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source: Level gauge http://yunrun.com.cn/product/list_87.html 1. Failure of the float level gauge of the water treatment decarbonization tower ◆Fault phenomenon: The liquid level of the 4# carbon removal tower suddenly dropped. When the instrument liquid level indicated 60%, the process glass plate liquid level gauge indicated 80%. This meter was running in the automatic state. Due to the lowering of the liquid level indication, the regulating valve continued to close, causing the actual liquid level of the system to continuously increase. ◆Fault analysis ① With the adjustment of the regulating valve, the liquid level changes linearly, indicating that the regulating valve is normal. ②Check the process glass plate liquid level gauge. The change is consistent with the actual liquid level, indicating that the process system is relatively stable. ③Check the electrical components on the instrument measuring panel for damage. ④Check the condition of the pontoon connection and the inner pontoon. ◆Troubleshooting ① Check the electrical components on the measurement board to see if there is any obvious burnt or damage. ②After water calibration, it was found that the zero point and range changed greatly every time the water was filled for calibration. It was determined that there was a problem with the inner float. The inner float was pulled out for inspection. The inner float was corroded and leaked in many places, and water entered. ③Replace the inner floating block and re-verify that it is normal. 2. Failure of the float level gauge in the coking oil seal tank ◆Fault phenomenon When the float level gauge is adjusting the liquid level in the oil seal tank normally, the meter always indicates 83% unchanged. Since the liquid level of the meter has an adjustment function, its erroneous indication causes the adjustment of the regulating valve to malfunction, thus causing great fluctuations in production. ◆Fault analysis ① When the float level meter transmitter is operating normally, the float medium is wax oil. When the wax oil is in liquid state, the temperature is 90°C to 100°C, and the self-condensation phenomenon occurs at about 50°C. Therefore, the float transmitter is equipped with heat tracing all year round. If the heat tracing fails and the temperature drops, the wax oil in the float will self-coagulate and block the float. At this time, even if the actual liquid level occurs, the float level gauge cannot measure the change in liquid level and the output value will not change. ②Go to the site to inspect the floating liquid level transmitter: close the primary valve and open the vent valve. The medium cannot be discharged after taking condensate recovery measures, and it is suspected that dirt has blocked the anti-air valve. After removing the anti-air valve, it was found that the process medium was condensed in the cylinder and could not be released. At this time, the heat tracing was checked. The temperature of the air inlet pipe was very high, about 100°C, but the temperature of the return pipe was about 30°C (the on-site temperature was about 10°C at the time). At this time, it was determined that the process medium was condensing due to poor heat tracing, leading to a malfunction. ③Check the heating system of the meter. Since the air inlet pipe of the meter is very hot and the temperature of the return pipe is low, it is suspected that the water trap is clogged. There is no problem after disassembly and inspection. The heat tracing was put back in, but the return pipe was not hot and the problem was not solved. Recall that this heating air intake pipe leaked many times in winter, but this phenomenon did not occur after treatment. It is suspected that the heating gasket of the float level gauge has blocked the air inlet due to repeated extrusion. ④Stop the air inlet heating valve, open the float level gauge heating pad plug, and find that the steam comes and goes. Therefore, it is judged that the fault is that the air inlet gasket is clogged, causing the wax oil to self-condensate, and the indication fails. ◆Troubleshooting: Open the heating air inlet joint of the float level gauge, dispose of the gasket, and turn on the heating. The liquid level indication is normal. ◆take measures: Check the heat tracing of the meter regularly. If leakage or blockage of heat tracing is found, troubleshoot in time. 3. There is no indication of the liquid level in the steam condensate recovery tank. ◆Fault phenomenon There is no indication of the liquid level of the steam condensate recovery tank. ◆Cause of failure: ①LT-8701-1 transmitter failure; ②The process flow is not connected, resulting in no liquid level in the tank. ◆Treatment method: After on-site inspection, it was confirmed that the float level gauge was faulty. The drain valve of the float was opened, but no condensate flowed out. After removing the floats and opening them, it was found that the tank had not been cleaned due to long-term use, causing a large amount of impurities in the tank to fill the float, causing the float level gauge to be unable to be used normally. After cleaning the impurities and re-calibrating, it was put into normal use. 4. The float level gauge has a large indication deviation. ◆Fault phenomenon The float level gauge has a large indication deviation, and the effect is still not good after two points of calibration. ◆Failure Cause Analysis In May 2007, the styrene process personnel reported that the LT-3005 indication was too large. After the instrument personnel used the 375 communicator to perform two-point calibration and put it into use, the effect was still not satisfactory. After analysis, it was believed that the rigidity of the pontoon torque tube had changed after being used for a long time, and general calibration could not overcome its error. The dry coupling point must be recalibrated to make the torque tube work within the normal range, and then perform two-point calibration before the instrument can be used normally. After using the above method to verify, the instrument returned to normal. ◆Precautions: You must read and understand the instrument instructions thoroughly so that you can more accurately judge and deal with problems when problems occur with on-site instruments. 