Frame9e vibration sensors

hussam295,

Vibration sensors--on any type of rotating equipment--fall into three basic types, depending on the equipment the sensors are installed on and the speed of the equipment and they desired type of measurement. There are velocity vibration sensors, distance vibration sensors and acceleration vibration sensors.

A "seismic" vibration sensor is another name for a velocity vibration sensor. Velocity vibration sensors are usually attached to some part of the machine which is very close to the rotating shaft and measures the velocity of the part the sensor is attached to. On GE-design Frame 9E heavy duty gas turbines, velocity (or "seismic") vibration sensors (or pick-ups) are usually mounted on the upper half of the journal bearing housing (often called the "bearing cap").

Acceleration vibration sensors (often called accelerometers) are also usually attached to some part of the machine in close proximity to the rotating shaft. Acceleration vibration sensors (pick-ups) are usually used on machines with a lighter frame and rotor--such as aircraft-derivative gas turbines which rotate at much higher speeds than single-shaft heavy duty gas turbines.

So, neither velocity- nor acceleration vibration sensors (pick-ups) measure actual shaft vibration, but rather measure the movement of the part of the machine the sensor is attached to. Using velocity vibration sensors to measure vibration of a heavy duty gas turbine is fine--since the shaft (of a single-shaft heavy duty gas turbine, which the Frame 9E is) has a LOT of mass (is very large and heavy--particularly the axial compressor portion of the shaft) and when it vibrates it will have a large affect on the bearing housings, where the seismic (velocity) sensors (pick-ups) are mounted.

Distance vibration sensors, or proximity vibration sensors, also sometimes called displacement vibration sensors, are mounted such that they measure the actual distance of the shaft from the face of the sensor. They require a second device to measure the speed of the rotating shaft to actually determine the magnitude of the movement of the shaft when it's vibrating. They are usually mounted near the bearing housing as the bearing housing is usually a very stable part of the machine.

For decades GE and packagers of GE-design heavy duty gas turbines only used seismic (velocity) vibration sensors. Even when distance or proximity vibration sensors became available they continued to use seismic vibration sensors for the protection of the machine (to trip the machine on high vibration as detected by the seismic (velocity) vibration sensors). Many purchasers of GE-design heavy duty gas turbines started requesting, then demanding, that distance (proximity) vibration sensors be installed on new machines they were ordering. GE, reluctantly, started providing these sensors (usually manufactured by Bently-Nevada Corporation) in addition to the seismic (velocity) sensors on many new machines. BUT, still GE steadfastly continued to use only the seismic (velocity) sensors for protection (tripping). (For a few years GE was installing proximity, or distance, vibration sensors on every machine they produced--because in the event of an increase in vibration during the warranty period when the machine was new they could connect special equipment to the proximity sensors to use in determining what was causing the high vibration and how to mitigate it. BUT, the GE turbine control systems could not be directly connected to the proximity vibration sensors for many years.)

Eventually, GE purchased and assimilated Bently-Nevada and started installing proximity vibration sensors on almost every heavy duty gas turbine they produced. One benefit of using distance, or proximity, vibration sensors is that when high vibration is detected the proximity sensors can, with the addition of special equipment, be used to determine what is causing the increase in vibration or how to place weights to reduce the vibration. GE then did start using the proximity vibration sensors for protection (tripping). And, once they owned Bently-Nevada, they were able to design printed circuit cards and modules which could be directly connected to the proximity vibration sensors also.

Which type of sensor is better? That depends on the type of information you want from the sensor. For basic machine protection, the seismic vibration sensors are fine and adequate. But, they don't provide any real useful information about the nature of the vibration or how to mitigate the vibration. That's where proximity vibration sensors excel--providing information about the nature of the vibration and how to mitigate it.

Again, accelerometers are used primarily on machines with lighter frames and rotors and which run at higher speeds--but they are not measuring actual shaft vibration or movement (displacement)--they are measuring the movement of the part of the machine the accelerometer is attached to--which is caused by the vibration of the rotating shaft.

