Oxygen Question

[twista]

Hey guys,

If you were flying an unpressurised aircraft at say, FL140, 160, 180, 200 what kind of mix would you want to set on the regulator to ensure that you will not pass out, but at the same time not chew through your supply.

How much use do you get out of a tank D or C size before it runs out?

Also I've herd not to use medical grade oxygen because there is a chance it can freeze at altitude. Any one had this happen to them?

Thanks in advance. :)

[tinpis]

Wacha got planned Twista? :uhoh:

[startingout]

http://www.casa.gov.au/download/orders/cao108/10826.pdf

Might be helpful.... CAO on oxygen use

FL140: 0.5L/min
FL160: 0.6L/min
FL180: 0.7L/min

(a) the minimum flow of supplemental oxygen available for each flight crew
member at various cabin pressure altitudes must not be less than 0.3 litre
per minute at 10 000 feet altitude, increasing by 0.1 litre per minute for
every 2 000 feet up to 18 000 feet altitude;
(b) the flight crew members must use the nasal cannula only during private,
aerial work, or charter, operations;
(c) the aircraft must not operate above 18 000 feet altitude.

[ForkTailedDrKiller]

I use a PreciseFlite portable oxygen system with a 22 cu ft tank and PreciseFlite "Conserver" regulator and nasal cannula.

I get about 16 hrs at FL140.

I monitor my O2 saturation with an oxymeter and aim to keep it above 90% at all times.

I have set up my own filling station and use only aviation grade oxygen.

Dr :8

[Runaway Gun]

Twista,

I can also recommend trying to do some Baro chamber runs to study your personal indications of hypoxia. If such an option is available in Oz. I've experienced it myself in flight, and being the only guy trained in such, was the only one who was aware of it. Sneaky and dangerous stuff matey.

[Captain Nomad]

If you have got the coin, 'Mountain High' do a great regulator that works it out for you automatically through a baro sensor (assumes unpressurized cabin of course). It also 'pulses' which means your supply lasts a lot longer. Multiple outlets from the regulator also if you plan on taking someone with you.

Horses for courses but cannular is more comfortable than a mask which can be probelmatic with a microphone.

Good points about hypoxia also. Know your own personal signs - they are different for everyone.

Normal Medical oxygen can have more moisture content and can definitely cause a problem when it freezes blocking regulators/valves/outlets etc. 'Aviators Dry Breathing Oxygen' is what you are after.

Last bit of advice, go pressurised instead! :}

[rutan around]

Dr, Can you give us any information on your oxymeter? Some time ago when I looked into one I was led to believe that when it's batteries were finished it became a throwaway item.Are there others at a reasonable price with replacable batteries ?
Cheers RA

[ForkTailedDrKiller]

RA - I have a Nonin 2500. It was relatively expensive but up near the top of the range in handhelds. A quick search for "pulse oximeters" on the web will reveal a range of cheaper models.

Dr :8

[bushy]

Have a look at AVWEB. There's one advertised there on line.

[rutan around]

Dr and Bushy, Thanks for the info.Now the dollar is starting to climb into an affordable range I can start thinking about these "nice to have" items.

[SNS3Guppy]

A myth abounds about medical oxygen and moisture content...and aviator breathing oxygen being dry. Despite the fact that some authorities still print publications saying as much, it's 100% patently untrue. Just as untrue are statements you'll hear about medical oxygen or aviators breathing oxygen, or even welding oxygen being more or less pure than another supply of oxygen.

It's the same oxygen, and comes from the same source. It has the same moisture content. It's no different.

Oxygen used in medical applications is just as "dry" as oxygen in your aircraft system. Medical oxygen used in the clinical environment is humidified to aid in comfort for patients; this is done downstream from the oxygen supply, prior to being administered to the patient. However, medical oxygen received in other settings, such as an emergency trauma scene, is identical in every respect to aviator's breathing oxygen. And to welding oxygen, for that matter.

As far as the use of nasal cannulas goes, once you go past 6 lpm, there's no further benefit in increasing the flow rate. This becomes especially true at altitude, as it's not the flow rate or even volume which is important, but the delivery pressure. At 18,000', the atmospheric pressure is roughly half that of sea level, and the gaseous partial-pressure of each atmospheric component (oxygen and nitrogen, comparitively) is likewise half that of sea level. You can be delivered all the oxygen in the world at altitude, but without pressure it does little good and doesn't aid in the respiration process.

Nasal cannulas shouldn't be used above 18,000.

How much time you get out of a particular bottle depends on your flow rate, and the number of attachments you have running at any given time, as well as the gas temperature and available pressure in the bottle.

[Captain Nomad]

Guppy, with all due respect I think there could be some difference. For example, why do RFDS make clear distinction in their operations between the 'medical' and 'aviators dry breathing' which goes into the aircraft (for crew and patients)? They also have documented problems from the past when medical oxygen was used for the patients but due to the altitude and temperatures involved they infact DID have freezing issues due to moisture content. Why is oxygen still separately labled for different applications if the grade of oxygen is no different? :hmm:

However despite what I've said, a read of the BOC MSDS for oxygen do show some remarkable similarities :confused:

http://http://msds.chemalert.com/?id=21&file=0010678.pdf

and

http://http://msds.chemalert.com/?id=21&file=0000785.pdf

[SNS3Guppy]

It's old misinformation and myth. Oxygen is oxygen. Medical oxygen does not come with moisture or humidity, and aviators breathing oxygen is not dehumidified.

Where medical oxygen does have humidity, it's applied after being routed from the oxygen source, and it's typically done bed-side for patient comfort. The oxygen source does not contain humidity. Neither does medical oxygen freeze, at altitude, or otherwise.

