Flow meter is one of the most commonly used meters in industry. Flow meter is one of the most commonly used meters in industry. Xiaobian summarizes the troubleshooting methods of common flow meters for you. Remember to collect and pay attention to us to help you judge and solve the problems encountered in the production process in time. Flow meter classification ★ There are many kinds of flow measurement methods and instruments, and there are also many classification methods. Up to now, there are as many as 60 kinds of flow meters available for industrial use. ★ According to the measured object, there are two categories: closed pipeline and open channel. ★ According to the purpose of measurement, it can be divided into gross measurement and flow measurement, and their instruments are called gross meter and flowmeter respectively. ★ According to the measurement principle, there are mechanical principle, thermal principle, acoustic principle, electrical principle, optical principle, atomic physics principle, etc. ★ According to the most popular and extensive classification at present, it can be divided into: positive displacement flowmeter, differential pressure flowmeter, float flowmeter, turbine flowmeter, electromagnetic flowmeter, vortex flowmeter, mass flowmeter and ultrasonic flowmeter. Common Flowmeter Faults and Treatment Methods 01 waist wheel flowmeter Question 1: The waist wheel does not turn. Reason: 1. Dirt is stuck in the pipeline. 2. The measured liquid solidifies. Treatment measures: 1. Clean pipes, filters and flowmeters. 2. Dissolve the liquid. Problem ②: The waist wheel rotates but the pointer does not move or stops when walking. Reason: 1. The header fork is out of line. Head transmission enters dirt. 2. The pointer or counter is stuck. 3. The transmission is out of line. Treatment measures: Remove the meter head, rotate the fork by hand, and the instrument rotates flexibly, so that the meter head is out of touch with the pin of the shaft; If not, it should be checked step by step. Problem ③: The steering seal coupling shaft leaks oil. Reason: Sealing packing wear Treatment measures: Tighten gland or replace packing. Problem ④: Device error compensation and small flow error bias. Reason: The waist wheel collides with the shell, because the bearing is worn, or because the main body of the fixed driving gear is displaced. Treatment measures: Replace the bearing, and check whether the driving gear and wheel body rotate and whether the screws fixing the gear are loose. Problem ⑤: The error varies greatly. Reason: 1. The liquid pulsates greatly. 2. It contains gas. Treatment measures: 1. Reduce pulsation. 2. Add a getter.
02 Differential pressure flowmeter Question ①: Indicates zero or little movement. Reason: 1. The balance valve is not fully closed or leaked. 2. The high and low pressure valves at the root of the throttling device are not opened. 3. The valve and pipeline between the throttle device and the differential pressure gauge are blocked. 4. The steam pressure guide pipe is not completely condensed. 5. The gasket between throttling device and process pipeline is not tight. 6. Internal fault of differential pressure gauge. Treatment measures: 1. Close the balance valve, repair or replace it. 2. Open the high and low pressure valves. 3. Flush the pipeline, repair or replace the valve. 4. Open the meter after complete condensation. 5. Tighten the bolt or change the gasket. 6. Check and repair Question 2: The indication is below zero. Reason: 1. Reverse connection of high and low pressure pipelines. 2. The signal line is reversed. 3. The pipeline on the high pressure side is seriously leaking or broken. Treatment measures: 1-2. Check and connect correctly. 3. Replace parts or pipes. Question ③: The indication is low. Reason: 1. The pipeline on the high pressure side is not tight. 2. The balance valve is not tight or closed tightly. 3. The air in the pipeline on the high pressure side is not discharged. 4. The differential pressure gauge or secondary instrument has zero offset or displacement. 5. The throttling device and differential pressure gauge are not matched and do not meet the design requirements. Treatment measures: 1. Check and eliminate leakage. 2. Check, close or repair. 3. Exhaust the air. 4. Check and adjust. 5. Replace the matching differential pressure gauge. Question ④: The indication is high. Reason: 1. The low pressure side pipeline is not tight. 2. The low-pressure side pipeline accumulates air. 3. The steam pressure is lower than the design value. 4. Zero drift of differential pressure gauge. 5. The throttling device is not matched with the differential pressure gauge. Treatment measures: 1. Check and eliminate leakage. 2. Exhaust the air. 3. According to the actual density correction. 4. Check and adjust. 5. Replace the matching differential pressure gauge. Question ⑤: The indication fluctuates greatly. Reason: 1. The flow parameters themselves fluctuate too much. 2. The load cell is sensitive to parameter fluctuation. Treatment measures: 1. Turn down the high and low pressure valves appropriately. 2. Adjust the damping function appropriately. Question 6: The instruction does not move. Reason: 1. The anti-freezing facilities fail, and the differential pressure gauge and the hydraulic pressure in the pressure guide pipe freeze. 2. The high and low pressure valves are not opened. Treatment measures: 1. Strengthen the effect of anti-freezing facilities. 2. Open the high and low pressure valves. 03 supersonic flowmeter Question ①: The display data of flow velocity changes dramatically. Reason: The sensor is installed in the place where the pipeline vibrates heavily or downstream of the regulating valve, pump and orifice. Treatment measures: The sensor is installed in the place where the pipeline vibrates heavily or downstream of the regulating valve, pump and orifice. Question ②: The sensor is good, but the flow rate is low or no flow rate. Reason: 1. Paint and rust in the pipeline are not cleaned. 