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CrackedConch
07-10-2007, 04:09 AM
So I've been reading the posts on Steel vs. Aluminum, etc...

I usually use AL80's, but I have liked steel tanks very much every time I've used them. Mainly because of getting weight out of the BC and because I can carry more air in a smaller tank. I'm looking at getting a set of Steel 100 or 110 tanks...

Could someone please educate me about High Pressure and Low Pressure Steel? When to use/choose each?

Thanks!

The Publisher
07-10-2007, 04:18 AM
It really depends on whether you can get a fill to 3450 or not. If not, then get a steel LP 105. If so, either get a smaller tank that at HP will hold the equivalent, or you can now get Faber steel tanks in the U.S. that are 3450 psi that hold 148 cubic feet.

Joel here is one of the largest Faber dealers anywhere, so I bet he could spark you up good with a Faber LP or HP tank.

acelockco
07-10-2007, 05:08 AM
I have used the 2500 psi steel 95 and LOVED it. It was about the same size and weight as a Aluminum 80, but gave me a bit of additional air and better buoyancy.

Being that they are similar size and weight to Alum 80's they could be put together to make a nice and fairly lightweight set of doubles.

I don't know how much this matters to you, but I have heard that the higher pressures of the 3500 psi cyls help to wear out regulator parts easier. I don't know if it is true at all, but I thought I would toss that out there.

The other consideration as The Publisher said is getting the correct fills. I am under the impression that any dive shop in the US would be able to give you full fills, the problem would be on a dive boat. Some of the compressors onboard diveboats might not have the ability to give you complete fills. So you have to look into how much air you actually have at 3000 psi for those conditions. I guess it depends on what you are going to be using them for.

Now lets see what kind of great Faber deels pop up here. :)

Mountain Dog
07-10-2007, 01:56 PM
I have a collection of steel HP100's and I couldn't be happier with them. Once you go steel, you never want to go back to aluminum. Steel tanks have negative bouyancy characteristics, which means you can drop a lot of weight off your belt. I leave about 7 pounds of lead behind.

The tanks are also physically smaller than AL80's.

As for fills with an HP tank, I have never had a problem getting a solid 3450 pound fill at a good dive shop. I have however, run into some short fill issues at quarry shops where they do fast hot-fills. I am usually lucky to get 2800 pounds at these places. However, that problem exists in the same shops with al80's, too. All in all, even at places like this, I get more gas in an HP100 than I would in an al80.

As for wearing out regulator parts, I don't know. It hasn't happened to me yet. But my thinking is that if you get your regulator serviced every year like you should, this is probably not an issue anyway.

The only downside to steel is the cost. Those babies are expensive. But since they will basically last forever, you have to look at them as a long term investment.

Mountain Dog

BamaCaveDiver
07-10-2007, 04:21 PM
I have used the 2500 psi steel 95 and LOVED it. It was about the same size and weight as a Aluminum 80, but gave me a bit of additional air and better buoyancy.

Being that they are similar size and weight to Alum 80's they could be put together to make a nice and fairly lightweight set of doubles.

I don't know how much this matters to you, but I have heard that the higher pressures of the 3500 psi cyls help to wear out regulator parts easier. I don't know if it is true at all, but I thought I would toss that out there.

The other consideration as The Publisher said is getting the correct fills. I am under the impression that any dive shop in the US would be able to give you full fills, the problem would be on a dive boat. Some of the compressors onboard diveboats might not have the ability to give you complete fills. So you have to look into how much air you actually have at 3000 psi for those conditions. I guess it depends on what you are going to be using them for.

Now lets see what kind of great Faber deels pop up here. :)

You are right Ace, the higher pressures can cause lesser regulators to develop problems. However, there are regulators made for these higher pressures. I have had the high pressure seat go on my SP firsts, but my DR's are still holding strong seeing 4000psi on a regular basis.

As to shops not being able to provide a full fill - many of your rec oriented shops have a cut off on their compressors set at just above 3000psi. This is done to ensure safety when filling AL cylinders (keep in mind that most tank monkeys are young kids working for minimum wage); if the fill operator gets distracted while filling a cylinder the compressor will shut off prior to the cylinder being overfilled. This is why most cave divers prefer the lp steels, you can always get a full fill on them, and most times you can go beyond the rated capacity, using any compressor set up for Scuba.

CrackedConch
07-11-2007, 03:17 AM
I understand about the HP risk to my reg. Aside from that, should how my shop does air fills be my main consideration??

I'm thinking an HP100 filled to 3000psi and an LP100 filled to 3000psi will give me the same bottom time...same volume and pressure...

It seems HP tanks would give me more flexibility. I can mostly dive at 3000psi if that's what I usually get at my shop, but have the capacity to go up to 3450 when I need to.

Are there any diving differences between HP and LP tanks? I'm guessing the HP will be slightly heavier because it would require thicker walls to hold the pressure... Anything else I need to worry about?

Mountain Dog
07-11-2007, 03:40 AM
If your shop sells HP tanks, they ought to be able to fill them as well.

I haven't used LP steels, so I can't tell you if they weigh less or not, but I can't believe any weight difference would be significant.

