English
русский(1) The pressure display value is abnormal. Abnormal pressure value display is a common fault of pressure transmitters. In addition to the common zero drift and range migration problems, the causes include damage to components, sensor faults, line faults, electromagnetic interference, pressure tube/ Capillary problems, etc., need to be checked item by item.
(2) Components are damaged. It is necessary to consider whether there is a short circuit or open circuit caused by lightning strike, excessive voltage, wrong wiring or cable damage. If it is verified that the electronic components are indeed burned or physically damaged, the damaged components or cables should be replaced in time, and the instrument grounding system should be checked for problems and repaired and maintained in time. It is necessary to pay attention to whether there is water entering the instrument and causing corrosion of the internal electronic components. When the cable interface is not tightly sealed and the sealing ring of the transmitter is aging, it is easy to cause water to accumulate in the meter, resulting in damage to the internal components. At this time, the damaged components should be replaced, and the sealing treatment and inspection of the transmitter should be done well. In a certain project, due to the limited space on site, the cable entry position of the transmitter is installed upwards, resulting in the accumulation of water in the transmitter, which should be taken as a warning.
(3) Sensor failure. The diaphragm of the diaphragm pressure transmitter will condense on the diaphragm due to the crystallization of the medium, or the medium contains block solids that impact the diaphragm for a long time, resulting in deformation and damage of the diaphragm and affecting the measurement. At this time, the diaphragm should be replaced in time, and according to the actual working conditions, consider adding purging or adding a filter screen at the front end.(4) Line failure. Line faults are generally internal wiring, which can be checked by measuring resistance and voltage with a multimeter. Perform wiring operations according to the transmitter instructions to ensure the correct connection of the lines.
(5) Electromagnetic interference. This kind of fault is generally more difficult to troubleshoot, but the frequency of occurrence is very high. The signal cable of the instrument should not be placed in parallel with the electrical high-voltage signal cable, otherwise it is easy to cause signal interference, resulting in communication errors and inaccurate measurement values. Be sure to follow the standard requirements for distance control and shielding measures. The transmitter installation should also avoid locations with strong magnetic/electric fields or strong vibration sources.
(6) The problem of pressure tube and capillary tube. The pressure pipe problem usually occurs due to the characteristics of the medium, non-clean medium, or medium with high viscosity, which causes the blockage of the pressure pipe and cannot feedback accurate pressure values. Or the pressure tube may leak due to long-term use, resulting in measurement inaccuracy. If this happens, replace the pressure tube in time, and do regular cleaning and maintenance work. The capillary will have problems due to the inaccurate selection of the pressure oil temperature resistance. In low temperature conditions, it is necessary to select the appropriate pressure guiding oil to avoid the phenomenon that the pressure guiding oil solidifies due to the low temperature. Similarly, when it is necessary to pay attention to the high temperature, the pressure guiding oil should be avoided to vaporize.
From this topic, a case is drawn: in a project, because the medium is steam, the method of connecting the condensing ring to the transmitter is adopted, but it is ignored that the ambient temperature will reach below -30 °C in winter, which results in that although the medium is steam , but in winter, the liquid in the condensation ring is still frozen into ice, which makes the pressure transmitter unable to sense pressure. Therefore, it is reminded that when selecting and designing the instrument, it is not only necessary to consider the medium conditions, but also the actual use environment.
