Abstract: This paper introduces detailed troubleshooting methods for typical faults of the EJA intelligent dual-flange differential pressure transmitter, focusing on its specific application. Practice has proven that only proper use and maintenance can ensure the long-term stable operation of the instrument. Keywords: Intelligent transmitter, fault, communication 0 Introduction Compared with conventional transmitters, microprocessor-based field intelligent transmitters have the characteristics of high accuracy, high reliability, good stability, wide measurement range, and large range ratio. They not only have data communication functions with DCS systems or field communication controllers and setters with the same communication protocol, but also functions such as modifying and setting various parameters of the intelligent transmitter, realizing remote adjustment, input dialogue, and online monitoring. Like all intelligent instruments, intelligent transmitters also have relatively complete self-diagnostic functions. 1 Typical Faults of EJA Intelligent Dual-Flange Differential Pressure Transmitter The EJA intelligent dual-flange differential pressure transmitter is a product of Yokogawa Electric Corporation of Japan. At Fushun Petroleum Plant No. 1, this product is widely used for level measurement in towers, tanks, and containers. During use, improper operation has caused many faults, seriously affecting the normal use of the instrument. The author conducted extensive analysis and research on actual faults, and found that the faults mainly fall into the following three categories: ① No display value caused by measurement exceeding the limit. ② Incompatibility with safety gates, resulting in no measurement signal or a low signal in the circuit. ③ Inability to communicate with DCS. 2 Typical Fault Handling Methods 2.1 Handling Methods for Measurement Exceeding the Limit Through research and analysis, it was found that this type of fault is usually related to the following factors: ① Improper instrument operation Taking the C-101 level control system (LICA-1201) of the ketone-benzene unit of Fushun Petroleum Plant No. 1 as an example, as shown in Figure 1, if the instrument is always running at a high liquid level (above 100%) or always running at a low liquid level (below 5%), the instrument may indicate an over-limit reading. Therefore, process operators are required to be able to correctly judge whether it is an instrument fault or improper process operation based on the process flow and process control requirements. Therefore, close cooperation between process personnel and instrument maintenance personnel is needed to ensure that the process medium is within the measurable range of the instrument, and to avoid operators mistakenly believing that the instrument is faulty. [align=center]Figure 1 C-101 Liquid Level Control System Process Diagram[/align] ②Inappropriate Instrument Range Selection During the inspection of the measurement range of the EJA intelligent dual-flange transmitters in the ketone-benzene unit of this plant, design calculation errors were found in the transmitter ranges. For example, when checking the ranges of transmitters such as LICA-1201 on the DCS engineering station, it was found that the dual-flange range had no migration. This is an important reason for inaccurate instrument measurements and exceeding limits, as shown in Figure 2. [align=center]Figure 2 Tower 101 Range Calculation Parameter Diagram[/align] The original design used a range of 0～19.71kPa, without range migration. Therefore, the measurement results were outside the instrument range, resulting in measurement exceeding limits. Therefore, only by calculating according to the correct calculation method and referencing the migration amount can the accuracy of the instrument range be guaranteed. 2.2 Incompatible Safety Gate Causing Instrument Output Defects and Inaccurate Measurements Since intelligent transmitters require the use of compatible safety gates, using safety gates without the necessary certification for use with intelligent transmitters often leads to various problems. The main faults include: ① Excessive voltage drop across the safety gate, with the entire circuit voltage below 16.4V, resulting in insufficient power supply to the transmitter and the circuit failing to operate, as shown in Figure 3. [align=center]Figure 3 Relationship between EJA Intelligent Transmitter Power Supply Voltage and Load Resistance[/align] The dashed area indicates the range within which the instrument can operate normally; the external resistance should be between 250 and 600 ohms. Sometimes the measurement circuit resistance is >700 ohms, causing measurement deviations or even transmitter malfunction. ② Lack of intrinsically safe grounding on the safety gate causes large common-mode interference signals, leading to abnormal operation of the intelligent transmitter. Taking the P+F Z787H used in the ketone-benzene plant as an example, the correct connection is shown in Figure 4, but it was found that sometimes the safety gate was not grounded, resulting in no transmitter output. [align=center]Figure 4 Connection method between safety gate and intelligent transmitter/DCS[/align] ③Although there is compatibility certification between instruments, an intrinsically safe safety gate was selected when a transformer-isolated safety gate should have been used. This resulted in insufficient power supply voltage and lack of independent power supply, leading to poor anti-interference capability and causing the transmitter to malfunction. Therefore, selecting a suitable, certified safety gate is also a necessary condition to ensure the normal operation of the transmitter. 3 Communication failure with DCS Generally speaking, the management, configuration, uploading, and downloading of all intelligent transmitters can be accomplished through the DCS. Among instrument failures, most are caused by improper internal parameter settings, and the parameters of intelligent transmitters are configured through communication on the DCS operator station. Therefore, their communication with the DCS is extremely important. Most of the EJA transmitters used in this factory communicate with the CENTUM-CS system. Its ICS operator station can communicate with the field intelligent transmitters through the FCS field control station to configure the transmitter's measured values, range, self-diagnostic information, and tag number, as shown in Figure 5. In actual production, if a communication failure occurs between the transmitter and the DCS, it will cause significant inconvenience for instrument maintenance personnel to check instrument parameters and faults, and may even prevent the transmitter from functioning properly. [align=center] Figure 5 Schematic diagram of communication between DCS and intelligent transmitter[/align] 4 Conclusion The EJA intelligent dual-flange differential pressure transmitter is a relatively advanced intelligent instrument with powerful functions and high reliability. With proper use and maintenance, it can maintain long-term normal operation, thereby effectively ensuring the measurement accuracy and reliability of the entire control system.