The volumetric flowmeter is a kind of flowmeter with high accuracy. After the flowmeter is put into use, pay special attention to the following aspects of use and maintenance:
1. Exhaust gas: Usually, after the solid liquid is swept, more air remains in the pipeline. With the pressurized operation, the air flows through the flowmeter at a higher flow rate, and the active measuring component may be over-speed in a short time. Cause damage to the bearing. Therefore, the flow should be slowly increased at the beginning to make the air gradually overflow.
2. After starting, pass the lowest pointer or word wheel and stopwatch to confirm that the over-flow is not reached. The optimal flow should be controlled at 70~80% of the maximum flow to ensure the service life of the instrument.
3. Check the filter: The new pipeline is the most vulnerable to destroying the filter. After the test run, it is necessary to check whether the net is in good condition. At the same time, when the filter is clean and free of materials, it is best to record the two parameters of the pressure loss under the common flow rate, so that in the future work, it is not necessary to remove the blockage of the inspection net, that is, the degree of increase in pressure loss can be judged whether it is to be cleaned.
4, measuring high viscosity liquid: for high viscosity liquid, generally should be heated to make it flow. When the meter is deactivated, its internal liquid is cooled and thickened. When it is activated, it must be heated before the viscosity of the liquid is lowered before the liquid flows through the meter. Otherwise, the moving parts will be bitten to damage the meter.
5. Avoid sudden flow changes: When using a volumetric flowmeter, be careful not to have a sharp flow change (such as using a quick-open valve). Due to the inertia of the flowmeter, a sharp flow change will generate a large additional inertial force, causing damage to the rotor. .
6. When flushing the pipeline with steam, steam should be prohibited from passing through the flowmeter.
Coriolis mass flowmeter
1. Zero drift is a problem often encountered in the actual operation of Coriolis mass flowmeters: there are many factors causing zero drift, such as the installation stress of the sensor, the structural asymmetry of the measuring tube, and the change of the physical property parameters of the measured fluid. Especially in small flow measurement, the effect of zero drift on measurement accuracy is more serious. Therefore, it is necessary to perform zero check and adjustment on a regular basis.
2. During the use of the flowmeter, always pay attention to whether the set working parameters have changed. Whether the displayed flow, density and temperature values ​​are normal, if there is a large difference between the actual and the actual, it can be described in the instruction manual. The method re-zeros the flow calibration. If the above work still does not feel normal after completion, you should check whether the working parameters set inside the transmitter are correct.
3. When the flowmeter measures the fouling (such as scaling and waxing) fluid, it should always check the operation of the device. When it is found that the flowmeter is not working properly or the deviation is large, it should first consider the possibility of scaling inside the sensor. Remove the sensor and dispose of it by appropriate methods such as purging or cleaning.
4. Regular calibration. According to the application of the flowmeter, the calibration is carried out according to the requirements of the standard system.
Orifice flowmeter
1. The newly installed instrument or the standard orifice plate that is re-applied after a period of time should be checked before use. Check whether the pressure piping is blocked or not. If the joint is leaking, the liquid medium should be filled with liquid in the pressure guiding pipeline. Discharge the gas mixed in the pressure guiding tube, and pay attention to the liquid in the pressure guiding tube for the gas medium.
2. Before using the meter, check the zero position, close the shut-off valve on the positive and negative pressure guiding tube, open the balancing valve, check and correct the zero position of the differential pressure transmitter, and pay attention to the “zero point†in the positive and negative pressure chamber. When the pressure (ie, the differential pressure is zero), verify the differential pressure transmitter. It is best to open a small plug to connect the positive and negative pressure chambers to the atmosphere.
3. When measuring the flow rate of dirty fluid, it is necessary to configure a settler or isolator that meets the characteristics of dirty fluidized vapor. Pay attention to the reasonable choice of the inlet, outlet and drain outlet of the pressure guiding tube, try not to block the pressure guiding tube and drain the sewage smoothly.
4. When measuring the flow rate of corrosive fluid, it is necessary to use corrosion-resistant isolator to select the appropriate spacer liquid according to the specific gravity of the corrosive fluid, and pay attention to the sealing and fastening of the joint to properly select the population of the spacer fluid and the fluid to be tested.
5. Whether the design parameters of the standard orifice plate are consistent with the actual parameters will directly affect the accuracy of the meter measurement. After the standard orifice flowmeter is used, if the measured data is within the design range, the measurement accuracy will generally meet the design calculation accuracy; however, if the measured data is not within the design parameters (if the standard orifice and differential pressure transmitter are selected) Type, manufacturing, and installation are all in compliance with the requirements. It is possible that the design parameters provided are incorrect. The design parameters should be changed and all data of the standard orifice plate should be recalculated.
6. After using the standard orifice plate throttling device for a period of time, due to impurities in the measured medium, the friction plate is rubbed for a long time, causing the orifice plate to wear, causing additional errors. In this case, the throttling element should be considered for replacement; The longer the time, the more likely it is that dirt will accumulate in the lower corner of the upstream side of the orifice plate, which will cause the outflow coefficient to change, so it is necessary to check regularly to completely remove the dirt. If necessary, you can stop and purge the medium in the replacement pipe and remove the inspection. If the sharpness and smoothness of the right-angle entrance edge of the orifice opening, the parallelism of the end face of the orifice plate, and the perpendicularity are out of tolerance, the orifice plate shall be corrected or replaced.
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