High or Low pressure steel tank?

[ckjacques53198]

I'm in the market for my first tank. I'll be diving in new england with a full 7mm suit so I'm trying to get rid of any weight I can. I like the price of the aluminum 80's but I've decided to bite the bullet and get a steel. How much smaller are the HP tank's than the LP's. I remember diving with a HP 100 and liked the size. Also, do you need a DIN reg with the HP?

 

[S. starfish]

HP tanks are considerably smaller than LP tanks. For example, a high pressure 100 cubic foot tank is almost exactly the same size and weight as a low pressure 80, a high pressure 130 and a low pressure 104 are the same in size and weight. Essentially, the difference between HP and LP tanks is the grade of steel used which allows the HP tanks to be filled to a higher pressure as their equivalent volume low pressure tank. This site : http://www.huronscuba.com/equipment/scubaCylinderSpecification.html should give you some idea.

It's not necesary to use a DIN valve with High pressure tanks, i know many people who don't, but if you have the option I'd go for it as it's much more secure.

 

[Crazy Fingers]

I know some groups of people prefer LP tanks... this way they can fill say a LP100 to 3000 psi and have HP114s! Or 3300 psi and have HP125s!

This is officially not recommended, however. :no

 

[xiSkiGuy]

I know some groups of people prefer LP tanks... this way they can fill say a LP130 to 3000 psi and have HP150s! Or 3300 psi and have HP165s!

This is officially not recommended, however. :no

And which company makes the mythical LP130? :huh:

 

[Crazy Fingers]

And which company makes the mythical LP130? :huh:

Don't know because I never shopped for them. I'm too much of a cheapskate to buy steel. I just assumed they were made. I changed it to LP100 instead.

At any rate, the point is still the same.

 

[xiSkiGuy]

Don't know because I never shopped for them. I'm too much of a cheapskate to buy steel. I just assumed they were made. I changed it to LP100 instead.

At any rate, the point is still the same.

FWIW, no one makes a LP100, either. There are LP95s, LP98s, LP104s, and LP108s.

To the original poster - there are tons and tons of threads about the "merits" of LP and HP tanks. Lots of people are somewhat confused by this topic, so I suggest you read a few threads and study a comparison chart.

Armed with this knowledge, go to a store with a decent selection of LP and HP tanks. Look over the selection to gain a better understanding of the actual dimensions and weight of the various options. Choose the tank who's size best matches your physique, capacity needs and budget.

 

[Warren_L]

I know some groups of people prefer LP tanks... this way they can fill say a LP100 to 3000 psi and have HP114s! Or 3300 psi and have HP125s!

This is officially not recommended, however. :no

Why not get a high pressure tank instead? A LP 104 and HP 130 are going to be very similar in weight and size, given the internal volumes are almost the same. With the LP 104 overfilled to the HP 130 pressure, you're going to get about 130 cu ft of gas. But if you underfill the HP 130 to the rated pressure of the LP 104, you'll get about 104 cu ft of gas. Difference being, the HP is rated to the higher pressure while the LP is not. Otherwise, the tanks are more or less identical. So why illegally overfill an LP tank when the HP tank can do all the LP tank can and more?

 

[Splitlip]

And which company makes the mythical LP130? :huh:

OMS 135 (actual 131) with 10% overfillto 2640

OMS 135 (131) 2400 +10% 131 8 Triple 30.7 47 0.75 -10.31

Close enough I guess.

 

[spectrum]

It's not necesary to use a DIN valve with High pressure tanks, i know many people who don't, but if you have the option I'd go for it as it's much more secure.

Be careful here, if you pick up a 3500 PSI HP cylinder (probably used) it will be strictly DIN.

If you get a more common pseudo HP cylinder, usually rated at 3442 but certainly something under 3500 PSI you will probably have the convertible DIN/yoke valve. As mentioned plenty of divers use these with yokes by many of us prefer to run the DIN configuration.

Any cylinder that never goes positive has effectively reduced your weight requirement. The HP cylinders by their nature are also lighter on land further reducing your walking weight which can mean a lot to shore divers.

Pete

 

[xiSkiGuy]

OMS 135 (actual 131) with 10% overfillto 2640

OMS 135 (131) 2400 +10% 131 8 Triple 30.7 47 0.75 -10.31

Close enough I guess.

Nice.

I believe that was when OMS was rebadging Faber LP tanks, but I've never seen the Faber marketed equivalent. They since have been rebadging PST E series tanks and when those dried up, I think they went back to Faber for the FX series.