High Pressure cylinder & Reg. question

[BethO]

Hi out there -

I had a problem with my reg over the weekend and was hoping maybe someone out there could help. I know little about tanks and regs.

I've always rented aluminum 63 and 80 tanks with no problems. I finally decided to buy my own tanks. So I rented a steel high pressure 80 to check it out and see if I liked it. I'm thinking I would like a high pressure steel tank b/c I'm small and I like the size of these tanks. I also like the buoyancy better.

The problem is that my reg. kept free flowing throughout the entire dive. It wasn't free flowing full blast - but there was a constant stream of bubbles coming out. I couldn't get it to stop and I went through my air much more quickly than is normal for me. My reg is a Aqualung Titan LX and it was my understanding that it would be compatible with a HP cylinder.

I've never had any problem like this before with my reg with other tanks. As the problem occurred the first time out with this high pressure tank, I'm wondering if this is a common problem or possibly my reg is not compatible. I'm also now concerned as to how much stress is put on my reg. with a HP cylinder.

Thanks for any help anyone has to offer.

Beth

 

[Rick Inman]

By HP do you mean 3500psi? Your Titan is good to go at at these pressures (yoke vrs. din aside here). This could be one of those timing things, like, if you get in a car accident on a Tuesday, saying it's not safe to drive on Tuesdays. The two things have nothing to do with each other. Maybe some sand in the 2nd stage caused the free-flow or something. The fact that it free-flowed "the entire dive" means that it free flowed at lower tank pressures.

I'd do a good reg cleaning (have it looked at if you want) and try again.

 

[Hank658]

Hi Beth,

First questions to help understand your gear set up: is your reg a yoke set up (the A shaped clamp) or a DIN set up (where the first stage screws into the tank valve)?

The HP tank you rented- is it a DIN valve (big hole with threads inside and no o-ring) or a convertible valve (where the piece with the o-ring can be screwed out)?

I apologize if these questions sound too basic. Since you do not give too much info in your post it would help to eliminate possible problems to get you to a solution.

Thanks for the question. I'm sure folks here on the Board can get you straightened out!

Hank

 

[Scared Silly]

As Rick said the two are unrelated.

A free flow can be due to several things. For instance, the intermediate pressure (IP) may be too high or the cracking pressure too low. Also you do not note which reg? Your primary or your backup (aka octo)? If both regs free flowed I would look at the IP otherwise I would look at the reg. Octos do not get a lot of love so if it was the only one free flowing give some love and it will save you some air.

 

[BethO]

Thanks so much for your help Rick, Hank and Silly and sorry to leave information out of my question. My diving is not bad - but my knowledge of equipment needs work!

I had tried to get the 2nd stage open to see if it was a piece of sand lodged in there - but I couldn't get it open. I didn't want to force it so I swung by the dive shop with it. I had just had the reg serviced several weeks ago and had only taken it out a few times (with no problems) so I thought the reg would be fairly clean and maybe there was more to the problem than sand. I use a yoke connector set up and the tank I rented was 3442psi. Also, my primary reg was streaming bubbles out of it - I was so busy trying to get this to stop that I didn't check my octo. So I'm not sure if that was streaming bubbles also. Now that I'm getting a better understanding as to how this works, I will think to check my octo next time.

At any rate, it seems the first stage should be reducing pressure to 140, but mine was reducing pressure to 145 instead. (I pressume this is the IP - intermediate pressure?) I'm sure I'm putting this all in laymen's terms. They adjusted that for me so I'm going to try again next weekend with the same tank and see if that does the trick. Hopefully, this will solve the problem.

Thanks so much again for explaining how some of this works. I'd like to have a better understanding of how my equipment works.

Beth

 

[DA Aquamaster]

With a balanced first stage regulator like the legend the IP is stable regardless of supply pressure and 3500 psi versus 3000 psi would not make any difference.

Similarly, a 5 psi difference in IP (145 versus 140 would also not make any difference on a balanced second stage like the LX.

