Sign up Calendar Latest Topics Donate
 
 
 


Reply
  Author   Comment  
adam615651

Member
Registered:
Posts: 25
Reply with quote  #1 
Hi.
I am a bit confuse with the concept of enveloping.
Can someone provide a good explaination of it and when do we need to use this for measurement?

Secondly, for Env 3 and Env 2 which one will be the most severe? I include a sample.

Attached Images
jpeg 20190508_094427.jpg (402.90 KB, 26 views)

MarkL

Avatar / Picture

Sr. Member
Registered:
Posts: 1,120
Reply with quote  #2 
With envelope 2 and 3 your looking at two different band pass filter ranges so hence get different results.
This may be of help. It's written by a far technically superior communicator than I.
I primarily use gE3 ( envelope filter 3) almost exclusively as it covers most of my particular applications with a standard 100mv/g sensor.

I would be curious to why both gE2 and gE3 are being taken at the same point? Did you set this database up yourself or based on a wizard or osmone else's creation?






http://www.maintenance-engineering.eu/downloads/public/envelope%20bearing.pdf
adam615651

Member
Registered:
Posts: 25
Reply with quote  #3 
Quote:
Originally Posted by MarkL
With envelope 2 and 3 your looking at two different band pass filter ranges so hence get different results.
This may be of help. It's written by a far technically superior communicator than I.
I primarily use gE3 ( envelope filter 3) almost exclusively as it covers most of my particular applications with a standard 100mv/g sensor.

I would be curious to why both gE2 and gE3 are being taken at the same point? Did you set this database up yourself or based on a wizard or osmone else's creation?






http://www.maintenance-engineering.eu/downloads/public/envelope%20bearing.pdf


Hi Mark.
By that, you mean Env3 is a wider range of frequency measurement?
By Env2 or Env1, it means the vibration had entered the lower range,hence the severity is more? It has entered the range where we can see the spectrum clearly on the plot?
OLi

Sr. Member
Registered:
Posts: 1,914
Reply with quote  #4 
When I used this way back as a consultant only taking 1 reading and writing a report I used both 2 and 3 rarely 1 as I could never really know from a unknown machine what filter would give data so having both and getting nothing increased the odds that it was a good bearing. If something did pop up in one but not the other then it was down to find out what it was and how bad. So I can see a reason to have both just in case. I have not seen the case where it moves down to lower filter ranges in connection to deterioration I think the filters are to wide but may be wrong, just didn't see that in my data, only increase in level and multiples. It may however anyway normally be seen in normal reasonably hi freq. range spectra before it fails if you look for it. 
__________________
Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
http://www.vtab.se
adam615651

Member
Registered:
Posts: 25
Reply with quote  #5 
Quote:
Originally Posted by OLi
When I used this way back as a consultant only taking 1 reading and writing a report I used both 2 and 3 rarely 1 as I could never really know from a unknown machine what filter would give data so having both and getting nothing increased the odds that it was a good bearing. If something did pop up in one but not the other then it was down to find out what it was and how bad. So I can see a reason to have both just in case. I have not seen the case where it moves down to lower filter ranges in connection to deterioration I think the filters are to wide but may be wrong, just didn't see that in my data, only increase in level and multiples. It may however anyway normally be seen in normal reasonably hi freq. range spectra before it fails if you look for it. 


So it means it is a normal practice to set two band which is for env3 and env2 when taking measuremeant.Is that what you mean?
I thought if we set the band for env3, automatically env2 band will also falls within the env3 band.
OLi

Sr. Member
Registered:
Posts: 1,914
Reply with quote  #6 
There was a difference when I used the settings anyway that was noticeable IRL and I don't think they changed them but may be wrong. Sometimes I got data in one slot or the other or neither. I am not so sure I recall seeing things in both so that may be more rare for me anyway. How common practice it may be, I have no idea it was not really proposed by the OEM. It may be connected to what type of machinery are your normal ones and if they do variable speed a lot maybe.
__________________
Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
http://www.vtab.se
MarkL

Avatar / Picture

Sr. Member
Registered:
Posts: 1,120
Reply with quote  #7 
Quote:
Originally Posted by adam615651


Hi Mark.
By that, you mean Env3 is a wider range of frequency measurement?
By Env2 or Env1, it means the vibration had entered the lower range, hence the severity is more? It has entered the range where we can see the spectrum clearly on the plot?



No, Each filter range is similar coverage scale just different parts of the spectrum, the gE3 is the one skf advocate for most common rolling element bearing defects. ge2 will show a bearing at the later stage of degreadatin...as a rule of thumb... I tend not to make decisions on gE alone and use it more so as an early warning tool as its very sensitive to consistent mounting and trending and a few mm's deviations per survey can show very different levels.

fburgos

Sr. Member
Registered:
Posts: 670
Reply with quote  #8 
Afaik envelope needs a resonant area "haystak" and away from any forcing frequency, different filters catch different resonant area
OLi

Sr. Member
Registered:
Posts: 1,914
Reply with quote  #9 

Well if the resonance excited by the bearing fault suddenly don't move or the pulses from the bearing change to another resonance I have a problem to see that a damage would move down to another filter range when damage are getting older unless you have another convenient resonance waiting there and it would not be the case so often. If you look at a standard spectrum it behaves like that but if your technology enhance the resonance amplified haystack it should not. What I have seen is that the signal do get reduced when the signal get lower as the damage ages, flats out and contain less higher and more lower frequencies but that is only what I have seen.

If you have simple parameters that are just filters (True RMS rectified naturally) and no more they behave like that. I normally use one that is a HP 2kHz and another that is HP 600Hz and they behave exactly like that damage first give a hi HP 2kHz reading and when damage ages it get lower again and the HP 600 increase but that is not envelope treated parameters, those are just filtered signals one way or another. So that is what I have seen, repeatedly.


__________________
Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
http://www.vtab.se
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.