Oxygen leak

[Marek7]

Happy Friday everyone, 

 

I'm having a little bit of trouble trying to diagnose an oxygen leak. The system seems to hold pressure while all the valves are closed. However I only get about 2 hours of oxygen time at altitude per complete fill of the bottle. This is using the flow regulated nasal cannula by airox usually around FL200. just left the supply valve open overnight and I did not get any leaks.  I have sprayed soapy water over all the connections after removing the interior and nothing.  

 

My theory is that this old regulator gets cold and starts dumping oxygen in the back.

 

 

I am all for your ideas.   More creative the better! 

 

Happy flying, 

 

Marek

[neilpilot]

Are you absolutely sure your pressure gauge is correct, and that you are really getting a fill?

[Marek7]

11 minutes ago, neilpilot said:

Are you absolutely sure your pressure gauge is correct, and that you are really getting a fill?

I would say so. I've gotten it filled at various places. But I like the way you think

[Marauder]

19 minutes ago, Marek7 said:

Happy Friday everyone, 

 

I'm having a little bit of trouble trying to diagnose an oxygen leak. The system seems to hold pressure while all the valves are closed. However I only get about 2 hours of oxygen time at altitude per complete fill of the bottle. This is using the flow regulated nasal cannula by airox usually around FL200. just left the supply valve open overnight and I did not get any leaks.  I have sprayed soapy water over all the connections after removing the interior and nothing.  

 

My theory is that this old regulator gets cold and starts dumping oxygen in the back.

 

 

I am all for your ideas.   More creative the better! 

 

Happy flying, 

 

Marek

I am not sure where the shutoff is on your plane. If it is at the tank through an electronic valve, then you still could have a leak anywhere from the tank to the outlet for your masks/cannulas. There may be several T fittings in the system to allow distribution to each passenger seat. As well, if the tubing has rubbed on something, it is possible for a hole to develop. Again, all of this is a moot point if the tank shutoff is not at the tank.

I have worked with compressed gases for years. It most likely is a fitting that is leaking. Either someone has bent a tube close to the fitting or one of them is loose.

[Danb]

 

Plus 2 on a loose fitting I had a similar issue, it ended up being a small fitting that could not be detected by soapy water, I purchased spray which detects gas leaks. I found the leak in five minutes after utilizing the proper detection spray.

[N201MKTurbo]

Are you sure none of your passenger outlets are leaking?

[Danb]

Chris I’m about ready for an 02 refill if your still available 

[Marauder]

2 minutes ago, Danb said:

Chris I’m about ready for an 02 refill if your still available 

You betcha! If you have the fitting to connect to your plane, we can fill you up. 

[Danb]

Don’t, I’ll order one. TY

[Bryan]

8 minutes ago, Danb said:

I purchased spray which detects gas leaks. I found the leak in five minutes after utilizing the proper detection spray.

Can you share what the proper detection spray is?

[Danb]

Bryan I’ll look for it and report back..

[Danb]

Nu-calgon., Cal-blue... Blue fluid, gas leak detector spray

[Marauder]

12 minutes ago, Bryan said:

Can you share what the proper detection spray is?

You can use anything that is considered O2 safe. Something like this: https://www.amazon.com/Nu-Calgon-4182-24-Detector-Bottle-1-Quart/dp/B000R7Z6L4/ref=sr_1_1?ie=UTF8&qid=1529693723&sr=8-1&keywords=oxygen+leak+detector

 

[Marauder]

Just now, Danb said:

Nu-calgon. Blue fluid, gas leak detector spray

You are scaring me Dan!

 

[DonMuncy]

When you say you left the valve open overnight and no loss of pressure, I presume you did not have any cannula (mask) hoses plugged in.

My best guess would be that there is a leak at the valve where one of the hoses plug into the system.  Plug one hose in, but shut off the flow valve. Use soapy water around the connection of the hose. Repeat for the other one(s).

[kortopates]

Are you sure none of your passenger outlets are leaking?

+1, start here, very easy to do! These shouldn't be leaking O2 when you turn on the O2 without anything plugged in.


Sent from my iPhone using Tapatalk

[Danb]

Good stuff Chris

[Marek7]

1 hour ago, DonMuncy said:

When you say you left the valve open overnight and no loss of pressure, I presume you did not have any cannula (mask) hoses plugged in.

My best guess would be that there is a leak at the valve where one of the hoses plug into the system.  Plug one hose in, but shut off the flow valve. Use soapy water around the connection of the hose. Repeat for the other one(s).

Hey Don,
Nope there were no ports connected.    I'll try and plug in some and see what happens.    I did do soapy water around all of the ports (with and without a connector)  and there was nothing obvious.

[Marek7]

3 hours ago, Marauder said:

I am not sure where the shutoff is on your plane. If it is at the tank through an electronic valve, then you still could have a leak anywhere from the tank to the outlet for your masks/cannulas. There may be several T fittings in the system to allow distribution to each passenger seat. As well, if the tubing has rubbed on something, it is possible for a hole to develop. Again, all of this is a moot point if the tank shutoff is not at the tank.

I have worked with compressed gases for years. It most likely is a fitting that is leaking. Either someone has bent a tube close to the fitting or one of them is loose.

Shutoff is in the back with the tank actuated by a push/pull line.  Seems to shut off quite well.

 

Is there anything that would be temperature/vibration sensitive.  On the ground this moment I cant find any leaks.   In the air I could put my money on them coming back.

Edited June 22, 2018 by Marek7

[Awful_Charlie]

As you have the altitude compensating regulator, don't forget the output depends on the altitude!

