be reset as an assembly due to the nuances of each component.

Here's some light reading:
http://www.njscuba.net/gear/eqpt_06_regulators.html

Pete

 

[Ed Palma]

I hear this site has a lot of information on it, but its just hearsay... here's the link: scubaboard.com



Sorry, couldn't help myself, but really, I learned a lot from this site. And listen to DA. His input is the one I usually look for.

 

[Ed Palma]

Oh, by the way, I thought you were looking for a splitter so that you could have an extra LP port? Any luck on that?

 

[JahJahwarrior]

The reg that is "freeflowing" is the Conshelf 2nd. The first stage is also Conshelf. (I'm calling the 2nd conshelf because I don't know what exactly it is, the sticker on the purge button is long gone, but it is what came with the conshelf 1st) They were both serviced at the same time and I would have assumed that the reg guy set them up with each other.

The Scubapro 2nd that I bought to use as an octo (that I need to buy a splitter for, but went ahead and switched out with the Conshself 2nd just to see how well it worked) seems to work fine without this freeflowing from the exhaust valve.

Why is the reg I sent in the one that doesn't seem to work as well as the one I didn't send in? Did the person not set it right, or did the person tune them to each other, but the regs "broke in" a little more and are now a little off?