Tagged With "Gear Mesh Frequency"

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Re: Gear tooth count selections

John from PA ·
Originally Posted by John from PA: Originally Posted by Rusty Cas: Forgive me John for not saying it properly. Is the proper terminology codified somewhere? By the way, in my previous response, does the box with the non-hunting tooth combination have three or four gears (see my previous attachment)? Rusty, you never replied to my question so let me provide some insight as to why I asked. If the gearbox has three rotors and three gears, i. e., one per shaft, then it is referred to as a simple...
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Gear tooth count selections

Rusty Cas ·
I monitor a double-reduction gearbox that has a 20 tooth high speed (1200 rpm) pinion, and a 34 tooth 1st intermediate gear.  Why would a designer use a combination like this with so many common factors? With the advanced milling machinery in use...
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Re: Gear tooth count selections

John from PA ·
Originally Posted by John from PA: With the limited info you have provided, I would agree. But there may be some other issues forcing a tooth number selection. Cutting 19 teeth can be more of an issue than cutting 20, although both may require some special considerations to avoid tooth interference. If you go the other way, increase the number of teeth, then the pitch becomes finer and the ability of the tooth to sustain shock loading goes down. Can you provide a drawing (preferable) or...
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Re: Gear tooth count selections

Rusty Cas ·
My terminology is just what was used by others already on the job when I started 25 years ago. Input shaft was "high speed pinion shaft". 2nd shaft was "1st intermediate". Output shaft was called "output shaft. For a triple reduction, the 3rd shaft was called "2nd intermediate". So for consistency, the 2nd shaft was always called the "1st intermediate" even if there was no 2nd intermediate. Most plant people I've ever been around know next to nothing about the details of any gearbox. So I...
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Re: Gear tooth count selections

John from PA ·
Originally Posted by Rusty Cas: Forgive me John for not saying it properly. Is the proper terminology codified somewhere? I'm actually not certain if an AGMA Guideline exists on nomenclature. Having said that I would suspect that this most recent attachment would be what most AGMA member companies would follow. By the way, in my previous response, does the box with the non-hunting tooth combination have three or four gears (see my previous attachment)?
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Re: GEAR BOX VIBRATION MONITORING

John from PA ·
I take note that the OP uses the term "monitoring" as opposed to "diagnostics". For routine day to day monitoring I don't feel 6400 lines of resolution is needed for an as yet non-existent accelerometer (OP states "There is no online accelrometer installed on it." Further, and as William Foiles has stated, I support that the need for an accelerometer that is capable of "seeing" 4X of mesh is not needed. API 613 states that the upper limit of the accelerometer should be 10 kHz, although in...
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GEAR BOX VIBRATION MONITORING

ALI HAIDERR ·
Daer All, Can you please assist me to set FMAX,and Resolution for Gear box vibration monitoring, Gear Mesh Frequency (GMF) = No. of teeth x Shaft Speed = 73 x 7950 = 580350 CPM or 9672.5 HZ How much Fmax and Reolution? Is 100 mv/g sensor is recommended to take vibration data by off line data collector.? There is no online accelrometer installed on it.Only proximeter probes are installed. No. of teeth at input shaft 73 No. of teeth at output shaft 43 Rated Input speed 7950 Rated output speed...
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Re: GEAR BOX VIBRATION MONITORING

John from PA ·
...and how many of those gearboxes had a mesh frequency of 9672.5 hz?
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Re: GEAR BOX VIBRATION MONITORING

John from PA ·
...and I will state again, you need permanently mounted accelerometers on the Voith unit, even perhaps two and at least one on what you are referring to as the gearbox. You could use some form of connection panel for taking readings, but the signal characteristics, mainly the high frequencies, dictate that the transducers be permanently mounted. The accelerometers can be either 25 mV/g or 100 mV/g although I would lean toward 25 mV/g on the gearbox that has the 9672 Hz mesh frequency to...
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Re: GEAR BOX VIBRATION MONITORING