5. The indication of the electric float level gauge does not change ◆Fault phenomenon When the liquid level of the electric float level gauge LT653 is adjusted normally, the indication will always remain unchanged when the meter is changed. Since the liquid level of the meter is adjustable, its error indication brings great difficulty to the regulating valve LV653 in adjusting the liquid level. Process operators cannot use this meter for automatic adjustment and can only control it manually. ◆Failure Analysis and Treatment When the float transmitter LT653 is operating normally, the medium in the float is always in a relatively static state, causing many impurities to precipitate in the float. Over time, the sludge will jam the float. At this time, even if the liquid level changes, the float is stuck, and the liquid level output value will not change. After arriving at the scene, we first closed the root stop valve, opened the drain valve, and cleaned the inner wall of the float with water. After cleaning, the meter was turned on and it was running normally. ◆Preventive measures: Clean the float and float regularly, and check the operation of the float amplifier regularly. 6. The electric float level gauge indicates low ◆Fault phenomenon The electric float level gauge LT101 is used to measure the liquid level of ethylene in the copolymer tank. The glass plate level gauge indicates that it is full, while the liquid level transmitter indicates about 40%. ◆Failure analysis and treatment. No abnormality was found in all components of the liquid level transmitter. The gas phase and liquid phase were checked for sewage discharge. Ethylene was discharged. Open the float and check the torque arm and float. No abnormalities were found. Later, when the float was taken out, it was discovered that there was a sand hole in the float. The float was hollow. After hexene was poured into the float, the weight of the float increased and the measured liquid level was low. ◆Measures: Weld the float, replace it, calibrate it, and return the liquid level to normal. 7. The indication of the smart float transmitter is inaccurate ◆Fault phenomenon: The ZTD smart float transmitter used on site had inaccurate indications, the zero point and range had been adjusted out of order, and could not be put into use. ◆Treatment method: ①“Mark the "dry coupling point", the operation steps are as follows: a. Hang the barrel weight; b. Slide the entry handle to the locking position to expose the access hole; c. Insert a 10mm deep concave socket wrench through the access hole to the torque tube shaft clamp, clamp the nut in, and tighten the clamp nut. d. Slide the access handle to the released position and cover the access hole. e. Operate through the 275 (375) interface: base setting - sensor calibration - mark the dry coupling point - mark the zero point according to the prompts of the HART protocol communicator. ②Check the float parameter information through the 275 (375) interface and correct the errors. ③Through the 275 (375) interface, check the density of the measurement medium and correct the errors. ④PV offset is cleared. ⑤Calibrate the zero point and span of the transmitter. 8. The output linearity of the float level transmitter is not good. ◆Fault phenomenon The output linearity of LT322 is not good. ◆Fault analysis and treatment: LT322 is a float level transmitter, and the output linearity is not good. Check whether there is any jamming in the movable part and make sure there is no jamming. Check whether the upper limit of the overload protection spring range is disengaged and confirm it is not. Check whether there is any contact between the buoy and the outside of the measuring chamber and make sure there is no contact. Check the installation position of the measuring lever and the shaft seal frame, and find that the installation position is wrong. After reinstalling it correctly, it was put into operation normally. ◆Preventive Measures Instrument personnel should be careful during installation and repair to avoid carelessness and recklessness. 9. The float level gauge does not follow the change when the liquid level drops. ◆Fault phenomenon LT-3106 liquid level suddenly drops to 60%, and the meter display no longer works. ◆Failure Cause Analysis: The instrument normally displays the liquid level at 80%~90%. When the liquid level drops to about 50% and then rises to 60%, the instrument display does not rise with the liquid level. The possible reasons are as follows: The transmission unit of the transmitter fails. ； Signal output is defective ； The reason for measuring children's float. ◆Troubleshooting Based on observations and phenomena reflected in the process, the possibility of failure of the transmission unit and transmission side is very small, and we should start with the inspection of the float. Empty the liquid in the float and discharge it as required. Open the upper valve cover, separate the float from the transmitter, take out the float, and find that there is sticky matter in the cylinder stuck to the float. After cleaning, reset the float. The instrument is put into use and calibrated with the main control room based on the on-site liquid level. The instrument displays normally. ◆Precautions: Floats should be inspected and drained regularly. 10. Liquid level fluctuation caused by vapor-liquid mixing◆Fault phenomenon Fluctuation of liquid level in isopentane recovery tank◆Cause of failure Most of the isopentane required for the reaction is recovered. The liquid level in the recovery tank is inaccurate, which directly affects the reaction process. The condensed material recovered from the degassing bin still carries a large amount of reaction gas, which will cause pressure fluctuations in the tank. The gas will also escape into the float of the liquid level gauge, causing liquid level fluctuations and inaccurate measurement. ◆Treatment method: Close the upstream and downstream stop valves of the liquid level gauge, sweep open the discharge valve at the bottom of the float, vent the gas, close the vent valve, and sweep the stop valve to allow the recovered liquid to slowly fill the float, and the liquid level measurement returns to a stable indication.