Dear Friends;

I work at Thermal Power Plant. I have some RTD & TCJ at Boiler, Turbine and other place. I must test RTD and TCJ for calibration with a period. I have two questions: 1) What is your guideline for Calibration Period Interval? (2 years, 3 years, or depend on manufacture offer)

2) After TCJ installation I cannot access it for test. in this situation what is the guideline for Period interval?

i don't need any doc. about calibration way or other things. i want only the time of calibration that is practically used at another power plant or industrial
plant. if you know of a standard about this subject for example ISA, etc. please inform me.

thanks
masod

 

Hello Friend

I have asked this question before on the Alist and never got a definite answer. That has been some time ago and now I know a couple things about testing intervals. Basically it boils down to the application and how harsh and/or critical it may be. Ask yourself, does the temperature device monitor or control. Naturally the ones that only monitor are less critical. Many of the rtds I had to test were modified with a thermal well type connection so the process did not have to be compromized when testing. The loop could be put in manual during the test.

My experience does not include a TCJ testing and I cannot comment how to make those tests.

Hope that is some help.
Regards, Mark Ray

 

For TCJ problem it is better to have HART transmitter so that you can do the calibration remotely.

 

Be careful with the term "calibration" because it means different things.
Calibration can mean:
- Adjusting the reading from the sensor: "sensor trim"
- Setting a range corresponding to 4 mA and 20 mA
- Adjusting the current output of the transmitter circuitry: "current trim"

Only the second (Setting a range corresponding to 4 mA and 20 mA) can be done remotely on a HART or other fieldbus protocol transmitter.

However, I think this person is asking about the first (Adjusting the reading from the sensor: "sensor trim") there remote communication is not the solution since you must always apply a known input before you make sensor trim "calibration".

Always be wary of the expression "remote calibration".

For more information on calibration of intelligent transmiters take a look at chapters 4 and 9 of the yellow book "Fieldbuses for Process Control: Engineering, Operation, and Maintenance" buy online:
http://www.isa.org/fieldbuses

Jonas Berge
SMAR
===========
[email protected]
www.smar.com
Learn fieldbus and Ethernet at your own pace: www.isa.org/fieldbuses
Learn OPC and automation software at your own pace: www.isa.org/autosoftware