A differential pressure controller and measurement method for liquid level detection

Abstract

In order to solve the potential safety hazard caused by the need for sensors to directly contact the oil when measuring the oil level in the prior art, the present invention provides a new differential pressure controller for liquid level detection, including a passive detection head for detecting the liquid level height and a gas-to-electric converter for receiving the output signal of the passive detection head; the characteristics are: the passive detection head includes two mutually isolated liquid inlets, one high and one low from the liquid surface; the gas-to-electric converter includes two air pressure sensors and a control unit for receiving the difference between the two air pressure sensors; wherein the two liquid inlets, one high and one low, are respectively connected to the two air pressure sensors for detecting the change data of the air pressure at the two liquid inlets, one high and one low. The present invention uses air pressure changes to respond to liquid level changes, so that the sensor can measure the height of the liquid surface without contacting the liquid surface, and the electrical components that generate sparks are separated from the oil, thereby improving safety.

Description

Technical Field

[0001] The invention relates to the field of petrochemical industry, and in particular to a differential pressure controller for liquid level detection which is not in direct contact with oil products and a measuring method. Background Art

[0002] At present, in the field of liquid level detection in the modern petrochemical industry, voltage technology is generally used, with electronic components and cable connections, and the formed circuit is in direct contact with the oil product; in actual use, cables are often damaged, resulting in poor sealing and sparks, which seriously threaten the safe production of petrochemical enterprises. Summary of the invention

[0003] In order to solve the potential safety hazard caused by the need for sensors to directly contact the oil when measuring the oil level in the prior art, the present invention provides a new differential pressure controller for liquid level detection. The present invention uses air pressure changes to react to liquid level changes, so that the sensor can measure the height of the liquid level without contacting the liquid surface, and the electrical components that generate sparks are separated from the oil, thereby improving safety.

[0004] The differential pressure controller for liquid level detection comprises a passive detection head for detecting the liquid level height and a gas-to-electric converter for receiving the output signal of the passive detection head; the characteristics are:

[0005] The passive detection head includes two mutually isolated liquid inlets, one high and one low from the liquid surface;

[0006] Among them, two liquid inlets, one high and one low, are respectively connected to two air pressure sensors for detecting the change data of the air pressure at the two liquid inlets; the gas-to-electric converter includes two air pressure sensors and a control unit for receiving the difference between the two air pressure sensors; when the difference in the electrical characteristic signals output by the two air pressure sensors is greater than the threshold set in the control unit, an alarm signal is issued.

[0007] The passive detection head comprises a lower shell for immersion under the liquid surface, a straight tube with one end connected to the end of the lower shell away from the liquid surface, and a hose with one end connected to the other end of the straight tube;

[0008] The gas-to-electric converter further includes a housing for arranging the first air pressure sensor and the second air pressure sensor, a filling body for encapsulating the first air pressure sensor and the second air pressure sensor, and a circuit board for arranging the single-chip microcomputer; the other end of the hose is connected to the housing;

[0009] Among them, a low-level through hole is arranged at one end of the lower shell body close to the liquid surface; a high-level through hole is arranged on the side wall of the lower shell body; the low-level through hole and the high-level through hole are respectively connected to the detection ends of the first air pressure sensor and the second air pressure sensor in the outer shell after passing through the straight pipe and the hose in sequence through the low-level connecting pipe and the high-level connecting pipe respectively; the signal output ends of the first air pressure sensor and the second air pressure sensor are electrically connected to the single-chip microcomputer.

[0010] A protective component is provided between the lower shell and the straight pipe;

[0011] Wherein, the protection component includes a metal hose and a spring coaxially arranged in the metal hose;

[0012] Among them, the metal hose is detachably connected to the lower shell and the straight pipe;

[0013] Wherein, the low-position connecting pipe and the high-position connecting pipe are both arranged inside the spring.

[0014] As mentioned above, a differential pressure controller for liquid level detection also includes an explosion-proof box; wherein the explosion-proof box includes a box; a circuit board is detachably arranged in the box; and the box is detachably connected to the outer shell.

