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Abstract: To address the problem of natural gas entering oil storage tanks or crude oil entering gas pipelines during the separation process at scattered well sites, due to the inability to automatically adjust and control the liquid level inside the separator, an automatic liquid level control system for separators was developed by utilizing existing components of the separator and by adding instruments such as reed switches for remote monitoring, digital displays, recorders, solenoid valves, and alarms. This system features a high degree of automation; it enables the separator to carry out gas-liquid separation automatically, provides continuous measurement, and offers alarms when the liquid level exceeds limits. It eliminates the need for manual operation in existing technologies, where staff are required to monitor the liquid level 24/7. If the staff are not paying close attention, it can lead to accidents such as liquid entering the natural gas pipelines or natural gas entering the storage tanks. During oil field development, many blocks have small oil-bearing areas that are scattered across the area. The oil and gas produced in these blocks cannot be collected together; instead, gas and liquid separation must take place at each well site. The liquid is sent to storage tanks and transported away using tank trucks, while the natural gas, aside from being used locally, is supplied to nearby users. By manually adjusting the opening degree of the discharge valve, the inflow and outflow rates of liquid in the separator are kept balanced over a certain period of time. However, due to differences in the production conditions of the oil wells and the amount of gas used by customers, the inflow and outflow rates of liquid in the separator can become unbalanced. When there is more liquid inflow than outflow, the liquid inside the separator can flow into the natural gas pipeline, causing blockages in that pipeline. This not only leads to equipment damage and economic losses but also undermines the reputation of the company ； When the inflow volume is low and the outflow volume is high, gas and liquid are both discharged through the drain valve into the liquid storage tank, resulting in a large amount of natural gas escaping. This not only leads to losses of gas but also causes environmental pollution as well as safety hazards. To address the aforementioned difficulties, a highly automated control system for separator level should be developed and designed in order to solve the problems existing in current technologies. I. Improvement ideas and plan implementation 1. Design concept. The liquid discharge valve of the separator has been changed from a regular valve to a solenoid valve with automatic control. The level of liquid in the separator, which was previously controlled manually, is now automatically regulated by electrical signals. Additionally, this system features an automatic alarm function; an alarm device is installed in the control room. When the separator’s drainage system fails to discharge liquid automatically and the liquid level in the separator exceeds the upper or lower warning limits, the alarm system activates, issuing sound and light alerts to prompt workers to take action promptly. By making modifications to the existing measurement system, these functions can be implemented without violating safety regulations, while also minimizing costs. Make full use of the functions already available in the magnetic flap level gauge installed in the separator. As the magnetic float inside this level gauge moves upward or downward depending on the liquid level in the separator, and based on the principle that magnetic field lines are generated at the position where the float is located, magnetic sensor elements are placed at the upper and lower measurement marks of the level gauge as well as at the upper and lower liquid level warning levels of the separator. When the magnetic float reaches a specific measurement level, the magnetic sensor elements, influenced by the magnetic field lines generated by the float, convert this into an electrical signal that controls the solenoid valve, thereby enabling the drainage valve of the separator to open and close automatically according to the set height value ； If a fault occurs and the drain valve cannot be turned off or on manually, the magnetic float will continue to rise or fall. When it reaches the separation alarm height, the magnetic sensor element generates an alarm signal, and the alarm bell or light in the control room activates, warning the personnel on duty to resolve the fault; the alarm will continue to sound as long as the fault remains unaddressed. 2. Composition and characteristics. The automatic liquid level control system for separators consists mainly of four components: the separation and metering system, the signal transmission system, the automatic drainage system, and the liquid level alarm system. It includes components such as magnetic flap level gauges, reed switch remote transmitters, digital display instruments, recorders, solenoid valves, alarms, and various connection wires. (1) The separation metering system consists of a magnetic flap level gauge, a reed switch for remote transmission, a digital display, a recorder, and wires. The magnetic flap level gauge and the separator form a communicating vessel; the magnetic float inside the magnetic flap moves in sync with the level of liquid in the separator, always remaining at the same height as the liquid level within the separator. The