O2 cylinder

I think you got it right Gary. Those 180 and 173 rules are all about
transportation in commerce. However, most IA's will still want to see a
hydro date if that bottle is in your glider during your annual.

Jim

Jim, Gary - did you guys read the following (FAA Order 8000.40D)?
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgOrders.nsf/0/ed3ccb2b0c40bdad86256abf006f380c/$FILE/8000-40.pdf

1. It applies to Part 91 aircraft, among others (para 1)
2. It says the FAA Adminstrator has adopted "the rules and regulations
of DOT, RSPA, USCG, UL, MIL-SPEC, and applicable manufacturers as
acceptable methods for controlling the hydrostatic tests and life
limits of pressure cylinders" (para 4d)
3. It says "pressure cylinders used aboard aircraft should be
maintained under the same specifications prescribed by the appropriate
regulatory agency and manufacturers if no other requirements are
available." (para 4e)
4. It says "Cylinders which have reached their hydrostatic test due
date cannot be recharged or installed until hydrostatically tested."
(para 6e)

This seems pretty clear - even if your oxygen tank is non-DOT approved,
you have to follow the manufacturer's specs and you have to have it
hydrostatically tested in order to use it in your aircraft.

-John

jphoenix wrote:
I think you got it right Gary. Those 180 and 173 rules are all about
transportation in commerce. However, most IA's will still want to see a
hydro date if that bottle is in your glider during your annual.

Jim

John,

That Order was cancelled. It is replaced by HBAW 02-01B.

http://www.airweb.faa.gov/Regulatory...light=8000.40d

Jim

Jim, well that's a bummer! Someone writes an order to bring clarity to
a murky area, then that order is made obsolete by a superceding
directive which leaves us in the dark again. Perhaps this is why my
ASTM buddy hasn't been able to find anything to answer George's
question. It may be that use of pressure systems is not driven by
regulation so much as common sense, fear of litigation, and the
influence of insurance companies.

To answer JW's questions, aluminum and steel are pretty equal with
regard to safety. Of course, aluminum is generally more susceptible to
stress corrosion cracking than steel, and it will have a lower fatigue
life, so I would chose steel if you can stand the weight. The metal
alloys chosen for this application are ductile, so in neither case
would shrapnel be likely to be an issue. (The exception might be if the
bottle were cold enough at altitude to be below its ductile to brittle
transition temperature.) But, exploding in flight would be a pretty
unlikely event; refilling is the dangerous process as it puts rising
tension on any crack tip that may exist.

That said, you really don't want to be anywhere near a failing high
pressure cylinder! There will be an extremely high speed, high pressure
jet going in one direction, and a metal bottle going in the opposite
direction. Failing bottles have been known to go through solid concrete
walls, while high pressure jets have been known to cut people apart.

No one has remarked on the engineering behind these bottles. There are
three main concerns, flaws, fatigue life and corrosion. Flaws are
mostly found through hydrotesting; if a bottle passes it means any flaw
is below the critical crack size for the material. The crack growth
rate per fatigue cycle figure is determined for the material, and the
retest interval is chosen such that a sub-critical crack cannot grow
through refill cycling to critical crack size during the interval. But
fatigue cracking isn't the only mechanism of failure, stress corrosion
crack growth can occur simply by the passage of time, without any need
for stress cycles (it can happen to a full cylinder sitting on the
shelf).

A careful and prudent individual will get his high pressure cylinder
hydrotested every five years (or whatever the manufacturer recommends).
Remember, it's not just the number of refills, it's time passing itself
that can get you. If you think hyrotesting is expensive or
inconvenient, then I recommend you keep in mind Dirty Harry's question
"do you feel lucky?"

-John

jphoenix wrote:
John,

That Order was cancelled. It is replaced by HBAW 02-01B.

http://www.airweb.faa.gov/Regulatory...light=8000.40d

Jim

At 17:18 08 February 2006, Jcarlyle wrote:
Jim, Gary - did you guys read the following (FAA Order
8000.40D)?
http://www.airweb.faa.gov/Regulatory...brary/rgOrders
.nsf/0/ed3ccb2b0c40bdad86256abf006f380c/$FILE/8000-40.pdf

1. It applies to Part 91 aircraft, among others (para
1)
2. It says the FAA Adminstrator has adopted 'the rules
and regulations
of DOT, RSPA, USCG, UL, MIL-SPEC, and applicable manufacturers
as
acceptable methods for controlling the hydrostatic
tests and life
limits of pressure cylinders' (para 4d)
3. It says 'pressure cylinders used aboard aircraft
should be
maintained under the same specifications prescribed
by the appropriate
regulatory agency and manufacturers if no other requirements
are
available.' (para 4e)
4. It says 'Cylinders which have reached their hydrostatic
test due
date cannot be recharged or installed until hydrostatically
tested.'
(para 6e)

This seems pretty clear - even if your oxygen tank
is non-DOT approved,
you have to follow the manufacturer's specs and you
have to have it
hydrostatically tested in order to use it in your aircraft.

-John

jphoenix wrote:
I think you got it right Gary. Those 180 and 173 rules
are all about
transportation in commerce. However, most IA's will
still want to see a
hydro date if that bottle is in your glider during
your annual.

Jim



Yes, that was covered several posts back. FAA wants
the cylinder tested as if it were DOT approved which
is very reasonable. Getting a hydro on a non-DOT 02
cylinder is no problem.