[0015] The box body is provided with a power hole for passing the power line, a low level indicator light for indicating that the liquid level is lower than the high level through hole, a high level indicator light for indicating that the liquid level exceeds the high level through hole, and a sound alarm for alarming that the liquid level exceeds the high level through hole;

[0016] Among them, the low-level indicator light, the high-level indicator light and the sound alarm are all electrically connected to the single-chip microcomputer.

[0017] The circuit board also includes a filter circuit, a voltage difference comparison circuit, a differential amplifier circuit and a voltage follower;

[0018] Among them, the output ends of the first air pressure sensor and the second air pressure sensor are respectively connected to a filter circuit for filtering high-frequency interference signals, and then connected to a pressure difference comparison circuit for comparing the output signals of the first air pressure sensor and the second air pressure sensor. The output end of the pressure difference comparison circuit is connected to a differential amplifier circuit, and then connected to a voltage follower for voltage stabilization, and finally connected to a single-chip microcomputer.

[0019] A detection method for a differential pressure controller for liquid level detection as described above, characterized in that: after a passive detection head is lowered into an oil tank, the output electrical characteristic values ​​of two air pressure sensors are subtracted, and the difference is finally sent to a control unit; as the liquid level rises, a lower liquid inlet contacts the liquid surface first, so that a sealed air plug is formed between the lower liquid inlet and the air pressure sensor; at the initial moment, two liquid inlets, one high and one low, arranged on the passive detection head have the same air pressure when they are not in contact with the liquid surface; as the liquid level rises, a sealed air plug is formed between the lower liquid inlet and the air pressure sensor, and the air pressure gradually increases until the higher liquid inlet also enters the liquid; the difference between the output electrical characteristic values ​​of the two air pressure sensors shows a gradually increasing trend until the pressure threshold set in the control unit is reached; the control unit controls the actuator to sound and light alarms.

[0020] The beneficial effects brought by the present invention are as follows: the passive detection head of the present invention is provided with two mutually isolated liquid inlets, one high and one low, and then connected to the air pressure sensor through the low-position connecting pipe and the high-position connecting pipe respectively. When the passive detection head is lowered into the oil tank along with the oil loading crane pipe, when the liquid level does not immerse the passive detection head, the pressure in the low-position connecting pipe and the high-position connecting pipe is equal, and the integrated circuit on the circuit board is in a standby state;

[0021] When the oil level rises, different air pressures are generated in the low-level connecting pipe and the high-level connecting pipe. The two air pressures are input into the pressure difference comparison circuit, and the output is a weak mV-level pressure difference voltage signal. The voltage signal passes through the filter circuit to filter out possible high-frequency interference signals and is sent to the differential amplifier circuit for signal amplification. The amplified voltage signal is stabilized by the voltage follower and sent to a control unit such as a single-chip microcomputer. When the liquid level continues to rise, the control unit detects that the voltage difference signal is greater than the threshold, drives the relay to output the switch value, and issues a voice alarm at the same time.

[0022] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0023] 1. Air pressure signal detection is used in tank trucks and oil and gas high concentration areas. All parts of the passive detection head are made of aluminum, which essentially realizes non-electric detection and is safe and explosion-proof.

[0024] 2. Isolation is used for air pressure detection to ensure that oil and gas will not be transported to the energized unit, and to improve the accuracy and safety of detection.

[0025] 3. The piezoelectric converter is installed away from oil and gas intensive areas and transmitted through gas cables, which not only improves the detection speed, but also fundamentally eliminates the safety hazards of using cables to introduce detection into the tank truck.

[0026] 4. The present invention utilizes a differential pressure detection system to detect the liquid level, which greatly improves the accuracy of detection.

[0027] 5. The present invention utilizes a pressure difference detection probe without a mechanical action structure, which greatly reduces failures and improves detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the present invention.

[0029] Figure 2 for Figure 1 A partial enlargement of the figure.

[0030] Figure 3 for Figure 1 A partial enlargement of the figure.

[0031] Figure 4 This is a partial circuit schematic.

[0032] Figure 5 This is a partial circuit schematic.