The only other thing I can think of to be aware of is the type of valve on the tank - yoke or DIN. DIN valves are quite common for HP rigs. Make sure you get valves that match your reg. My tanks have "Thermo Pro" valves which can actually be used with either yoke or DIN regs. There is an insert in the valve that is simply unthreaded to turn the valve into a DIN. These valves have a higher pressure rating that a standard yoke. Here's the Thermovalve website: http://www.thermovalves.com/stand_alone_valve.htm


Mountain Dog

Sarah
07-11-2007, 03:50 AM
That would be this valve, and they do have higher psi versions:

http://www.thermovalves.com/images/5651-5000.jpg

amtrosie
07-13-2007, 05:48 PM
I have used the 2500 psi steel 95 and LOVED it. It was about the same size and weight as a Aluminum 80, but gave me a bit of additional air and better buoyancy.

Being that they are similar size and weight to Alum 80's they could be put together to make a nice and fairly lightweight set of doubles.

I don't know how much this matters to you, but I have heard that the higher pressures of the 3500 psi cyls help to wear out regulator parts easier. I don't know if it is true at all, but I thought I would toss that out there.

The other consideration as The Publisher said is getting the correct fills. I am under the impression that any dive shop in the US would be able to give you full fills, the problem would be on a dive boat. Some of the compressors onboard diveboats might not have the ability to give you complete fills. So you have to look into how much air you actually have at 3000 psi for those conditions. I guess it depends on what you are going to be using them for.

Now lets see what kind of great Faber deels pop up here. :)



Ace,
I don't know where you came away with the impression that LP 95's and Al. 80's are comparable in size and weight. I have both, dive both, and the difference is significant. The Steel tanks have superior bouyancy characteristics, and for that purpose, they are more advantageous. The LP 95's are more than 6 lbs. heavier than AL 80's EACH. You double them up and you really notice the weight difference. The circumference of the tanks are 7.25" (80's) to 8" (95's). This is not to say that I dislike 95's, I don't, I have had them for years and continue to use them for certain dive applications.

The web is full of sites that give you comparisons on all manner of tanks. It can be quite interesting to look them up.

acelockco
07-13-2007, 08:49 PM
I don't know, maybe the cylinders we are speaking of are made by a different manufacturer. I recently rented a steel 95 for a dive in California and it looked like the same size as my AL80 at home. It might have been slightly larger or smaller, but it was close. My wife rented a steel 80 and it was a lot shorter than the AL80 she usually uses at home. They probablly were 8" instead of 7.25", but that is not much of a difference at all! It really did not seem to be wider, but 3/4" of an inch is not much to notice when you are looking at a lot of more intresting things on the ride to Anacapa.

Now about the weight issue: the steel is about 6lbs heavier than the aluminum, BUT remember that you also get to take about 6lbs off of your weight belt. So this question is just for you....ready

If you are wearing 28lbs of weight on your weight belt (or in your bc or whatever) and you add 6lbs of weight to your gear by adding a steel 95, but then you remove 6 lbs of led from your weight belt, how much did you change your total dive weight?



ready



3




2




1





You don't change your weight at all.

No do the same problem again, but add 2 steel 95 tanks so we are at a total weight of 12 additional lbs, now remove 12 lbs of led from your weight belt. Let me know what you come up with.

amtrosie
07-14-2007, 03:28 AM
I don't know, maybe the cylinders we are speaking of are made by a different manufacturer. I recently rented a steel 95 for a dive in California and it looked like the same size as my AL80 at home. It might have been slightly larger or smaller, but it was close. My wife rented a steel 80 and it was a lot shorter than the AL80 she usually uses at home. They probablly were 8" instead of 7.25", but that is not much of a difference at all! It really did not seem to be wider, but 3/4" of an inch is not much to notice when you are looking at a lot of more intresting things on the ride to Anacapa.

Now about the weight issue: the steel is about 6lbs heavier than the aluminum, BUT remember that you also get to take about 6lbs off of your weight belt. So this question is just for you....ready

If you are wearing 28lbs of weight on your weight belt (or in your bc or whatever) and you add 6lbs of weight to your gear by adding a steel 95, but then you remove 6 lbs of led from your weight belt, how much did you change your total dive weight?



ready



3




2




1





You don't change your weight at all.

No do the same problem again, but add 2 steel 95 tanks so we are at a total weight of 12 additional lbs, now remove 12 lbs of led from your weight belt. Let me know what you come up with.



It is way too late to do math problems tonight, besides that is Bama cave divers slice of the diving pie. What I was refering to, was the weight characteristics AT THE SURFACE. Once you hit the water, that is a whole new ball game. As for the size thing, you may have steel 94's. I have not seen these in many years, but they are slightly taller than a standard AL 80 but the same circumference (if memory serves me correctly). I don't have the specs. handy. The LP steel 80's are shorter and fatter, and rather nice to dive. As I said before, I like the steel tanks, it is just that they are not the solution for every dive profile. I strongly advocate steel tanks as a way to remove weight from the hips (on a belt). The results are better gas consumption, due to less work pulling weight through the water. Better trim, due to less weight on the hips. Much better comfort during the dive equals better dive experience. :D :D :D