Use of Heliox in Drager

EDB · 11th May 2005, 22:58

Its no big deal if you decide on some fairly standard mixes and learn the scaling factors for those mixes, a few % either way is not going to make a great difference.. but no helium to say 25% helium makes a difference...Today 01:47 AM

This is why I am asking about Heliox in the Dolphin; gauges can accurately measure the amount of 02 in the system, but if the amount of N or He bounces around unpredictably, it could make for a bad day. My hope is that a Heliox Dolphin would be a useful and pleasant tool for those 140-180' dives where a modest amount of deco makes for a good dive.

EDB

***jradomski*** · 12th May 2005, 00:36

Quote: (Originally Posted by EDB)

Its no big deal if you decide on some fairly standard mixes and learn the scaling factors for those mixes, a few % either way is not going to make a great difference.. but no helium to say 25% helium makes a difference...Today 01:47 AM

This is why I am asking about Heliox in the Dolphin; gauges can accurately measure the amount of 02 in the system, but if the amount of N or He bounces around unpredictably, it could make for a bad day. My hope is that a Heliox Dolphin would be a useful and pleasant tool for those 140-180' dives where a modest amount of deco makes for a good dive.

EDB

The inert portion does not bounce around.. it will change proportional to the change in oxygen, it doesnt matter if there is 1, 2 or 10 inert gases...

The idea is to set your unit up with the correct starting flow.. the chaneg in loop contents due to metabolism will not change the flow... Helium can be as easily measured as oxygen.. portable Helium analyzers have been available for at least 5 years now..

If you use heliox you still will have to scale your flow meter to get the correct rate.. plus your required decompression times will be increased.

for most divers, with depths up to 200fsw/60m 25-30% helium is all that is needed..

If you are worried about blending mistakes, a mix with 30% helium ~21% oxygen can be made by using 32% nitrox and helium.. fill helium to 1000 PSI and top to 3000 with 32%.. In this way you can verify that the oxygen addition part was correct.. and its now a simple top off...

Just figure out the mixes you need for specific dpeth ranges and learn how to mix them yourself.. With a Rebreather you dont need huge gas supplies, you could do hombrew blending just by burchasing a portable booster pump like the one from jetsam or the hydraulics international 3 series..

11th May 2005, 22:58	#11 (permalink)
EDB New Member Current Rebreather/s: Other Rebreather/s: Join Date: May 2005 Location: NC USA Posts: 3	Its no big deal if you decide on some fairly standard mixes and learn the scaling factors for those mixes, a few % either way is not going to make a great difference.. but no helium to say 25% helium makes a difference...Today 01:47 AM This is why I am asking about Heliox in the Dolphin; gauges can accurately measure the amount of 02 in the system, but if the amount of N or He bounces around unpredictably, it could make for a bad day. My hope is that a Heliox Dolphin would be a useful and pleasant tool for those 140-180' dives where a modest amount of deco makes for a good dive. EDB
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12th May 2005, 00:36	#12 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 2,997	Quote: (Originally Posted by EDB) Its no big deal if you decide on some fairly standard mixes and learn the scaling factors for those mixes, a few % either way is not going to make a great difference.. but no helium to say 25% helium makes a difference...Today 01:47 AM This is why I am asking about Heliox in the Dolphin; gauges can accurately measure the amount of 02 in the system, but if the amount of N or He bounces around unpredictably, it could make for a bad day. My hope is that a Heliox Dolphin would be a useful and pleasant tool for those 140-180' dives where a modest amount of deco makes for a good dive. EDB The inert portion does not bounce around.. it will change proportional to the change in oxygen, it doesnt matter if there is 1, 2 or 10 inert gases... The idea is to set your unit up with the correct starting flow.. the chaneg in loop contents due to metabolism will not change the flow... Helium can be as easily measured as oxygen.. portable Helium analyzers have been available for at least 5 years now.. If you use heliox you still will have to scale your flow meter to get the correct rate.. plus your required decompression times will be increased. for most divers, with depths up to 200fsw/60m 25-30% helium is all that is needed.. If you are worried about blending mistakes, a mix with 30% helium ~21% oxygen can be made by using 32% nitrox and helium.. fill helium to 1000 PSI and top to 3000 with 32%.. In this way you can verify that the oxygen addition part was correct.. and its now a simple top off... Just figure out the mixes you need for specific dpeth ranges and learn how to mix them yourself.. With a Rebreather you dont need huge gas supplies, you could do hombrew blending just by burchasing a portable booster pump like the one from jetsam or the hydraulics international 3 series.. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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