Tank Prices

[SparticleBrane]

What was your average depth?--you'll use that to determine your SAC rate.

 

[Empty V]

Between 19 and 22ft.

 

[spectrum]

Between 19 and 22ft.

So you were at .6 ATM (@20')
1.38 / (.6+1) = .86 SAC

Use that to back into your gas planning.

Pete

 

[moneysavr]

I love my Worthington HP 130's and man good price I was buying them from my pal Barry at
www.divesales.com
for about $327.00 to my door 2 days! prior and during the PST death throws,now they are up a few bucks.
Its got the air I need to dive deep o2 on our cold and deep wrecks,it gives me mass amount of safety gas,and shops that cant fill em full screw em! and I tell em so!
they ain't now stinking AL 80s so fill em till they bulge!
ask some Florida DMs how they pull two 60' dives at 40-55 min each on one can! and have gas left good sac rate yeah but,,,can you say major over fills!
you will love the old water heaters as we call em!
dive safe!
Brad
A boat is a piece of dive gear (extension) and about the price of a regs and doubles,pony's,DUI Dry suit,deco gas tanks,computers and BT's and training C-cards on a DIR rig you could own one!
quote J.B.

 

[Empty V]

So you were at .6 ATM (@20')
1.38 / (.6+1) = .86 SAC

Use that to back into your gas planning.

Pete

So you divide the cubic ft/m by the atm? Interesting. Why do you add 1 to it? What kind of rate is .86 SAC considered? As you can see I dont have hundreds of dives under my belt.

My LDS recommended (off the record) that I not fill my new tank (once I acquire it) past 3300psi since I am using a yoke 1st stage. Is this something that's genereally known or recommended?

Thanks!
Billy

 

[riguerin]

So you divide the cubic ft/m by the atm? Interesting. Why do you add 1 to it? What kind of rate is .86 SAC considered? As you can see I dont have hundreds of dives under my belt.

Billy,

The air that you breathe under water is denser than that at the surface. The absolute quantity of air that you breathe is a function of surrounding pressure … on SCUBA this in turn is a function of depth. To establish a meaningful air consumption rate, it is common to normalize it to the ambient pressure at the surface ... this eliminates the depth dependancy. This is done by multiplying your absolute air consumption rate by a simple ratio of ambient pressure on the surface to that at depth.

By definition, the ambient pressure at sea level is 1 ata (under standard day conditions). At depth, you have the pressure exerted by the water column + the pressure of the atmosphere (that’s where the +1 comes from). For your example, this ratio would be 1 ata / (.6 ata + 1 ata). The units cancel and you get 1/1.6. As you’ll recall from basic algebra multiplying by 1/X is the same as dividing by X. That's why you divide your absolute air consumption rate (CuFt/Min) by 1.6 to get your SAC.

As a new diver, I wouldn't get too hung up on how your SAC rate compares to others. But it good to know where you're at for planning purposes. Your SAC rate will improve as you get more dive experience under your belt. As an example, I've seen Josh's SAC improve tremendously over the past few months. Hommie's been diving like a freak'n mad man

 

[HBDiveGirl]

...
My LDS recommended (off the record) that I not fill my new tank (once I acquire it) past 3300psi since I am using a yoke 1st stage. Is this something that's genereally known or recommended?

Thanks!
Billy

Before I finally saw the light and drank the Refreshing Beverage of Choice... I used a yoke reg on hp tanks for 2 straight years.

My fav shops routinely and deliciously filled those puppies up to 3442 and.... (we're OFF the record, right???!!!)... sometimes a little more. All the time. 400+ dives.

NEVER did an o-ring blow during fills, even if the yoke adaptor plug was in place and the tank was being filled on the yoke whip.

NEVER did an O-ring blow under water.

I do think I went through a couple more O-rings than my buddies, when one would pop as I pressured-up the system during pre-dive checks.

I switched to those yellow (Vyton?) o-rings, and that stopped.

So, my experience?

• Plump those puppies Up and go play!
• Always carry the appropriate hex key to remove the yoke plug. Some shops won't fill to 3442 on the yoke fill-whip. Store preference.
• Always carry good o-rings in all your needed sizes.... Always!
• Always do a thorough pre-dive pressure check.
• Go DIN.... when you can. It's just a better connector.

hbDIN-lovin'Chica

 

[Empty V]

Do you know if LDS's in general sell those super duper special Viton (I looked 'em up) o-rings?

Billy

 

[HBDiveGirl]

But that's not how RB really "works" though right -- you both reserve the same cft of gas, just different PSI in each tank. So if you hit RB on the 130, and your buddy goes OOA, then you are in exactly the *same* position as if the person on the 80 hits RB and you go OOA.

Of course, you can (with good reason) argue that the smaller tank person will usually hit RB first, but as long as you have a good RB calculation it should be fine.

However, I definitely hear you on the taking longer than expected to fix something.
We spent about 5 mins fixing a valve problem (in doubles) on our T1 class.

Absolutely, limeyx! I know how RB works when the team is knowledgeable and plans the dive correctly. But fresh in my memory are my pre-fundies dives wherein dives were turned on rather arbitrary psi values that often did not take into account differing tank sizes within the team.

I think I was aiming this discussion at those memories, since this thread is in the General Scuba Equipment Forum.

But you're completely right that correct RB calculations remove the risk of diving in a team with large variations in SAC rates and tank volumes/pressures.

Thanks for following up with your comments .

Claudette

 

[HBDiveGirl]

Do you know if LDS's in general sell those super duper special Viton (I looked 'em up) o-rings?

Billy

All my local LDS's sell them... $3 comes to mind. Each. Startlingly expensive. Chris Grossman over at diver.net purchases o-rings in bulk from a supplier in downtown L.A. I don't know if they offer Viton.
Ken just this weekend told me the name of a generic O-ring supplier that he purchases from... and I can't remember their name. (I had nitrogen on board... what can I say :14

I bought 6 from my LDS and have used only two in a year.
Make sure you get the Right size. They are not as stretchy as the black rings, so they pop out more easily if it's not a near perfect fit.

Claudette