Tank sizing, HP & LP?

[sabbath999]

I tried searching for this, and frankly I didn't even really know what to ask for in the search criteara, so I will just ask it and please forgive me if it was recently answered.

I am going to be getting a steel tank (or two -- as singles, I always like to have a apare) for when I wear my drysuit. I am planning on getting one with DIN with the yoke adapter (my first stage is yoke).

My question comes in about HP vs LP.

I understand that a 100 CF tank is going to contain 100 CF of air (more or less), so that the HP vs. LP comes down to a matter of size and weight.

I am trying to reduce the amount of lead that I am carrying by switching to steel, and also to enjoy the improved buoyancy characteristics of steel over aluminum. That is my stated goal in the switch.

I am thinking about getting either a 100 HP or 95 LP.

Is the 95 LP significantly heavier than the 100 HP?

If my stated goal is to replace lead with tank weight, would I be better off with a LP 95 (which is also easier on the rest of my rig)?

Thanks.

 

[Blackwood]

An LP95 is a couple pounds heavier than an HP100.

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

 

[M_Bipartitus]

There are several places where you can find list of common tank sizes, such as Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

Also X-Series Steel SCUBA Tanks by Worthington Cylinders - Dive Gear Express has a lot of good info on tanks.

and yes, there are many threads for "LP vs HP" and "overfilling" searching for those should get a number of useful threads and a few spirited debates.


Edit: I guess Blackwood beat me to Huron Scuba's site. It makes me wonder how much web traffic they get just from that table.

 

[GrumpyOldGuy]

Depends on manufacturer, it varies significantly, just compare PST vs Faber to see. Weight and buoyancy can be very different and people tend to mix terminology.

 

[elan]

So far I have failed to see any improvement in buoyancy characteristics in steel vs. AL they are just different , for each their own.

Questions to ask first, are you planning to double them up ? If so what is your height, you should consider your height if you plan to double them up eventually.

HP100 is 7.25 LP95 is 8'

Different makes have different tanks as well. I like LP more now as it's easier for me to have a fill at rated pressure in place where I live. Though my LDS has a good compressor I tend to get better fills from them on LP tanks.

 

[GrumpyOldGuy]

So far I have failed to see any improvement in buoyancy characteristics in steel vs. AL they are just different , for each their own.

I am not sure what your definition of improvement is. When I look at at HP100 vs an AL80, I see 35% more air, same land weight and 5lbs less lead. That is improvement for me, although I have to admit I cannot afford any right now and dive with AL80s.

 

[elan]

I am not sure what your definition of improvement is. When I look at at HP100 vs an AL80, I see 35% more air, same land weight and 5lbs less lead. That is improvement for me, although I have to admit I cannot afford any right now and dive with AL80s.

I'm not sure what the OP meant by "enjoy the improved buoyancy characteristics of steel over aluminum".

Each tank has it's own properties including but not limited by buoyancy, weight and capacity. These mostly receive the attention. There are also other ones like weight distribution and physical dimensions. The latter two are important when you dive doubles, this is why I asked the OP if he is planning to do it. Some people like me do not take those characteristics into account in the beginning and later find out that those tanks do not work well as doubles for them. This is the reason my HP100 are sitting more and more in the locker, I dive LP72s and we doubled up AL80 to give them a try. After a dive I can tell that AL80 has improved buoyancy characteristics as it gives more options with the trim with many types of exposure protection at an expense of increased dry weight . I'm just saying that so the OP takes more factors into account for the type of diving he does now and planning to do in the future.

 

[GrumpyOldGuy]

My response was in the framework of single tank diving. If you open it up to dual tanks, it is much more interesting question and as you pointed out not as clear cut.

FWIW: Let me know if those HP100's in your gear locker need a new home. I have lots of AL80's and would love to trade up.

 

[iztok]

IAfter a dive I can tell that AL80 has improved buoyancy characteristics as it gives more options with the trim with many types of exposure protection at an expense of increased dry weight . I'm just saying that so the OP takes more factors into account for the type of diving he does now and planning to do in the future.

Yup. I've read that AL80s doubles would be preferred for balanced rig vs. steel when diving 3mm wetsuit for example.

 

[v--Locke--v]

i think its more of a logistics factor than a buoyancy factor when selection lp to hp.

lp tanks are easier to get fills for and much easier to get nitrox fills for as when partial pressure blending often just a tank transfer is done and often times those levels of pressure is lower than the 3500psi a hp tank can take.

if you can always get HP fills w/o a problem than hp might be a better solution.