Hope this helps! Here's a pretty useful explanation of how displacement (distance; proximity) vibration sensors work:

https://instrumentationtools.com/vibration-sensors-work/

(Unfortunately, although it mentions the three basic types/classifications of vibration sensors, it only really details how distance, or proximity or displacement, sensors work.

Finally, people ask me quite frequently why the velocity vibration sensors on a GE-design heavy duty gas turbine are called "seismic" vibration sensors (pick-ups). Seismic shaking or a seismic event is usually associated with an earthquake or volcano eruption, where the ground moves pretty violently. When mounted on bearing caps velocity vibration sensors usually require a pretty large amount of vibration to actually detect shaft vibration--especially in the alarm and trip regions. When the shaft is vibrating that much, one can usually feel it in their feet when standing on the grating or even the ground next to the turbine--hence, a "seismic" shaking or event! Isn't the English language wonderful? (Some manufacturers of velocity vibration sensors refer to their products as seismic sensors (pick-ups); others don't. It's a common term, but it actually seems to be falling out of usage--except for GE-design machines. GE had a philosophy of, "If it ain't broke--don't fix it!" for many years (decades). Which was quite good for people who worked on or with GE machines because they stuck with consistent equipment and terms (even if the terms weren't exactly perfectly descriptive). But, things change, so do tried and true philosophies and practices.... Change, for change's sake, isn't always a good thing. But, the assimilation of Bently-Nevada into the GE "family" of companies almost forced GE to start equipping every gas (and steam) turbine and generator (and centrifugal compressor) with B-N vibration (and axial position) sensors (profit margin is their most important product, after all).

That is probably a little more information than you, hussam295, were looking for, but I write as much for other readers (now and in the future) as for the original poster.
 
hussam295,

Vibration sensors--on any type of rotating equipment--fall into three basic types, depending on the equipment the sensors are installed on and the speed of the equipment and they desired type of measurement. There are velocity vibration sensors, distance vibration sensors and acceleration vibration sensors.

A "seismic" vibration sensor is another name for a velocity vibration sensor. Velocity vibration sensors are usually attached to some part of the machine which is very close to the rotating shaft and measures the velocity of the part the sensor is attached to. On GE-design Frame 9E heavy duty gas turbines, velocity (or "seismic") vibration sensors (or pick-ups) are usually mounted on the upper half of the journal bearing housing (often called the "bearing cap").

Acceleration vibration sensors (often called accelerometers) are also usually attached to some part of the machine in close proximity to the rotating shaft. Acceleration vibration sensors (pick-ups) are usually used on machines with a lighter frame and rotor--such as aircraft-derivative gas turbines which rotate at much higher speeds than single-shaft heavy duty gas turbines.

So, neither velocity- nor acceleration vibration sensors (pick-ups) measure actual shaft vibration, but rather measure the movement of the part of the machine the sensor is attached to. Using velocity vibration sensors to measure vibration of a heavy duty gas turbine is fine--since the shaft (of a single-shaft heavy duty gas turbine, which the Frame 9E is) has a LOT of mass (is very large and heavy--particularly the axial compressor portion of the shaft) and when it vibrates it will have a large affect on the bearing housings, where the seismic (velocity) sensors (pick-ups) are mounted.

Distance vibration sensors, or proximity vibration sensors, also sometimes called displacement vibration sensors, are mounted such that they measure the actual distance of the shaft from the face of the sensor. They require a second device to measure the speed of the rotating shaft to actually determine the magnitude of the movement of the shaft when it's vibrating. They are usually mounted near the bearing housing as the bearing housing is usually a very stable part of the machine.

For decades GE and packagers of GE-design heavy duty gas turbines only used seismic (velocity) vibration sensors. Even when distance or proximity vibration sensors became available they continued to use seismic vibration sensors for the protection of the machine (to trip the machine on high vibration as detected by the seismic (velocity) vibration sensors). Many purchasers of GE-design heavy duty gas turbines started requesting, then demanding, that distance (proximity) vibration sensors be installed on new machines they were ordering. GE, reluctantly, started providing these sensors (usually manufactured by Bently-Nevada Corporation) in addition to the seismic (velocity) sensors on many new machines. BUT, still GE steadfastly continued to use only the seismic (velocity) sensors for protection (tripping). (For a few years GE was installing proximity, or distance, vibration sensors on every machine they produced--because in the event of an increase in vibration during the warranty period when the machine was new they could connect special equipment to the proximity sensors to use in determining what was causing the high vibration and how to mitigate it. BUT, the GE turbine control systems could not be directly connected to the proximity vibration sensors for many years.)

