In order to make the electromagnetic flowmeter work stably and reliably, the following aspects should be noted when selecting the installation location:
1. Try to avoid ferromagnetic objects and equipment with strong electromagnetic fields (large motors, large transformers, etc.) to prevent the magnetic field from affecting the working magnetic field and flow signal of the sensor.
2. It should be installed in a dry and ventilated place to avoid sun and rain. The ambient temperature should be -20~+60°C, and the relative humidity is less than 85%.
3. There should be plenty of space around the flowmeter for easy installation and maintenance.
The measurement principle of the electromagnetic flowmeter does not depend on the characteristics of the flow. If there is a certain turbulence and vortex in the pipeline, it will be generated in the non-measurement zone (such as elbow, tangential current limit or half-opening shut-off valve upstream). Nothing.
If steady-state eddy currents in the measurement zone affect the stability of the measurement and the accuracy of the measurement, then some measures should be taken to stabilize the flow rate distribution:
a.increase the length of the straight pipe before and after; b. use a flow stabilizer; c. reduce the cross section of the measuring point.
Vortex flowmeter analysis and solution
3. Reasons for parameter setting direction. The instrument is incorrectly indicated due to a parameter error. The parameter error makes the secondary meter full frequency calculation error, and the reason for this is mainly related to questions 1 and 3. The full-scale frequency is similar, indicating that the long-term inaccuracy is indicated. The full-scale frequency of the actual full-scale frequency and large-dry calculation indicates that the range is fluctuating and cannot be read. The inconsistency of the parameters on the data affects the final determination of the parameters, and finally passes. Recalibration combined with mutual comparison to determine the parameters solves this problem.
4. The secondary instrument is faulty. There are many faults in this part, including: when the instrument board is disconnected, the range setting has individual bit display bad, and the K coefficient setting has individual bit display bad, which makes it impossible to determine the range setting and K factor setting. Part of the reason is mainly related to questions 1, 2. The problem is solved by fixing the corresponding fault.
5, Four-way line connection problem. On the surface of some circuits, the line connection is very good. Check carefully. Some connectors are actually loose and the circuit is interrupted. Some connectors are tightly connected, but the fastening screws are fastened to the wire due to the secondary line problem. Interruption, this part of the reason is mainly related to question.
The installation position and installation method of the ultrasonic flowmeter.
Selecting the installation pipe segment has a great influence on the test accuracy. The selected pipe segment should avoid the interference and eddy current, which have great influence on the measurement accuracy. Generally, the pipe segment should meet the following conditions:
1. Avoid installing the machine in the pump, high-power radio, frequency conversion, that is, where there is strong magnetic field and vibration interference;
2. Select the pipe section where the pipe should be uniform and dense, and it is easy to transmit ultrasonic waves;
3, to have a long straight pipe section, the upstream straight pipe section of the installation point must be greater than 10D (Note: D = diameter), downstream is greater than 5D;
4, the installation point upstream distance pump should have a distance of 30D;
5. The fluid should be filled with pipes;
6. There should be enough space around the pipeline to facilitate the operation of the on-site personnel. The underground pipeline needs to be a test well. The test well is as follows:
Ultrasonic flowmeters generally have two types of probe installation methods, namely Z method and V method.
However, when D < 200mm and the site condition is one of the following conditions, it can also be installed by the Z method:
1. When the measured fluid has high turbidity, when the V method is used to measure the signal or the signal is weak;
2. When the inner wall of the pipe is lined;
3. When the service life of the pipeline is too long and the inner wall is fouled seriously;
For those with better pipeline conditions, even if D is slightly larger than 200mm, in order to improve the measurement accuracy, the V method can be used for installation.