Cold weather operations

Cold weather operations

Postby f4dj79 on Mon Nov 30, 2009 9:04 am

Yup its that time of the year November
The leaks and oozing have started. The gearbox is the problem here at Boeing we see more leakage and oozing do to long periods of inactivity. We even see leakage on the fuel rail interface mainly from the lack of operations. As with any turbine engine if it sits too long it will develop troubles. What kind, the high bypass engine main cold path fan will spin freely and if the engine is not started often the bearings can starve for oil. The other things are leaks and turbine wheel warpping with the constant rubbing of the tip shrouds against the case can erode the metal and over time it all adds up. The options are cover the inlets and keep the engines running as much as possible.
So if you own these engines an once of protection is worth a pound of cure.
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Re: Cold weather operations

Postby j79guy on Mon Nov 30, 2009 7:11 pm

Our industrial units, we keep the lube oil warm, to about 90F. or so, and idle for 30 minutes before loading the units up.
On the test cell, we have a sump heater and get the oil cooking before light off.
Of course, most of our units run on vapourous fuels, so we don't see the same leaks on the fuel system, but often on liquid fuel engines we do see leaks stemming from incorrect O-ring material specifications. When an engine is going to see some down time, a little preservative in the fuel certainly seems to help, to keep all the O-rings "swelled" up.

Some of the Rolls' engines actually lose oil temp while idling, even though the oil cooler thermostat is closed. The Avon units for example will slowly lose oil temp at idle, as the mass airflow through the engine simply cools the oil down faster than is can heat up from running. For these engines, we get the oil as hot as practical in the sump prior to light off, start the unit and ramp to power as soon as we can. One engine we test run at -26C ambient, we cooked the compressor fwd bearing due to low oil flow. It just was too darn cold and the oil turned to jelly.

Robin.
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Re: Cold weather operations

Postby f4dj79 on Thu Dec 03, 2009 7:55 am

Robin
That is the same thing on R/R RB211's on the 777. The oil coolers sit out in the cold path air stream and get an excess of cold air from the big fan thing up front. The other troubles on RB211 the fule oil exchangers they sit under the fan cowl, which gets cold soaked sitting or in flight and this allows the fuel and oil to not exchange heat as well. We lost a British airliner a few years back from icing troubles realted to this.
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Re: Cold weather operations

Postby f4dj79 on Mon Feb 09, 2015 7:30 am

update to the cold weather ops on the GE-90 engines. After numerous tags and bitching GE started a program two years ago to tighten up the leakage. The biggest things is the advent of 'o'ring seals that use fuel pressure to help seal up the gaps. The idea was to put small holes in both side of the gasket plate/ oring seal area and let the fuel pressure swell in the cavity, the leaks stopped! Now these seals are being used on most of GEAE engines. Wow what a concept listen to the mechanics then develop a fix and use it.
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