HP v Lp steel and DIN v yoke

[freewillie]

while looking at accumulating new scuba gear, the subject of a high pressure v low pressure steel tank comes up and the type of rugulator connector DIN v yoke that is required also becomes an issue.

as I understand it, a high pressure steel tank will hold more air per cubic foot than equivalent low pressure tank but will require a DIN valve to connect the first stage.

so far my diving has been limited to So Cal beach dives in a 7 mm wetsuit with hood, gloves, and booties. I have been renting regulators and AL 80's, but since I have been diving more often considering buying my own. Dive vacations would be limited to about once a year, so most of my diving would be local.

questions:

1. would be do you favor a HP steel tank over LP steel tank,
2. if yes, then would you recommend DIN connector as baseline then use DIN to yoke converter for vacation/travel when likely getting AL 80's.

thanks for the input.

fun and safe diving to all

 

[50Fathom]

LP steels and 300-bar DIN connections for me.

I get a good volume of gas at a low-pressure, which is easy on seats, seals and o-rings of the reg. Getting a full-fill is easy, since EVERYWHERE pumps to 3000, but not everywhere pumps to 3500. Also 3AA tanks are SO overbuilt and understressed, they last forever. They're also cheaper than their HP counterparts, and Hydro is never an issue, (search for HP tanks and hydro issues regarding pre-expansion testing and testing of "exemption" tanks.)

Which relates to point two. If and when I desire or need more gas, my "LP85s" become "HP120s" if you know what I mean. If you don't know, then don't worry about it, you don't need that capability.

Yet.

 

[JahJahwarrior]

What you should consider is the "tank factor." That is how many cubic feet per psi the tank contains. Divide the cubic feet by the rated fill pressure.

LP 95= 95/2640
aluminum 80= 77.7/3000
HP 130=130/3442

Then, consider the fill pressures available locally. Multiply that by the tank factor to figure out how much your tanks will hold when you get them filled locally. Also consider the value of things like the weight that a steel tank will allow you to take off of your weightbelt.


I don't dive yoke valves. DIN valves are less likely to fail when the tank is dropped or hits something hard. However, traveling divers are likely to face yoke valves. You should be able to get tanks that are DIN with a yoke "donut" to convert them to handle yoke valves. If you do and use them as yoke valves, take out the donut every so often, or it has a tendency to seize in the valve.

There are hundreds of threads on this subject. If you use the search function, you might be able to dig up some posts that are really useful for you. You can also use google to search scubaboard by using "site:scubaboard.com" then putting in search terms. On this site, use wildcards "*" to use search terms that are shorter. For example, "AL" won't work, but "*AL*" should. You can find things from transporting your tanks to storing your tanks to painting your tanks to the best price for your tanks, it's really almost too much information to take in in only a day

 

[lsorensen]

HP tanks in north america tend to be 3442psi which is 230bar, so they don't require a 7 thread DIN. Yolk and 5 thread DIN are both rated for 230bar use. Some parts of the world have 4500psi tanks which require 7 thread 300bar DIN.

The HP steels with 3442psi and convertible valves are very popular. Use with yolk if you want, or unscrew the insert and it works for DIN (both 5 and 7 thread).

 

[FritzCat66]

yolk = runny stuff in the middle of an egg
yoke = a type of attachment for SCUBA valves (among other definitions)

 

[lsorensen]

Oops. I didn't get enough sleep. Stayed up too late watching election coverage.

 

[scubadiver888]

Hey freewillie,

For flexibility, I would buy regulators with a DIN connector and a yoke (or a-clamp) adaptor. This configuration will let you use tanks with DIN or yoke valves. When purchasing your own tanks, purchase with DIN connectors.

For recreational diving, yoke or DIN will be fine but if you get into wreck penetration or overhead environments, it is good to make a solid DIN connection rather than a yoke connection.

If you get a 3442 PSI HP tank, you can still use yoke with it. Once you get to 3500 PSI or higher the valves are only DIN. You will find that new 3442 PSI HP tanks tend to come with a valve which can be switch to yoke or DIN. The 3500 PSI or higher tanks are only DIN. There is no way to convert them to yoke.

