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Shurafa

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Reply with quote  #1 
Calibration of Online Loops

Hello everyone.

I'd like to hear from you about your practice when it comes to checking the plant online monitoring and protection systems. Im primarily referring to vibration, position, bearing temperature and speed.

I guess many of us have an existing procedure on the portable data collectors. Some perform the calculations very seriously in house or with an assistance from an outsider.

I rarely heard from others on a regular calibration checks for their online systems.


What do you do at the facilities you work for? Do you issue formal certificates? What levels of verification do you have to ensue the calibration checks are adequately done?

Do you have lessons learned from your experience to be shared?

Regards- Ali M. Al-Shurafa
OLi

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Reply with quote  #2 
When working in  a Nuke all sensors and complete signal channels were tested every year and calibrated only confirmed by signing work order and maybe some numbers in a file.
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Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
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Shurafa

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Reply with quote  #3 
How about other industries?
OLi

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Reply with quote  #4 
I doubt they care unless the readings go crazy, possibly petrochemical at least offshore I know they check the Bently systems sometimes as they trip the machine.
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Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
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Shoveldr

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Reply with quote  #5 

For the most part you are just verifying calibration, not actually calibrating.  

The online systems I deal with have internal calibration verification for the hardware.

On larger systems its not practical to remove all the sensors and send them off for calibration, in some cases you may take a portable shaker out to confirm the signals from the probes are good, but normally I only see that when they are questioning the accuracy of the readings.

For displacement probes it is often impossible to remove the probes without major disassembly, what I've seen done where calibration is a concern is they unplug the probe from its driver, plug in a spare probe and attach it to a wobulator, the wobulator really isn't a calibrated source, but you can confirm frequencies and increase the vibration and see if the system is tripping off when the displayed values exceed those levels.

On major outages they will do linearity curves on the probes.

 

Shurafa

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Reply with quote  #6 
Shoveldr,

I completely agree with you on the necessity to distinguish between a calibration and a calibration check. In fact, in the company where I work we have a formal procedure for portables. After a long debate, the title was changed to calibration check instead of calibration based on the difference you highlighted.

For shaft relative probes, couldn't you use the shaker to verify the signal? Wobulators (at least the ones I used) do not give reliable vibration amplitudes.

Regards- Ali M. Al-Shurafa
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