Messrs. Forum:

Good morning, as I have seen in the different literatures with regard to the configuration of the Acceleration Envelope to detect faults in the bearings, you have to select the filter and then capture the data with the accelerometer, however, in the technique SKF Acceleration Envelope does the opposite, that is, it captures the unfiltered data with the accelerometer and then in its software they select the filters to find fault in the bearings, is this reliable or do you have to select the filters? Envelope of Acceleration and then capture the data with the accelerometer?.

Best regards.

Original Post

In my book it does not matter in what order the filtering comes or if it is analog or digital. It is a pure signal processing procedure you are looking for. If you have enough  dynamic in the A/D otherwise you may get more sensitivity by filtering first, in these days it should not be a problem. PeakVue was a pure software upgrade in the day but it could still be that they used existing analog filtering in the box.

I like to collect an acceleration spectrum with a high fmax (40kHz), just to identify the "haystack" or mound. Look for sidebands around this mound or "haystack". If the sidebands are equal to a bearing fault frequency, I then modify my envelope filter  so the "haystack" falls within that band.

Has been working very well for me for years.

I also use the 2000-5000 Hz filter for regular speed rotating equipment (900-1200-1800-3600 RPM) and it works very well also.

Hello jorgeluis-2000

This is really tricky and will vary vendor to vendor (tyoe of instrument used) on rolling element bearings.

Based on my experience with SKF and other products, the guidelines are as follows.

1. General filters will be high pass 500-1000Ha and low pass will be >10KHz. When set this values the evaluation of g values as below

<2g - New brg.
2 to 4 g- good condition.
4-15- started deteriorating early  - can run for 1 -3 month
>15 to 25g must plan for replacement ( within week)
>25g- can leads to secondary failure and need to stop immediately.

Basically the filter must be applied  considering the followings

2. 10x of running speed or 3x of impeller pass frequency or 3 times of GMF - are the criteria for high pass filter.

3.The low pass filter will be depends upon instrument capability , usually 10Khz is enough. When go >20Khz it picks up surrounding noise also. which may not be good for noisy environment.

I hope the above info may helps you.



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