LP vs HP?

[S. starfish]

I have to admit, I don't really understand LP tanks. As far as I can tell the only difference between HP and LP tanks is the rating, so why would you bother getting an LP 104 at 26 inches high and 43 pounds empty and put up with the hassel of "do gooders" not over filling your tanks when you could get an HP 130 at 26 inches and 43 pounds empty and have it legitimately filled, no issues? Same capacity, different stamp.

Merxlin If you're really concerned with getting 100+ cuf I'd go for an HP120, which at 3000 psi will hold about 107 cuf, otherwise it has been my experience that HP 100 tanks are just about perfect, not crushing my spine and holding approx 90cuf at 3000 psi.
Have a look at this http://www.pstscuba.com/PST Scuba Product Specification Sheet.pdf to see what I mean.

 

[merxlin]

Merxlin If you're really concerned with getting 100+ cuf I'd go for an HP120, which at 3000 psi will hold about 107 cuf, otherwise it has been my experience that HP 100 tanks are just about perfect, not crushing my spine and holding approx 90cuf at 3000 psi.
Have a look at this http://www.pstscuba.com/PST Scuba Product Specification Sheet.pdf to see what I mean.

My concern is that on boat dives, because they use 85's, they set the compressor at 2450. In an HP, thats not a "full fill". I can get them to go 2600, but not 3000.

 

[Leadking]

Stu, unless I am mistaken (entirely possible) I believe 85's are full at 2400, the 2640 is for the + 10%, no? (http://www.techdivinglimited.com/pub/tanks.html)

ALL cylinders that are +rated (3AA) include the 10% overfill. An 85 is 85cf with 10% overfill

 

[Randy-TDL]

Ok guys you will get it from the horses mouth as they say. I have been selling Fabers cylinders from OMS, Abyss and now at Tech Diving Limited.

A low pressure cylinder must get its 10% (+) fill to be filled to the rated pressure. An lp-85 must be filled to 2640 just like all low pressures. If you get it filled to 2400 than you have a short fill! Keep this in mind when planning your dive!!!!!

Now if you have a dive shop or other that only fills them to 2400 psi and thinks they are full you can have them call us or Blue Steel which is the distributor of Fabers cylinders to help them understand....

Dive safe and if you have any questions just call... That is what we are here for to serve you and answer your questions...

Regards
Randy

 

[limeyx]

I have to admit, I don't really understand LP tanks. As far as I can tell the only difference between HP and LP tanks is the rating, so why would you bother getting an LP 104 at 26 inches high and 43 pounds empty and put up with the hassel of "do gooders" not over filling your tanks when you could get an HP 130 at 26 inches and 43 pounds empty and have it legitimately filled, no issues? Same capacity, different stamp.

..

Exactly the only issue really is that the HP's are usually more $

 

[limeyx]

My concern is that on boat dives, because they use 85's, they set the compressor at 2450. In an HP, thats not a "full fill". I can get them to go 2600, but not 3000.

but why the heck does it matter if it's not a "full" fill ?

What I am concerned with when I buy a tanks is how much gas I think I am going to need for my diving. Then I look at the pressures I can get fills at, and what form factor of tank I feel like handling, and finally cost.

If your boat fills to only 2450, then sure, get an LP, but you have to get a physically larger LP tank to match up to the HP fill.

Simply saying get the LP because 2450 psi in an LP is "fuller" than 2450 in an HP of the same physical size doesn't make logical sense.

 

[merxlin]

but why the heck does it matter if it's not a "full" fill ?.......Simply saying get the LP because 2450 psi in an LP is "fuller" than 2450 in an HP of the same physical size doesn't make logical sense.

OK, I could be dense, but if I get a 2450 psi fill in an LP 100, I'll have 92 cf of gas. If I get the same 2450 psi in an HP 100, I'll only have 81 cf of gas. I think that makes logical sense, don't you?

 

[in_cavediver]

OK, I could be dense, but if I get a 2450 psi fill in an LP 100, I'll have 92 cf of gas. If I get the same 2450 psi in an HP 100, I'll only have 81 cf of gas. I think that makes logical sense, don't you?

Actually 2450 in an HP tank is 70% (hp is full at 3500, or 3442). with that, 2450 in an HP100 is really 70-71cf not 81cf.

Essentially, for LP tanks, you get 92-93% of the rated capacity at 2450. HP tanks give 70-71% of the rated capacity at 2450.

 

[merxlin]

Actually 2450 in an HP tank is 70% (hp is full at 3500, or 3442). with that, 2450 in an HP100 is really 70-71cf not 81cf.

Essentially, for LP tanks, you get 92-93% of the rated capacity at 2450. HP tanks give 70-71% of the rated capacity at 2450.

Thanks in_cavediver, that is the point I was trying to make. If I can only get a 2450-2600psi fill, then an LP makes more sense, as it would have more c.f at that PSI. Now I have to do the math for larger capacity HP tanks, in the event I get off this boat and can get a higher PSI fill. Then they will make sense (if the numbers work out).

 

[Flatliner]

Correct me if I am wrong, but don't HP tanks have thicker walls (and thus smaller actual volume) than the LP tanks. Isn't that why they can handle the higher pressure?

Flat