How to monitor buddy's air with different tanks

[kramynot2000]

Was out diving with boomx this weekend and we usually check each other's air periodically. He was diving an LP95 and I was diving an HP80. We use the ol' PADI system of signaling to each other how much psi we have left but with the first check, I realized this doesn't really work with different tanks. He was at 1500 psi and I was at 2000 psi.

I'm wondering what other methods people use to signal to your buddy how much air you have when you're diving different tanks. Do you signal when 1/2 the air is gone, 1/3, etc?

 

[Sharky]

I would be nervous diving with you if you are reaching over to my consol every time to read my pressure

I like safety and helping each other, is this not a bit to far. Just give signals when you are running low and when you hit the 50 bar. It doesn't matter with what kind of tank you dive. The safety limits are still the same for every tank.

 

[Spectre]

When you're planning your dive, you should plan out what your turn and ascent psi will be. E.g. if you have two people with different sized tanks, and you decide to turn at a third, and ascend with a third, you need to comunicate what a third is.

e.g. if one is diving an HP tank, your turn might be 2400 psi, and your ascent at 1300 psi. Where a low pressure tank diver may have the turn @ 1800 and ascent at 600. [for example]

The key is to figure out what you both need to get back, and what you both need to ascend together. You then communicate those pressures to each other so you both know what pressure the other person is turning/ascending on.

A better example than yours would be two people diving, one with a low pressure 104, one with high pressure double 100s. When the 104 user has used 1/3 of their supply, the double 100 user will still be at ~2900 psi.

The key is pre-dive planning, to communicate to your buddy how much gas, in psi, you will be turning and you will be ascending with.

 

[Uncle Pug]

You need to plan you gas useage ahead of time. Not only do you need to take into account the difference in size of your tanks... but also difference in SAC as well as proposed dive plan itself.

For a simple out and back shore dive with no overhead and no necessity to return to the exact point of entry you could dive the rule of halves backing out your emergency reserve before figuring your turn pressures.

You want to figure what your turn pressure will be when your buddy reaches his/her turn pressure.

During the dive you inform your buddy when you reach your turn pressure.

If you are diving with the unknown *buddy of circumstance* it is prudent to check their SPG periodically... I do this, especially with n00bs, without them knowing.

After diving with the same buddy for several dives you should be able to guess their PSI just by looking at your bottom timer... if you have been paying attention to such things.

 

[Sharky]

Apperently I'm used to a different system than you guy's. I never planned a dive based on pressure readings, only on time readings. I ask my buddy what his average bottom time is on the planned depth and cirumstances with his tank. With that information in mind we start planning the dive.

During the dive there will be just regular communication about the pressure. For our planning we always use the conservative approach and the information of the person who normally uses the most air.

 

[Spectre]

Sharky once bubbled...
I never planned a dive based on pressure readings, only on time readings. I ask my buddy what his average bottom time is on the planned depth and cirumstances with his tank. With that information in mind we start planning the dive.

Well, you have to have _some_ sort of PSI plan; how do you not run out of gas if you happen to be breathing higher than normal?

What happens if, at the end of your dive, someone misplanned and is out of gas, or something happens and one of the divers looses their gas supply? Did you plan enough reserve to get both of you up on the one reserve?

 

[Epinephelus]

Certainly any gas integrated computer manufacturer could easily allow the diver to specify the pressure/CF value prior to the dive and then just have the gauge read out CF remaining directly instead of having to think about what pressure in one is equivalent to what pressure in the other... Wouldn't even have to engage yer brain (rotted or not, Pug).
E.

 

[Spectre]

Epinephelus once bubbled...
Certainly any gas integrated computer manufacturer could easily allow the diver to specify the pressure/CF value prior to the dive and then just have the gauge read out CF remaining directly instead of having to think about what pressure in one is equivalent to what pressure in the other...

IMHO, Gas reserves are something that needs to be planned before you get in the water; not based on any breathing rates being used in the water. Just because you're having a nice peaceful dive and you're breathing at .5, or have had great dives for a month and have had rates of .5, that doesn't mean you're going to have those rates when the feces hits the fan.

You need to have your reserve planned on a realistic stressed SAC rate...

 

[Sharky]

Spectre once bubbled....
Well, you have to have _some_ sort of PSI plan; how do you not run out of gas if you happen to be breathing higher than normal?

The plan is at turning points we will update eachother about the pressure, depending on that we will continue the original plan or adjust it to the current situation. This will be the same as when you start planning on pressure readings.

 

[CuriousMe]

Sharky once bubbled...
I would be nervous diving with you if you are reaching over to my consol every time to read my pressure

I like safety and helping each other, is this not a bit to far. Just give signals when you are running low and when you hit the 50 bar. It doesn't matter with what kind of tank you dive. The safety limits are still the same for every tank.

I didn't see that kramynot2000 was reaching over to their buddie's console...but using signals to communicate what their consoles said.

Whether we have different tanks or not, we agree on turn pressure ahead of time (figuring for each tank). I regularly ask my buddy at different points of the dive what their pressure is, and tell them mine, especially if it's someone I haven't dove with before.

Peace,
Cathie