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#1
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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 |
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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 |
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John,
That Order was cancelled. It is replaced by HBAW 02-01B. http://www.airweb.faa.gov/Regulatory...light=8000.40d Jim |
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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 |
#5
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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. |
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