John from PA ·
If indeed this is the case, in summary, monitoring with an off line data collector and 100 mV/g accelerometer, you should have stated the potential problems. For one, any accelerometer that would "see" a 1X mesh of 9672.5 Hz would have to be permanently mounted. You just would not be able to have a temporary mounted transducer deliver reliable data at that frequency. In addition, the need for 6400 lines of resolution just doesn't exist in this instance. The gear generated sidebands would be...
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HIGH VIBRATION AT GEAR MESH FREQUENCY

dominich.vo ·
Hi all, please help me to diagnose one case about gearbox system. The system has been described in detail on attachment. The spectrum indicate high vibration at Gear mesh freq. (GMF) with harmonics and sideband of rotating speed. Base on spectrum data...
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Re: Gear box data

John from PA ·
Nothing unusual that I see as far as gear generated frequencies (see attached).
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Re: HIGH VIBRATION AT GEAR MESH FREQUENCY

John from PA ·
Originally Posted by dominich.vo: Hi all, please help me to diagnose one case about gearbox system. The system has been described in detail on attachment. The spectrum indicate high vibration at Gear mesh freq. (GMF) with harmonics and sideband of rotating speed. Base on spectrum data , can i judge the pinion gear has been wear or it is just a incorrect tooth meshing condition ? Your ideas will be appreciated Thanks a lot. First of all what are all your tooth combinations? In a case like...
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Re: GEAR BOX VIBRATION MONITORING

Ralph Stewart ·
John of PA, I am not sure why you are quoting my reply inside your reply to the original poster's questions. My reply was referencing the question the original poster asked about, at the beginning of the posting: "Can you please assist me to set FMAX,and Resolution for Gear box vibration monitoring,....... How much Fmax and Reolution? Is 100 mv/g sensor is recommended to take vibration data by off line data collector.? ". The quota about the accelerometer: " There is no online accelrometer...
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Gear Coupling Configurations

vibramac ·
Does anyone know the reason for the raised section on each tooth on the gear coupling associated with the blower? Have a concern , can this be a problem with one coupling have this configuration and the other (turbine) not. The coupling hub I assume is orginally for the blower's configuration.
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Re: Gear Coupling Configurations

vibramac ·
Thanks John, very informative. Clarity needed, is the crown you mentioned not on the blower hub or am I wrong. Onsite throught is: Blower 1 turbine rotor was removed, refurbished and then fitted to Blower 2 hence the different hub configurations. Blower 1 is the operational unit currently so the coupling arrangement cannot be confirmed as yet. Standard oil nozzle sprays into the coupling gears
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Re: Gear Coupling Configurations

John from PA ·
Gear couplings are made to fit with fairly small clearances at the major diameter of the hub root diameter of the sleeve. In a non-crowned hub I have seen what you are picturing on the blower. Crowned hubs usually are manufactured to closer tolerances so the major diameter of the teeth at the center provide the proper fit. In operation, and depending on the speed, the teeth mate at the pitch line. On the subject of crowning there are three types. The crowning can includes tip crowns where...
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Re: Gear Coupling Configurations

John from PA ·
I see all three types of crowning on the blower hub, or at least two types and a form of the 3rd type, the major diameter fit (see image attached). As far as a major diameter fit on the turbine side that type of crowning may be present there as well. If you lay a straight edge across the top of the teeth is the top edge straight or curved? I've drawn attention to an area that looks like it is pitted. Is it or just the photo? I'm still a bit puzzled why the holes and now I notice it is...
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Re: GEAR BOX VIBRATION MONITORING

Soumya Mishra ·
F max should be at least 4 times of GMF and resolution may be set 800
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Re: GEAR BOX VIBRATION MONITORING

Shurafa ·
Good question and good discussion. I second the comments given on the limitations of the hardware: 1. Typical general purpose accelerometers have limitations on Fmax, usually 10 kHz or less. Readings above this limit are not reliable especially if you analyze the data without a history with consistent measurements. 2. Any frequencies say higher than 5 kHz need a very good mounting method for the sensor (e.g. stud). Despite the accelerometer and analyzer capabilities, the mounting is very...
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Re: GEAR BOX VIBRATION MONITORING

ALI HAIDERR ·
Thanks for your kind input. I just want to set up offline data collector periodically routine with 100mv/g sensor.We dont have 10 or 25 mv/g sensor. Thanks Ralph Stewart,You always come forwad to assist me. Regards
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Re: GEAR BOX VIBRATION MONITORING

