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Gravitational by-passes the hood
- Thread starter Merabiko8
- Start date
I couldn't resist reading this thread, based on the title/subject.... It gave me quite a chuckle, as did the questions.
Merabiko8,
I think you are referring to what are frequently called air inlet implosion doors in the turbine (axial compressor) air inlet structure (ductwork) of a GE-design heavy duty gas turbine. Gravity is usually part of what keeps them closed; sometimes there are also springs. Sometimes it's just weights and gravity which keep the doors closed.
Let's say the turbine inlet air filters are REALLY dirty, OR ice has formed on the outside of the filter elements, or rain has soaked the filter elements causing them to swell and block air flow, which means the turbine (axial compressor and turbine, to be exact) are not getting enough air.
If the filter elements rupture (which vacuum can cause--vacuum is a very power force, just like pressure!) then lots of dirt and debris, or ice, or pieces of filter element and structure can be ingested (sucked into) the axial compressor inlet. (Yes, there is a "trash screen" downstream of the filter elements and upstream of the axial compressor inlet (bellmouth), but it's really not going to catch any dirt and not too much debris--it's a very coarse screen (large opening).
Worse, if the filter elements don't rupture, then the vacuum inside the turbine inlet duct work can cause the sheet metal of the duct to collapse (yes; again, vacuum is a very powerful force when combined with ambient pressure on the other side (creating a pressure differential on the sheetmetal (or the filter elements)).
So, to prevent this (ruptured filters; collapsed ductwork) from happening, there are usually large, heavy, occasionally spring-loaded, "doors", usually in the bottom of the inlet ductwork (downstream of the filter element) which will be opened when the vacuum gets great enough--but hopefully not great enough to rupture the filters or collapse the inlet ductwork--which will open, allowing unfiltered air to enter the axial compressor and turbine. (Unfiltered air is better than possibly collapsing/rupturing filters and/or ductwork!) These are the implosion doors--which prevent an implosion of filters and/or ductwork because of problems with the filters.
There are usually limit switches on these doors which tell the turbine control system, "The axial compressor and turbine are being starved of air flow and have operated (opened)." The turbine control system does one of two things when the implosion doors open--either initiate an automatic, orderly turbine shutdown a fired shutdown), or trip the unit.
Gravity keeps these implosion doors closed (and sometimes, as was written, there are also springs which help keep the doors closed). And, again, it is vacuum on the inside of the ductwork (downstream of the air filters) along with the ambient pressure outside the ductwork which opens the doors. There is no actuator which is driven by the turbine control system (that I have even seen--why would one want to allow unfiltered air into the axial compressor and turbine?).
As for opening them manually (as in with your hands, arms, shoulders, legs, back); go ahead--give it a try. But, please don't hurt yourself! They are very difficult to open, and usually they have never been operated or opened so they rubber gaskets used to prevent leaks have stuck to the doors and sills making them even more difficult to open. And make sure to keep you hands and body clear of the opening if you do get them open because they usually close with great force, as well.
I have heard of--but haven't actually seen or experienced--excessive fuel flow during firing (starting) cause the air inlet implosion doors to operate briefly (they open a small amount very quickly then close very quickly). This happens when there is excessive fuel trapped between the Stop/Ratio Valve and the Gas Control Valve(s), or when the Stop/Ratio Valve (usually) opens excessively during firing (it could be the Gas Control Valve(s) opening excessively during firing also, or a combination of the SRV and GCV(s) opening excessively). The sudden high natural gas flow into the combustors is ignited and that draws a LOT of air in through the bellmouth--through the filters and ductwork--causing the implosion doors to open and shut.
Now, this is all a SWAG (Scientific Wild-Arsed Guess) based on you description of "gravitational bypass hood doors"--and we all know (or at least most of us, anyway) that GE Belfort has done and continues to do some very unusual things. So, because the control philosophy for GE-design 6FA heavy duty gas turbines is "controlled" by GE Belfort, it's anyone's guess what is being done. Without being able to see the P&IDs for the unit and the programming in the Mark* turbine control system we can't know for sure.
You should definitely be able to find the air inlet implosion doors on the 'Inlet & Exhaust' P&ID (presuming the inlet was provided by GE or its packager). P&IDs and the System Descriptions in the Operations and Maintenance manuals provided with the equipment by GE or the packager of the equipment are REALLY important drawings and documents to study and learn if you're working on or operating or maintaining or troubleshooting GE-design heavy duty gas turbines. REALLY IMPORTANT drawings and documents.
Hope this helps--actually, I hope it was what you were looking for.... I would suggest this thread would have been best added to the 'Power Generation' topic area, not 'Process Control.'
Merabiko8,
I think you are referring to what are frequently called air inlet implosion doors in the turbine (axial compressor) air inlet structure (ductwork) of a GE-design heavy duty gas turbine. Gravity is usually part of what keeps them closed; sometimes there are also springs. Sometimes it's just weights and gravity which keep the doors closed.
