High pressure or low pressure tank

[BB`]

I am looking at getting a 120CF tank and am trying to decide if there is any downside to using a low pressure tank.

I assume that the HP tank would be harder to find someone able to to fill it all the way to 3400psi vs the 2600psi for a low pressure tank.


Am I missing anything?

 

[rhwestfall]

Length? Diameter? Weight of tank? Buoyancy? How it trims out? These can all be factors in addition to fill "issues"...

 

[tbone1004]

they are very very different sized tanks. I generally recommend getting HP tanks when you can most shops can fill to 3600psi, just have to make sure you check pressure before leaving to make sure you didn't get a short fill.

Three basic tanks you're looking at in that range
AL80 size for reference. 7.25" diameter, 26" height

E8/X8-119- 8" diameter, 24" height. 2lbs negative when empty
HP/E7/X7-120- 7.25" diameter, 28" height. Depending on the tank, neutral to 2lbs negative depending on the brand
LP 120/121/125 -8" diameter, 29" height. 1lb positive to 2lbs negative depending on brand

Fabers are generally the most positive, PST in the middle, and Worthington are most negatively buoyant.

3" might not sound like a big deal, but it is quite noticeable when the tanks are on your back, and you have to sit. How tall are you? The tall and skinny tanks are generally only recommended for people 6'2" or taller.

 

[RJP]

I assume that the HP tank would be harder to find someone able to to fill it all the way to 3400psi vs the 2600psi for a low pressure tank.

I can't imagine any shop with a fill station that couldn't fill HP tanks.

 

[BB`]

3" might not sound like a big deal, but it is quite noticeable when the tanks are on your back, and you have to sit. How tall are you? The tall and skinny tanks are generally only recommended for people 6'2" or taller.

6'3" and bulk out at 330lbs

 

[kr2y5]

FWIW, a lot of folks of various lengths and sizes seem to be very happy with HP100 as an all-around tank, and the Faber HP100 are very close in shape to the ubiquitous AL80.

 

[tbone1004]

is it in your back or your legs? I'm 6'4" with a 32" inseam.

Sorry the picture is so ****ty, but that's me on the left with a PST HP120 on my back. You can see how high the tank valve is and it is almost too long for me in singles. Doubles is a little less of an issue, but for singles they really are a little long. For your size you may want to look for some PST LP104's, epic tanks. Keep in mind with the old PSTHP120's they are DIN only



edit, can't believe that picture goes back to 2009 when I was getting rescue training.... yikes

 

[spoolin01]

I am looking at getting a 120CF tank and am trying to decide if there is any downside to using a low pressure tank.

I assume that the HP tank would be harder to find someone able to to fill it all the way to 3400psi vs the 2600psi for a low pressure tank.


Am I missing anything?

I could never get a decent HP fill so I switched from HP120 to LP120. You still have to watch the fills and remind the shops what a "+" rating means if your tank has that, but it's easier to get closer to 120 cu ft with the LP tank, at least around here. Plus you have the bonus that 1/3 of the time, the shop will fill the tank to 3000psi (well, 2800 actually, but that's what they call 3000).

I haven't checked the spec tables lately, but the LP tank is probably quite a bit heavier than the HP. My Faber LP120s are slightly positively bouyant when near empty, I believe, and you may or may not like that. I am used to it now, if it ever bothered me.

 

[Peter69_56]

So just for my curiosity, in usa you have LP 2600psi 180 bar, HP 3400psi 232bar
so what about 4350 psi 300 bar

here in OZ the standards are 200/210 bar aluminium, 232 bar and 300 bar

 

[tbone1004]

we have the old LP steels at 2250 then a 10%+ overfill. These are the old LP72's primarily, not made anymore. Overfill can be removed at hydro if the tank is showing signs of stress hardening

newer LP Steels, 2400 then 2640 with the overfill, same overfill + rules as above.

Most aluminum tanks at 3000psi

Mid-Pressure Steels at 3180/3190-Faber and Heiser made these, super negative, not made anymore

High pressure AL tanks at 3300psi- Catalina makes a C60, C80, and C100, and Luxfer makes a 100, about it. Don't see these often

Modern "HP" Steels at 3442-Faber is only current one, Worthington and PST formerly made these. This was done to facilitate the sale of the 200 bar convertible valves as it circumvented the DoT law for tanks over 3450 to have 300 bar DIN valves, no yokes.

True HP steels at 3500, not made anymore, only by PST, and had the "skinny neck" and funky valves.

No true 300 bar tanks sold here

The debate is typically only done between the LP and HP tanks at 2400+/2640 and 3442. Very rare to see the 3300psi aluminum tanks, never personally seen a mid pressure 3180psi tank, but I do own a few 2250 tanks and 3500psi tanks.