If you have a leak at a seal/joint (as opposed to a hole) it may be that the leak does not manifest itself until higher pressures

[Marek7]

10 hours ago, Awful_Charlie said:

As you have the altitude compensating regulator, don't forget the output depends on the altitude!

If you have a leak at a seal/joint (as opposed to a hole) it may be that the leak does not manifest itself until higher pressures

Thanks for the chart.   This is the conclusion where I'm at.  I am planning to do a test flight, get everything to altitude and cold soak.    I have half the interior apart and going to put leak testing fluid to see if it manifests.     

 

The almost 40 year old regulator is a bit of a concern too. 

 

 

[kortopates]

2 hours ago, Marek7 said:

Thanks for the chart.   This is the conclusion where I'm at.  I am planning to do a test flight, get everything to altitude and cold soak.    I have half the interior apart and going to put leak testing fluid to see if it manifests.     

The almost 40 year old regulator is a bit of a concern too. 

I am really not buying a flight test is required. If the system holds pressure when turned off that proves the high pressure lines are okay as well as the regulator is shutting off and the fill  port isn't leaking. If you are only losing air when operating it, that suggest a leak in the low pressure lines and outlets. Have you turned on the regulator and then checked all the outlets and low pressure lines? Despite being altitude compensating its still putting out enough pressure at sea level to find a leak - just try leaving it on. Its hard to believe the regulator that isn't leaking when off then leaks when on somehow? 

You can also try contacting https://www.c-l-aero.com/ in Redding CA, they specialize in O2 systems and can help you troubleshoot and are the ones to rebuild your regulator when the day does come.  So they know all the possible failure modes. I'd give  them a call, they're very helpful folks.

[larryb]

I spent the better part of a year getting my built-in o2 system to hold pressure. My system would leak down over several days when the valve was shut. Sometimes it would leak down to 600 psi and hold, other times 500 psi or 300 psi. There were several problems, and every time I found an fixed one I thought I had it, but did not.

1. Broken push-pull cable at cabin knob.
2. Leaky fitting at oxygen fill port.
3. Old o-ring where fill port tube connects to regulator.
4. Shutoff valve leak, valve did not fully shut off when the lever was in the shutoff position. 

#4 was finally fixed by a valve overhaul at c-l-aero in Redding. 1 week total turn-around including shipping, $600. 

Your system has 2 regulators. There is a combination first-stage regulator in the same body as the shutoff valve. This drops the tank pressure to 125 psi or so. Then there is the altitude compensating regulator as a 2nd stage regulator. If you send the whole tank/regulator setup to c-l-aero they will fully test it including putting the altitude compensating regulator in an altitude chamber and test that it meets specs at the range of altitudes. 

I found #2 in the list with the blue leak detector fluid mentioned above. Fixed with new Swaglok fitting. Somebody prior to me had over-tightened it and crushed the insides of the compression fitting. 

#3 was just done because the o-ring was old and cheap. I never did prove there was or was not a problem here.

I found #4 when I had the idea to connect a temporary tube to the output of the altitude compensating regulator and put the other end in a water bottle. I saw steady bubbles coming out even when the valve was shut. My MSC didn't really believe me that this was the issue, having never seen that particular fail before. Jeff at c-l-aero wasn't sure either, but was willing to overhaul the valve. I was pretty confident in the test so sent the whole tank and regulator setup up to Redding. They verified my diagnosis (valve did not shut off fully) and the overhaul fixed it. I am now finally leak-free. This one drove me crazy because I could not find it with the leak detect fluid. 

In your case I would suspect one of the unused passenger o2 supply ports. And the altitude compensating regulator will have a higher pressure at altitude, so it is entirely possible that one of these ports will leak more at altitude than on the ground. Perhaps you could fly and have a passenger spray the leak detection fluid around at altitude? Or you could be correct that you have a leak when it is cold but not otherwise. Or, perhaps your pilot breathing setup is flowing way too much, more than you expect.

Larry

[Awful_Charlie]

8 hours ago, Marek7 said:

The almost 40 year old regulator is a bit of a concern too.

Hmm - I hope you've had that looked at in the meantime:
MM Section 5.10.01

My regulator leaked (albeit on the ground too) before one of the previous overhauls but then came back fine

5 hours ago, kortopates said:

I am really not buying a flight test is required. If the system holds pressure when turned off that proves the high pressure lines are okay as well as the regulator is shutting off and the fill  port isn't leaking. If you are only losing air when operating it, that suggest a leak in the low pressure lines and outlets. Have you turned on the regulator and then checked all the outlets and low pressure lines? Despite being altitude compensating its still putting out enough pressure at sea level to find a leak - just try leaving it on. Its hard to believe the regulator that isn't leaking when off then leaks when on somehow? 

You can also try contacting https://www.c-l-aero.com/ in Redding CA, they specialize in O2 systems and can help you troubleshoot and are the ones to rebuild your regulator when the day does come.  So they know all the possible failure modes. I'd give  them a call, they're very helpful folks.

I agree getting the professionals involved would be a good idea, but unfortunately I do slightly disagree with the pressure holding - I've got one airline extension which will hold 60PSI, but with 100PSI behind it will leak down to 60 - it's just a worn out O ring in one of the connectors  (but to fix it means putting on a new connector, and it's only used for doing the tyres and that job is bottom of the pile for the moment)

[Marek7]

Got the bugger.    Doesn't seem to leak when the Scott connector is installed though. 

Thanks for help team. 

 

Mark