% Helium in stages to make them float

gallathan · 10th September 2007, 10:43

In the interest of streamlining, avoiding bad trim / tanks stirring silt, I'm interested in rules of thumb for how much Helium is needed in a stage to make it float. Here in the UK, seems an ALI80 / ali tanks need about 30 to 35% Helium to make them float, and at the weekend my buddy had a steel 232 bar 12ltr that had a floating tail with 60% helium in it. It was noticable too that with 10 bar less (i.e. 200 -> 190) bar, the tail cam up a lot. So wondering what the %He vs reducing pressure in the tank trade off is.

Mark Chase · 10th September 2007, 11:24

Quote: (Originally Posted by gallathan)

In the interest of streamlining, avoiding bad trim / tanks stirring silt, I'm interested in rules of thumb for how much Helium is needed in a stage to make it float. Here in the UK, seems an ALI80 / ali tanks need about 30 to 35% Helium to make them float, and at the weekend my buddy had a steel 232 bar 12ltr that had a floating tail with 60% helium in it. It was noticable too that with 10 bar less (i.e. 200 -> 190) bar, the tail cam up a lot. So wondering what the %He vs reducing pressure in the tank trade off is.

Mt steel 10s float arse up with 250 bar 18/45in. My ali 80 sinks like a stone with 235bar 50% in.

ATB

Mark

Fresh water its better in the sea.

Marc T · 10th September 2007, 12:11

for simple computation count 1,3 gramme for 1liter of air or of o2 ( 1,3kg for one cunic meter ) and zero for helium ( yes I know it isnt true ).

For no computation at all and admitting that hélium count for nothing in the weight you deflate progressively in water your tank filled with air and note the pressure remaining in the tank when the buoyancy seems correct so what is NOT in the tank is the place for hélium.

cheers

Marc

lizardland · 10th September 2007, 12:30

I made up a buoyancy calculator for myself a while ago, I'm not a chemist or engineer so feel free to point out the errors

Cheers,

Stuart

Mikel-Deko · 10th September 2007, 13:21

Hi
My two cents,
This weekend i've been diving a wreek in -50 mtrs. Two stages:
Ali80 Tx 17/40 200 bar FLOATS
7Litrs Aluminium Tx 45/25 170 bar SUNKS
And we found a tank that we lost two years ago. I took it with me to bring it to the anchor line to bring it up with the bouy. It was a 18 steel full of air. It was like a ton on my side.

Hope that this will help you.
Best
Mikel

Ben Field · 10th September 2007, 14:38

Have you been diving Helium in your fish pond AGAIN?

Quote: (Originally Posted by Mark Chase)

Mark Chase · 10th September 2007, 15:54

Quote: (Originally Posted by Ben Field)

Have you been diving Helium in your fish pond AGAIN?

I had to get the bloody hours up some how M8 and Layborns £5.00 to get in

ATB

Mark Chase

10th September 2007, 10:43	#1 (permalink)
gallathan New Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Join Date: Mar 2006 Location: Laleham, Middlesex, England, UK Posts: 42	% Helium in stages to make them float In the interest of streamlining, avoiding bad trim / tanks stirring silt, I'm interested in rules of thumb for how much Helium is needed in a stage to make it float. Here in the UK, seems an ALI80 / ali tanks need about 30 to 35% Helium to make them float, and at the weekend my buddy had a steel 232 bar 12ltr that had a floating tail with 60% helium in it. It was noticable too that with 10 bar less (i.e. 200 -> 190) bar, the tail cam up a lot. So wondering what the %He vs reducing pressure in the tank trade off is.
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10th September 2007, 11:24	#2 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Jan 2005 Location: Kent Posts: 2,410	Re: % Helium in stages to make them float Quote: (Originally Posted by gallathan) In the interest of streamlining, avoiding bad trim / tanks stirring silt, I'm interested in rules of thumb for how much Helium is needed in a stage to make it float. Here in the UK, seems an ALI80 / ali tanks need about 30 to 35% Helium to make them float, and at the weekend my buddy had a steel 232 bar 12ltr that had a floating tail with 60% helium in it. It was noticable too that with 10 bar less (i.e. 200 -> 190) bar, the tail cam up a lot. So wondering what the %He vs reducing pressure in the tank trade off is. Mt steel 10s float arse up with 250 bar 18/45in. My ali 80 sinks like a stone with 235bar 50% in. ATB Mark Fresh water its better in the sea. __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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10th September 2007, 12:11	#3 (permalink)
Marc T hell is in the details Current Rebreather/s: RB80 / Clone Home Build Other Rebreather/s: Not Bought Yet RB80 / Clone Home Build Join Date: Sep 2005 Location: FRANCE Carcassonne Posts: 433	Re: % Helium in stages to make them float for simple computation count 1,3 gramme for 1liter of air or of o2 ( 1,3kg for one cunic meter ) and zero for helium ( yes I know it isnt true ). For no computation at all and admitting that hélium count for nothing in the weight you deflate progressively in water your tank filled with air and note the pressure remaining in the tank when the buoyancy seems correct so what is NOT in the tank is the place for hélium. cheers Marc
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10th September 2007, 13:21	#5 (permalink)
Mikel-Deko Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Other CCR Join Date: Jul 2005 Location: Basque Country -Sp- Posts: 406	Re: % Helium in stages to make them float Hi My two cents, This weekend i've been diving a wreek in -50 mtrs. Two stages: Ali80 Tx 17/40 200 bar FLOATS 7Litrs Aluminium Tx 45/25 170 bar SUNKS And we found a tank that we lost two years ago. I took it with me to bring it to the anchor line to bring it up with the bouy. It was a 18 steel full of air. It was like a ton on my side. Hope that this will help you. Best Mikel __________________ Mikel-Deko Basque Country www.olatu.net "DIR is the nanny state for divers who cannot think on their own" Ron Micjan
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10th September 2007, 14:38	#6 (permalink)
Ben Field CK+Shearwater Current Rebreather/s: Classic Kiss Other Rebreather/s: Sport Kiss Join Date: Aug 2005 Location: London, England Posts: 1,442	Re: % Helium in stages to make them float Have you been diving Helium in your fish pond AGAIN? Quote: (Originally Posted by Mark Chase) __________________ www.hugsac.org.uk Beware Fridge Suck
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10th September 2007, 15:54	#7 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Jan 2005 Location: Kent Posts: 2,410	Re: % Helium in stages to make them float Quote: (Originally Posted by Ben Field) Have you been diving Helium in your fish pond AGAIN? I had to get the bloody hours up some how M8 and Layborns £5.00 to get in ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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