Intelligent pressure transmitter fault judgment analysis

Abstract: Intelligent pressure transmitters are increasingly used in chemical companies. In the actual use of intelligent pressure transmitters, various faults or problems often occur. Only by correctly judging the faults of intelligent pressure transmitters can we properly handle them based on comprehensive analysis. fault, effectively improving the stability and accuracy of the intelligent pressure transmitter. This article mainly analyzes the fault judgment method of intelligent pressure transmitter through three fault handling cases of intelligent pressure transmitter.

Currently, with the continuous improvement of my country's automation level and industrial monitoring and control technology, intelligent pressure transmitters are increasingly used in the refining and chemical industry to ensure the stability and accuracy of pressure monitoring data. , timely handling of intelligent pressure transmitter faults will help ensure the stability and safety of the device, and at the same time, it can also reflect the true technical level and work ability of the personnel maintaining the instrument.

1 Method to judge the fault of intelligent pressure transmitter

The output signal of the intelligent pressure transmitter used in the refining and chemical equipment is connected to the DCS system through a cable, and the operation Personnel monitor the on-site pressure of the device through the DCS system operating station. When a fault occurs in the intelligent pressure transmitter, the DCS operating station will display that the measured value is too high or too low, or the measurement loop IOP (-) alarm will appear. When handling a fault, you must first determine whether it is a fault with the on-site instrument or the DCS system. If it is an on-site instrument failure, then it is necessary to conduct a comprehensive analysis of the actual situation of the instrument failure, and take corresponding processing measures according to the characteristics of the instrument used; if the fault detection result shows that it is a DCS system failure, the system needs to Maintenance personnel will cooperate with the problem.

2 Troubleshooting Case Analysis of Intelligent Pressure Transmitter

2.1 Fault of high pump outlet pressure value

2.1.1 Fault phenomenon

2.1.2 Troubleshooting

The instrument maintenance personnel first went to the site to confirm and found that the value displayed on the LCD screen of the transmitter's on-site meter was the same as the value displayed on the process site pressure gauge, but the DCS The system display value is 0.15MPa too high. The standard current signal is output on site and the displayed value in the test DCS system is normal, so it is judged that the fault occurs in the on-site instrument. Through the handheld terminal of the intelligent pressure transmitter, it is found that the measured value is the same as the value displayed on the transmitter meter. Calculate the output current through the measured value and measurement range, and find that the calculated current value is lower than the actual output value, so the fault occurs in the transmitter output circuit. After replacing the transmitter output circuit board, the pressure transmitter was recalibrated, and the pressure display in the DCS system returned to normal.

2.2 Low fuel gas pressure value fault

2.2.1 Fault phenomenon

The fuel gas pressure is sent to the SIS system through the three-select-two mode for interlocking protection, and the pressure signal is displayed on the in the DCS system. The device operator reported that a pressure transmitter showed a low value.

2.2.2 Troubleshooting

When we went to the site for troubleshooting, we found that the field meter display of the faulty transmitter was the same as the display value in the DCS system, indicating that there was a problem with the field instrument. . Since the pressure has a relatively stable deviation, the following three conditions can be considered during the treatment process: the lichen type is that the on-site pressure pipeline contains water, the second type is that the transmitter is damaged, and the third type is zero point drift. Some liquid was found in the discharge pressure line. After discharge, the three pressure transmitters displayed basically the same value.

2.3 No display of the top pressure of the distillation tower

2.3.1 Fault phenomenon

The operating staff reported that there was no display of the top pressure of a certain distillation tower.

2.3.2 Troubleshooting

The instrument maintenance personnel first checked at the DCS operating station and found that the pressure control loop displayed IOP- (that is, the signal received by the DCS system was lower than 4mA) , indicating that the pressure measurement circuit may have an open circuit or short circuit fault. Looking at the on-site wiring test of the DCS control cabinet, the fuse terminal light of the terminal block is on, and the test results show that the fuse has been blown. After replacing the fuse, the pressure measurement is normal, but the fuse blowout occurs again after a period of time. This indicates a short circuit or ground fault in the measuring line. Remove the on-site wiring of the control cabinet and use a multimeter to measure the grounding of the positive and negative wirings. It is found that the negative terminal wiring is short-circuited to the ground, indicating that the negative terminal wiring is grounded. By checking the main cable and branch cable, the graphic and text dynamic synchronization contest.