Discrepancy between control room and transmitter indications
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1. The reading of the field transmitter for the inlet pressure of the main converter PT-009 is 3.09 MPa, while the display in the control room shows 3.04 MPA; previously, the readings were the same. The reading of the field transmitter for the outlet pressure of PT-010 is 3.09 MPA, and the display in the control room also shows 3.09 MPA； The field transmitter has the same range as that in the control room ； Using 475 and an ammeter to measure the current allows it to correspond with the readings shown in the control room ； After replacing the wiring connections for PT-009 and PT-010 at the safety barrier, the reading of the field transmitter for PT-009 was 3.09 MPa, while the display in the control room showed 3.04 MPA; the reading of the field transmitter for PT-010 was 3.09 MPa, with the control room display also showing 3.09 MPA.
It seems to be a problem with the PT-009 transmitter; let’s try replacing it...
It’s likely the PT-09 that has a problem; to determine exactly what the issue is, it’s necessary for the instrument technicians and DCS staff to conduct an on-site inspection!
You can solve it by replacing the power module of PT-009; I’ve encountered this kind of problem many times.
Based on your description, we can rule out the section from the field terminal to the site
Swapping them can confirm that there are no issues with the safety barrier and the card slot; you also need to check what the current values for 09 and 10 are. Calculate by yourself the current value corresponding to 3.09 MPa through range conversion. The output section of model 09 is likely to be faulty; for many brands of transmitters, the measurement and output functions are handled by separate circuit boards
I want to know which part’s input current you are measuring with the ammeter
I guess you only measured the current on the isolation barrier side, without measuring it on the side of the field instruments. If you had measured the current using the field instruments, it should have matched the 3.04 MPa value as well; therefore, the problem is still likely to lie with the field pressure transmitter.
I didn’t see it clearly just now; I took a closer look now. For this issue, you can simply perform the operation at normal pressure – setting it to 0 will do
I agree with your view. In many modern smart transmitters, the measurement and output functions are carried out by separate circuits. If the measured output current value of the transmitter corresponds to the value expected in the control room, then it is a problem with the measurement section of the smart transmitter; otherwise, it is a problem with the output section of the transmitter or with the transmitter as a whole.