Ralph Stewart ·
To get 1st gearmesh, you will need an Fmax of 10,000 Hz, and at least 6400 line (if possible) if your meter and 100 mV transducer can be trusted out to that high of an Fmax. Thanks, Ralph
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Re: GEAR BOX VIBRATION MONITORING

William_C._Foiles ·
In the example give, do you recommend 4X GMF? Do you have an accelerometer that can read that high?
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Re: GEAR BOX VIBRATION MONITORING

John from PA ·
At the frequency under discussion, 9672.5 hz, it will be essential to permanently mount the accelerometer.
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Re: GEAR BOX VIBRATION MONITORING

ALI HAIDERR ·
Thanks to all,Really appreciated for giving your valuable time.
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Re: GEAR BOX VIBRATION MONITORING

Barry ·
How do you know I didn’t There is a great big real world out there that some live in that must get by with what they have to work with. Just because you have not blessed it in one of your committees you always condemn it. Bill I suggest you try to be helpful with the fast knowledge you have and be less arrogant.
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Re: GEAR BOX VIBRATION MONITORING

William_C._Foiles ·
I did have some gearboxes with studs mounted on them for periodic measurements. You have to keep the studs from being damaged, clean the surface, but it can be done. We did have people using the studs to help climb, but some will use anything in this manner.
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Re: GEAR BOX VIBRATION MONITORING

Barry ·
I agree with Ralph. I collected a lot of gear box data with a 100 mV/g acc on a two rail magnet (the square ones that CSI had back then) and always had good trends and I don’t remember a bad or missed call on a gearbox.
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Re: GEAR BOX VIBRATION MONITORING

William_C._Foiles ·
Do you have a helpful answer as to how you know? I did not say you didn't know, but I may change.
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Re: GEAR BOX VIBRATION MONITORING

William_C._Foiles ·
How did you know whether you had good or bad readings? Consistent readings?
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Re: GEAR BOX VIBRATION MONITORING

Ralph Stewart ·
Re: GEAR BOX VIBRATION MONITORING
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Re: GEAR BOX VIBRATION MONITORING

ALI HAIDERR ·
Ralph Stewart,Ali M. Al-Shurafa, Data taken by 100 mv/g sensor,with Fmax 10KHZ and LOR 6400. Dominant vibration peaks are 97594 CPM,165281CPM and 426750 CPM Is below data is Okay for further trending? It is train of (Motor+Voith+LP compressor+GB+HP compressor) Velocity Spectrum Velocity TWF Acceleration Spectrum Acceleration TWF
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Re: GEAR BOX VIBRATION MONITORING

John from PA ·
Your anticipated frequencies are summarized below. Like Walt has said, the source of the components at 97594 CPM, 165281 CPM and 426750 CPM may be from something else as they are unlikely to be from the gearbox as you've presented it. By the way, I see your comment "It is train of Motor+Voith+LP compressor+GB+HP compressor". Are your speeds correct? How do you get from typical motor speed to 7950 RPM?
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Re: GEAR BOX VIBRATION MONITORING

Barry ·
Same answer as above to you Mr John from PA
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Re: GEAR BOX VIBRATION MONITORING

Walt Strong ·
PCB-IMI has an accelerometer (10-mv/g) with flat magnet base that is claimed to get 3-dB flat frequency response to 30 kHz! The kit is 600A12. I have not used it, and don't sell it. Walt
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Re: GEAR BOX VIBRATION MONITORING

ALI HAIDERR ·
Ralpha, Aplogized for late reply. Please see below real Picture but unfortunetly,I donot have full snap at the moment. Vibration spectrum which I shared has been taken from Gear Box horizontal. Real Picture in which GB and HP compressor Missing
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Re: GEAR BOX VIBRATION MONITORING

John from PA ·
Based on your "pictorial" that shows the machinery arrangement, I think you have a Voith KGS drive that provides an increase in motor speed through a two-stage gearbox. There may or may not also be a Voith fluid drive integral to the unit. The Voith as pictured in your pictorial shows the 1st stage as speed increasing (gear is the driver) and the 2nd stage as speed decreasing (pinion is driver). This is just based on the relative sizes (of the gears) as shown but I wouldn't trust a simple...
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Re: GEAR BOX VIBRATION MONITORING

