Aircraft Oxygen Bottles

[av8erab]

If an aircraft oxygen bottle leaks to zero, what must be done? Just refill it or is there more?

 

[Coool Hand Luke]

First, how do you know it's your O2 bottle leaking and not one of your O2 masks? What's the leak rate per day?

 

[avbug]

If your oxygen system isn't holding oxygen, then obviously it needs to be fixed. Perhaps I missed something, but I think you just asked if when a system is found to be malfunctioning, should you ignore it, or fix it. Is this so? Of course you fix it.

If the system is bleeding down, the source of the leak must be located and the problem solved, period. A bottle should never leak. If the bottle is leaking, you have a major problem and definitely should not fill the system or put it under pressure. Leaks occur at joints and fittings, and at the mask.

Gas pressure lines leak the gas under pressure around threaded fittings, cracks in lines, at the mask. If a soap solution is sprayed onto each potential leak site, bubbles will form where the gas leaks. What type of soloution depends on the gas. In this case, oxygen. You can't use any soloution with a petroleum base, because it reacts with with the oxygen. While some mechanics will use a dishsoap solution, a special solution is sold just for use with oxygen systems which doesn't leave a deposit, doesn't attract dirt or contaminants, and doesn't react with oxygen.

Finding and fixing the leak isn't preventative mx, especially with an oxygen system. Simple mistakes like improper use of sealant tapes or compounds can cause big problems in the oxygen system, to say nothing of improper torque on fittings, line flarings, etc.

Fix it.

 

[wrightflyer]

Depends on the operation but at the airlines the whole bottle must be replaced you cant just re-fill it, but of course you want to find the leak so it wont happen again.

 

[Mr Wu]

I think you're asking if there is any special inspection on the bottle itself because the pressure dropped to zero, like in scuba tanks?

I'm not quite sure but you should probably send it to overhaul to make sure that no crap or water got in there. Cheap insurance for when you need it.

 

[erj-145mech]

Check your type/model/series maintenance manual for specifics, but generally after a leak is located and repaired, the system must be purged before the airplane is released for service.

Also refer to your component maintenance manual, but your bottle may required a special internal inspection before servicing if the pressure was allowed to be reduced to less than 50 psi.

 

[av8erab]

That was it, is there any special procedure since it went really low? Obviously it needs to be fixed but is there more?

 

[avbug]

Depends on the bottle and system. Generally if the pressure drops and the bottle is within it's life limits, hydrostatic tests, and pressurization cycles (if applicable), then you'll do nothing more than purge the system and refill once the leak has been located and fixed.

In many cases, once the leak has been located and handled, the bottle will simply be refilled.

Different requirements apply to composite, aluminum, or steel bottles or tanks.

 

[A-Track]

If the pressures went below a certain level (I forget what it is off the top pf my head) then the bottle must be sent to a shop to be serviced and have a new / overhauled certification issued, once it's empty or below that level you can't just fill it up at the local FBO.

 

[avbug]

That is not correct as a general rule. Certain systems may have this as a requirement, but this is not a standard practice with all oxygen systems.

 

[Gatorman]

If a soap solution is sprayed onto each potential leak site, bubbles will form where the gas leaks. What type of soloution depends on the gas. In this case, oxygen. You can't use any soloution with a petroleum base, because it reacts with with the oxygen. While some mechanics will use a dishsoap solution, a special solution is sold just for use with oxygen systems which doesn't leave a deposit, doesn't attract dirt or contaminants, and doesn't react with oxygen.

Wow, I sould start visiting the site again more often.

It appears that his question is what to do with the bottle if it is found to have no pressure in it. Of course he will locate and repair the leak. BTW it is not recommended to use 'dish soap', the product used for detecting oxygen leaks is call SHERLOCK ( http://wintonproducts.com/id21.htm )
Anyway, back to the subject matter - I have always taken the safety route, so when it doubt sent it out and have it inspected. I was going to just leave it at that, but I knew that if I did some one would bust me on it.
So, here is what Uncle Fed sez :

Do not attempt to charge oxygen cylinders if any of the following
discrepancies exist:
1. Contaminated fittings on the manifold, cylinder, or outside filler valve.
If in doubt, wipe with stabilized trichloroethylene; however, do not permit
solvent to enter any internal parts. Let air dry.
2. Cylinder out of hydrostatic test date. DOT regulations require ICC or
DOT 3AA designation cylinders to be hydrostatic tested to 5/3 their
working pressure, every 5 years. Cylinders bearing designation ICC or
DOT 3HT must be hydrostatic tested to 5/3 their working pressure every 3
years, and retired from service 15 years or 4,380 filling cycles after date of
manufacture, whichever occurs first.
3. Cylinder is completely empty. Do not charge, as the cylinder must be​

removed, inspected, and cleaned

Here is the link where I found it:
http://www.tc.faa.gov/logistics/grants/pdf/1997/97-g-005.pdf

 

[avbug]

A random text by the technical center is not regulatory, so no, "Uncle Fed" doesn't dictate that a bottle be removed for testing if depleted.

Many mx manuals specify purging if the bottle drops below a certain pressure or is depleted, primarily because with no positive pressure in the system, an unsealed system can admit atmospheric pressure, and therefore moisture.

Sending the bottle out for testing when depleted is not necessary unless specifically called for. Neither is hydrostatic testing or other inspection proceses, unless specifically called out.

You'll note that with regard to dish soap, I specifically stated that while many mechanics do use it, it's not acceptable...work on your reading comprehension.

Liquid leak detection will assist in locating gross leaks, but not all leaks. Many leaks do not even produce a bubble. Additional methods are available to locate system leakage, ranging from flourescent to ultrasonic to pressure systems using helium, to electronic detectors and gas analyzers. However, the most common method today is still visual detection using a liquid spray and bubble method.

 

[Gatorman]

Well, since you do not know from what manufacture this oxygen bottle comes from and you do not have a copy of their maintenance data.... you go ahead and just fill that puppy up!

I would rather go the safe route, maybe spend a few bucks more than to have an incident from being right all the time. Seems that an "I told you so" would not quite fair too well if this oxyen bottle got a little chip of corrosion (saying that is is a steel bottle) and it cloggs the regulator during a flight at altitude.

 

[avbug]

How about he just follows the mx data that he's required by law to follow, instead of blindly wasting time and money in the first place?

Nothing to do with knowing it all. The counsel that the bottle must be or even should be sent out for an inspection is ridiculous. "Uncle Fed" doesn't require it, we don't have enough information to go on with the original poster, nor do we know if the original poster is a mechanic.

Sending the bottle to "overhaul" is a bit over the top, simply because the system pressure bled down.

 

[STAL6]

The maintenance manual of the aircraft I'm currently working on says if the oxygen cylinder pressure drops below 50psi the cylinder must be replaced. It does not say what to do with it, so I would contact the manufacturer. I found that in ch. 12 servicing.