tank size and pressure

[bigolred]

I'm trying to do some research on tanks, if I'm ever in the place to buy some. I'm interested in high pressure steel 133s, the weight of large tanks doesn't bother me. The information I've found on one website for Faber tanks says "these are the same as Faber low pressure 108, just in high pressure". Does anyone know if that means that for a 133 tank it's just plus rated for now, and eventually will be de-rated to low pressure (i.e. 108)? Thanks for any help

edit: website where I found my info
133 Cubic Foot - High Pressure Faber Cylinder

 

[JackD342]

If you include the link to the website where you read that you will get a lot more specific help in explaining and interpreting, and a lot less speculation and discussion of what you might have read.

 

[runsongas]

no, the hp133 are exemption tanks. they do not receive a + rating like 3AA tanks. so if they pass hydro, they are rated up to 3442 psi. the lp108 and hp133 are also slightly different tanks as you can see by the specs. the lp108 is more positively buoyant when empty.

Blue Steel Scuba - Cylinder Specs

 

[tbone1004]

133's are roughly the same dimensions as a 108 but are made to a different engineering standard.
What that means is the 108 that is rated at 108cf at 2640psi will hold 133cf at 3442psi. Conversely the 133 will hold 108cf at 2640 psi because the tank volumes are the same.
Very different tanks in terms of what they're made of, but the same dimensions. Same roughly holds true for LP85/FX100, LP120/FX149, and several others.

There are two reasons to buy LP tanks. First one is because you need their specific buoyancy like we often do when sidemounting in caves. This is why Faber LP121's are my primary sidemount bottles. The second is because you come across good deals on them and can't pass them up. Otherwise, especially for single tank diving, there is never any reason to get LP tanks. You will hear all sorts of bullsh!t about buy a LP tank because you'll always get a good fill. While that may hold true when coming say a HP100 against a LP104, the reality is those are two drastically different tanks. Since the information above holds true, whether you have a FX133 or a LP108, they will always have the same amount of gas when at the same pressure, so just get the high pressure version and you'll be better off

 

[DogDiver]

We use LP 2400 psi steel cylinders here in north Florida and fill them to 3800-4000 psi.

 

[Superlyte27]

A 108 at 3442 is NOT 133CU'

 

[Superlyte27]

Here's the math


108 / 2640 * 3442 = ???

I'm surprised TBone is wrong on something so commonly known.

 

[bigolred]

We use LP 2400 psi steel cylinders here in north Florida and fill them to 3800-4000 psi.

and with all gentleness and respect, that is why I won't consider any used tanks from Florida, especially any that have been doubled. I understand tanks are built with a safety factor, and burst disks are a first line of defense. But you're overfilling your tanks to over 150% pressure rating, it's just not good for longevity.

 

[Superlyte27]

, it's just not good for longevity.

That's not factual.

 

[tursiops]

it's just not good for longevity.

Might drop their life from 100+ years to 90+. Just sayin'.