Peter 14-Mar-13 18:33 03
There is zero water in modern oxygen.
Well, there are tiny impurities – of the order of 0.1 to 0.01%. I spoke to British Oxygen about this and they gave me the figures, and they are all the same for
Welding oxygen
Food fresh oxygen
Medical oxygen
Aviation oxygen
Only the paperwork (and maybe quality supervision) differs.
The manufacturing process is the same nowadays – cryogenic with some variations (example).
Don’t confuse this with “oxygen concentrators” (also discussed in this forum) which pump air through zeolite and remove most of the nitrogen, which is OK for altitude breathing but AFAIK most of the water vapour remains, and so do all other gases.
I use welding oxygen, and have been since 2003, with Aerox, Precise, and now Mountain High. The reason I use it is because I can get the cylinder swapped for a new one by a local welding gas depot, no questions asked. I also get argon gas from there for TIG welding (really expensive stuff).
“Freezing” is nonsense anyway. The equipment is in your cockpit. The 1st stage regulator cools a tiny bit; maybe a few degrees C.
For those who still DON’T believe that ”Oxygen is Oxygen” they might be interested in this page from the December edition of U.S. AOPA Pilot Magazine:
Out of pure stupidity I’ve sent in my built-in oxygen cylinder to have done a new check that lapsed.
Today I received the message from the shop that the cylinder was beyond repair due to corrosion. I really have my problems to believe it, but anyway I have to decide on how to proceed now. They told me that they can’t get a replacement cylinder. Additionally, I have a gut feeling that – if one was found – a replacement cylinder could top 2000 Euros or more, because it is a huge one for six POB.
I really enjoy the benefit of my built-in system because it is so easy to operate. Plug in and enjoy. At least until now. Any advice on how to continue using the built-in components, maybe with a semi-portable system? I am reluctant to accept that I should have to move to a complete portable system now having all the parts installed.
Why not just install it again and get on with it?
boscomantico wrote:
Why not just install it again and get on with it?
Because it is disassembled and I have actually no idea whether it is still working (it WAS when I sent it in)
Enquire with some other shops if there is a chance of some remedial work?
The cost of replacement is high, but may have,
a, an impact of resale of the aircraft to the tune of that, or more without built-in
b, messing around with portable equipment is not a fuss with only 2 onboard but may be a pain with more Pax. Thus the investment helps with your appreciation/enjoyment of the aircraft.
I was specifically looking for built-in when I purchased our aircraft.
A cylinder is a cylinder. The fitted ones are normally steel. 2k sounds quite cheap actually; this stuff is normally a major part of the extra cost of a turbo aircraft (top overhauls being another).
A guy called Paul Turner – @paul – here spent a lot of time and £££ certifying a composite one for his TB21.
The other option is to plumb in a “portable” cylinder, like the MH “48 cu ft” one, 1st stage regulator, and feed the 20psi or so into your o2 plumbing, and then use an O2D1 for each seat, or O2D2 for 2 seats at a time. The fitted systems are constant flow and terrible on gas usage – see here – but way back there was a lot less knowledge within GA (pre-internet) and people just didn’t care. You are wasting at least 80% of the gas in your fitted system. The one thing you need to sort out is that the pressure gauge (which is on the cylinder) needs to be visible to the pilot, and the valve (likewise) needs to be accessible to the pilot also. The fitted systems feed the 2000psi gas to the front panel via a copper or steel pipe with a tiny internal diameter, like 0.5mm, and the 1st stage reg is pilot-accessible.
Peter wrote:
The fitted ones are normally steel.
No. They are usually kevlar or carbon.
Peter wrote:
2k sounds quite cheap actually
No. $2k is max price – the usual aviation price is $1.7k, normal price is $300-$500.
Maybe on new models, but the TB21 was steel (and heavy) and AFAIK all the old turbo airframes were also steel – they long-pre-date composite-anything.
Emir wrote:
No. They are usually kevlar or carbon.
My cylinder dates 1967.
Peter wrote:
was steel (and heavy)
Yes that’s closer to mine. Good point about steel: 10 years time between checks. Bad thing is it IS heavy.
GA_Pete wrote:
messing around with portable equipment is not a fuss with only 2 onboard but may be a pain with more Pax. Thus the investment helps with your appreciation/enjoyment of the aircraft.I was specifically looking for built-in when I purchased our aircraft.
Well initially I wouldn’t have bothered to carry along some portable stuff. But I had my experience already with a blocked oxygen hose in FL190. Aditionally with 4+ POB it is just more stuff flying around the cabin.
Actually I’m using the oxysaver cannulas and they’re quite ok on gas usage, really. 2 POB 12 hours of flight, half of that FL140, other half FL190, still plenty of oxygen left, maybe half cylinder used. That’s ok for me. I refill in my hangar.
I’ll relax and wait for what happens.
I’m surprised you say 10yrs test interval.
I know some types are 10yr but didn’t think that was types usually used in aircraft. Thats great for you.
5yr is very common in the older airframes with steel cylinders.
Fortunately most Cessna Cylinders are Steel and ‘on condition’ forever.
The downside is that while I’ve a contact licensed to do the American test (DOT) it’s still a bit of hassle to get them out, every 5 years.
