Measuring principle of electromagnetic flowmeter
The principle of electromagnetic flowmeter measurement is based on Faraday's law of electromagnetic induction. The measuring tube of the flow meter is a non-magnetic alloy short tube lined with an insulating material. The two electrodes are fixed to the measuring tube through the tube wall in the tube diameter direction. The electrode tip is substantially flush with the inner surface of the liner. When the exciting coil is excited by the bidirectional square wave pulse, a working magnetic field having a magnetic flux density B is generated in a direction perpendicular to the axis of the measuring tube. At this time, if the fluid having a certain conductivity passes through the measuring tube, the cutting magnetic line induces the electromotive force E. The electromotive force E is proportional to the product of the magnetic flux density B, the inner diameter D of the measuring tube and the average velocity V. The electromotive force E (flow signal) is detected by the electrode and sent to the converter through the cable. After the converter amplifies the flow signal, it can display the fluid flow, and can output signals such as pulse and analog current for flow control and regulation.
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.
Precautions before gas turbine flowmeter is enabled
Keywords: gas turbine flowmeter, Tianxin gas turbine flowmeter, gas gas turbine flowmeter
First, the precautions before the gas turbine flowmeter is enabled
In order to ensure trouble-free, safe start-up and commissioning of the ultrasonic flowmeter, the following pre-checks must be carried out:
1. Before starting the flowmeter officially, be sure to handle each leak point;
2. Check the power supply voltage on the terminal block and the corresponding positive and negative polarity;
3. Check the polarity of the frequency output lead connected to the RS485 converter;
4. Check whether the gas turbine flowmeter and temperature/pressure transmitter display are correct and reliable, including the installation direction and verticality of the flowmeter; the sealing performance of all joints;
5, wiring inspection: should be in accordance with the system wiring diagram provided by Jiangsu Tianxin Instrument Co., Ltd., check all wiring is correct.
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.