HP Tanks - What's the point?

[johnmckenzie]

I am asking for some intelligent dialogue on this topic for an article I am composing. The question is, "Except for those where size really does really matter, do the cons of HP steel tanks out weigh the pros?" (i.e. small divers do get a great advantage by using short steel HP thanks)

When I got back into diving and buying gear I noticed there was a big push to buy HP 100s and HP 80s. This was great for my wife. She is smaller and needed the compact size of the HP 80. It seems like the message we see from many shops is that, if you are poor you live with an aluminium 80 but if you want the best you buy and HP steel tank.

ONE PRO
The only pro of the HP steel tank over the LP steel tank seems to be the compact size. But for divers who can comfortable dive a tank that is a bit larger, why buy an HP tank? As I have
gained experience and got connected with a dive shop that HP tank pitch sounds more like hype.

LOTS OF CONS
With and HP tank (e.g. 3450 psi) I found that some shops do not even have HP compressors. Even shops that have HP compressors do not really like HP tanks. That last 400 psi create a lot of wear and tear on the compressor and the fill system. If the shop is filling from banks, it means you are going to be boosting to fill the HP tanks which wastes a lot of extra air to run the booster and attain a fill pressure. Many shops in our are will just not give you a full fill (after cooling) or want you to leave it over night if you want a full fill. Theoretically the higher presser is going to put more strain on you regulator and hp hoses. Some older yokes are not even certified to be used on HP tanks.

I keep thinking why did I get talked into this HP tank. If I had an LP 85 (2400 psi), I could fill from the banks in minutes and never have to boost. I could always get full fills wherever I travel.

What are you thoughts?

Thank you,
John

 

[JohnN]

I am asking for some intelligent dialogue on this topic for an article I am composing. The question is, "Except for those where size really does really matter, do the cons of HP steel tanks out weigh the pros?" (i.e. small divers do get a great advantage by using short steel HP thanks)

When I got back into diving and buying gear I noticed there was a big push to buy HP 100s and HP 80s. This was great for my wife. She is smaller and needed the compact size of the HP 80. It seems like the message we see from many shops is that, if you are poor you live with an aluminium 80 but if you want the best you buy and HP steel tank.

ONE PRO
The only pro of the HP steel tank over the LP steel tank seems to be the compact size. But for divers who can comfortable dive a tank that is a bit larger, why buy an HP tank? As I have
gained experience and got connected with a dive shop that HP tank pitch sounds more like hype.

LOTS OF CONS
With and HP tank (e.g. 3450 psi) I found that some shops do not even have HP compressors. Even shops that have HP compressors do not really like HP tanks. That last 400 psi create a lot of wear and tear on the compressor and the fill system. If the shop is filling from banks, it means you are going to be boosting to fill the HP tanks which wastes a lot of extra air to run the booster and attain a fill pressure. Many shops in our are will just not give you a full fill (after cooling) or want you to leave it over night if you want a full fill. Theoretically the higher presser is going to put more strain on you regulator and hp hoses. Some older yokes are not even certified to be used on HP tanks.

I keep thinking why did I get talked into this HP tank. If I had an LP 85 (2400 psi), I could fill from the banks in minutes and never have to boost. I could always get full fills wherever I travel.

What are you thoughts?

Thank you,
John

A quick search showed only one LP85 tank (OMS), that LP tank will only continue to hold 85 cu-ft if you can keep its "+" rating. There are a bunch of threads about how this can be "challenging". Getting a 'cave' fill may be relatively easy in FL, in the Pacific NW will be more difficult if you lose that rating and you'll only get 2400 PSI fills and have a working capacity of 77 cu-ft (same as an AL80).

Compare to a HP100. 2" shorter, only 2 lbs heavier empty (full the extra air will add about 1 lb), about the same buoyancy characteristics and a whole lot more gas.

 

[nimoh]

comparing HP steel to LP steel, I don't see that there is much of a difference, as long as you compare apples to apples.

I have a set of HP130s and a dive buddy has a set of LP104s. He overfills his tanks to about 3000psi, and I underfill my tanks to about 3100psi and we have the same amount of gas. The tanks have very similar characteristics with respect to size, weight and buoyancy, although I don't have to hope for a plus rating on my HP tanks when they go through a hydro.

