LP vrs HP Tanks

[lamont]

my rix fills my 95 faster than an al80 because of the lp.

no, it doesn't. your rix fills your 95 faster because its a larger tank. if you used an HP119 it would fill it at an identical rate, and if you used an HP130 it would fill slightly faster.

physics doesn't know the difference between the stamped service pressure, so if you have two tanks of the same internal volume, they'll both fill to 2640 at the same rate and have the same amount of gas in them.

 

[NAM001]

Here's the thing though, an HP119 has virtually the same dimensions as your LP95 and holds the same amount of air at the same pressures. As far as size and trim goes you'd be hard pressed to tell the difference and the weight only varies a couple of pounds. The only significant differences are the 119 is rated for about 1000 PSI more, costs an additional $100 and can hold an additional 24 cf of air when filled to capacity.

i agree with you. at the time that was the decision i made when i bought my 2 lp95's.
later they had a lp120 for 100 bucks and i bought it. it certainly may be a whole different thought process if i were buying a set of doubles today. i bought 95's also because after several years not diving i thought i would be a definate air hog and did not want to cut others dive short so the extra cubes was insurance to not be the early one to the surface. also talks of nitrox not allowed above 3000# was in the air at the time. so i went with the lp 95 that would give me 108 at 3k. and my 120with 150 at 3k.

all the points being made are correct but with all things equal the price dominated my decision in the full lp fill vs the short hp fill. the only thing i do not like is the weight of the tank.

regards

 

[NAM001]

no, it doesn't. your rix fills your 95 faster because its a larger tank. if you used an HP119 it would fill it at an identical rate, and if you used an HP130 it would fill slightly faster.

physics doesn't know the difference between the stamped service pressure, so if you have two tanks of the same internal volume, they'll both fill to 2640 at the same rate and have the same amount of gas in them.

let me put t this way the first half of the tank fills faster than the last half because of tank back preasure on the cmopressor. the fuller it gets the less cubes per minute is pumped. i have timed it. it starts around 7.2 cubes when empty and reduces to under 6 at >3000# thats physics. my point ws to fill to a 95 to 2640 is a lot quicker than filling an al to 3000 because of the back preasure from 2640-3000. 0-2k is about the same time as 2k-3k

regards

 

[syntaxerrorsix]

I'm surprised no one has mentioned the pressure placed on regulators during deep dives with HP tanks compared to LP tanks or the fact that LP tanks do not meet their rated pressure unless overfilled by 10%. Quite a few shops will not fill + stamped bottles to 2640 to get a true 'regular' fill. Me I like getting getting 251cuft of air in my double LP95's. Fit and a divers ability to trim out with his/her equipment just doesn't mean a darn thing if they can't carry enough gas to do the dive. Are there really that many people that cannot adapt to differing tank sizes?

 

[syntaxerrorsix]

let me put t this way the first half of the tank fills faster than the last half because of tank back preasure on the cmopressor. the fuller it gets the less cubes per minute is pumped. i have timed it. it starts around 7.2 cubes when empty and reduces to under 6 at >3000# thats physics. my point ws to fill to a 95 to 2640 is a lot quicker than filling an al to 3000 because of the back preasure from 2640-3000. 0-2k is about the same time as 2k-3k

regards

There are one way check valves on compressors that prevent back fill through the system. Your compressor should pump the same PSI the entire fill unless its simply to anemic to fill to HP.

Without that check valve I would be wary about topping off any primed bottles of o2 because you are increasing your fire risk.

 

[lamont]

let me put t this way the first half of the tank fills faster than the last half because of tank back preasure on the cmopressor. the fuller it gets the less cubes per minute is pumped. i have timed it. it starts around 7.2 cubes when empty and reduces to under 6 at >3000# thats physics. my point ws to fill to a 95 to 2640 is a lot quicker than filling an al to 3000 because of the back preasure from 2640-3000. 0-2k is about the same time as 2k-3k

regards

And your use of an LP95 tank compared to an Al80 still illuminates nothing useful about HP vs. LP.

An LP95 fills to 2640 precisely as fast as an HP119 fills to 2640.

So, instead of buying an LP95 you can buy an HP119 and get the same fill rate to 2640, plus another 24 cubic feet of gas on top of that without needing to get into an argument with a fill guy about overfilling tanks.

The argument that LP tanks fill faster than HP tanks is only true if you compare two tanks that have different internal volumes -- LP104 will fill faster to rated pressure than an HP100. But those are fundamentally different tanks. Comparing LP104s to HP130s, the HP130 wins in nearly every way (except possibly cost).

And I understand the physics extremely well. I'm not disputing that your LP95 fills faster than an Al80.

 

[NAM001]

And your use of an LP95 tank compared to an Al80 still illuminates nothing useful about HP vs. LP.

An LP95 fills to 2640 precisely as fast as an HP119 fills to 2640.

So, instead of buying an LP95 you can buy an HP119 and get the same fill rate to 2640, plus another 24 cubic feet of gas on top of that without needing to get into an argument with a fill guy about overfilling tanks.

The argument that LP tanks fill faster than HP tanks is only true if you compare two tanks that have different internal volumes -- LP104 will fill faster to rated pressure than an HP100. But those are fundamentally different tanks. Comparing LP104s to HP130s, the HP130 wins in nearly every way (except possibly cost).

And I understand the physics extremely well. I'm not disputing that your LP95 fills faster than an Al80.

well lamont

we aparently are not in the same book let alone the same page. since you have DI RIGHT in your title i will just conceed to end it all. continuing changes nothing.

regards