PDA

View Full Version : HP vs LP



rktman26
07-17-2007, 18:38
I don't want to come off like an idiot, but could someone explain the differences between a HP and LP tank?

If a tank holds 80cf of air, what difference does it make if it's HP or LP?

Thanks,

rktman

cummings66
07-17-2007, 18:50
HP vs LP. HP comes in two flavors, the 3500 psi tanks and the 3442 tanks. I suppose there is another one that's 43xx, it's one of those wrapped tanks.
<DIV></DIV>
<DIV>Here's the difference. The HP tank is smaller, it fits kids and smaller people better if we're talking about the HP80. The main difference is for the same amount of gas the HP tanks will be smaller and lighter.</DIV>
<DIV></DIV>
<DIV>Otherwise consider HP100 to AL80. The HP tank is about 1.6 lbs heavier and has 20 cf more air, actually more like 23 cf. How's that for a trade off? Of course the extra 23 cf of air will weight a bit more, but in the end you'll not notice it.</DIV>
<DIV></DIV>
<DIV>LP tanks, if you compared equal volume LP to HP tanks you'd find the HP tanks weigh a lot less than the same LP tank.</DIV>
<DIV></DIV>
<DIV>Now, LP tanks pretty much always get a full fill, HP tanks often do not.</DIV>
<DIV></DIV>
<DIV>Steel vs Al. The steel tanks will often be negative when empty so you can take some lead off the weight belt, sure it's now in the form of a tank but in the case of an HP100 there really isn't much difference and you get quite a bit less weight to carry around.</DIV>
<DIV></DIV>
<DIV>Steel is more expensive andmight last longer given good care. I have a working HP100 from the mid 80's that's still in good shape. My LDS has several of them as well. Very few AL tanks from that era are around, and those that are have problems getting filled at some shops.</DIV>

medic001918
07-17-2007, 19:24
HP vs LP. HP comes in two flavors, the 3500 psi tanks and the 3442 tanks. I suppose there is another one that's 43xx, it's one of those wrapped tanks.
<DIV></DIV>
<DIV>Here's the difference. The HP tank is smaller, it fits kids and smaller people better if we're talking about the HP80. The main difference is for the same amount of gas the HP tanks will be smaller and lighter.</DIV>
<DIV></DIV>
<DIV>Otherwise consider HP100 to AL80. The HP tank is about 1.6 lbs heavier and has 20 cf more air, actually more like 23 cf. How's that for a trade off? Of course the extra 23 cf of air will weight a bit more, but in the end you'll not notice it.</DIV>
<DIV></DIV>
<DIV>LP tanks, if you compared equal volume LP to HP tanks you'd find the HP tanks weigh a lot less than the same LP tank.</DIV>
<DIV></DIV>
<DIV>Now, LP tanks pretty much always get a full fill, HP tanks often do not.</DIV>
<DIV></DIV>
<DIV>Steel vs Al. The steel tanks will often be negative when empty so you can take some lead off the weight belt, sure it's now in the form of a tank but in the case of an HP100 there really isn't much difference and you get quite a bit less weight to carry around.</DIV>
<DIV></DIV>
<DIV>Steel is more expensive andmight last longer given good care. I have a working HP100 from the mid 80's that's still in good shape. My LDS has several of them as well. Very few AL tanks from that era are around, and those that are have problems getting filled at some shops.</DIV>
<DIV></DIV>
<DIV></DIV>
<DIV></DIV>
<DIV></DIV>
<DIV></DIV>
<DIV>
A great post that clearly spells out the differences. I dive with LP tanks, and my fiance uses HP tanks. I use a LP108, and she's on HP100's. But we definatly both dive steel for the weight savings on our belt. With my LP tank and my SS backplate, I don't need a weight belt when diving my drysuit. The best tank for you depends on your diving and where you are.</DIV>
<DIV></DIV>
<DIV>Although, after carrying her tanks I'm tempted to see if anyone wants to trade a set of HP tanks for my LP ones...her's are pretty nice.</DIV>
<DIV></DIV>
<DIV>Shane</DIV>

