First of all, slightly off topic - bear with me Agaricus Bisporus - but I refer to Mad Jock;
Theory alert could be bollocks.
Surface tentsion allows fluids to do some very strange things when in capillarys liquified gases are famous for it. They will allow fluid to travel uphill so to speak.
My theory is that they have a slight leak and there is Oxygen fluid forming, if it manges to bridge the hole the surface tension will start doing its work and cappilary action will work pulling it up stream. Now because the fluid will be travelling into a cooler temp it will aid heat transfer to the outside it will cause even more oxygen to become liquid and supply the capilary action. Once its inside if there is any sort of height difference between top and bottom of the seal you will have started a syphon. Liquid oxygen being relatively heavy compared to He will have no probs overcoming the 4 psi differential. And thus you have an up hill (in pressure differential terms) leak. Look on the bright side though it means your not loosing highly expensive He through a seal leak.
My sincerest thanks for that Jock, because in my eighteen years as an MRI engineer (33 as CT eng)
nobody, including all our support engineers and factory Service Engineering types, have
ever come up with any more than a half ar8ed answer to that particular conundrum. Particularly when there is almost never any water ice in there - only Oxygen ice. You sir, I believe, have it exactly. Thank you again - I will be offering it to my colleagues who, I trust, will think I am truly the dog's bo11ocks.
Right, back on thread; Agaricus Bisporus asked;
Mods, please close this thread if it doesn't come back onto topic.
I asked a topical question that had nothing to do with odd behaviour in gas capilliary action or labyrinth seals.
Which I thought a bit disingenuous as Forget then reminded us;
But it does. As Smudge said -
Quote:
gas turbine engines employ labyrinth seals which rely on air tapped of the compressors to function ,this air actually enters the bearing sumps therefore any contaminants which are in that air will possibly enter the engine oil system,
Which I suspect held the nugget there, entirely cogent to the overall question - to which L337 posted the answer.
I know a lot of people, all engineers or interested in engineering, who were absolutely gagging to know what you BA Aero Engineers found when you got your hands on that 744 at Cardiff. Like others, I had thought the flight was a bit of a
PR stunt, but when I learned that the short hop to Cardiff had taken some three and a half hours and stepped all the way up to 40,000ft, I began to suspect that Willie Walsh was going to be standing next to you when you carried out your checks.
Thank you for that L337.
Roger.