Differential pressure type pressure transmitters in daily maintenance and fault diagnosis

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Industrial automation instruments are devices used in the industrial production process to monitor, display, record, or control process parameters. Monitoring the industrial production process is a fundamental means of understanding and controlling it. Only by being able to accurately understand the overall situation of the process at all times and exercise control over it can production proceed smoothly, enabling the manufacture of qualified products with high productivity and low consumption. As a manufacturer of Hua Heng transmitters, it has developed two core technologies: sensors and smart circuit boards. It not only possesses full control over the core component technologies for all its products, but also continues to improve the accuracy of its industrial automation instruments, raising it from 0.2 grade to 0.1 grade. Other products for measuring flow rate and temperature can also be developed by extending the core technologies already in possession. When performing routine maintenance on differential pressure type pressure transmitters, the following points should be noted: 1. Do not apply a voltage higher than 36V to the differential pressure type pressure transmitter, as this may cause damage to it ； 2: Do not touch the diaphragm with hard objects, as this may damage the isolation diaphragm ； 3: The medium being measured must not freeze; otherwise, it will damage the diaphragm of the sensor elements, leading to damage to the differential pressure type pressure transmitter. Where necessary, temperature protection for such transmitters is required to prevent freezing ； 4: When measuring steam or other high-temperature media, their temperature should not exceed the maximum temperature limit for use with differential pressure transmitters; if the temperature is higher than this limit, a cooling device must be used ； 5: When measuring steam or other high-temperature media, a heat dissipation tube should be used to connect the differential pressure transmitter to the pipeline, and the pressure in the pipeline should be transmitted to the transformer. When the medium under test is water vapor, an appropriate amount of water must be filled in the heat dissipation tube to prevent overheated vapor from coming into direct contact with the differential pressure transmitter, thereby avoiding damage to the sensor ； 6: During pressure transmission, the following points should be noted: a) Ensure there is no air leakage at the connection between the differential pressure type pressure transmitter and the heat dissipation tube ； 　　b. Before starting use, if the valve is closed, it should be opened very carefully and slowly during use, in order to prevent the medium being measured from directly impacting the sensor diaphragm and thus damaging it ； c. The pipeline must remain unobstructed; deposits in the pipes can be ejected and damage the sensor diaphragm ； Methods for checking faults in various components of differential pressure type pressure transmitters I. Inspection of the measuring section of differential pressure type pressure transmitters Faults that occur in the measuring section of differential pressure type pressure transmitters can cause no output or abnormal output from the transmitter; therefore, it is necessary to first check the sensitive components used for measurement in such transmitters. 　　1. Remove the flange and check whether the diaphragm of the sensitive component is deformed, damaged, or leaking oil. 　　2. Remove the compensation plate without taking out the sensitive components, and check the insulation resistance between the pins and the housing; at a voltage not exceeding 100V, this insulation resistance should be no less than 100MΩ. 　　3. Connect the electrical and gas circuits; when the pressure signal reaches the upper limit of the range, shut off the gas supply, and the output voltage and reading value should remain stable. If the output voltage drops, it indicates that there is a leak in the differential pressure pressure transmitter, and the location of the leak can be identified using soapy water. 　　II. Inspection of the circuit part of the differential pressure type pressure transmitter 1. Turn on the power supply, and after applying the specified input pressure signal, check the status of the voltage signal at the output terminal of the differential pressure type pressure transmitter. If there is no output voltage, check first whether the power supply voltage is normal ； Does it meet the power supply requirements? ； Check for any wiring errors between the power supply, the differential pressure pressure transmitter, and the load equipment. A lack of voltage at the terminals of a differential pressure pressure transmitter, or an incorrect polarity, can both result in no voltage signal being output by the transmitter. If the above reasons are ruled out, further inspection should be carried out to check for any damage to the components in the amplifier board circuit ； To check for poor contact in the circuit board connectors, one can compare the measured voltage with a normal instrument to that of the faulty instrument, in order to identify the fault point; if necessary, the faulty amplifier board can be replaced. When inspecting flow-type and differential-pressure type pressure transmitters, special attention should be paid to taking anti-static measures for the J-type amplifier board. 　　2. After powering on and applying a given input pressure signal, if the output of the differential pressure type pressure transmitter is too high (greater than 10VDC) or too low (less than 2.0VDC), and there is no change in the output even after altering the input pressure signal as well as adjusting the zero and range screws. For such faults, in addition to checking for any abnormalities in the sensitive components of the measuring section of the differential pressure type pressure transmitter, it is also necessary to verify whether the \"oscillation control circuit\" on the amplifier board of the differential pressure type pressure transmitter is functioning properly. The normal peak voltage between high-frequency transformers T1-12 should be 25~35 VP-P ； The frequency is about 32kHz. Next, check the operating condition of each operational amplifier on the amplifier board ； Check for any damage to the components in each part. Such faults require the replacement of the amplifier board. 　　3. Differential pressure type pressure transmitters have very strict requirements regarding circuit design and manufacturing quality. In actual use, in the event of circuit failures, it is advisable to contact the manufacturer to have the faulty circuit board replaced after verification, in order to ensure the stable and reliable operation of the instrument over the long term. 　　III. On-site Fault Inspection 　　The vast majority of faults that occur at construction sites are caused by improper usage and installation methods, which can be summarized into several categories. 　　1. Blockage of primary components (orifice plates, remote sensing connectors, etc.) or incorrect installation, as well as unreasonable pressure tapping points. 　　2. Leakage or blockage in the pressure lead pipe, residual gas in the filling pipe or residual liquid in the filling tube, as well as deposits in the process flange of the differential pressure pressure transmitter, all create a measurement dead zone. 　　3. The differential pressure type pressure transmitter is wired incorrectly, the supply voltage is too high or too low, or there is poor contact at the connection between the indicator gauge and the instrument’s terminal connections. 　　4. It was not installed in strict accordance with the technical requirements; the installation method and the on-site environment did not meet those technical specifications. Hua Heng Transmitter Manufacturer’s Understanding of the Spirit of Craftsmanship ； The true essence of the craftsman spirit is to dedicate one’s life to doing one thing well, and thus one inevitably becomes a ‘craftsman’. ”In the view of manufacturers of Hua Heng transmitters, it is not too difficult to dedicate one’s entire life to a particular industry; their generation was one that loved what they did and focused on doing their job well. Indeed, when technology or an industry is in its early stages, we strive to master everything. But as the industry progresses and enters more complex phases, both individuals and companies need to delve deeper, mastering a core technology and becoming experts in it, just like Huabian Transmitter manufacturers, who manage to \"deal with all changes with constancy.\" Leveraging its core technologies in sensors and smart circuit boards, Huahuan Transmitter Manufacturers is able to modify these core technologies at low cost to meet customer requirements, thereby enabling the creation of customized products. The main products include the SMART series of pressure transmitters, multi-parameter transmitters, flow meters, temperature sensors, and level sensors. As a manufacturer of level transmitters, it supplies industrial automatic transmitters with a high performance-to-price ratio for industries such as electricity, petroleum, chemicals, metallurgy, cement, and mining in China; the information was provided by Huaheng Transmitter Manufacturer