przeor
07-18-2007, 07:25
<DIV>Cummings66 said it all! Added to it, HPs are typically DIN valves only, LP you might see some yoke. Nothing else except a short (3000) fill on HP130s is still plenty of air! </DIV>

cummings66
07-18-2007, 07:46
On my HP100 I will often get fills that give me around 80 cf of air, it's due to two things really. First a fast fill on an HP tank will always short you a LOT of air, and it doesn't matter if they pump it up to 3700 psi you'll end up way short if they do it fast.
<DIV></DIV>
<DIV>The other reason is older compressors often can't pump to the pressures needed for a HP tank. What I suggest is get it filled and wait an hour and top it off again. Let the tank cool and check it before you leave and by doing that you'll get a good fill. The other trick, get Nitrox. It's always done slow so you will almost always get a good fill with Nitrox because they KNOW to go slow.</DIV>

rktman26
07-18-2007, 16:58
AHA! That's the element that I didn't quite catch- the fact that a HP
tank that holds 80 cf will be physically smaller than a LP tank with
the sam capacity.

I couldn't figure out what the advantage of each tank was.

I understand the bouyancy characteristics are different based on capacity and material.

Thanks for all the info, I appreciate it.

WaterRat
07-18-2007, 17:20
I'm not an engineer but it has also been said that LP will put less wear and tear on your regulator. You are feeding it with 1000 PSI less at the beginning of the dive. Makes sense to me. http://www.scubatoys.com/forum/smileys/smiley24.gif
<DIV></DIV>
<DIV>Do we even mention cave fills on LP tanks...errrr no not in this thread. We'll save that for another day. http://www.scubatoys.com/forum/smileys/smiley1.gif</DIV>
<DIV></DIV>
<DIV>Ron</DIV>

cummings66
07-18-2007, 18:20
You can mention it. You won't get cave fills in the central US for the most part.
<DIV></DIV>
<DIV>Considering the maintenance schedule I don't think you've anything to worry about with an HP tank, the second stage is immune to it anyhow and only see's the IP. The first stage on the other hand see's it, but to be honest my Sherwoods have never had issues with it.</DIV>

CompuDude
07-18-2007, 23:50
Nicely done, Matthew. :-)

What's your preference? I prefer HP tanks in general, but LP have their place.

BSea
07-19-2007, 10:36
After having both, I'm now favoring LP. I had an HP 100, and still have an HP 120. But my latest tanks are LP 85's. They are about identical to the HP 100 physically. But getting good fills on the 100 was hard to get, and I can get fills to 3000 on my 85's (at my LDS). So my 85's with 3000 actually have more air than my old 100 had at 3200, and about the same at 3300. Then there is always the fact that the 85's were about $70 less each.

CompuDude
07-19-2007, 11:11
I hear you on the LP85s... they're definitely the most interesting to me, of the LP tanks, for the reasons you cite. The only thing I don't like about them is you can end up with a lot less gas than the HP100 if you end up somewhere that only wants to fill it to the rated pressure. (esp. in a hot fill context).

That's what I like about the HP100s... it's extremely rare (for me) to ever get less than 3000 psi (usually more like 3200-3300), and that level, I have 87 cf of gas, compared to the 85 on a straight fill on the LP85. At the 3200-3300 level, they're comparable... except one of them is underfilled, and one is overfilled. While I know 3AA tanks have a long a glorious overfill history, I'm still more comfortable, over the long term, with underfilling a tank.

And that's without getting into the Faber v. Worthington/PSI painted vs. hot dipped galvanized debate, since I'm a salt water diver. If Worthington made a galv tank out of 3AA steel in an LP85 format (at the 7.25" size) I'd probably be all over it. :)

BSea
07-19-2007, 11:28
If Worthington made a galv tank out of 3AA steel in an LP85 format (at the 7.25" size) I'd probably be all over it. :)

<DIV></DIV>
<DIV>You mean like these (http://www.seapearls.com/tanks-steel.html)?</DIV>
<DIV></DIV>
<DIV>They are what I have. And they are 3AA</DIV>

BSea
07-19-2007, 11:31
ST doesn't show LP 85's, but I bet if they don't have them, they'll order some.