reed switch for remote transmission is in close contact with the magnetic flip plate, and the resistance value within the reed switch varies in accordance with the magnetic float. When the liquid level in the separator reaches the lower measurement limit, under the influence of the magnetic field generated by the magnetic float of the level gauge, a signal is sent via a reed switch, which closes the outlet valve of the separator and starts measuring the oil production from the well. At the same time, the digital display in the control room shows the liquid level in the tank. When the liquid level reaches the upper measurement limit, again under the influence of the magnetic field from the magnetic float, a reed switch sends a signal with a different resistance value. The recorder uses this information to calculate the amount of oil produced by the well and stores the relevant data. (2) The signal transmission system consists of reed switches for remote transmission, digital displays, recorders, and wires. The reed switch for remote transmission is equipped with four signal transmission points: a lower measurement limit, an upper measurement limit, a lower alarm limit, and an upper alarm limit. During liquid volume measurement, the recorder sends out a signaling signal; when the liquid level in the separator is below (above) the set lower limit, the drain valve is closed (opened). Once the liquid level in the separator reaches the set lower limit, a reed switch sends a signal to close the separator’s drain valve. The digital display shows the liquid level in the separator, while the recorder captures the data related to fluid measurement and calculates the amount of fluid produced. The personnel on duty can monitor various parameters in real time on the instruments in the control room. With modern communication devices, it is also possible to transmit this data remotely, allowing technicians to stay informed about the data from each individual well at any time. (3) The automatic drainage system consists of a reed switch for remote control, solenoid valves, a recorder, and wires. When the separator discharges liquid, once the liquid level inside the separator reaches the lower measurement limit, the reed switch, under the influence of the magnetic field generated by the float of the level gauge, sends an electrical signal. This signal activates the control motor of the solenoid valve, causing the electronic handwheel to rotate and close the discharge valve of the separator, thereby allowing for a second measurement of the oil well’s production volume. The recorder then starts working. When the liquid level inside the separator reaches the upper measurement limit, the discharge valve opens to allow liquid to flow out; the recorder calculates the volume of liquid produced based on the time it took for the discharge to occur. Through appropriate settings, it is possible to monitor the oil well’s production volume throughout the day. (4) The level alarm system consists of a reed switch for remote transmission, an alarm device, and wires. If the drain valve cannot be opened in time, it will cause the liquid level inside the separator to continue rising. When the liquid level reaches the natural gas outlet, the produced liquid will enter the natural gas pipeline, causing losses for natural gas users. When the separator discharges liquid, if the liquid level reaches the lower limit set for measurement, the discharge valve does not close on its own. When the level drops to the discharge port, both gas and liquid will enter the liquid storage tank, resulting in a loss of gas volume; in severe cases, this can also cause environmental pollution. To prevent such accidents, lower and upper alarm marks are provided on the magnetic flip plate. When the liquid level in the separator reaches these alarm marks, the magnetic field generated by the magnet of the level gauge triggers an alarm signal. The alarm installed in the control room will emit audible and visual alerts until the duty personnel detect and resolve the fault, at which point the alarm stops. II. Structure and Principle of the Automatic Separator Level Control System 1. Schematic diagram of the automatic separator level control system. http://www.huoyumi.com/d/file/ywj/2019-06-26/864b9a0dc69a1f79e614b839a3277d6c.jpg http://www.huoyumi.com/d/file/ywj/2019-06-26/6e57813ba26b3ad46ede7158b42a8cca.jpg 2. Functions of the automatic level control system for the separator. Function 1: It enables automatic control of the liquid level inside the separator, ensuring that the liquid level remains within an appropriate range and preventing gas from entering the liquid storage tank as well as liquid from entering the gas pipeline. Function 2: It enables the measurement and recording of oil production from oil wells on a 24/7 basis, providing a basis for analyzing changes in the production capacity of these wells. Function 3: It features monitoring of the liquid level inside the separator; when the liquid level exceeds the set threshold, it emits alarms via sound and light signals to alert operators to take action promptly. 