ALI HAIDERR ·
John Motor Speed is 1500RPM then voith speed is upto 7900 attached with LP compressor.Voith speed varies between 7500RPM to 7900RPM only during operation Then there is GB between LP and HP compressor and out put GB speed is 13400RPM(Approx) which is the speed of HP compressor also. Voith,Gearbox are equiped with proximity sensors,my concern is to monitor gear or voith faults with my off line vibration meter as there is no online accelrometer is installed.I have only 100 mv/g senseor. Thanks...
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Re: GEAR BOX VIBRATION MONITORING

ALI HAIDERR ·
John, Many Thanks for your support.Really Appreciated. Regards
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Re: GEAR BOX VIBRATION MONITORING

ALI HAIDERR ·
Ali.M.Shurfa. Thanks a lot. It may help me a lot. Regards
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Re: GEAR BOX VIBRATION MONITORING

Shurafa ·
Ali, I assume you mean that is the data you collected with the general purpose sensor reliable to give an early warning for gear faults? If this is all you can have, simply use it. It will give you reasonable detection on low frequency faults like misalignment but it may not be accurate for higher frequency faults. So, you get something but there is a risk for missing some faults. If I were you, I'll let the owner know about the limitation and ask for his/her concurrence on the outcomes.
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Re: GEAR BOX VIBRATION MONITORING

Ralph Stewart ·
ALI HAIDERR Have you taken any more data on your gearbox? Thanks, Ralph
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Re: GEAR BOX VIBRATION MONITORING

ALI HAIDERR ·
Dear Ralph, No .I didn't take. Regards Ali
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Re: GEAR BOX VIBRATION MONITORING

Ralph Stewart ·
Thanks for the reply. I was sort of hoping you had so we could compare it with the 1st data taken with just a hand held transducer. Could you send me, or post on the forum, the acceleration spectrum you recently posted, except instead of having an "autoscaled" vertical Gs scale, but have it with a manually controlled vertical scale of 1 Gs so as to see if there is anything located near the gearmesh calculated frequency of 9672.5 Hz? Just my curiosity. Thanks and Have a Great Day, Ralph
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5000 ton cooling Tower gear box

Ahmed Kabir ·
Will there be any substantial change in the oil level from its normal mark while running? In the cooling tower of international airport HVAC system, the level of oil found very low from its normal mark. I know that a small drop can happen from the normal mark while running. Will there be any considerable drop?  Could anybody can help me?
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Constant Percentage Bandwidth spectrum

ALI HAIDERR ·
Dear Any body may please guide me how to analyze "Constant Percentage Bandwidth spectrum".I am using B&K system. Please find spectrum of gear box of compressor.
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Re: Constant Percentage Bandwidth spectrum

John from PA ·
I suggest you go back and retake the data using narrow band analysis. When you do a constant percentage bandwidth spectrum the width of the filters is based on the full scale span. That isn't clear in your plot but I see components between 1 kHz and 10 kHz so perhaps it is 10 kHz?. You might also scale the horizontal axis linearly as opposed to the current logarithmic scaling. What you've done is more applicable to acoustic analysis.
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Re: Constant Percentage Bandwidth spectrum

ALI HAIDERR ·
Dear John, Thanks for your reply. Please give me some basic steps how to analyze CPB spectrum and how it works I am not familar with CPB
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Re: Constant Percentage Bandwidth spectrum

John from PA ·
As I said CPB is more applicable to acoustics, not machinery vibration. I suggest you read the content at http://azimadli.com/vibman/log...frequencyscaling.htm .
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Re: Constant Percentage Bandwidth spectrum

Walt Strong ·
Ali, Are you trying to use an old analyzer for machine vibrations? Constant percent filter has a varying filter bandwidth = x% x Center Frequency For example if percent is 6% then bandwidth at: 10-Hz = 0.6 Hz BW 100-Hz = 6.0 Hz BW 1000-Hz = 60.0 Hz BW 10,000-Hz = 600.0 Hz BW http://www.bksv.com/Library/Search%20Resources I Searched on "constant percent" for two results I think you will not find many folks who use this frequency analysis method for machine vibrations; except a few B&K...
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