Through introducing the characteristics and working principle of electromagnetic flowmeter and its application in oil field combined station, this paper puts forward that the advantages and disadvantages of flowmeter in measuring flow are mainly analyzed, and technical improvement is strengthened to make electromagnetic flowmeter work stably and measure accurately in combined station. In the daily work of oil field joint station, electromagnetic flowmeter undertakes the task of monitoring water flow instantaneously, while flow controller undertakes the task of regulating water flow instantaneously. Energy measurement is often directly related to the benefits of enterprises. During the working process, the controller automatically controls the opening and closing of the valve by the data detected by the flowmeter, or manually controls the opening and closing of the valve. Because of the use of PID regulation in the work of flow controllers and the constant execution of valve opening and closing instructions, some of the controllers fail to open and close valves, and can not achieve water regulation. And in the installation and use of components consumption, measurement deviation and other problems often occur. Therefore, the correct use of flow controller and flowmeter plays a very important role in the stability of recovery ratio. Paired flanges, flowmeters and flanges are reserved in the process pipeline. The flow direction of flowmeters should be consistent with the flow direction of media. The wiring of instruments should meet the design and wiring requirements of manufacturers. Electromagnetic flowmeter is an instrument for measuring volume flow of conductive liquid, which is composed of flow sensor transmitter.
The flow sensor converts the volume flow of liquid flowing through the pipeline into a linear electric signal.
Transmitter is composed of excitation circuit, signal filter amplifier circuit, A/D sampling circuit, microprocessor circuit, D/A circuit, transducer circuit and so on. The principle is that conductor generates electromotive force by cutting electromagnetic wire through magnetic field. The conductive medium in the measuring tube is equivalent to the conductive metal rod in Faraday test, and two electromagnetic coils at the upper and lower ends produce a constant magnetic field. When the conductive medium flows through, thermostatic element the induced voltage will be generated. Flow controller is a high-precision pilot flow control device.
Under a certain pressure difference, changing the size of throttle resistance to control the throttle flow to complete the adjustment of the movement speed of the actuator.
When the flowmeter outputs 4-20mA signal according to the control requirements, the circuit board compares the given signal with the feedback signal and outputs the deviation signal. After amplification, the deviation signal determines the forward or reverse rotation of the motor, and drives the corresponding relay action to drive the motor to rotate in the right direction. When the controller runs to the upper and lower limit position, the trip switch sends an interruption command to the circuit board, and the motor stops. One is the fault of the instrument itself, that is, the fault caused by the damage of the instrument structure or components; the other is the fault caused by external reasons.
Converter components are damaged. Check the safety in the control cabinet and the output voltage of the power circuit board. Check the direction of liquid flow and whether the liquid in the tube is full. For the electromagnetic flowmeter which can be measured in both directions, although the direction is inconsistent, it must be corrected for the inconsistency between the positive and negative directions of the set display flow. It can also change the arrow direction on the sensor and reset the display symbol. Pipeline not full of liquid is mainly caused by inappropriate installation position of sensors. Measures should be taken during installation. Check whether the inner electrode of the transmitter covers the liquid scaling layer. For the measuring liquid which is easy to scale, it should be cleaned regularly. If it is judged that the failure is caused by the damage of components, the replacement of components is enough.
The parameter setting value of the converter is inaccurate. Check whether the circuit board of the transmitter is in good condition. When the junction box is watered or corroded by liquids, the performance of the electrical appliances may be degraded or damaged. The circuit board should be replaced at this time. Ensure that the liquid flow rate in the pipeline is above the minimum flow limit. Check the insulation performance of the signal cable connection and cable.
If the cable is loose, reconnect it. If the insulation of the cable does not meet the insulation requirements, new cables need to be replaced. The set value of the converter is set again, and the zero and full value of the converter are checked. Converter and sensor models do not match. Check the connection of the signal circuit. If the signal circuit is disconnected, the output signal will exceed the fullness value. At this time, it is necessary to re-check the signal cable and check the insulation performance of the cable. If it does not meet the requirements, it is necessary to replace the new cable. Check whether the parameters of the converter, zero and fullness meet the requirements. Check the type of converter and sensor, if not matched, the factory will need to change it. The pipe is not filled with liquid or contains bubbles in the liquid. Reasons. The insulation of the signal circuit decreases. Pipeline not filled with liquid or containing bubbles in liquid are the reasons for the process, please confirm that the output value can be restored to normal. If the inner wall of the measuring tube is scaled or contaminated with impurities or electrodes, there may be a change of zero point, which must be cleaned at this time; if the change of zero point is not large, you can try to reset zero. Due to the influence of environmental conditions, dust, oil pollution and so on may enter the case. It is necessary to check whether the insulation at the electrode position is reduced or damaged. If it does not meet the insulation requirements, it must be cleaned up. According to the fault analysis of the electromagnetic flowmeter and flow controller, the following measures are suggested to improve the qualification rate and ensure the service life. According to statistics, there will be aging of components in instruments with service life of more than 3 years.
Comprehensive inspection should be carried out to replace aging components in time to ensure measurement effect and prolong service life. For ternary liquid flowmeter, it is suggested that corrosion-resistant and scaling-resistant materials should be added to the inner lining of flowmeter to slow down scaling and prolong the working life of the instrument. In order to avoid the influence of scaling on movable parts, it is suggested to use speed flow meter in the flow detection of produced liquid. Only by strict management and careful maintenance can the instrument be guaranteed stable performance, reliable accuracy and reasonable life. In the process of using, we should do a good job of anti-corrosion and anti-scaling of the electronic part to avoid secondary meter failure; we should be responsible for cleaning the internal dirt and sensor solidification to eliminate the impact on measurement; we should handle and handle the instrument lightly to prevent physical damage; we should not arbitrarily pull all kinds of wiring inside the instrument to avoid short circuit, circuit breakage and loosening. In summary, electromagnetic flowmeters and flow controllers are widely used in centralized monitoring and unattended joint stations and injection stations, which are widely promoted in oilfields. The use of electromagnetic flowmeters of different brands is similar, and the problems are mostly concentrated in the above aspects. Only when the electromagnetic flowmeter and flow controller are fully maintained and carefully maintained, can the performance of the instrument be maximized, the measurement accuracy be achieved, the injection requirements be met and the production needs be met.