Manifold question...

[RoyN]

Hi guys,

I have a question on the manifold.

Now the manifold is supposed to make two tanks into one big one right? If so, how come the air gauge only reads 2700 psi? Isn't it supposed to read like 5400 psi if both tanks were to have 2700 psi? I left the manifold valve open too so don't know why the computer doesn't read both tanks as one. Am I missing something here?

[BSea]

Originally Posted by RoyN

Hi guys,

I have a question on the manifold.

Now the manifold is supposed to make two tanks into one big one right? If so, how come the air gauge only reads 2700 psi? Isn't it supposed to read like 5400 psi if both tanks were to have 2700 psi? I left the manifold valve open too so don't know why the computer doesn't read both tanks as one. Am I missing something here?

Your confusing PSI with Cubic feet. An AL 19 has 19 cubic feet at 3000 psi. An AL 80 has 80 cubic feet at 3000 psi. Same PSI, but different volume. Your doing the same thing with doubles instead of 100 cubic feet for 1 tank you have 200 cubic feet when 2 100's are combined. I just used 100's as an example. It would be 160 cubic feet for 2 80's at 3000 PSI. So when using doubles, double the volume, not the PSI.

[RoyN]

How do I know I'm breathing from both cylinders? I turned the isloating valve open and when I lightly purged the regulator from the first stage on my back right that doesn't have the dive gauge, the number doesn't go down a bit?

EDIt: I'll be in chat if anybody could help!

[BSea]

Originally Posted by RoyN

How do I know if the manifold is on? I turned the manifold valve on and when I lightly purged the regulator from the first stage that doesn't have the dive gauge, the number doesn't go down a bit?

I'm assuming you mean the isolator. Look at the knob. It should say open or closed. Just make sure it's open. That way you have access to the air in both tanks from either reg. Or, if for some reason you have a regulator failure, you can turn off that reg, and if the isolator is open, you'll still have access to both tanks of air.

[RoyN]

Okay, thats what I did. The isolater knob has been turned open and I turned on both tanks. So now its all set and ready to breath?

The only thing is the computer i have is the Smart Com and don't know if thats good for double tank at all.

[BSea]

Originally Posted by RoyN

Okay, thats what I did. The isolater knob has been turned open and I turned on both tanks. So now its all set and ready to breath?

The only thing is the computer i have is the Smart Com and don't know if thats good for double tank at all.

I'm not familiar with that computer, but it shouldn't matter. Your computer will monitor your time under depth, and give you a no deco time remaining regardless of your air volume remaining. If it's air integrated, it should give you dive time remaining based on the beginning pressure & air remaining, and the depth you are at. If it calculates your SAC rate, you'll have to tell it tank volume somehow, like 80, 100, 120, 160, 200, or whatever the volume is of the tank or tanks you are using on the dive. This is the only way it can calculate your SAC. Usually this is done after it's downloaded to a computer. Some models might have it imput directly to the computer, but mine doesn't.

For simplicity, don't think of your doubles as 2 tanks, just think of them as 1 large tank. For Example: Think of double 100's as a single 200. Your computer doesn't care what size tank you have for the basic information.

[RoyN]

Thanks Bsea, I'm giving it a try on Wednesday and will let you know how it works out!

[navyhmc]

As long as your isolator is open, your computer will read for both tanks. When it's closed, it will only read the tank it's attached to. As BSea said, doubles with the manifold open is one big tank. Think of you doubles set up as an old fashioned balance scale. As long as the isolator is open, the tanks will maintain a balance. so 2700 psi is the psi of both tanks individually as well. Now, with the isolator closed, you're only on one of the two tanks. That is the one your current breathing regulator is connected to.

Also, before you get going too much on doubles, remember that they have a few more steps involved in their use than a single. Ideally, both regulators must be on-part of the dafety factor of doubles is another full regulator setup. The isolator must be open as well. The additional skills comes with doubles in the form of shut down drills. What happens when one regulator free flows? Which one is it? What do you do? What about a tank seal or valve leak? This requires extra training. It's not difficult, but is a must.

Not trying to flame you in anyway, and please don't take this as such. You seem a little unfamiliar with doubles so I would encourage you at the very least to get with someone who is very experienced with doubles-possibly a tec diver if you know one or two-and do a few dives with them where they can help you with immediate action drills so you can dive doubles safe.

Congrats on taking the step into doubles, I hope that you have a great number of dives and that all your descents are followed by an ascent of your choosing.

Dive safe, dive often.

[SkuaSeptember]

As far as the SmartCom goes-When you download your dives, just input the total tank volume and the Smarttrak software will calculate the sac rate for you. The computer doesn't know the size of the tank you have it attached to, all it can do is track the change in pressure and the rate of change which the computer interprets as your breathing rate.