[0033] Figure 6 This is a partial circuit schematic. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0035] like Figures 1 to 3 As shown, the differential pressure controller for liquid level detection comprises a passive detection head 1 for detecting the liquid level height and a gas-to-electric converter 2 for receiving the output signal of the passive detection head 1; it is characterized in that: the passive detection head 1 comprises two mutually isolated liquid inlets, one high and one low from the liquid surface; wherein the two liquid inlets, one high and one low, are respectively connected to two air pressure sensors for detecting the change data of the air pressure at the two liquid inlets, one high and one low; the air-to-electric converter 2 comprises two air pressure sensors and a control unit for receiving the difference between the two air pressure sensors; when the difference between the electrical characteristic signals output by the two air pressure sensors is greater than the threshold value set in the control unit, an alarm signal is issued.

[0036] In actual use, if the passive detection head 1 only uses a single liquid inlet, if the liquid inlet is blocked, the control unit will not receive signals continuously, which may easily cause misoperation. However, using two isolated liquid inlets, one high and one low, can ensure that when one fails, an abnormal signal is issued, and the control unit determines that the passive detection head 1 fails based on the abnormal signal, and the control unit can issue an alarm signal to remind the user.

[0037] Specifically, when the low-level liquid inlet is blocked, the continuous pressure value of the low-level liquid inlet is zero. After liquid enters the high-level liquid inlet, the pressure signal of the high-level air pressure sensor gradually increases. When the difference between the two air pressure sensor signals reaches the threshold, an alarm signal is also issued, eliminating the hidden dangers of blockage of the liquid inlet and continuous increase in liquid level.

[0038] When the high-level liquid inlet is blocked, the continuous pressure value of the high-level liquid inlet is zero, and the pressure signal of the low-level air pressure sensor gradually increases. When the difference between the two air pressure sensor signals reaches the threshold, an alarm signal is also issued, eliminating the hidden dangers of blockage of the liquid inlet and continuous increase in liquid level.

[0039] The passive detection head 1 comprises a lower shell 101 for immersion under the liquid surface, a straight tube 102 with one end connected to the end of the lower shell 101 away from the liquid surface, and a hose 103 with one end connected to the other end of the straight tube 102;

[0040] The gas-to-electric converter 2 further includes a housing 201 for arranging the first air pressure sensor 2A and the second air pressure sensor 2B, a filling body 202 for encapsulating the first air pressure sensor 2A and the second air pressure sensor 2B arranged in the housing 201, and a circuit board 203 for arranging the single-chip computer 2C; the other end of the hose 103 is connected to the housing 201;

[0041] Among them, a low-level through hole 1A is provided at one end of the lower shell 101 close to the liquid surface; a high-level through hole 1B is provided on the side wall of the lower shell 101; the low-level through hole 1A and the high-level through hole 1B respectively pass through the straight pipe 102 and the hose 103 in sequence through the low-level connecting pipe 1C and the high-level connecting pipe 1D, and are respectively connected to the detection ends of the first air pressure sensor 2A and the second air pressure sensor 2B in the outer shell 201; the signal output ends of the first air pressure sensor 2A and the second air pressure sensor 2B are electrically connected to the single-chip computer 2C.

[0042] It should be clarified that: specifically, the straight pipe 102 and the hose 103, the hose 103 and the housing 201, and the housing 201 and the explosion-proof box 3 can all be detachably connected via a flexible joint.

[0043] A protection component 104 is provided between the lower shell 101 and the straight pipe 102;

[0044] The protection assembly 104 includes a metal hose 1041 and a spring 1042 coaxially disposed in the metal hose 1041;

[0045] The two axial ends of the metal hose 1041 are both provided with threads; the connection between the lower shell 101, the straight tube 102 and the metal hose 1041 is provided with bolt parts;

[0046] The metal hose 1041 is detachably connected to the lower shell 101 and the straight pipe 102;

[0047] Among them, the low-level connecting pipe 1C and the high-level connecting pipe 1D are both arranged inside the spring 1042.

[0048] It should be clear that the function of the filling body 202 is to isolate and encapsulate the charged first air pressure sensor 2A and the second air pressure sensor 2B from the oil surface. The material of the filling body 202 is corrosion-resistant material, such as resin.

