Originally Posted by category4jay
what situation would you use one vs the other?
A couple of comments. A Luxfer Al 80 is just a couple of pounds negative full, about a pound positive when empty so situations where I want neutral buoyancy and minimal weight swing during the dive I use the Al 80. Also, Al you don't have to worry about corrosion diving
in salt water
I think the preference for steel tanks is mainly because you can get more gas in the tank and being more negative you can take some wt off the belt. This is good within certain limitations.
- Warm water diving
without wet suit. I don't need a weight belt at all, in fact I've even dove with just a harness and no BC and maintain buoyancy with breath control.
- To carry extra gas in tech diving. I use to do cave dives using double steel back tanks and carry up to 4 Al 80s for the extra gas. Steel tanks would be much too heavy and negative for this.
- Al 40s to carry deco gas in deep wreck dives. Small, easy to carry and have sufficient gas for the deco.
- Al 80s in most ocean dives to keep my steel tanks out of salt water
- You can get much larger steel tanks. Up to 120 cu ft, Also most people overfill the steel tanks so can (safely) get about 15-20% more gas than their rated capacity.
- the old steel 72 is low pressure rated so for O2 fills from a cylinder cascade you can get more oxygen than a 3000 psi Al 80.
- If you have them the old steel 72s are light wt, slightly negative and will last forever. But you have to make sure you keep the inside dry, especially if you dive in salt water
. Problem is I don't think you can get new steel 72s
- Diving dry suit you need a LOT of weight so I use steel tanks to keep the weight belt smaller.
- Have used a steel 90 cu ft ocean diving with a wet suit, again to keep less wt off the belt. Just make sure that with the tank you are still slightly positive with the tank full. You should need at least some lead on the wt belt to be negative so you can ditch and be positive in an emergency