I've been an emergency medical technician in mountain locations with heavy snows and freezing locations, and I've flown air ambulance for three different operators over the years...all in mountain locations, all in freezing conditions. No difference between aircraft oxygen and medical oxygen.

Some sources still continue to perpetuate the myth. Much in the same way that some sources to this day perpetuate other myths in aviaton (such as ground effect being a cushion of air beneath the wing, or the old standby explaination of lift that shows two molecules starting at the front of the wing, and meeting at the rear). Such incorrect information is still granted a semblence of legitimacy by appearance in print...but it's just not so.

There is no difference aside from cost in the production, distribution, bottling, content, quality, or humidity between medical oxygen, aviators breathing oxygen, and welding oxygen.

[twista]

Fantastic answers, thanks

[ForkTailedDrKiller]

It's old misinformation and myth. Oxygen is oxygen. Medical oxygen does not come with moisture or humidity, and aviators breathing oxygen is not dehumidified.

This is true. It is all coming from the same source.

However, what is different is the pressure used in Aviation Oxygen cylinders from sources such as BOC vs that used for welding O2 and medical O2.

I don't have the info here with me but my recollection is that Aviation Ox cylinders from BOC are at about twice the pressure as welding and medical ox. This requires the use of extra high pressure regulators, but makes it easier to get a full fill into your portable or on-board O2 cylinders.

You can do it with welders O2 but you will need a bank of cylinders and will likely have to change them more often. The problem being that once the pressure in the refil cylinder equals that in your portable or on-board cylinder - you cant get any more O2 into the portable/on-board cylinder.

Given that welding O2 is maybe a quarter the price of aviation O2 then maybe that is not an issue but it does mean more buggerizing about.

My refill station consists of two high pressure aviation O2 cylinders in series. They cost about $250 each (for the gas). I have taken 5 full refills out of Cylinder 1 and its pressure is holding well. Will be interesting to see how many refills I get out of it.

As I cant get a refill for my portable cylinder anywhere in Townsville, including the aerodrome since Hawkers pulled out, I didn't have much choice but to set up my own refill station. I think my last refill from Hawkers cost me about $100, so after about 15 refills I will be in front.

Dr :8

[SNS3Guppy]

However, what is different is the pressure used in Aviation Oxygen cylinders from sources such as BOC vs that used for welding O2 and medical O2.

I don't have the info here with me but my recollection is that Aviation Ox cylinders from BOC are at about twice the pressure as welding and medical ox. This requires the use of high pressure regulators, but makes it easier to get a full fill into your portable or on-board O2 cylinders.


Actually, no. Unless someone is giving you half-filled oxygen cylinders, you should be seeing at a minimum 1,800 to 2,200 psi in your filled oxygen cylinders. Regardless of whether it's medical, welding, or ABO. Actual pressure depends on temperature.

Oxygen delivered to the various storage systems, whether it be medical, aviators breathing, or welding oxygen, is delivered from the same source, to the same grade and standard. What differentiates it in use is the container into which it is placed. Oxygen systems for consumption must be purged and evacuated any time pressure is lost in the system, to eliminate contaminates. Welding cylinders are typically emptied, but not evacuated. Without positive pressure to keep contaminates from entering the cylinder, the oxygen in the cylinder can't be considered 100% contaminant free.

Between medical grade and aviators breathing oxygen, both are from the same source. ABO is supposed to undergo an additional "drying" process...but oxygen is dry to begin with. It requires the introduction of hydrogen to gain moisture...H20. The chief difference between medical and aviator breathing oxygen? Cost.

[ForkTailedDrKiller]

Actually, no. Unless someone is giving you half-filled oxygen cylinders, you should be seeing at a minimum 1,800 to 2,200 psi in your filled oxygen cylinders.

Oh dear, silly me! What was I thinking?

I will write to BOC on Monday and suggest that they stop mislabelling their gas bottles.

Currently they are labelling welding and medical oxygen cylinders as: "filled to 16.3 MPa" (= 2364 psi) and aviation oxygen cylinders as: "filled to 25.0 MPa" (= 3626 psi).

Of course temperature could account for the difference!!!

Dr :8

PS: I wonder if I can get a refund on the extra high pressure regulator I bought to use with the aviation oxygen cylinders? I'll tell them Guppy says I've been conned!

[pcx]

Not sure about overseas but in Australia most Aviation Oxygen is delivered in EHP cylinders that have significantly more pressure in them than ordinary cylinders. From memory I think it is about 3500psi but not sure exactly. The spiggot on the cylinder is longer than on the normal cylinder and requires a special high pressure regulator to be used. It is not possible to fit a normal regulator to an EHP cylinder.
I believe that most aviation oxygen rigs in Australia use these cylinders due to the greater percentage of oxygen able to be used from the cylinder before it reaches an unusable pressure.

[Thermal Bandit]

pcx - your in the ball park

BOC deliver their Code 430 aviators dry breathing oxygen at about 3600 PSI for a full Size G bottle, most aircraft systems I have worked have maximum bottle pressure of between 1800 psi and 2200 psi. The Code 430 bottle uses what is referred to as a Type 11 high pressure manifold and you need a regulator to reduce the outlet pressure to work with this safely. .

The smaller bottles you refer to use a Type 10 outlet manifold - in theory we should be able to buy Code 420 in D size bottles, BUT unless you know where the only 8 bottles (as of last November) are in Australia and you live in Victoria you can’t buy it – these bottles are in a depot in Victoria and there are some paperwork rules as to why they can not be moved to a depot outside that state for sale.

When I work with Code 430 bottles I use a regulator that has a Type 11 inlet manifold and a Type 10 outlet manifold; this regulator was made to order for me, and allows me to use the remainder of the decanting equipment on either the regulator of a Type 420 bottle – I have also used Code 400.

Another source of portable Oxygen equipment is Mountain High in the States.