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Old 21st Dec 2002, 09:55
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gas path

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Yes! principle is the same. The oil is pressure fed to the bearings at a nominal 50psi (does vary with engine type and temperature, some engines do not have any pressure relief valve). The bearing sealing is done for example by carbon seals or scroll seals backed up by air bled from the engine hp compressor. This bleed air would pressurise the bearing compartments so has to be vented. The return oil and air mix, again depending on the engine type is separated and the excess air vented overboard.
The oil/air separator could be of a centrifugal type.
The breather pressure and/or breather temp guage gives some indication of the health of the engine internals ie sealing.
The P W JT9D had a breather temp guage.
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