Eventually, GE purchased and assimilated Bently-Nevada and started installing proximity vibration sensors on almost every heavy duty gas turbine they produced. One benefit of using distance, or proximity, vibration sensors is that when high vibration is detected the proximity sensors can, with the addition of special equipment, be used to determine what is causing the increase in vibration or how to place weights to reduce the vibration. GE then did start using the proximity vibration sensors for protection (tripping). And, once they owned Bently-Nevada, they were able to design printed circuit cards and modules which could be directly connected to the proximity vibration sensors also.

Which type of sensor is better? That depends on the type of information you want from the sensor. For basic machine protection, the seismic vibration sensors are fine and adequate. But, they don't provide any real useful information about the nature of the vibration or how to mitigate the vibration. That's where proximity vibration sensors excel--providing information about the nature of the vibration and how to mitigate it.

Again, accelerometers are used primarily on machines with lighter frames and rotors and which run at higher speeds--but they are not measuring actual shaft vibration or movement (displacement)--they are measuring the movement of the part of the machine the accelerometer is attached to--which is caused by the vibration of the rotating shaft.

Hope this helps! Here's a pretty useful explanation of how displacement (distance; proximity) vibration sensors work:

https://instrumentationtools.com/vibration-sensors-work/

(Unfortunately, although it mentions the three basic types/classifications of vibration sensors, it only really details how distance, or proximity or displacement, sensors work.

Finally, people ask me quite frequently why the velocity vibration sensors on a GE-design heavy duty gas turbine are called "seismic" vibration sensors (pick-ups). Seismic shaking or a seismic event is usually associated with an earthquake or volcano eruption, where the ground moves pretty violently. When mounted on bearing caps velocity vibration sensors usually require a pretty large amount of vibration to actually detect shaft vibration--especially in the alarm and trip regions. When the shaft is vibrating that much, one can usually feel it in their feet when standing on the grating or even the ground next to the turbine--hence, a "seismic" shaking or event! Isn't the English language wonderful? (Some manufacturers of velocity vibration sensors refer to their products as seismic sensors (pick-ups); others don't. It's a common term, but it actually seems to be falling out of usage--except for GE-design machines. GE had a philosophy of, "If it ain't broke--don't fix it!" for many years (decades). Which was quite good for people who worked on or with GE machines because they stuck with consistent equipment and terms (even if the terms weren't exactly perfectly descriptive). But, things change, so do tried and true philosophies and practices.... Change, for change's sake, isn't always a good thing. But, the assimilation of Bently-Nevada into the GE "family" of companies almost forced GE to start equipping every gas (and steam) turbine and generator (and centrifugal compressor) with B-N vibration (and axial position) sensors (profit margin is their most important product, after all).

That is probably a little more information than you, hussam295, were looking for, but I write as much for other readers (now and in the future) as for the original poster.
HI sir
Thank you very much for this very valuable information. I have benefited greatly ... I have another inquiry about (proximity sensor) in our units (frame9e) mark6e in proximity page there is two radial vibration sensor (1X&2x)what are they and what the relationship between them and if you don’t mind can tell me more about turbine keyphasor(77RP11)
Thanks
 
Sorry I have no answer.am just like you
I want to learn more on keyphasor and radial vibration sensor 1X & 2 X
Hussam 295

What I retained about 1X & 2X is that :
1X is indicating imbalancing
2X is indicating misalignement .


But I am still confused regarding the HMI view that you shared , mostly as I told you before about key phasor value reading.
Also I dont see over Y probes values, " O " value is mostly displayed on the probes ,

Are you sure that you are getting a best overview of unit vibration monitoring on this view???

