If an instrument is not working normally. what steps do you take to locate it on the DCS and isolate it?

Question

When an instrument such as a themocouple or an RTD is not functuioning properly, how do you locate it in the process DCS or PLC, isolate it and fix it. Please you can use general terms not specific to a particular type of DCS or PLC. In particular I would like to know how to get the address of that instrument and its configuration etc

Answer 1

Each instrument has a data sheet file on the DCS, where you state its calibration range, ID tag, function, location, alarm settings, and so on. If the instrument is part of a control loop, you cannot just take it out of service, because you would disrupt the process.

Only if it is an indicating instrument you can take it out of service. In order to take it out of service, you need to know the ID tag and look it up in the configuration files.
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Answer 2

Instrument connected to which system Is it effect the process or trip the process.Is it any stand by available if so isolate it,what is the condition if open, it may overshoot the temperature. whatever for replacement that particular system should be stopped.Example RTD in high voltage Motor showing erratic reading it should be stop & check the RTD junction box if there any open circuit in connection or RTD itself.Inbetween physical temperature raise available check with lasser temperature meter, running current is normal , Bearing loop system not blocked, a cobine checks are required by all the decipline and confirm the fault.The address of the equipment you have to find with drawing or temperature of which zone is abnormal like that only you can find it( DE Bearing temp ,NDE bearing temp or winding temp lijke that ).you can locate it with mouse in DCS screen.

Answer 3

If you mean that the sensor (the TC or rtd) itself is not working correctly, I know ot two things that are commonly done. For TCs, many PLCs will provide open circuit detection, which will alert you to a disconnected TC or a blown out junction. For RTDs (and for that matter any other sensor), you can program the PLC to alert you if the calculated measurement value is outside of expected boundaries. It is often called a "believability check". Hope this helps.