Steel HP 100 vs Al 80

[onca2002]

Sorry for such a newbie question, but I have never dove with steel tanks before, and I have the opportunity to buy a Hp steel 100 for $200. I have several Al80's, is it worth it to purchase this tank?

I understand the weight advantages, but what would my air advantages be? Will I see a big difference in available air? Will I be able to stay down much longer with a steel Hp100? If so, what percentage more do you think?

Again sorry for the simple questions, just want to see if it's worth getting the tank.

 

[redacted]

You would have about 25% more usable gas. What good that might do you depends on what is limiting your dives now.

 

[Teamcasa]

I love my HP100, it does give me more air vs a AL80 (which is only 77cf of air) when properly filled. You will, without a doubt, notice more bottom time, how much more is dependant on your SAC rate.
You all ready understand the weight issue but you should also understand that, in my experience, many boat or remote location fills are generally short of the max pressure and the end result is the volume of air work out about the same as a AL80. But you still have the weight advantages.

So, go and buy the tank!

 

[micklock]

Here's a couple links that might help you.

Dive Rite Express -- How to Select a SCUBA Tank​

SCUBA Knowtes, The Evil Aluminum 80

 

[DA Aquamaster]

Weightwise the HP 100 is about a pound and a half heavier but 5 lbs less buoyant so in the end you will be carrying 3.5 lbs less weight in terms of tank and lead weights carried.

Lenght wise the AL80 is about 2 inches a taller, and the two tanks are the same diameter.

An AL 80 holds 77 cu ft and an HP 100 holds an honest 100. If you have a SAC rate of .6, the extra 23 cu ft of gas equates to about 11 minutes more bottom time at 80 ft, about 14 minutes at 60 ft and about 20 more minutes at 30 ft.

I am a big fan of the HP 100. It is true that if you get a short fill to the same 2800 psi you get with a hot filled AL 80, you end up with only 81 cu ft, but I haver seldom gotten less than 3400 in mine and I often get 3500-3600psi. But evenw itha short fill,I have the smae amountof gas in a smaller and overall lighter package than I would with an AL 80.

 

[Jimmer]

Sorry for such a newbie question, but I have never dove with steel tanks before, and I have the opportunity to buy a Hp steel 100 for $200. I have several Al80's, is it worth it to purchase this tank?

I understand the weight advantages, but what would my air advantages be? Will I see a big difference in available air? Will I be able to stay down much longer with a steel Hp100? If so, what percentage more do you think?

Again sorry for the simple questions, just want to see if it's worth getting the tank.

If for some reason you decide you dont want it, let me know, $200 for an HP100 in good shape is a good deal in Ontario.

 

[Wayward Son]

do I want an HP100 for $200? That's like asking bill clinton if he wants a chubby chick, LOL

Yep, buy it & be happy

 

[BMW]

Yes, it is well worth it to go steel. You already mentioned the weight advantage, but you also get better trim. With an AL80 some BCs tend to pitch one forward onto one's face at the surface - very annoying. With steel one can be very vertical.

The air advantage of a 100 over an 80 is 25% more air . That extra 25% can be safety margin or a 25% longer bottom time for the same depth/workload. People who don't monitor their bottom time and depth, or fail to use their computer correctly, are at higher risk of DCS because the tank enables them to stay down longer.

The steel 100 is a great buy - physically smaller than an AL80 and all those benefits. I am a big guy so I am pretty happy lugging around a 130. I have read that steel tanks have a longer life than aluminum as long as they are not abused.

Some downsides to steel:

- tend to cost more than AL

- more potential for corrosion so be really picky about rinsing the tank well. Think twice before keeping plastic mesh or stickers on the tank because they can trap salt water/moisture. Any scratches provide an opportunity for corrosion.

- steel has poorer heat transfer characteristics than aluminum. The tank gets hotter when filled and cools slower. If you or the dive shop is in a hurry, you may get a 'hot fill' to 3442 but will end up with only 3100 by the time you hit the water. That means you will seldom get the full 100 cu ft unless the shop really takes their time

- heavier to lug around between dives

 

[DA Aquamaster]

Some downsides to steel:

- tend to cost more than AL

- more potential for corrosion so be really picky about rinsing the tank well. Think twice before keeping plastic mesh or stickers on the tank because they can trap salt water/moisture. Any scratches provide an opportunity for corrosion.

- steel has poorer heat transfer characteristics than aluminum. The tank gets hotter when filled and cools slower. If you or the dive shop is in a hurry, you may get a 'hot fill' to 3442 but will end up with only 3100 by the time you hit the water. That means you will seldom get the full 100 cu ft unless the shop really takes their time

- heavier to lug around between dives

Very true that steel tanks tend to cost more than AL tanks - but steel tansk seem to be developing a history of lasting longer (50-100 years is not an unreasonable expectation) compared to AL tanks where shops get picky about filling them after 20 years. And Steel tanks do not require a visual plus inspection each - something mandated for older 6351 T-6 tanks at hydro but applied annually in the scuba industry and often extended to newr 6061 T-6 alloy tanks as well. So over time, you make up for the extra intial cost.

Hot fills are a problem with both AL and steel tanks and I have never noted hot fills to be significantly worse with steel tanks. With regard to 34442 psi tank, my experience has been that shops fill them to 3600-3700 and I get around 3400-3450 psi when they cool. So if a shop has much of a history filling 3442 psi steel tanks, the odds are good you will get an honest full fill.

An X7-100 does not weight any more than an AL80. It hold holds 23 more cu ft of gas and that extra gas weighs a bit over pound, but the tank weight is almost identical.

Scratches in a galavanized steel tank won't rust - the electrochemical process of the galvanized surfaces around the scratch prevents it.

 

[John_B]

With regard to 34442 psi tank...

Talk about a cave fill!

(Yes, I know its a typo, just having a little fun...)