Well Thats not i use to see on this kind of HMI view

Please let us know if you have corrected ( key phasor /probes values displaying ...)

Hope this can help,
ControlsGuy25.
 
All,

I am prefacing this explanation by saying I am NOT a vibration analyst--not in any way shape or form. I only know what I've read (which isn't much--because vibration analysis has never been interesting to me), and what I have heard (which is always questionable, because we all "hear" the same thing differently (based on prior experience, if any; internal biases (about what is being said and who is saying it); and how well what is being said can be heard (over other noise (talking; mechanical noise (which is present a lot when I am hearing things related to my profession).

I believe "1X" and "2X" do not refer to actual sensors, but rather they refer to "multiples" of the vibration at each sensor as a function of the measured frequency. "1X" is the actual measured displacement ("1X" meaning "1 times actual measured displacement at the measured frequency"). "2X" means the displacement at "2 times the measured frequency." And when I'm referring to "displacement" a better word is probably "magnitude"--the amount of total movement at the measured frequencies. And, the measured frequency is related to the shaft speed, I believe.

These are analytical values which are useful in determining the cause and location of the excessive vibration. And, in addition to displacement (magnitude) the angle of the highest displacement (magnitude) can also be determined. So, by knowing the "nature" of the different displacements (magnitudes) and the angle of the displacements a more precise determination of the root cause of the excessive vibration can be made, and that can be used to determine the best course of action to resolve the problem(s).

As ControlsGuy25 has said, one multiple (1X) often (but not always) indicates imbalance, and a two multiple (2X) often (but not always) indicates misalignment. And, again, angle (phase angle) can be useful in further identifying the precise nature of the cause--and help in determining how to best resolve the vibration.

I have seen the display in a previous response to this thread before--and almost ALWAYS it has missing information. That's because the Mark* has to have software running in the I/O Cards or I/O Packs that produces the necessary information to populate all the fields (1X; 2X: phase angle; etc.)--and that software isn't always purchased by the Customer. These displays are "generic" and should be properly edited by the requisition engineer at the "factory" before shipping the software to the field (Mark* software AND HMI display software) to only show actual information which is available from the Mark*. Some older Mark* VI turbine control systems used MODBUS (serial and TCP) to get information from a Bently-Nevada monitor to populate the HMI display values. This was done soon after GE had purchased Bently-Nevada and hadn't yet had time to write algorithms to calculate the information in the Mark* I/O Cards and I/O Packs--which is now possible, IF the Customer purchases the enhanced information.

Again--most of the above is solely based on my weak understanding of vibration analysis methods, and my experience with non-working CIMPLICITY/PROFICY Machine Edition HMI displays (of which there are ALWAYS an excessive number (of non-working displays and missing data and incorrect indications which never get resolved during commissioning and persist for years, decades even). I may even have mis-spoken about some of the more nuanced things being discussed here, but it should get some people started on their journey of discovery--or just reinforce others' thoughts that vibration analysis is something that requires a LOT of study and experience. It's not something that can be understood in just a couple of sentences or paragraphs.

I would suggest to the original poster if he wants to pursue how the 1X and 2X values and information are used in vibration analysis he do more research on the World Wide Web using his preferred search engine. There is LOTS of information out there--some of it better than others. Remember, that vibration analysis is still something of a black art (meaning that a lot of if it is based on experience and intuition and even luck (more on that later!)), while it is becoming more and more mainstream, better understood and even "automated" (using very well-written software, and probably some AI (Artificial Intelligence) software, and even machine learning software).

Luck. A very intelligent person I worked with who had a reputation as being very "lucky" in troubleshooting and problem resolution was asked about his perceived "good luck." His answer was--and I'll never forget it: "The harder I work, the luckier I get." And I have put that to the test many, many times in my career and life--and it is 100% true. And, vibration analysis is also proof of this statement. The more, and better, information available about a vibration event the faster a plan of remediation or mitigation can be determined and put into action. This is possible because a lot of very smart people have spent a LOT of time (and money) looking at just about every element of available information, and probably a lot of it proves to be not useful. But, because of their hard work, many others can be very successful in their efforts.
 
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