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Shurafa

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Low-Temperature Alarms

This is not about vibration but I thought I might fit best here.

At your facilities do you use a low bearing temperature alarms?

Typically, the rotating equipment are monitored against hight bearing temperatures. If a temperature loop is faulty, it could show abnormally low reading but operators do not (at least in my world) pay a lot of attention to a low reading as long as there no alarm. Lower temperatures are not too bad, they may think.

Please share your experience and your practice.

Regards- Ali M. Al-Shurafa



ivibr8

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Posts: 163
Reply with quote  #2 
I worked on navy equipment and we had an RTD panel in Manuevering for data collection.
I believe (not 100% sure) any data not within an expected range was cause for a "flag".

You said it yourself, "If a temperature loop is faulty, it could show abnormally low reading but operators do not (at least in my world) pay a lot of attention to a low reading as long as there no alarm."

I would interpret that to mean "If a temperature loop is faulty, it could show abnormally low readings that indicate an abnormality in the detection system". 

In addition to the shipboard panel, we monitored numerous unmanned systems in which abnormal temperatures (both hi and low) told us that the crimp, connection, sensor, etc. was bad and needed replacement.   So on the remote thin clients' alarm page, we edited the PLC code to establish acceptable temperature ranges (again, both hi and low) when the system was in normal operation.

Hope this helps

regards
Jim P
Shurafa

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Posts: 310
Reply with quote  #3 
Thanks for sharing your experience.

For the typical systems we have in the mill here, not all temperature faults are detected by the system. So, many points turn faulty undetected, if the fault does not generate a high reading. In fact, many temperature loops in my site show low readings when they are crazy.

So, based on your experience how do you sit the lower limit in your "expected range" for these RTDs?

Regards- Ali M. Al-Shurafa
ivibr8

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Posts: 163
Reply with quote  #4 
Unfortunately all of my troubleshooting notes and data are at the navy training site where I worked prior to being retired....so i am going by memory which fades with time   [confused].

The main point I was making was that we used our PLC's Historian database to "data mine" and determine an appropriate temperature range when the system was in normal operation.

We also used it to look at past data to view the output readings prior to failures to help us correlate the type of failure. Since we used both RTD's and thermocouples I may be mixing up details of the low readings between the two.

I did find a good article on I&C temperature readings that may be of benefit to you.


http://www.burnsengineering.com/local/uploads/content/files/Troubleshooting%20RTDs%20and%20Thermocouples%202-14-18.pdf


 
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