CompuDude
07-19-2007, 12:13
If Worthington made a galv tank out of 3AA steel in an LP85 format (at the 7.25" size) I'd probably be all over it. :)

<div></div>
<div>You mean like these (http://www.seapearls.com/tanks-steel.html)?</div>
<div></div>
<div>They are what I have. And they are are 3AA</div>
Interesting... I didn't know any of Worthington's tanks were 3AA. Their HP tanks are different.

I guess next time I have some budget freed up for more tanks I'm going to have some tough decisions to make!

rktman26
07-19-2007, 20:16
It's amazing the education a person cab get by asking a question.

Thanks for all the information.

427Dave
07-26-2007, 21:43
After having both, I'm now favoring LP. I had an HP 100, and still have an HP 120. But my latest tanks are LP 85's. They are about identical to the HP 100 physically. But getting good fills on the 100 was hard to get, and I can get fills to 3000 on my 85's (at my LDS). So my 85's with 3000 actually have more air than my old 100 had at 3200, and about the same at 3300. Then there is always the fact that the 85's were about $70 less each.

HP100 at 3000 psi instead of 3442 psi is 87 cu ft. It still holds more than a 80 cu ft AL about the same weight but a lot different on bouyancy. My HP 100's are yolk valve with an adaptor that can be removed for DIN. the older HP100 that were 3500 psi are all DIN valve that I have seen.

dutchman
10-05-2007, 09:55
I was reading that the Worthington steel tanks require LP if used for Nitrox. They make them ready at the factory in Canada. So does this mean you can not use the LP?

dutchman
10-05-2007, 09:56
Sorry, should read HP with Nitrox.

CompuDude
10-05-2007, 11:56
Worthington tanks can be used with any Nitrox mix up to 40% out of the box. Higher percentages or partial pressure blending requires for the tank to be o2 cleaned, after which you're good to go. There are no special restrictions with any major tank manufacturer's products, that I have ever heard of.

mike_s
10-05-2007, 12:45
I was reading that the Worthington steel tanks require LP if used for Nitrox. They make them ready at the factory in Canada. So does this mean you can not use the LP?


Worthington tanks can be used with any Nitrox mix up to 40% out of the box. Higher percentages or partial pressure blending requires for the tank to be o2 cleaned, after which you're good to go. There are no special restrictions with any major tank manufacturer's products, that I have ever heard of.



I'd say that any tank, regardless of brand, that is used with percentages higher than 40% (or partial pressure blending) should be cleaned, regardless of how the tank manufacturer states their tanks are clean.

I've seen several different brand tanks that claim to be clean come in from the factory basically "filthy" inside. I don't trust any of them anymore to be clean, no matter what they promise.

CompuDude
10-05-2007, 12:59
I was reading that the Worthington steel tanks require LP if used for Nitrox. They make them ready at the factory in Canada. So does this mean you can not use the LP?


Worthington tanks can be used with any Nitrox mix up to 40% out of the box. Higher percentages or partial pressure blending requires for the tank to be o2 cleaned, after which you're good to go. There are no special restrictions with any major tank manufacturer's products, that I have ever heard of.



I'd say that any tank, regardless of brand, that is used with percentages higher than 40% (or partial pressure blending) should be cleaned, regardless of how the tank manufacturer states their tanks are clean.

I've seen several different brand tanks that claim to be clean come in from the factory basically "filthy" inside. I don't trust any of them anymore to be clean, no matter what they promise.

Of course. He asked specifically about Worthington, however... I don't know where the misinformation about LP tanks and Nitrox came from.

BSea
10-05-2007, 14:33
I was reading that the Worthington steel tanks require LP if used for Nitrox. They make them ready at the factory in Canada. So does this mean you can not use the LP?


Sorry, should read HP with Nitrox.

Here's a quote from XS Scuba Website (http://www.xsscuba.com/tank_steel_features.html) concerning worthington tanks.

Nitrox Ready

Cleaned and sealed at the factory
Free of hydrocarbons to a level of 40 mg per square meter
Ready for pre-blended Nitrox up to 40% FO2