Fault diagnosis and analysis of intelligent pressure transmitter
Intelligent pressure transmitters are widely used in the chemical industry. In the application of intelligent pressure transmitters, various faults or problems are often encountered. Only when the fault of the intelligent pressure transmitter is correctly determined can the fault be correctly handled on the basis of comprehensive analysis, and the stability and accuracy of the intelligent pressure transmitter can be effectively improved. This paper takes the intelligent pressure transmitter 3 fault treatment as an example to discuss the fault diagnosis method of the intelligent pressure transmitter.
At present, with the continuous improvement of automation level and the application of industrial monitoring technology, more and more intelligent pressure transmitters in the refining and chemical industry ensure the smooth and intelligent processing of pressure monitoring data. Ensure transmitter failure and ensure equipment stability and safety. At the same time, it can also reflect the actual technical level and working ability of maintenance personnel.
1. Determine the fault of the intelligent pressure transmitter.
The refinery uses a smart pressure transmitter and the output signal is connected to the DCS system via a cable. The operator monitors the site pressure through the DCS operator station. When the smart pressure transmitter fails, the DCS operator station will display the high and low measurements of the measurement loop or IOP(-) alarm. When dealing with a fault, first determine if the field instrument is faulty or if the DCS system has failed. If the field instrument fails, the actual situation of the instrument failure must be comprehensively analyzed, and corresponding measures should be taken according to the characteristics of the instrument used. If the fault detection result indicates that the DCS system has failed, the system maintenance personnel must process it.
2. Intelligent pressure transmitter example analysis
2.1 Pump outlet high pressure value.
The pressure at the outlet of the ethylene plant pump of the chemical company indicates that the pressure display value of the DCS system is higher than the on-site pressure gauge of 0.15 MPa. The display value of the DCS system is higher than the display value of 0.15 MPa.
The instrument maintenance personnel first arrived at the site to confirm that the LCD display value was the same as the process site pressure gauge display, but the DCS system display value was 0.15 MPa. The standard current signal is output on site and the DCS system displays normal values to determine field instrument failure. Through the manual of the intelligent pressure transmitter, the measured value is the same as the display value of the transmitter. The output current is calculated based on the measured value and the measurement range. The results show that the calculated current value is lower than the actual output value and the fault occurs at the transmitter output. After replacing the transmitter output circuit board, check the pressure transmitter again and the DCS system pressure returns to normal.
2.2 The gas pressure value has failed.
2.2.1 Failure phenomenon.
The gas pressure is sent to the SIS system for interlock protection by three options, and the pressure signal is displayed in the DCS system by communication. The equipment operator reflects the low value of the pressure transmitter.
When the fault was handled in the field, the head of the faulty transmitter was found to be the same as the displayed value in the DCS system, indicating that there was a problem with the field instrument. Due to the stability of the pressure deviation, the following three situations can be considered in the processing: one is the moisture content of the field pressure tube, the other is the damage of the transmitter, and the third is zero drift. Drain the pressure line to find some liquid. After discharge, the three pressure transmitters display the same value.
2.3 The pressure at the top of the distillation column did not show a failure.
2.3.1 Failure phenomenon.
The operator did not reflect the pressure at the top of the tower.
The instrument maintenance personnel first reviewed the DCS operator station and found that the pressure control loop showed IOP- (ie, the received signal of the DCS system was less than 4 mA), indicating possible circuit breaker pressure measurement circuits or short circuit faults. Check the field connection test of the DCS control cabinet. The terminal indicator is on the safety terminal indicator. Test results show that insurance has been integrated. After replacing the fuse, the pressure is measured normally and a fuse appears after a period of time. This indicates a short circuit or ground fault in the measurement line. Remove the field wiring of the control cabinet, measure the connection between the positive and negative poles and the multimeter, find the connection between the negative pole and the grounding short circuit, and display the negative grounding phenomenon. After checking the main cable and branch cable, it was found that the cable connection at the connection of the main cable junction box was damaged, and the pressure was normal after processing.
In summary, smart pressure transmitters are used in a variety of refineries and may have multiple types of faults. In order to solve the possibility of malfunction of the intelligent pressure transmitter, the instrument maintenance personnel should master the diagnostic method of the intelligent pressure transmitter, so that the intelligent pressure transmitter can be maintained with a more scientific, simpler and intelligent instrument. CE personnel are conducting at the same time. The ability of the pressure transmitter to fail can also increase the practical effectiveness of the smart pressure transmitter.
Xi’an Huaheng Instrument Co., Ltd., located in Xi'an National Hi-Tech Enter Prises Accelerator , is a manufacturer and supplier committed to the research and production of intelligent pressure transmitter.
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