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Troubleshooting Method Of Metal Flow Meter

Author:vacorda    Source:www.vacorda.com    Date: 2020-04-21 11:17:33
Metal tube float flowmeter is the most common type of flowmeter in industrial production process. It is suitable for medium flow measurement of small diameter and low flow rate within DN200. It has the feature of reliable operation, small maintenance and long life.
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About the troubleshooting method of metal flow meter:

First, the pointer of the metal tube float flowmeter stops at a certain position. The main reason is that the float of the metal tube float flowmeter is stuck.

Generally, when using the metal tube float flowmeter, the valve is opened too fast, the float quickly hits the stopper upwards, causing the stopper to deform and the floater stuck. However, it is not ruled out that the float is stuck because the float guide rod and the stop ring are not concentric. 

During processing, the instrument can be removed, the deformed stopper can be removed and reshaped, and check whether it is concentric with the guide rod. If not, you can correct it, then install the float, push the float by hand, and feel that the float is smooth.

In addition, the metal tube float flowmeter must be installed vertically or horizontally when installed, and cannot be tilted, otherwise it may easily cause card meters and bring errors to the measurement.

Second,  jitter of the metal tube float flowmeter pointer:

1. Slight pointer shake: Generally caused by media fluctuations. This can be solved by increasing damping.

2. Moderate pointer jitter: Generally caused by the state of media flow. For gas, it is generally caused by the unstable operating pressure of the medium. Can use voltage stabilization or flow stabilization device to overcome or increase the metal tube float flowmeter gas damping.

3. Vigorous pointer jitter: Mainly due to the pulsation of the medium, the unstable air pressure, or the pressure, temperature, and flow rate of the gas operating state given by the user do not match the actual state of the metal tube float flowmeter.

Third, no current output
1. First see if the wiring is correct.
2. Check whether the LCD has a display, if there is no output and has display, the output tube is mostly broken, and the circuit board needs to be replaced.
3. Lost calibration value. Due to the failure of E2PROM, the calibration data of the instrument is lost, and no output current will be caused, and the current will remain unchanged. Solution: Available operation of data recovery.

Fourth, no on-site display
1. Check that the wiring is correct.
2. Check whether the power supply is correct.
3. Reinstall the LCD module, and check that the contact is not correct.
4. For multi-wire power supply mode, check whether the terminal is connected to an ammeter or short circuit.

Five, the alarm is incorrect
1. Check that the deviation setting d cannot be too large.
2. Is the logic function correct? HA-A stands for positive upper logic. LA-A means lower limit positive logic.
3. Check the alarm value setting size.
4. If the LCD bar code is correct and the output has no action, you can check whether the external power source and the negative pole of the external power source are connected to the negative pole of the instrument.
5. The circuit board is faulty. Replace the circuit board.

Six, the field LCD always displays 0 or full scale
1. Check the set range and zero parameters. ZERO is required to be less than the value of SPAN, and the two values cannot be equal.
2. Check if the sampling data comes up, push the pointer with your hand to see the sampling value change. If there is no change, it is usually the circuit board sampling circuit failure that needs to be replaced.

Seven, large measurement error of metal tube float flowmeter
1. The installation does not meet the requirements. For vertical installation of metal tube float flowmeters, keep it vertical and the inclination angle is not greater than 20 degrees. For horizontal installation of metal tube float flowmeters, keep it horizontal. The inclination angle is not more than 20 degrees. object. The installation position should be far away from the valve reducer, the pump outlet, and the turning point of the process pipeline. To maintain the requirements of the first 5D after 250mm straight pipe section.
2. The large change in the density of the liquid medium is also a cause of the larger error. Before the instrument is calibrated, the medium is converted according to the density given by the user, and converted to the water flow in the calibration state for calibration. Therefore, if the medium density changes greatly, it will cause a large error in the measurement. The solution is to bring the changed medium density into the formula, convert it into an error correction coefficient, and then multiply the flow rate measured by the flow meter by the coefficient to replace the real flow rate.
3. Since the gas medium is greatly affected by temperature and pressure, it is recommended to use the temperature and pressure compensation method to obtain the true flow rate.
4. Due to long-term use and pipeline vibration and other factors, the metal tube float flowmeter's sensing magnetic steel, pointer, counterweight, rotating magnetic steel and other moving parts are loose, causing large errors. Solution: first push the pointer by hand to verify. First press the pointer at the RP position to see if the output is 4mA and whether the flow rate display is 0%, and then verify according to the scale. If a discrepancy is found, the position of the component can be adjusted. Generally requires professional adjustment, otherwise the position will be lost, and it needs to be returned to the factory for correction.

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