When selecting a tank you want to look at (a) how much air it holds (b) its dimensions (c) its buoyancy characteristics. If you are doing dives which needs 120 cubic feet of air then an HP100 is not a good choice. On the other hand, if you pick an HP130 it might have poor buoyancy characteristics for your body and rig. Also an HP130 is 10 pounds heavier than an HP100. Shore divers become harder if you add another 10 pounds.

In answer to your second question, buy a regulator with a DIN connector and a yoke adaptor. This will give you the most flexibility. The only reason I can think of to use a yoke regulator is to save some money.

For your first question the answer is a little harder. In my area, no one will overfill a LP tank. If people in your area are willing to overfill an LP, you can get a LOT of air with better buoyancy characteristics. If you are not comfortable with overfilling a tank (like me) then HP cylinders make more sense. One other considerations is that in some areas no one is willing to fill beyond 3000 PSI. So your HP tank will always be underfilled.

Personally, I like HP100 cylinders. If I get a short fill on an HP100 (only 3000 PSI) it has 87 cubic feet (an AL80 has 77.4 cubic feet) of air. In the water, the steel tanks are 5 pounds heavier than an AL80. So I can remove 5 pounds from my weight belt.

I should mention that for deep dives I use my HP119 and for some dives I use AL80s. My instructor tells me for sidemount, an AL80 has a better profile in the water than any steel tank.

Bottom line, which tank you use requires a little more experience and knowledge. You might want to rent AL80s for a bit and see what will work better for you.

 

[freewillie]

Thanks for the input so far. I have been leaning towards DIN for my regulator with yoke adaptor, this is even more likely now. Will be renting AL 80's for now, but at $25 to $50 each time out it's starting to add up!

 

[scubadiver888]

Thanks for the input so far. I have been leaning towards DIN for my regulator with yoke adaptor, this is even more likely now. Will be renting AL 80's for now, but at $25 to $50 each time out it's starting to add up!

My shop will rent a full AL80 for $10. To fill your own is $8. So essentially, you are paying $2 for the tank. For $25 to $50 you should be getting the tank for a weekend ($20 at my shop) or a week ($40 at my shop).

The way I look at buying versus renting was to look at how much it costs to own my tank and how much to rent.

Rent: $20 for a weekend, includes one air fill. I'd rent two tanks, fill them once at $8 each. So $40 + $16 for a fill. = $56/weekend.

Own: $400 (HP100). Cost me $800 to buy two. $8/fill would be $32/weekend. Difference is $24/weekend. After 34 weekends owning is cheaper. However, every year I have to have the tanks visually inspected ($20) and every five years hydrostatically tested + visually inspected ($45 or $9/year). Works out to $29/year.

So, in my area, if you are going to be diving 40+ a year, it might be worth buying a set of cylinders. However, buying the wrong cylinders could cost you hundreds (a used HP100 might go for $250. Even if you only used it twice, people will expect to get it for $200 to $250).

What you might want to do is find local divers and see if anyone is willing to loan you a tank (even in a pool) to see if you like it.

 

[elan]

DIN reg for local diving and get a yoke adapter to dive yoke tanks on vacations., this is what I do.

I had one set of HP tanks and sold it. I now only have LP steels and AL80 tanks.

It is not that much of an LP vs. HP it's the size of the tank and it's weight distribution that can make a difference. I'm 6' and I prefer longer tanks. Most of my tanks are now 26 inch long (that's roughly how long an AL80 is) and I love how they trim.

If you dive single tanks and salt water HP100 is an awesome tank. It's only 2lb heavier than an AL80 and you can take 6lbs off your belt. But it is a short tank - only 24"

Faber LP85 is an awesome tank as well . I believe it's of a weight of AL80 , 4lb less buoyant and holds more air. If you fill it to 3000psi it holds as much air as the HP100.

LP tanks are easier to blend. They do not get as hot as HPs.

One of the reasons I like LPs is that most shops that I fill my tanks at would prefer to fill them to the same pressure as the aluminums taht is to 3000psi so I always get more gas. They are just lazy to do their calculations for LP tanks And it's not a big deal for the LP tank to be overfilled by 300psi.