Hi, thank you all very much for responding! It was my first time posting to a blog. After reviewing your comments, I did some additional research and found that “Peak” or “Peak-to-Peak” is a Calculated Peak not a True Peak. GM’s vibration standard makes a reference to this on page 11 in the link below.
The TRUE pk-to-pk value is often higher than the derived peak-to-peak value, and the conversion factors used to convert pk-to-pk into RMS cannot be used the same way for True pk-to-pk. It really depends on whether the motion is harmonic or non-harmonic. I tested this by evaluating an old displacement measurement.
I believe the True pk-pk shows the real severity in comparison to the derived pk-pk value. Unfortunately, most severity charts and industry standards use derived mils pk-to-pk or micrometer pk-to-pk units for displacement. I have not found severity charts that use True pk-pk units.
I prefer to reference industry standard severity charts so staff can see where I’m getting my alarm values. Therefore, this means I have to setup our displacement alarms in mils pk-to-pk units, or convert a severity chart to mils RMS.
Ali, (In regards to the 9 mils RMS)
After reviewing ISO 20816-5:2018, I found that our pump’s displacement alarms should fall within 270-310 micrometers pk-pk. This equals 10-12 mils pk-pk or 3.7-4.3 mils RMS. These values are within the contractor’s recommended True pk-pk values. Therefore, the 9 mils RMS alarm we currently have is too high.
Thank you all!
GM Vibration Standard (page 11) https://www.maintenance.org/fi...7/GMVibeStandard.pdf
Overall Vibration Measurements and True Peak (See pages 3 and 4) http://citeseerx.ist.psu.edu/v...ep=rep1&type=pdf