2. The pipeline surface is uneven or installed at the welding seam. 3. The sensor is not well coupled with the pipeline, and there are gaps or bubbles on the coupling surface. 4. When the sensor is installed on the casing, the ultrasonic signal will be weakened. Treatment measures: 1. Clean the pipeline again and install the sensor. 2. Grind the pipeline flat or install the sensor away from the weld. 3. Reinstall the coupling agent. 4. Move the sensor to the pipe section without casing. Question ③: The reading is incorrect. Reason: 1. Sensors are installed at the top and bottom of horizontal pipes, and sediments interfere with ultrasonic signals. 2. The sensor is installed on the pipe with downward water flow, and the pipe is not filled with fluid. Treatment measures: 1. Install sensors on both sides of the pipeline. 2. Install the sensor on the fluid-filled pipe section. Problem ④: The flowmeter works normally, and suddenly the flowmeter no longer measures the flow. Reason: 1. The measured medium changes. 2. The measured medium is gasified due to high temperature. 3. The measured medium temperature exceeds the limit temperature of the sensor. 4. The coupling agent under the sensor is aged or consumed. 5. The instrument exceeds its own filtering value due to high frequency interference. 6. Data loss in the computer. 7. The computer crashed. Treatment measures: 1. Change the measurement method. 2. cool down. Step 3 cool down. 4. Repaint the coupling agent. 5. Stay away from interference sources. 6. Re-enter the value. 7. Restart the computer. 04 mass flowmeter Question ①: Instantaneous flow constant maximum. Reason: 1. The cable is disconnected or the sensor is damaged. 2. The fuse tube in the transmitter is burnt out. 3. The sensor measuring tube is blocked Treatment measures: 1. Replace the cable or replace the sensor. 2. Replace the safety tube. 3. After dredging, pat the sensor shell, and then measure the AC and DC voltages. If it is still unsuccessful, the installation stress is too great, so reinstall. Question ②: When the flow rate increases, the flowmeter indicates a negative increase. Reason: The flow direction of the sensor is opposite to the indicated flow direction of the housing, and the signal line is reversed. Treatment measures: Change the installation direction and change the signal wire connection. Problem ③: When the fluid flows, the flow rate shows positive and negative jumping, with a large jumping range and sometimes maintaining a negative maximum value. Reason: 1. The grounding of AC/DC shielded wire of power supply is greater than 4Ω. 2. Pipeline vibration. 3. The fluid has gas-liquid two-phase components. 4. There is strong magnetic field or radio frequency interference around the transmitter. Treatment measures: 1. Re-ground. 2. Change the connecting pipe with the flowmeter into a metal hose connection. 3. Open a hole in the pipeline above the flowmeter and install a valve to discharge the gas phase components. 4. Change the environment around the transmitter. 05 turbine flowmeter Problem ①: There is no display when the fluid flows normally. Reason: 1. The power cord and fuse are broken or have poor contact. 2. The display instrument has poor internal contact. 3. The coil is broken. 4. There is a fault inside the sensor flow channel. Treatment measures: 1. Check with an ohmmeter. 2. Check by replacing the “standby version” method. 3. Check the coil for broken wire or solder joint desoldering. 4. Remove foreign bodies from the sensor and clean or replace damaged parts. Problem ②: The traffic display is gradually decreasing. Reason: The filter is clogged. The valve core on the sensor pipe section is loose, and the valve opening is reduced. The sensor impeller is blocked by sundries or foreign matter enters the bearing gap, and the resistance increases. Treatment measures: Clean the filter. Judging whether the valve core is loose from whether the valve handwheel adjustment is effective Remove the sensor to remove sundries, and recheck it if necessary. Problem ③: The fluid does not flow, and the flow display is not zero. Reason: 1. The transmission line is poorly grounded. 2. When the pipeline vibrates, the impeller will shake. 3. The cut-off valve is not closed properly. 4. The internal circuit boards of the display instrument or the electronic components are deteriorated and damaged. Treatment measures: 1. Check whether it is well grounded. 2. Reinforce the pipeline, or install supports before and after the sensor to prevent vibration. 3. Repair or replace the valve. 4. Take the “short circuit method” or check one by one to determine the interference source and find out the fault point. Question 4: There is a significant difference between the display value and the empirical evaluation value. Reason: 1. Internal fault of sensor flow channel. 2. The back pressure of the sensor is insufficient, and cavitation occurs, which affects the rotation of the impeller. 3. The reasons of pipeline flow. 4. Internal failure of the indicator. 5. The permanent magnet elements in the detector are demagnetized by aging. 6. The actual flow through the sensor has exceeded the specified range. Treatment measures: 1-4. Find out the cause of failure, and find countermeasures for specific reasons. 5. Replace the demagnetizing element. 6. Replace the appropriate sensor. Source: Network Disclaimer: This article is reproduced from the network, and the content of the article is only for learning and communication. The air compressor network is neutral to the views in the article. The copyright of the article belongs to the original author and the platform. If there is any infringement, please contact to delete it.
