The structure of the electromagnetic flowmeter is mainly composed of a magnetic circuit system, a measuring conduit, an electrode, a casing, a lining, and a converter.
Magnetic circuit system: its role is to produce a uniform DC or AC magnetic field. The DC magnetic circuit is realized by a permanent magnet, which has the advantages of simple structure and less interference by the alternating magnetic field, but it is easy to polarize the electrolyte liquid in the measuring duct, so that the positive electrode is surrounded by negative ions, and the negative electrode is positive ion Surrounding, that is, the polarization phenomenon of the electrode, and causing an increase in internal resistance between the two electrodes, thus seriously affecting the normal operation of the meter. When the diameter of the pipe is large, the permanent magnets are correspondingly large, bulky and uneconomical, so the electromagnetic flowmeter generally adopts an alternating magnetic field and is generated by the excitation of a 50HZ power frequency power source.
Measuring catheter: its function is to let the conductive liquid to be tested pass. In order to make the magnetic flux diverted or short-circuited when the magnetic flux passes through the measuring catheter, the measuring catheter must be made of non-magnetic, low electrical conductivity, low thermal conductivity and mechanical strength. Non-magnetic stainless steel, FRP, high strength can be used. Plastic, aluminum, etc.
Fourth, the liquid turbine flowmeter put into operation the opening and closing sequence
1. The sequence of opening and closing of the operation
For flow sensors without a bypass line, first open the flow sensor upstream valve at a medium opening and then slowly open the downstream valve. Run at a small flow rate for a period of time (eg 10 minutes), then fully open the upstream valve, then open the large downstream valve opening to adjust to the required normal flow.
The flow sensor equipped with the bypass pipe first opens the bypass pipe valve to open the upstream valve at a medium opening degree, slowly opens the downstream valve, and closes the opening of the small bypass valve to make the instrument run for a period of time with a small flow rate. Then fully open the upstream valve, fully close the bypass valve (to ensure no leakage), and finally adjust the downstream valve opening to the required flow.
2. Activation of low temperature and high temperature fluids
The low-temperature fluid pipeline should drain the water in the pipeline before the flow, and then run for 15 minutes at a small flow rate, and then gradually increase to the normal flow. Slow down when stopping, so that the pipe temperature and ambient temperature are gradually approaching. High temperature fluid operation is similar to this.
Second, the gas turbine flowmeter projection operation steps
1. Open the bypass shut-off valve;
2. Open the flow upstream shutoff valve;
3. Slowly open the downstream shutoff valve of the flowmeter;
4. Slowly close the bypass shutoff valve.
Third, the gas turbine flowmeter stop table operation steps
1. Open the bypass shut-off valve;
2. Turn off the downstream shutoff valve of the flowmeter;
3. Close the flow upstream shutoff valve;
Fourth, gas turbine flowmeter use precautions
1. The newly installed or repaired pipeline must be purged. When purging the metering line, the flow meter must be removed and the corresponding short section replaced the flow meter for purging.
2. When the gas turbine flowmeter pipeline is put into production, it should be slowly boosted and gradually increase the flow rate. When the production is stopped, it should be slowly depressurized.
3. Check the sound of the gas turbine flowmeter or the vibration of the casing during operation to determine whether the turbine blades and bearings are working properly. At low flow rates, attention should be paid to the change in sound, and the vibration of the casing is observed at high flow rates.