Emerson Exchange 365

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Rosemount line pressure 3051 T

Dear all,
I have point pressure transmitter PT. When i accessed on hart i found the value is 140 psi but on plc (controllogix) is 114 psi. The ranges on transmitter and plc is 0 to 800 psi.when i isolate the transmitter from service and inject pressure by hand pump all values on hart and at ma is right with no deviation. When i put it in service but isolated it reads at hart 0 psi but at plc reads -60 psi. I inject plc channel found it passes the test without any deviation. At the end, i replace the transmitter, everything is ok and all readings are the same.I want to know what is happened to the transmitter? I mean can anyone show me what is the root cause of this problem...

hashem ali

• 31 Mar 2018 5:37 AM
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6 Replies

• salehatiyyat

  

  • 31 Mar 2018 12:26 PM

  Have you checked the 4-20mA outout? Maybe it needs to be calibrated.
  You can simulate a pressure value and measure the actual output

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• hashem ali

  

  • 31 Mar 2018 12:35 PM

  In reply to salehatiyyat:

  all this is ok and tested(put MA source series at the loop and inject with hand pump and hart already connected to transmitter then all reading at hart is accurate but at PLC is deviated) .At normal case, I wondered from how the transmitter reads at HART 140 PSi and at the same time at PLC is 114 PSI.

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• hashem ali

  

  • 2 Apr 2018 5:04 PM

  In reply to hashem ali:

  Any reply for my above issue

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• Michael Olivier

  

  • 2 Apr 2018 7:46 PM

  In reply to hashem ali:

  Hello,

  Based on the information that is provided, it is difficult to determine the root cause.  Some additional information that would be helpful:

  • What is the full model number and serial number for the 3051T transmitter?
  • How are you communicating to the transmitter via HART (475, TREX, AMS)?
  • When the transmitter was reading 140 PSI and the PLC was reading 114 PSI, which pressure reading did you think was the correct one?  
  • When you replaced the transmitter, was it replaced with an identical transmitter model number?
  • Were any wiring changes made when installing the new transmitter?  

  The information you provided earlier does not strongly indicate this to be a transmitter issue, especially as evident by the fact that it behaves as expected when you isolate the transmitter from service and apply pressure via the hand pump.  Rather, it sounds more like a wiring or PLC input channel issue.  It is difficult to further troubleshoot the transmitter given that it has been removed from service.  However, you could send the suspected transmitter to our Failure Analysis laboratory for more investigation.  Your local Emerson representative for Rosemount instrumentation should be able to assist with this if you are interested.  

  Best regards,

  Michael

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• hashem ali

  

  • 4 Apr 2018 11:59 AM

  In reply to Michael Olivier:

  Dear sir,
  please find below the required answers:
  
  • What is the full model number and serial number for the 3051T transmitter?Full model no.: 3051T-G-A-2B-21-A-B4-C6-Q8 and serial no.: 1676639
  • How are you communicating to the transmitter via HART (475, TREX, AMS)?Hart 375
  • When the transmitter was reading 140 PSI and the PLC was reading 114 PSI, which pressure reading did you think was the correct one? Hart reading as there is a pressure gauge connected to the same point of transmitter reads also 140 PSI.
  • When you replaced the transmitter, was it replaced with an identical transmitter model number?Yes
  • Were any wiring changes made when installing the new transmitter?No
  The information you provided earlier does not strongly indicate this to be a transmitter issue, especially as evident by the fact that it behaves as expected when you isolate the transmitter from service and apply pressure via the hand pump. Rather, it sounds more like a wiring or PLC input channel issue. It is difficult to further troubleshoot the transmitter given that it has been removed from service. However, you could send the suspected transmitter to our Failure Analysis laboratory for more investigation. Your local Emerson representative for Rosemount instrumentation should be able to assist with this if you are interested. (No as i inject PLC channel with the five calibration points without any deviation and at the transmitter is isolated the reading also at hart 0PSI but at PLC is -60 PSI)

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• Michael Olivier

  

  • 4 Apr 2018 9:14 PM

  In reply to hashem ali:

  Hello,

  I have further consulted with some of our Emerson experts.  Based on your responses, it is hard to pinpoint this as a transmitter issue, especially given that it appears to be reading correctly at both 0 and 140 psi, but the PLC reading is the one that is incorrect.  However, it is puzzling that the issue has gone away when replaced with a new device.  The reason for the mismatch between the device and the PLC could be due a wiring or grounding issue.  Some potential reasons:

  • Using supply voltage cable that is not twisted pair
  • Not having the cable shield properly landed at the power supply and isolated from the transmitter.  This could result in electrical interference.  We have seen instances where an electrical charge can be built up and maintained on the supply wiring.  And then when the wiring is disconnected, it dissipates the charge for a while until it slowly builds up again once the connection is re-established.  
  • Any new piece of equipment that has been installed near the transmitter could be generating transient voltage.  

  Other things to potentially consider

  • If you take the suspected unit and install it on a different application, do you have the same issue?  
  • If the replacement unit from the original application exhibits the same behavior over time, it may be worth evaluating the signal wiring.  

  I am glad that your installation is back up and running, but unfortunately I do not know there is much more we can do with remotely troubleshooting this apart from the above considerations.  Otherwise, sending the unit in to one of our Failure Analysis laboratories is also an option as earlier noted.  

  Best regards,

  Michael

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