Having the reg serviced several weeks ago is probably the key issue. After servicing the second stage seat will develop a seating groove after several weeks or a few dives. Normally, the tech accounts for this by adjusting the orifice or spring pad to seat the orifice slightly deeper or add a bit more spring pressure to accommodate the groove that will eventually develop as the seat breaks in. Too much compensation and the reg breathes much harder than it needs to, but not enough compensation will result in a very slight continuous freeflow like you describe. So if a tech is concerned with getting maximum performance for you from the reg, the greater the chance he or she may get it slightly wrong increases. In any event, it is always a good idea to check the reg a few weeks after service anytime you get it serviced and if you rent tanks, this is a good time to just hook it up and check it - it beats getting to the dive shop or on a trip and discovering the problem.

So all in all, I suspect the issue had nothing to do with the use of an HP tank, it was just coincidence that you experienced an adjustment problem on the first dive with the HP tank.

That said, adjusting the IP downward 5 psi will not make any significant difference in reducing the freeflow. What will make a difference is readjusting the orifice and or spring pressure in the second stage. Anytime the Ip is adjusted, the second stages should also be adjusted, so it should be taken care of, but check before you leave the shop with a tank the next time out.

 

[spectrum]

I agree, your recent servicing needs a touch-up.

The HP you rented 3442 or 3500 PSI is not that much higher than your 3000 PSI AL80 and after the first 10 minutes you are certainly down into a common pressure range.

BTW as far as I'm concerned you're on the right track with HP steel.

Pete

 

[fl-diver]

I use an Aqualung Titan LX converted to DIN with my Genesis HP 100's (3500 PSI and sometimes slightly higher ) all of the time with no problems.
I would definitely go with coincidence on this one.
I'm assuming you tried the "smack the 2nd stage against your hand" repair technique. JK
Get your regs checked out and I would definitely go with steel tanks.

FWIW
You might want to look at the LP 85's while shopping. They are almost as small and much easier to get a proper fill.

 

[BethO]

I guess things are not always as they appear. Here I thought that the servicing of my reg was not the problem b/c I had it serviced weeks ago and had no problems with it. The only variance as far as I could see at the time of my problem was the HP steel tank. So I thought - well that must be the problem! As it turns out, it seems the problem is literally right under my nose - my 2nd stage!

Yesterday, when the shop adjusted the IP to 140 psi (from 145psi), no adjustments were made to the 2nd stage. After adjusting the IP, they put the 2nd stage in water and it appeared that the bubbling had stopped. After reading your posts though, I think I'd better head back to the shop as the 2nd stage may need to be readjusted as well. Thanks for explaining how that works Aquamaster.

I'd hate to spend another dive trying to get that 2nd stage to stop bubbling. And yes, FL-diver, I did try the "smack the 2nd stage against my hand technique" - to no avail! It's one of the few fix-it techniques I actually know.

I'm still researching and shopping for tanks. The only thing I'm certain of at this point is that I want steel and that was confirmed by reading your link Spectrum. Thanks for sending it. I was under the impression that the LP tanks were much larger so I haven't really looked into them - but it sounds like I should. I know I still have homework to do. I've heard people mention having difficulty getting a proper fill on an HP tank. Having never tried to get an HP tank filled, I haven't been sure of how much of a problem it is. I presume the issue is that many dive shops do not have the proper equipment to fill a HP tank?

Thank you so much for all of your help, Aquamaster, Spectrum and fl-diver. I really appreciate it.
Beth

 

[DA Aquamaster]

One additional thing to consider....not all balanced regs are perfectly balanced. For example piston regs with a straight stem piston do nopt fully account for the area of the seat due to the finite amount of metal on the sharp edge of the seat. The end result is that there is still some downstream effect and the IP may vary by 4-6 psi between 300 and 3300 psi. The same can potentially apply to a diaphragm reg if the area inside the orifice and behind the seat in the balance chamber of the seat carrier are not exactly equal.

I am not sure if that applies to the Legend or not - you;d ahve to check the IP at high and low pressures to ensure it was the same. In any event the short story is that a "balanced" reg may not freeflow at low pressure but if it is finely tuned enough, may still freeflwo slightly at high tank pressures. With unbalanced regs like the Scubapro Mk 2 or Aqualung Calypso, it is a noteable concern that requires the reg to be tuned at the maximum service pressure it will see in service.