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Metal tube float flowmeter fault judgment method
Dec 28, 2018

The metal tube float flowmeter has been widely used in the industrial field, but there are some faults in the work, which brings some trouble to the staff. In order to enable the instrument staff to quickly grasp and judge the cause of the fault, the following is a brief discussion on the common fault judgment and treatment methods for the metal pipe float flowmeter field application, for reference.


First, the pointer stops at a certain position and does not move


The main reason is that the float is stuck. Generally, when the instrument is used, the valve is opened too fast, so that the float quickly impacts the stopper upward, causing the stopper to deform and the float to be stuck. However, it is not excluded that the float is stuck due to the difference between the float guide rod and the stop ring. When disposing, the instrument can be removed, the deformed stopper can be removed and shaped, and checked whether it is concentric with the guiding rod. If the heart is not correct, the float can be installed and the float can be pushed by hand, and the float is smooth and unobstructed. Yes, in addition, it must be installed vertically or horizontally when the instrument is installed, and it cannot be tilted. Otherwise, it may easily cause the card table and bring errors to the measurement.


Second, jitter:


1. Slight jitter: Generally caused by media fluctuations. It can be overcome by increasing the damping.


2, moderate jitter: generally due to the state of the medium flow. Gases are generally caused by unstable media operating pressures. Regulatory or steady flow devices can be used to overcome or increase instrument air damping.


3. Severe jitter: mainly due to medium pulsation, unstable air pressure or the pressure, temperature and flow of the gas operating state given by the user do not match the actual state of the instrument.


Third, the measurement error is large


1. Installation does not meet the requirements


For vertical installation, the instrument should be vertical and the inclination angle should be no more than 2o.


For horizontal installation of the instrument to maintain the level, the inclination is not more than 2o.


2. There must be no ferromagnetic objects in the 100mm space around the meter.


3. The installation position should be away from the valve variable diameter port, pump outlet, process pipeline turning and so on. To maintain the requirements of the 250mm straight pipe section after the first 5D.


4. The large change in density of the liquid medium is also a cause of large errors. Since the instrument is converted according to the density given by the user before the calibration, the flow rate of the water in the calibration state is calibrated. Therefore, if the density of the medium changes greatly, the measurement will cause a large error. The solution can bring the density of the medium after the change into the formula, convert it into the error correction coefficient, and then multiply the flow measured by the flow meter by the coefficient to replace the actual flow.


5. Since the gas medium is greatly affected by the temperature and pressure, it is recommended to use the temperature and pressure compensation method to obtain the real flow rate.


6, due to long-term use and pipeline vibration and other factors caused by the instrument sensing magnetic steel, pointers, counterweight, rotating magnetic steel and other moving parts loose, resulting in large errors. Solution: You can verify by hand pushing the pointer first. First press the pointer to the RP position to see if the output is 4 mA, whether the flow display is 0%, and then verify according to the scale. If the discrepancies are found, the parts can be adjusted. Generally require professional adjustment, otherwise it will cause the position to be lost, need to return to the manufacturer for correction.


Fourth, no live display


1. Check if the wiring is correct.


2. Check if the power supply is correct.


3. Reinstall the LCD module and check that the contact is not true.


4. Check whether the 12 and 13 terminals are connected to the ammeter or short circuit for the multi-wire power supply mode.


Five, no current output


1. First, see if the wiring is correct.


2. Whether the LCD has a display, if there is no output, there is a bad output tube, and the circuit board needs to be replaced.


3. Lose the calibration value. Due to the E2PROM failure, the meter calibration data is lost, and there will be no output current, and the current will remain unchanged. Solution: Data recovery operation can be used. If it does not work, you can set the data in password 2000 first, and then set the password in 2008. The method is to push the pointer to calibrate the data from RP - 100%.


Sixth, the on-site LCD always shows 0 or full scale


1. Check the set range and zero point parameters in the 2000 password. ZERO is required to be less than the value of SPAN, and the two values cannot be equal.


2. Check if the sampled data is up. Press the pointer to see the sample value change. If there is no change, the circuit board sampling circuit is faulty and the circuit board needs to be replaced.


Seven, the alarm is incorrect


1. Check the deviation setting d value can not be too large.


2. Check the alarm value setting size in the SU.


3. In the FUN function, whether the logic function is correct. HA-A represents the upper limit positive logic. LA-A indicates the lower limit positive logic


4. If the LCD bar code indication is correct and the output is not active, check whether the negative pole of the external power supply and the external power supply is connected to the negative pole of the meter power supply.


5. The circuit board is faulty and the circuit board is replaced.


Eight, the cumulative pulse output is incorrect


1. Check if the alarm value of the selected cumulative pulse output is set to zero.


2. The circuit board is faulty and the circuit board is replaced.


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