Safety, Ali v Steel

[Gaz Overland]

I'm buying a tank at the moment, i have heard every one is now selling their ali tanks due to too many fractures and accidents, though I know the MIddle East only deal in Ali. am going steel because of the rumours and because they are in my opion safer although i find the weight of an Ali on my aged back more comfortable, any opions yourselves.......

 

[cbrich]

If you go with Aluminum cylinders get Catalina or post 1990 Luxfer. The aluminum you need to worry about is the 6351 alloy; 6061 alloy is the stuff to get. You will need to look at the orginal hydro date for the cut off.

 

[elan]

You should not worry about your back say HP100 is only 2 lb heavier on land but takes of lead ff 6lb your back and it holds 100 cuf. LP 66 weights 25lb - 6lb less than AL80 + the weight you take off with your experience you can make a lot out of that tank. LP85 just couple of lbs heavier than AL80 and have more gas + lead taken off the back. So in fact you are helping your back if you switch to steel

 

[rstofer]

If everyone in the neighborhood uses Al 80s, why not join the crowd? Sure, an HP100 looks attractive but if you can't get complete fills, it is just a steel 80.

Luxfer rates their Al 80s at 100,000 cycles or 2 dives per day, every day of the year, for 136 years.

Al 80s cost about half as much as HP 100s.

As to whether the more negative buoyancy of the HP 100 is a help or a hazard depends on whether you have any ditchable weight left after you remove 6# for the change. When I dove SE Asia, I only had 6# of weight so I wouldn't have had any ditchable weight if I used an HP 100.

Traveling from Singapore to Malaysia in 1988, we weren't allowed to bring steel tanks, only aluminum I guess they thought that all steel tanks were rusted out hulks.

I certainly wouldn't base a buying decision on tanks that were made back before '88. No modern aluminum tanks uses that alloy.

FWIW, I have a couple of Al 80s but for cold water diving HP 100s are better. So, I have 6 of those for 3 divers.

Richard

 

[elan]

If everyone in the neighborhood uses Al 80s, why not join the crowd? Sure, an HP100 looks attractive but if you can't get complete fills, it is just a steel 80.

Luxfer rates their Al 80s at 100,000 cycles or 2 dives per day, every day of the year, for 136 years.

Al 80s cost about half as much as HP 100s.

As to whether the more negative buoyancy of the HP 100 is a help or a hazard depends on whether you have any ditchable weight left after you remove 6# for the change. When I dove SE Asia, I only had 6# of weight so I wouldn't have had any ditchable weight if I used an HP 100.

Traveling from Singapore to Malaysia in 1988, we weren't allowed to bring steel tanks, only aluminum I guess they thought that all steel tanks were rusted out hulks.

I certainly wouldn't base a buying decision on tanks that were made back before '88. No modern aluminum tanks uses that alloy.

FWIW, I have a couple of Al 80s but for cold water diving HP 100s are better. So, I have 6 of those for 3 divers.

Richard

Richard but if you do not have ditchable weight and still can stay neutral it means you are well balanced and just can swim up. Why would it be a concern ? It is even safer IMHO as your accent is more controllable. Am I missing something ?

 

[McCainiac]

I'm buying a tank at the moment, i have heard every one is now selling their ali tanks due to too many fractures and accidents, though I know the MIddle East only deal in Ali. am going steel because of the rumours and because they are in my opion safer although i find the weight of an Ali on my aged back more comfortable, any opions yourselves.......

Gaz you have over 2500 dives???

 

[rstofer]

Richard but if you do not have ditchable weight and still can stay neutral it means you are well balanced and just can swim up. Why would it be a concern ? It is even safer IMHO as your accent is more controllable. Am I missing something ?

Maybe, maybe not...

Assume you are the victim and, for one reason or another, your BC doesn't work (broke the elbow fitting when you jumped in and you went straight to the bottom). When the rescuer gets you to the surface, the number one task is to get you positive. This usually involves ditching the weights.

To float your head out of the water, you need to net about 10# positive (I think) so being neutral isn't really good enough. This figure comes from the 'sticky' Ultimate Wing Lift Calculator' spreadsheet over in the BC's forum. Whether it is right or not isn't the point, you need to float with your head out of the water.

Now, assume the rescue occurs with a full tank, when the tank is the most negative. Sure, if the tank is really negative, the rescuer could eventually cut you out of your rig but this removes the opportunity to use your regulator during the rescue. And there is the complication of keeping your head above water with one hand while they ditch your rig with the other.

I'm a big fan of ditchable weight. At least a few pounds worth. That's a problem for warm water divers (I used to be one) because they may not even need weight if they use a SS backplate. I used to use a floaty BC with 6# of lead and an Al 80. A steel HP 100 would have been a poor choice.

Anyway, whether this is an issue or not, think about it when you're figuring out your strategy. Wetsuit divers have it made; unless they go to a lot of effort they will always have ditchable weight. I don't know much about drysuit diving but I understand the drill is to fill the drysuit like the Pillsbury dougboy.

Richard

 

[Graeme Tolton]

This discussion seems to have changed topic. The OP has not stated what type of exposure protection he is using (if any). With a drysuit, a steel tank is usually the best way to go. Even with my hp119 and my winter undergarments under my drysuit, I still need 28LB to be neutral with a low tank. if that had been an al80, it would be in the 34lb range!.. now if i were to lose a 34LB weight belt at depth, it would more than likely be game over. However, when diving dry, I like to keep most of my weight unditchable. When I dive in warm water with an al80, i have no ditchable weight. I keep 6lb in the pockets on my bcd and that it all. My body is about 4lb positive... so even in the event of a buoyancy failure, with no wetsuit, I will never have positive 10 lbs!

Back to the original question. The old luxfer al tanks that have been rumored to fail.. (officially i think about 13 of them)... has been while the tanks are being filled, not while submersed. Do some research on sustained load cracking.

 

[Hatul]

I'm buying a tank at the moment, i have heard every one is now selling their ali tanks due to too many fractures and accidents, though I know the MIddle East only deal in Ali. am going steel because of the rumours and because they are in my opion safer although i find the weight of an Ali on my aged back more comfortable, any opions yourselves.......

I think you're concerned with two non issues. Current aluminum tanks are safe from the point of view of explosive hazard and when you take into account the amount of lead you can shed, a HP steel tank Scuba unit is lighter than an aluminum unit above water.

Adam

 

[widget]

Modern Aluminium cylinders are perfectly safe and the sustained load cracking issue you are probably refering to is pretty much only relevant on pre 1990 aluminium cylinders.

I think, in the end, its a personal choice, I like the characteristics of steel cylinders, others may prefer those of Aluminium, I dont think one is "better" than the other, they are just differant, and if you weight yourself for your personal cylinder characteristics and diving conditions, you will concievably be quite happy with either.