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Why Axial position sensor in Gas turbine is so important?
niazbibiyana,
We haven't heard from you in a long time; welcome back!
Axial position is important because it can tell the operator and mechanical department about the condition of the thrust bearing and runners. If the unit thrust is too great (in the active direction) then the seals in the turbine section can allow hot combustion gases to get into the wheelspaces which can damage the turbine wheels and rotor. That's probably the biggest reason axial position is monitored for gas turbines.
While a rotor would have to move pretty far to allow rotating axial compressor blades to come into contact with stationary axial compressor blades, it could happen if axial position was allowed to get too far out of tolerance.
Some vibration issues can be traced to axial position.
Hope this helps!
We haven't heard from you in a long time; welcome back!
Axial position is important because it can tell the operator and mechanical department about the condition of the thrust bearing and runners. If the unit thrust is too great (in the active direction) then the seals in the turbine section can allow hot combustion gases to get into the wheelspaces which can damage the turbine wheels and rotor. That's probably the biggest reason axial position is monitored for gas turbines.
While a rotor would have to move pretty far to allow rotating axial compressor blades to come into contact with stationary axial compressor blades, it could happen if axial position was allowed to get too far out of tolerance.
Some vibration issues can be traced to axial position.
Hope this helps!
N
niazbibiyana
thanx CSA for your quick reply. Now I am busy with combined cycle operation of our plant. I have more question about GAS TURBINE vibration sensor. You you kindly help me to understand, i will be much grateful.
1. Why Eccentricity measurement sensor is not used in GE heavy duty GT? As it is so important to check shaft condition during operation.
2. By Proximity sensor is it possible to measure radial vibration? Why it is so important to know about radial Vibration? Kindly look at my Photo:
http://tinypic.com/usermedia.php?uo=uW4M4OjFxsZiGqTVG8UMcoh4l5k2TGxc
What are about all arrow direction of radial vibration?
have a nice day
1. Why Eccentricity measurement sensor is not used in GE heavy duty GT? As it is so important to check shaft condition during operation.
2. By Proximity sensor is it possible to measure radial vibration? Why it is so important to know about radial Vibration? Kindly look at my Photo:
http://tinypic.com/usermedia.php?uo=uW4M4OjFxsZiGqTVG8UMcoh4l5k2TGxc
What are about all arrow direction of radial vibration?
have a nice day
niazbibiyana,
So, eccentricity is not so critical for gas turbines as it is for steam turbines. Why, you ask? Well, most gas turbines only have three stages of the turbine section, where most steam turbines have many more stages. Steam turbines, when they have eccentricity, can rub and cause a lot of damage, and loss of efficiency.
The axial compressors of gas turbines are the longest portion of the turbine shaft (16 or 17 stages) and the clearances, while important, are not as tight as for steam turbines. Steam turbine rotors are much more susceptible to sagging or hogging (bowing down or bowing up) that gas turbines--either the turbine section or the axial compressor section. While it's not desirable to have compressor rubs on a gas turbine, it's not as damaging as steam turbine rubs can be.
Proximity sensors are very good at measuring radial vibration. USUALLY, but not always, seismic (acceleration) vibration sensors have the signal name 39VS-nn, and proximity sensors have the designation 39VV-nn--but not all packagers of GE-design heavy duty gas turbines use the same device names/designations. So, I have to trust the labeling in the area at the upper right of the display is, indeed, for proximity sensors (the units on the graph seem to be for proximity measurement, so, it's likely just an unusual choice of device naming).
The section labeled "Proximity Vibration" is actually radial vibration....
The lower section with all of the arrows and such is one of the things which makes proximity sensors so useful for vibration analysis--being able to determine the angle of the highest displacement, so that when determining what kind of corrective action to take or what might be causing the high vibration the angle is very useful. (Seismic vibration sensors aren't able to do this by themselves.) So, all of that data at the bottom of the display is useful when the vibration is higher than normal, and the vibration gurus use it to decide what might be causing the vibration and what kind of corrective action to take; it's not generally useful for most operators. The data there is really only useful for vibrations experts--and it's very handy to have that information when there is abnormal vibration. Usually, another piece of equipment has to be connected to the proximitors to be able to have that information--and it's not cheap to rent the equipment and to pay the people who connect it and analyze the data.
Hope this helps!
So, eccentricity is not so critical for gas turbines as it is for steam turbines. Why, you ask? Well, most gas turbines only have three stages of the turbine section, where most steam turbines have many more stages. Steam turbines, when they have eccentricity, can rub and cause a lot of damage, and loss of efficiency.
The axial compressors of gas turbines are the longest portion of the turbine shaft (16 or 17 stages) and the clearances, while important, are not as tight as for steam turbines. Steam turbine rotors are much more susceptible to sagging or hogging (bowing down or bowing up) that gas turbines--either the turbine section or the axial compressor section. While it's not desirable to have compressor rubs on a gas turbine, it's not as damaging as steam turbine rubs can be.
Proximity sensors are very good at measuring radial vibration. USUALLY, but not always, seismic (acceleration) vibration sensors have the signal name 39VS-nn, and proximity sensors have the designation 39VV-nn--but not all packagers of GE-design heavy duty gas turbines use the same device names/designations. So, I have to trust the labeling in the area at the upper right of the display is, indeed, for proximity sensors (the units on the graph seem to be for proximity measurement, so, it's likely just an unusual choice of device naming).
The section labeled "Proximity Vibration" is actually radial vibration....
The lower section with all of the arrows and such is one of the things which makes proximity sensors so useful for vibration analysis--being able to determine the angle of the highest displacement, so that when determining what kind of corrective action to take or what might be causing the high vibration the angle is very useful. (Seismic vibration sensors aren't able to do this by themselves.) So, all of that data at the bottom of the display is useful when the vibration is higher than normal, and the vibration gurus use it to decide what might be causing the vibration and what kind of corrective action to take; it's not generally useful for most operators. The data there is really only useful for vibrations experts--and it's very handy to have that information when there is abnormal vibration. Usually, another piece of equipment has to be connected to the proximitors to be able to have that information--and it's not cheap to rent the equipment and to pay the people who connect it and analyze the data.
Hope this helps!
