Dear every body,

9FA exhaust diffuser has three supports, one for 88BN fans to cool the bearing and another one acts as manhole to access the bearing tunnel. and this manhole is uncovered (open to atmosphere) during normal operation so air from cooling fans is escaping from this manhole to the compartment. is this is normal or this manhole should be covered and sealed?

thank you

 

Dear kamel,

Have you consulted the 'Heating & Ventilation' P&ID for details about cooling supply and venting of the #2 bearing?

There should also be a drawing in the Parts Manual for the #2 Bearing Enclosure that shows a cover or not on the entrance you are referring to.

I would also suggest that if there are fire extinguishing nozzles to distribute a fire extinguishing agent inside the bearing enclosure that the opening should have some kind of cover, even if it has louvers (gravity-operated or latched) to contain the fire extinguishing agent in the enclosure.

For a most direct answer, I would suggest contacting the packager/OEM of the turbine, supplying your turbine serial number and perhaps a picture or two of the opening.

Please write back to let us know what you learn.

 

Dear CSA

I could not confirm anything from the drawings.

There is a CO2 fire extinguishing nozzles in this area but there is no kind of covers and this is the reason of my confusion. so I need feedback from other 9FA users to tell me about the condition in their units.

I will write back whenever I get information.
Thank you

 

Dear kamel,

a picture would be worth a thousand words in this case.

I am not familiar with the 9FA, but I believe it is very close to the 7FA. On the 7FA there is piping that supplies cooling air from the #2 bearing cooling fans. Another pipe vents the cooling air outside of the exhaust diffuser. Lastly there is typically a cover on the rear of the #2 bearing housing to keep out the air from the exhaust. Without this cover the #2 bearing housing, and instrumentation are subjected to the heat of the exhaust, as well the CO2 fire suppression would be almost useless. Very curious to see if your 9FA is the same.

 

Dear MIKEVI,

I think it is almost the same.

In 9FA there are three struts between bearing tunnel (housing) and the exhaust diffuser. Through one of them the cooling air piping is going into the housing and another one for oil supply and CO2 piping and the third one is open to atmosphere so cooling air will go out through this one. And I’m not sure about its effect on:

Bearing cooling
Bearing sealing
CO2 in case it is released

Thank you

 

Dear Kamel,

I agree it sounds very similar to a 7FA(I think the 9FA is a little bigger) as far as #2 bearing area and exhaust diffuser.

If the bearing manhole cover is indeed "Missing" I would definitely say that:

Bearing instrumentation is going to be effected
CO2 fire protection is compromised.

Bearing temperatures and sealing are not be harshly effected since cooling air is still being directed in the area, and bearing sealing air is being supplied to bearing air seals. Bearing temps should not be affected much since oil is doing the cooling.

But the bearing manhole cover should be installed, if GE didn't feel it needed they would not have put it on!

 

The cover SHALL be installed.

As mentioned if there is no cover: the CO2 system will not be effective and the flow of the fans will be affected.

If the cover was left off, somebody forgot to install it during the installation, last inspection, etc.

 

thank you all and i will give you feed back for any news

 

Hi,

How do you know that the cover for Bearing No# 2 tunnel is not installed. We do inspections before closing the duct manway to ensure that Bearing tunnel cover is closed.

1) Is your machine running with high temperature reading of TTIB?

2) Any effect on the BN Fan operation?

3) Any alarms on Fire protection system as the cables may not withstand the high temperatures as the tunnel is not under positive pressure.

It is interesting to know.