O2 cylinder

At 18:06 07 February 2006, Eric Greenwell wrote:
Gary Evans wrote:


Here's the current FAA guidance on the subject: (HBAW
02-01B)
http://www.faa.gov/library/manuals/e...ors/8300/hbaw/


2002/

An excerpt below, but please read the whole bulletin
in the link above
as this policy should not be taken out of context.
Most IA's will not
sign off an annual on an aircraft with an out-of-date
hydro.

'C. Title 49 CFR parts 171 through 180, Hazardous Materials
Regulations
(HMR), pertains to the retest and inspection of cylinders
in
transportation in commerce. However, cylinders used
as components in
aircraft are not considered to be in transportation
in commerce when
installed in an aircraft. As a result, the retest period
for cylinders
used as a component of and installed in an aircraft
is not subject to
the HMR. However, 49 CFR part 180, =A7 180.205, formerly
part 173, =A7
173.34(e), would apply to a cylinder that is removed

from the aircraft

and offered for transportation as an article of commerce.
In this case,
the cylinder must include the appropriate exterior
packaging and hazard
communication requirements (i.e., shipping papers,
marking, and
labeling).'

Jim




Two observations.

1) This bulletin appears to apply only to type certified
aircraft.
2) Section 1,3,C,3 shown below only requires that
non-DOT
cylinders must be tested as per DOT specifications.

'All other cylinders must be inspected and tested
as
required by subparagraph 3C(1) above as it applies
to DOT 3HT cylinders unless alternative testing and
inspection procedures are specified by the manufacturer
or referenced authority'.

The bulletin also states that that existing dot requirements
do not apply to aircraft 02 cylinders which makes
me
wonder if DOT requirements are only for the transportation
of cylinders. Can anyone come up with the actual DOT
regulation that a non-DOT aircraft 02 cylinder cannot
be legally filled?

I'm under the impression that the cylinders we use
in our gliders are
NOT classified as aircraft components, but are, instead,
considered
'portable' equipment. To be aircraft components, the
glider would have
to be certified with an oxygen system, and none of
them are. What we do
is (I believe) no different than the airplane pilot
that carries on a
cloth bag with the cylinder and regulator in it, then
uses the seat belt
to strap it down next to him. In other words, our gliders
do not have
oxygen systems in them, just carry-on baggage that
happens to be an
oxygen system.

If true, then the cylinders have to meet the regulations
for carrying
these cylinders around in cars, busses, etc, which
would be DOT
regulations.


--
Change 'netto' to 'net' to email me directly

Eric Greenwell
Washington State
USA

www.motorglider.org


There seems to be consensus (FAA included) that DOT
regs do not apply to a 02 cylinder in an aircraft so
what about in your car? As I read DOT regs on pressure
cylinders they apply to cylinders in transportation
in commerce. The definition of commerce is 'the exchange
or buying and selling of commodies on a large scale
involving transportation from place to place.'
Transporting your own 02 cylinder would not fit this
definition.
Am I missing something? I still haven't found a reg
that makes it illegal to fill your personal non-DOT
02 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