Let's say the turbine inlet air filters are REALLY dirty, OR ice has formed on the outside of the filter elements, or rain has soaked the filter elements causing them to swell and block air flow, which means the turbine (axial compressor and turbine, to be exact) are not getting enough air.
If the filter elements rupture (which vacuum can cause--vacuum is a very power force, just like pressure!) then lots of dirt and debris, or ice, or pieces of filter element and structure can be ingested (sucked into) the axial compressor inlet. (Yes, there is a "trash screen" downstream of the filter elements and upstream of the axial compressor inlet (bellmouth), but it's really not going to catch any dirt and not too much debris--it's a very coarse screen (large opening).
Worse, if the filter elements don't rupture, then the vacuum inside the turbine inlet duct work can cause the sheet metal of the duct to collapse (yes; again, vacuum is a very powerful force when combined with ambient pressure on the other side (creating a pressure differential on the sheetmetal (or the filter elements)).
So, to prevent this (ruptured filters; collapsed ductwork) from happening, there are usually large, heavy, occasionally spring-loaded, "doors", usually in the bottom of the inlet ductwork (downstream of the filter element) which will be opened when the vacuum gets great enough--but hopefully not great enough to rupture the filters or collapse the inlet ductwork--which will open, allowing unfiltered air to enter the axial compressor and turbine. (Unfiltered air is better than possibly collapsing/rupturing filters and/or ductwork!) These are the implosion doors--which prevent an implosion of filters and/or ductwork because of problems with the filters.
There are usually limit switches on these doors which tell the turbine control system, "The axial compressor and turbine are being starved of air flow and have operated (opened)." The turbine control system does one of two things when the implosion doors open--either initiate an automatic, orderly turbine shutdown a fired shutdown), or trip the unit.
Gravity keeps these implosion doors closed (and sometimes, as was written, there are also springs which help keep the doors closed). And, again, it is vacuum on the inside of the ductwork (downstream of the air filters) along with the ambient pressure outside the ductwork which opens the doors. There is no actuator which is driven by the turbine control system (that I have even seen--why would one want to allow unfiltered air into the axial compressor and turbine?).
As for opening them manually (as in with your hands, arms, shoulders, legs, back); go ahead--give it a try. But, please don't hurt yourself! They are very difficult to open, and usually they have never been operated or opened so they rubber gaskets used to prevent leaks have stuck to the doors and sills making them even more difficult to open. And make sure to keep you hands and body clear of the opening if you do get them open because they usually close with great force, as well.
I have heard of--but haven't actually seen or experienced--excessive fuel flow during firing (starting) cause the air inlet implosion doors to operate briefly (they open a small amount very quickly then close very quickly). This happens when there is excessive fuel trapped between the Stop/Ratio Valve and the Gas Control Valve(s), or when the Stop/Ratio Valve (usually) opens excessively during firing (it could be the Gas Control Valve(s) opening excessively during firing also, or a combination of the SRV and GCV(s) opening excessively). The sudden high natural gas flow into the combustors is ignited and that draws a LOT of air in through the bellmouth--through the filters and ductwork--causing the implosion doors to open and shut.
Now, this is all a SWAG (Scientific Wild-Arsed Guess) based on you description of "gravitational bypass hood doors"--and we all know (or at least most of us, anyway) that GE Belfort has done and continues to do some very unusual things. So, because the control philosophy for GE-design 6FA heavy duty gas turbines is "controlled" by GE Belfort, it's anyone's guess what is being done. Without being able to see the P&IDs for the unit and the programming in the Mark* turbine control system we can't know for sure.
You should definitely be able to find the air inlet implosion doors on the 'Inlet & Exhaust' P&ID (presuming the inlet was provided by GE or its packager). P&IDs and the System Descriptions in the Operations and Maintenance manuals provided with the equipment by GE or the packager of the equipment are REALLY important drawings and documents to study and learn if you're working on or operating or maintaining or troubleshooting GE-design heavy duty gas turbines. REALLY IMPORTANT drawings and documents.
Hope this helps--actually, I hope it was what you were looking for.... I would suggest this thread would have been best added to the 'Power Generation' topic area, not 'Process Control.'
Merabiko8,
There was most likely a manual provided by--or available from--the ”hood” manufacturer. (Though I'm sure you're just interested in what signal(s) do I force to manipulate the louvers?”
[I completely fail to understand the juvenile fascination with forcing signals.... But, then I am the definition of ”old school.”]
There was most likely a manual provided by--or available from--the ”hood” manufacturer. (Though I'm sure you're just interested in what signal(s) do I force to manipulate the louvers?”
[I completely fail to understand the juvenile fascination with forcing signals.... But, then I am the definition of ”old school.”]
Merabiko8
Are you referring to the inlet compartment wheather hood also called louvers wheather....
Also what is the origin of the thread:
-Is there any issue you facing with equipment...
-Do you get OEM /Vendor Manual of this equipment (Not Ge I mean the original manufacturer technicaldocuments...
Can you share a drawing showing these "doors "and OEM manual it can help us to give a better help from here...
There would be a solution for you if you can add more details
Thanks for clarifying ...
Controlsguy25.
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