 

[BRT]

HP steel tanks hold more air with the same tank weight as LP steel tanks. If you overfill the LP's the HP's lose that advantage but your LDS may not be willing to exceed the LP tanks rating. Filled to the rated pressure you get more air with less weight and similar buoyancy characteristics except for more swing between full and empty because of more weight of air in the HP's.

 

[mala]

I like the hp tanks

more gas ,more time ,more reserve
they only weigh more when you have to carry them as when diving you will have less lead.

in the uk the hp tanks are around 4500psi and the lp tanks 3500psi
the only time you get a lower rating is really for ali stage clyinders of around 3000psi when gas capacity isn't as critical.

 

[Dr. Lecter]

I often dive double HP130s and find they're fairly heavy, unweildly tanks at 44.7lbs each (empty/no valve). They're the same diameter as the largest LP tanks but 4" shorter. But for anywhere near the same amount of gas in LP tanks, I'd have to deal with an even bulkier rig.

The LP121 weighs 49.9lbs (empty/no valve), is 8" in diameter and 29.2" long, and holds only 121cf (if + rated and filled to 2640psi). Comparing it to the HP130 is silly since the 130 is better in almost every way, sharing only the wide 8" diameter. The LP121's closest HP analogue is the HP120: 120.6cf of gas at working pressure, but only 39.7lbs (empty/no valve), and only 7.25" in diameter and 27.7" long.

So, "the point" of an HP tank is 10lbs dry weight less per tank (20extra lbs saved if doubling) and a shorter, narrower rig for the same gas volume. Lots of people, whether because they have to wrangle the tanks on a pitching small boat and/or have to work them through wreck/cave restrictions, care about that.

 

[WetLens]

IMHO, not much point to the HP80 unless the smaller size is needed or really wanted. I, too, questioned the value of the HP100 until I dove an AL100. Night and day. I wouldn't use an AL100 again even if offered one free. Buoyancy characteristics are the key that makes the HP100 the ideal tank. Bought 2 HP100s in 2009 and another in 2011. Also picked up an HP120 and while I do not like the length while on-deck, it dives quite nicely. I own four AL80s and haven't used them since getting the HP100s - even stopped yearly VIPs (probably should sell them). A short fill on the HP100 is equal to or better than the AL80 and, again, the buoyancy characteristics of the HP tanks are just so much better.

 

[SailNaked]

two HP 100s will fit in the bands that I have for 2 Al80s so for me I am looking for another HP100 to complete the set. (200f^3 vs 145f^3) rule of thirds, and you get more bottom time.

 

[ajduplessis]

Gas volume, compact size and "stable" buoyancy bebaviour in steels are big pros for me. Getting HP fills is not an issue where I dive. I cant comment on ALI's besides the 40/80's I use. I have never liked ALI cylinders except for deco/stage bottles. That said, I am considering 12l steel bottles (longs) as deco/stage. I know they also make great side mount options.

 

[MXGratefulDiver]

As in most things it depends on the application. I own a bunch of tanks ... Faber LP95's, Worthington HP100's, PST HP119's and PST HP130's. I use them according to the dive I'm planning to do. I have friends who dive the LP120's, and they wouldn't work well for me. They're long, heavier than my HP119's and 130's, and they don't trim out nearly as well. I use the HP100's primarily for sidemount diving. When I started sidemount, I used LP95's, because I already had them and they give me enough air for almost any dive I'd want to do. But once they get below about 1000 psi they tend to get butt-light ... so they don't work well for that application. The HP100's don't have that problem, plus they're smaller-diameter and less heavy, which make them easier to manage getting into and out of the water in a sidemount rig. On the other hand, the HP95's work well for training dives or just toodling around the dive site.

If your issue with HP cylinders is not getting good fills, then I'd suggest you need to find a shop that can accomodate them. Lord knows there are plenty in the Puget Sound area that do. Since you're in Kingston, I'd recommend Octopus Gardens in Pt. Townsend ... Don knows how to fill a tank properly.

Oh, and if you're really unhappy with that HP tank, go post a note on NW Dive Club forum looking for someone who'll trade with you for a comparable LP cylinder ... I think you'd get several offers.

... Bob (Grateful Diver)