HP vs. LP / High Pressure versus Low Pressure steel tanks

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Who needs 120 cu ft? I don't know, maybe your buddy who is out of air? Also comes in handy if you need to decompress, or jump back in to unsnag the anchor. No need to tap a fresh tank.

Here's a clue, you can get an HP120 which weighs seven pounds less than your LP102.
 
Originally posted by devjr
Who needs 120 cu ft? I don't know, maybe your buddy who is out of air?
Isn't that what you guys use Spare Airs for???
Also comes in handy if you need to decompress, or jump back in to unsnag the anchor. No need to tap a fresh tank.
Decompress from an air dive using air... uh huh.... and about that anchor.... isn't that what you guys use Spare Airs for???
Here's a clue, you can get an HP120 which weighs seven pounds less than your LP102.
Times that by two for doubles... but then I know of a petite gal who shore dives double LP120s... weight out of water isn't as important to some folk. :eek:ut:
 
Spare air? Is that DIR's newest, oldest bogeyman? LOL. Go ahead and dive those 8 inch dia LP monsters, but don't call yourselves "streamlined" anymore.

I like the image of a petite diver with twin 102's. What does that look like from above?...a submersible vehicle with no apparent means of propulsion?
 
Originally posted by devjr
Go ahead and dive those 8 inch dia LP monsters
OK.... Thanks devjr :D
but don't call yourselves "streamlined" anymore.
Awhhh.... shoot.... why not.... do you really mean to tell me that you think the pointy end of an 8 incher produces much more drag than the pointy end of a 7.5 incher???

Especially with those boots you've got on yours making all that turbulance and causing induced drag!!! :eek:ut:
 
I use both LP and HP 120s. LPs are better for the fills. I fill my own tanks and my compressor has a part that needs to be replaced after 1575hrs if I pump over 3500 and if I pump to 3000psi or less it will last 15750hrs. Other than that LP 120s to 3000psi is 138cf of air. Whereas HP120 to 4000psi is only about 127cf. so if people are going to over fill you are better off overfilling a LP. I don’t recommend overfilling but some folks do.
Regards
G
 
I think one of the advantages of Hp tanks is weight. Sure, when you are on a nice big charter boat on a calm day with a helpful crew, anyone, and their mother, can handle a set of doubles. But, if you are crawling over a couple hundred yards of rocks and ice to get the water (after which you have to deal with submerged alage coverd boulders) or if you are diving off a 16' in rolling seas, a single tank may be your only option. And if you have a need for a good ammount of air a HP 120 is a nice option, as is a HP 82 or even an HP 45 for a shallow dive.
 
Sounds good JW but since I know nothing about HP's maybe you or someone here can tell me what the weight difference is between a 'work horse' aluminum 80 and a HP 82? There are so many el cheapo aluminums around and the cost difference is pretty good...I would think they'd be the choice for the rough shore dives you describe. Me ,I like the alum. 80's and LP's. And boats. I am amused by those days gone by when we immitated seals in climbing over slippery rocks in choppy seas. Na duh.:wink: :froggy: :yuck:
 
I'm not sure what the weight difference is between a hp 82 and alum 80, although I can tell you it's noticable and the 82 is much shorter. Cost is a big disadvantage of hp, and (apparently because people like them so much) it's very hard to find a used hp tank. The nice thing about the hp 82 is that it stays neutral throughout the dive unlike a lp 80 that starts to float off your back when you get below 1,00psi. My hp 120 isn't that much longer than my lp 80. Very nice tank for some situations.
 
HP Steels are lighter and more compact than others including aluminum and LP. The differences in partial pressure Nitrox filling a LP tank overfilled to 3000 psi and a HP tank @3500 are insignificant. A HP tank holding 102 cu ft weighs the same as an aluminum tank holding 77.4 cu ft, and the steel has a huge advantage in trim and buoyancy. A 102 LP tank of 8 inch dia has 25% more drag than a comparable HP steel and 50% more drag than an older steel 72 or SP 3300 psi 72. A HP steel 102 weighs seven pounds less than a LP 102 and yet has about the same buoyancy characteristics. IOW, the LP user pays the price of extra weight but still cannot count this as negative buoyancy. He still has to carry as much lead as the HP diver who is toting the lighter tank. If you don't understand this, you are probably DIR .
 
https://www.shearwater.com/products/peregrine/

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