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RustyCas

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Reply with quote  #1 
I have HFD set up in some of my parameter sets but never paid much attention to it, or really given it much thought.  Apparently it collects an acceleration waveform from 5k-20kHz and calculates the parameter from that.  I'm thinking this would be good mostly for lubrication issues since most bearing defects (3600 rpm and under) show up at < 5kHz.

Does anyone use HFD?  And what about vHFD?  Does anyone use this for special cases, or even routinely?

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MarkL

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Reply with quote  #2 
I'm using HFD on some pumps in a power station I run routes in but the setup was done before my condition monitoring career by my predecessor, I just went with the flow and kept using them. (My boss says they were used for lubrication detection) They don't produce spectra just an overall for trending. I still mainly rely on the Velocity acceleration and Envelope readings.
Curran919

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Reply with quote  #3 
Rusty, isn't the upper band limit adjustable between 20-60 kHz? As far as I know, this is just another broadband, resonant-sensor, ultrasound indicator quite similar to SPM/gSE. It is indeed still used for rollerbearings. Its classified as a HFNBRI (High Frequency Natural Bearing Resonance Indicator) that picks up the resonant vibration of the outer race, which responds due to the defect impulses, regardless of the actual defect frequency itself. The absolute value means nothing, just the trend. Of course, that bandwidth will pick up a lot of energy from different sources, including frictional waves related to poor lubrication.
RustyCas

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Reply with quote  #4 
I think HFD is fixed at 5k-20k but vHFD (variable HFD) can be anything you want it to be. I was just wondering if anyone had used it intentionally. I’m thinking of just using it for lubrication.
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Chris184

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Reply with quote  #5 
You can change it in the AP and AL set ups. Mine defaults to 1k-20k. I use it and PeakVue for lubrication mainly.
RustyCas

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Reply with quote  #6 
I've recently started doing some motor lubrication, so thought I'd revisit this.  From the MHM help screen (duh!)...

HFD   Signal amplitude above 5 kHz. No lower or upper frequency need be specified.

Hz/CPM vHFD   Variable high frequency detection band. This parameter is calculated from a high frequency spectrum                                   over the interval (specified in Hz/CPM).

So if the parameter type is HFD the upper and lower limits (if specified) are ignored -- you're just getting what's there above 5 kHz, which is where I'm finding the lube issues using a 10 kHz spectrum.

What I don't understand is how I can clearly "hear" the lube noise using my headphones, and can hear it dissipate when the grease hits the bearing, but I don't see a change in the 10 kHz spectrum.  If I'm hearing it, then the accel is seeing it, right?


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Noknroll

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Reply with quote  #7 
Quote:
you're just getting what's there above 5 kHz, 


Maybe the vibration is below 5KHz?
RustyCas

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Reply with quote  #8 
I'm taking an extra spectrum with a 10 kHz Fmax.  I have had HFD set up as a parameter on a number of machines, but have never looked at it - just have really never thought too much about it until I started using the headphones.  In backtracking and looking at the HFD trends, it's pretty interesting. Makes me wish I had understood - and used it - all along. 

I am trying to determine the best way to document the lubrication program that I am starting from scratch (19 large fan motors & 18 Centac compressors that have never been lubricated on any consistent basis).  I am experimenting with 10 kHz spectra/waveforms, HFD, and PeakVue.  I have not been as rigorous in my investigation as I should have been to this point but I'm not charging them yet, so no foul I guess.  I am adding 'static' (keypad input) points for the amount of grease added (digital grease gun) so that I have a record of when and how much grease I add and can reference that in the trends.

Pretty interesting stuff, and perhaps something that not many of us ever get to do with complete freedom.  But I think "lubrication as a service" is a great opportunity -- many plants are clueless about lubrication, in my experience.

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Noknroll

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Reply with quote  #9 
I take a 10KHz Fmax on most bearings, I also use it for live mode monitoring of lubrication when the situation arises, I don't do the actual greasing, but the clients Lubeys love seeing that haystack go flatline, they watch the analyser as the grease goes in, it adds a high tech aspect to there mostly mundane task.
I created a monster once where one particular lubey had a work order made for me to accompany him on his critical motor greasing route, we had one particular motor that regularly took a full cartridge to settle the raised noisefloor.
RustyCas

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Reply with quote  #10 
Nok, is that 10 kHz Fmax your "normal" spectrum, or do you take an extra spectrum on each bearing?  I will likely set up an extra point for each bearing since collecting 2 points takes only an extra second or two with the 2140.  Of course, it's extra data to deal with, but also increases the point count and lowers the cost/point (for the day a competitor finally comes calling).

"Over-greasing" seems to be their biggest fear.  A lot has been said/printed about that over the years.  Plus they think if they can't hold their hand on something it's "too hot".  But that's typically ony 140F, so not that hot.  I am proceeding cautiously.  If we get a motor failure after I've started greasing them, it's probably going to be "Rusty's fault."

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Noknroll

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Reply with quote  #11 
Rusty, I group 3 readings on most bearings, velocity, peakvue & a 10KHz acceleration.
fburgos

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Reply with quote  #12 
Do you take extra point with 10khz spectra? Or just hfd on PA?
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