Steel tanks dangerous?

[DanielRJones]

If I had an aluminum tank, let say an al 100. I would have about 12 lbs dichable weight at the surface. With the 120 hp steel, I would only have 4 lbs. Both would have about 10 lbs of negative force I would have to swim against at the surface with a full tank. This might not be a big burden for some... but for me and others it might be.

How are you 10lb over weighted at the start of a dive. A 15l 232 steel has 2.5kg of air in it. So 6lb max

 

[fisherdvm]

No. I am only about 2 lbs overweighted. I don’t understand the physics of each tank. But it has to do with volume of water displaced vs volume of air carried. Usually steel tanks allow you to carry less lead to maintain a safety stop with a near empty tank. And weight often less than an aluminum tank. I noted that steel 80hp saved me alot of lead compared to a cheapo 80al I had in Michigan. I understand that you can not generalize each tank just based on composition. But there is a general understanding that one is under greater risk diving steel doubles and wetsuits. A concept I do not totally understand yet. But with single tank - I can only speak from my personal experience of my own two tanks - al vs steel hp. Now that I regularly dive with a 120 HP - single - I am posing the task to myself- can I handle a BC failure with a full tank? Should I worry? Or just dive?

 

[boulderjohn]

But there is a general understanding that one is under greater risk diving steel doubles and wetsuits. A concept I do not totally understand yet.

With steel doubles, the weight of the tank is obviously doubled, and that includes the amount of air being carried. If I am diving an AL 80 at 3,000 PSI, I am carrying about 6 pounds of gas at the beginning of the dive. If I am diving my steel LP 108s at 3,000 PSI, I am carrying about 18 pounds of gas at the beginning of the dive, and that is in addition to the weight of the tanks themselves. I cannot possibly swim that up to the surface without some sort of buoyancy assistance. In technical diving, you need to have a lot of gas in reserve in case of emergencies, so we are never in the situation of being low on gas at the end of a dive.

 

[fisherdvm]

With steel doubles, the weight of the tank is obviously doubled, and that includes the amount of air being carried. If I am diving an AL 80 at 3,000 PSI, I am carrying about 6 pounds of gas at the beginning of the dive. If I am diving my steel LP 108s at 3,000 PSI, I am carrying about 18 pounds of gas at the beginning of the dive, and that is in addition to the weight of the tanks themselves. I cannot possibly swim that up to the surface without some sort of buoyancy assistance. In technical diving, you need to have a lot of gas in reserve in case of emergencies, so we are never in the situation of being low on gas at the end of a dive.

John, but my impression is that if one wanted to dive doubles with wetsuit, it is preferable to do so with al tank. Is that correct? Better weight distribution? Or more ditchable weight?

 

[EireDiver606]

You’re trying to solve a problem you wouldn’t have in a Drysuit.

But you won’t get a Drysuit (?).

 

[boulderjohn]

John, but my impression is that if one wanted to dive doubles with wetsuit, it is preferable to do so with al tank. Is that correct? Better weight distribution? Or more ditchable weight?

Double AL 80s filled to 3,000 PSI = about 155 cubic feet.
Double LP 108s filled to 3,000 PSI = about 240 cubic feet.

Go to Cave Country Dive Shop, and they will fill those LP 108s to 4,000 PSI, which is 320 cubic feet, more than you would get in two sets of AL 80 doubles.

You are very limited on planning for depth and dive time with aluminum tanks.

 

[fisherdvm]

Double AL 80s filled to 3,000 PSI = about 155 cubic feet.
Double LP 108s filled to 3,000 PSI = about 240 cubic feet.

Go to Cave Country Dive Shop, and they will fill those LP 108s to 4,000 PSI, which is 320 cubic feet, more than you would get in two sets of AL 80 doubles.

You are very limited on planning for depth and dive time with aluminum tanks.

Amazing

 

[Steve_C]

There are lots of ways to help
-take your time and use up some air
-swim/crawl to the anchor line and use that to aid the assent.
-with integrated weights you can choose to drop just a little lead and put the pouch back.
-shoot a bag and use the line to help
-pass the pony to the buddy
=etc

 

[DanielRJones]

Double AL 80s filled to 3,000 PSI = about 155 cubic feet.
Double LP 108s filled to 3,000 PSI = about 240 cubic feet.

Go to Cave Country Dive Shop, and they will fill those LP 108s to 4,000 PSI, which is 320 cubic feet, more than you would get in two sets of AL 80 doubles.

You are very limited on planning for depth and dive time with aluminum tanks.

the uk you get what is stamped on the side so 200 bar in my alu 80 232 in my twin 12 euros and 300 bar in my HP 12l steel

 

[Scared Silly]

But there is a general understanding that one is under greater risk diving steel doubles and wetsuits. A concept I do not totally understand yet.

The concept behind doubles is no different than singles. It is all about several concepts:

1) BCD should be able to float your rig at the surface without you in it
2) BCD should be to compensate for the change in buoyancy at depth in one's thermal protection.
3) Finally one should have a balanced rig that can be swum up in case of a BCD failure. Which may include ditching weight.

Where one gets into more trouble with doubles whilst wearing wetsuit is not having a balanced rig because of the loss of buoyancy and the lack detachable weight.