3. Working principle of the automatic separator level control system. The working principle of liquid level measurement involves the operator sending a measurement signal via the recorder 6. The reed switch transmitter 5 uses a magnetic flap level gauge 4 to determine the liquid level. When the liquid level in the separator falls below the set measurement threshold, the resistance component of the reed switch transmitter sends a signal to close the oil outlet valve. Once the liquid level in the separator reaches the set threshold, the resistance component 503 of the reed switch transmitter sends a signal; the digital display and recorder 6 convert the received resistance value signal into an electrical current signal and begin to record the oil volume information, thereby measuring the oil production rate of the well. When the liquid level reaches the upper measurement limit, the resistance component 504 sends a signal. The digital display and recorder 6 analyze the received information to calculate the oil production volume of the well; meanwhile, it converts this signal into a control signal for the solenoid valve, which opens to allow the liquid in the separator to be discharged into the oil storage tank. When the liquid level in the separator drops to the lower limit, the reed switch connected to the resistance component 503 sends another signal, causing the solenoid valve used for discharging liquid from the separator to close again, so that the next measurement of the liquid level can be carried out. When the liquid level in the separator is above the measurement lower limit, the reed switch remote resistance element sends a signal to open the drain valve; when the liquid level in the separator reaches the measurement lower limit, the reed switch remote resistance component 503 sends a signal to close the separator’s drain valve. In the automatic control system, the digital display instruments and recorders 6 will begin to measure the oil production volume of the well once again. The workers on duty can adjust the digital display and recorder 6 according to the oil measurement requirements of different wells, determine the number of measurements taken, and obtain accurate information on oil production from those wells. Control principle of the liquid level height in the poultry separator: To ensure the continuous operation of the separator and the stable supply of natural gas, the inflow and outflow rates of liquid into the separator must be balanced, so as to maintain the liquid level inside the separator at a reasonable level. This system controls the level of liquid in the separator based on the following principle: when the amount of liquid entering the separator is less than the amount being discharged, the liquid level inside the separator drops. When it drops to the position of the resistor 503, the reed switch 5 sends a signal to the recorder 6. The recorder 6 then converts this signal into a control signal for the solenoid valve that regulates liquid discharge, thereby reducing the valve’s opening degree and decreasing the amount of liquid discharged. When the amount of liquid entering the separator is greater than the amount being discharged, the liquid level inside the separator rises. When it reaches the position of the resistor 504, the reed switch 5 sends a signal to the recorder 6. The recorder 6 converts this signal into a control signal that increases the opening degree of the solenoid valve 3 used for discharging air from the separator, thereby increasing the discharge volume and keeping the liquid level inside the separator at a reasonable height. When the drain valve cannot be opened (or closed), the liquid level inside the separator continues to rise (or fall). When the liquid level reaches the position of the resistor 509 (508), the reed switch 5 sends a signal to the digital display and recorder 6. After converting this signal, the digital display and recorder 6 send it to the alarm element 7 installed in the control room. The alarm element 7 continuously emits sound and light alerts to prompt the personnel on duty to resolve the fault; the alerting stops only once the fault is resolved. III. Promotion and Efficiency Gains of the Automatic Level Control System for Separators: After the development of the automatic level control system for separators, it was put into use at various scattered well sites such as Wu 3 and Wu 4 in the North China Oilfield. After more than a year of use, it has not only enabled automatic measurement of the oil production volume from the wells, but also allowed for automatic adjustment of the output volume based on changes in the inflow volume to the separator, thus maintaining the liquid level inside the separator at an appropriate height. The tasks that previously required manual handling are now carried out automatically by the separator level control system. This not only reduces the workload of the staff on duty but also increases the safety factor of operation, while reducing the incidence of failures caused by liquid entering the natural gas pipelines and natural gas entering the oil storage tanks. Each system can reduce the workload of one employee per year, cut natural gas losses by 50,000 cubic meters, and generate savings of over 500,000 yuan annually. This technology has been in use for over a year and has become mature enough to be promoted; it can be applied in oil and gas production sites that meet the required conditions. IV. Conclusion The automatic level control system for separators utilizes electronic components to achieve automatic control of the separator’s liquid level, automatic measurement of the liquid production volume, and alarm functionality at the preset level thresholds for the separator’s liquid level. In its application, this automatic level control system not only reduces the workload of employees and minimizes the need for manual labor, but also offers higher measurement accuracy and safer operation compared to traditional manual methods, thus holding good prospects for future use.