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I would like to know, how other start to troubleshooting for example a valve is not moving or instrument is reading different than what is expecting
In Instruments Field there are 5 Basic Elements which control an instrument.
1. Power supply
2. Instrument itself
3. Calibration of instruments
4. PLC
5. Testing & calibration tools
Now if an instruments Fails , the possible cause of failure is one or more of the above elements.
First step : Always use precise and healthy testing tools
2nd step : Check the power supply
3rd step : Check the calibrated data through meter
4th step: If the calibration is OK or not OK, in both the cases at least once calibrate the instrument again
5th step: Problem solved? Yes- its ok if NO then Remove the power supply and check the instrument physically.
6th step: If the instrument has become faulty replace with new and if repairable, repair first and then calibrate and power up again.
Hope full all is correct now.
1. Ask the operator about the problem.
2.run the machine (if possible) and observe the problem.
3.Ask about the history of the fault , like when was the last time the machine was working properly ? , who the first person observe the problem and what did he see ?
4.start tracking with power circuit.
5.start tracking with control circuit and track the signal from up to bottom
for example ;
A.check the programming
B.check that the signal is come out from PLC or the controller.
C.check that the signal is delivered to the valve or the faulted component.
Finally , I detect the fault and repair it .
Simply follow the method of elemination rest the Tariq Ayaz has given very detail answer of the question.
The Basic Protocol of trouble shooting is
1. Observation
2. Define Problem Area
3. Identify Possible Causes
4. Determine most probable cause
5. Repair and Test
Verify that a problem actually exists.
Isolate the cause of the problem.
Correct the cause of the problem.
Verify that the problem has been corrected.
Follow up to prevent future problems.
Verify in field first, Valve whether moving or not. (dont beleive reading in DCS)
Check Air supply, Check Control signal 4-20 or HART.
Check Solenoids if Shutdown valve.
Check DO or AO card in system (Fuse) if above all are ok.
Reg Instrument reading
Check real process valuve with local guage.
Check AO scale in transmitter.
Check AI scale in DCS
we need to chceck the Proper Specficatication of the valve
1. Listen carefully to the trouble reporter to understand the trouble well and make right analysis.
2. Prepare the technical supported documents for troubleshooting (SLD, PID, Wiring diaghram, manuals, . . .etc)
3. Sit with the team to list down all causes (fish pone) .
4. Eliminate the un-doubted (impossible) causes.
5. Work around the doubted (possible) causes.
6. Plan for the troubleshooting sequence (try to start by the easier/fast ways of troubleshooting).
7. After trouble solving, document the trouble by clear good reporting with all proper attachments ( sketches, drawings, photos, . . .etc)
Within the four general guidelines previously mentioned, there are several action items that are important to the successful achievement of the goal of troubleshooting:
1) Record the failure or malfunctioning. Check the process logs for the parameters reading.
2) Check the power supply., air supply, fuses, cables, connections in the circuit for their healthiness.
3) Individually check each component of the circuit for their functinality.
4) Verify with their calibrated functioning.
5) Identifying the faulty component.
6) Replacing or reparing the component.
7) Puting componenet back in process and testing.
