Author Topic: Oxygen?  (Read 11104 times)

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Offline dee

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Oxygen?
« on: July 12, 2011, 10:02:23 AM »
Ive just read 607 again and i know that Martin and Co had to have oxygen going down to the Falklands. I was wondering now that she is back displaying do the crew have to have oxygen? I know that they arn't getting to heights that they used to, but say, by law or  health and safety do they have to have an oxygen supply?
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Offline mackrick

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Re: Oxygen?
« Reply #1 on: July 12, 2011, 11:07:12 AM »
Quick answer is yes. The crew do have oxygen.
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Offline brains_mt

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Re: Oxygen?
« Reply #2 on: July 12, 2011, 11:09:35 AM »
Better check what Kevs having then!! :lol:
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Offline Nickolas

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Re: Oxygen?
« Reply #3 on: July 12, 2011, 12:52:26 PM »
Quote from: "mackrick"
Quick answer is yes. The crew do have oxygen.
Good now that's sorted, can we have the long answer Rick?
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Offline Sad Sam

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Re: Oxygen?
« Reply #4 on: July 12, 2011, 01:01:05 PM »
Here you go then.  (Rick is busy with his day job)

Oxygen contents are checked on the Before  service.

Minimum contents is 5/8 full.

There are 12 bottles in the jet (8 in the bomb bay and 4 in the rear equipment bay) Which incidentally all have to come out for next years winter service.

When the system is full it is charged to 1800 psi and I think it's 125 litres of oxygen.

At some point I must ask Barry if he can remember what the contents looked like when they got back to Ascension as with six of them on board at high altitude I would have thought the consumption would have been pretty high (the regulator at each crew station alters the oxygen/air mix according to altitude)

Even though we are restricted to 17,000 feet and should not in fact need oxygen (Commercial flights are pressurized to 8,000 feet with no discomfort to the passengers or crew) The system is kept charged so that in the event of an emergency (fumes in the cockpit for example) the crew can select 100% oxygen to breathe.
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Offline Nickolas

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Re: Oxygen?
« Reply #5 on: July 12, 2011, 01:04:11 PM »
Quality service as usual. Thanks Sam.
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Offline Nickolas

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Re: Oxygen?
« Reply #6 on: July 12, 2011, 01:05:42 PM »
Errr why do they have to come out? Is it to check the bottles for corrosion?
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Offline Sad Sam

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Re: Oxygen?
« Reply #7 on: July 12, 2011, 01:13:49 PM »
All the bottles will have to come out for a bay service this year.

Each has a five year installed life (add it up on your fingers)

They will go away to the OEM for inspection and certification.

I would have thought that corrosion would be one of the things they are looking for as well as dents or other damage.  They will probably charge them to a higher pressure than normal (pipes are pressurized to 1.5 times normal working pressure) this so that if I get things seriously wrong while I'm charging the system I won't end up with a load of shrapnel holes in the jet.
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Offline JeremyC

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Re: Oxygen?
« Reply #8 on: July 12, 2011, 02:56:49 PM »
Presumably 125 litres of liquid oxygen.

125 of gaseous wouldn't go far.
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Offline TimS

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Re: Oxygen?
« Reply #9 on: July 12, 2011, 04:38:17 PM »
Quote from: "Sad Sam"
I would have thought that corrosion would be one of the things they are looking for as well as dents or other damage.  They will probably charge them to a higher pressure than normal

Don't know whether the procedure is the same (maybe not since the pressures involved are lower), but SCUBA tanks are pressure tested with water, not with air. This is because in the event of a failure, water, being (effectively) incompressible will simply split the tank with no harm.

Some members of my old diving club had a minibus fire a few years ago, & a mere 3-litre 'pony' tank at 230bar cooked off & blew the whole side of the minibus out.

Tim.
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Offline dee

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Re: Oxygen?
« Reply #10 on: July 12, 2011, 04:39:22 PM »
Thanks for the answers, and the indepth one too Sam. :)
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Offline Fonseca

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Re: Oxygen?
« Reply #11 on: July 12, 2011, 11:26:16 PM »
Quote from: "JeremyC"
Presumably 125 litres of liquid oxygen.

125 of gaseous wouldn't go far.

If I remember my "O" level chemistry the oxygen will be gaseous. Liquidity being a function of temperature rather than pressure. The critical point (change from gas to liquid or the other way) for oxygen being around -118 degrees centigrade.  :geek:  :)

And just to alienate myself further... Sam, are the bottles smaller than those fitted as o/e? My book says the bottles are 2250 litres each not 125...
It also says...
The system runs at 1800psi reducing to 400psi through a pressure reducing valve and onto the oxygen/air regulator. This feeds to the crews pec (personal equipment connector) and on to the facemask. The regulator system varies oxygen/air ratio automatically up to 34000ft depending on altitude and demand. Above 34000ft it feeds 100% oxygen. The crew can switch to "Emergency" 100% oxygen at any time...
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Offline eddief

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Re: Oxygen?
« Reply #12 on: July 13, 2011, 12:56:37 AM »
It's a function of both...  Pressure & temperature both affect the state - solid, liquid, gas... and plasma for anybody who wants to get clever ;o)
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Offline Fonseca

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Re: Oxygen?
« Reply #13 on: July 13, 2011, 01:47:39 AM »
True. Ok, would you be happier with oxygen's state being gaseous rather than liquid given the pressure and temperature ranges encountered in this case? And we did not do plasma so I'll leave that to you Eddie!
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Offline Fonseca

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Re: Oxygen?
« Reply #14 on: July 13, 2011, 02:09:31 AM »
And at the risk of going off topic... As a product of the educational system of the 70's and 80's I thought it was my generation who battled with Imperial/Metric mix up misery. Here is a design from the late 40's and early 50's with an Aircrew Manual quoting cylinder capacities in litres. Go figure...
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