[0049] It should be clarified that when the low-level through hole 1A and the high-level through hole 1B pass through the low-level connecting pipe 1C and the high-level connecting pipe 1D respectively, in order to prevent the low-level connecting pipe 1C and the high-level connecting pipe 1D from moving up and down during use, the low-level connecting pipe 1C and the high-level connecting pipe 1D are fixed to the straight pipe 102 through the filling body 202.

[0050] It should be made clear that during use, it was found that the metal hose 1041 was very easy to break, and it was easy to break after being impacted by a heavy object or bent multiple times. Therefore, a spring 1042 is coaxially arranged inside the metal hose 1041. When impacted by a heavy object, the force exerted on the metal hose 1041 is transmitted to the spring 1042, and then transmitted on the spiral structure of the spring 1042 to decompose the force. Therefore, during use, the metal hose 1041 of the present invention will jump when impacted by a heavy object, but will not deform. At the same time, when the metal hose 1041 is axially deformed by an external force, the metal hose 1041 can be made to rebound to prevent multiple bending and fracture.

[0051] In the present invention, after the spring 1042 is coaxially arranged in the metal hose 1041, the service life is increased.

[0052] As mentioned above, a differential pressure controller for liquid level detection further includes an explosion-proof box 3; wherein the explosion-proof box 3 includes a box 301; the circuit board 203 is detachably arranged in the box 301; and the box 301 is detachably connected to the housing 201.

[0053] It should be noted that studs are provided on any inner side surface of the explosion-proof box 3 , and the circuit board 203 is fixed by screws.

[0054] The box body 301 is provided with a power hole 301A for passing a power cord, a low level indicator light 301B for indicating that the liquid level is lower than the high level through hole 1B, a high level indicator light 301C for indicating that the liquid level exceeds the high level through hole 1B, and a sound alarm 301D for alarming that the liquid level exceeds the high level through hole 1B;

[0055] Among them, the low-level indicator light 301B, the high-level indicator light 301C and the sound alarm 301D are all electrically connected to the single-chip computer 2C.

[0056] It should be clear that using the single chip microcomputer 2C to control the indicator light to turn off, power on and the sound alarm 301D is a prior art.

[0057] like Figures 4 to 6 , the circuit board 203 further includes a filter circuit 2031, a voltage difference comparison circuit 2034, a differential amplifier circuit 2032 and a voltage follower 2033;

[0058] Among them, the output ends of the first air pressure sensor 2A and the second air pressure sensor 2B are respectively connected to the filter circuit 2031 for filtering high-frequency interference signals, and then connected to the pressure difference comparison circuit 2034 for comparing the output signals of the first air pressure sensor 2A and the second air pressure sensor 2B. The output end of the pressure difference comparison circuit 2034 is connected to the differential amplifier circuit 2032, and then connected to the voltage follower 2033 for voltage stabilization, and finally connected to the single-chip computer 2C.

[0059] The output ends of the first air pressure sensor 2A and the second air pressure sensor 2B are connected to the circuit board 203 via the plug-in terminal 203A. Since the plug-in terminal 203A and the circuit board 203 are arranged in the explosion-proof box 3, the first air pressure sensor 2A and the second air pressure sensor 2B are isolated and sealed by the filling body 202, so that the electrical components are completely isolated from the oil and gas, and the safety and durability are greatly improved.

[0060] Preferably, Figure 4 In the circuit, capacitors C2, C3, C4, resistors R7, R10, and common-mode inductors are interference elimination circuits, which together form a low-pass filter to suppress radio frequency interference signals. Integrated block U1-ABD forms a differential signal amplification circuit, such as a voltage difference comparison circuit 2034 and a differential amplifier circuit 2032. The circuit has a very high common-mode rejection ratio and can well suppress common-mode signals.

[0061] The method of using the present invention is as follows: after the passive detection head 1 is lowered into the oil tank along with the oil loading crane pipe, the two air pressure sensors output electrical characteristic values ​​to the pressure difference comparison circuit 2034, and the output electrical characteristic values ​​are subtracted, and finally the difference output by the pressure difference comparison circuit 2034 is sent to the control unit; as the liquid level rises, the lower liquid inlet first contacts the liquid surface, so that a closed air plug is formed between the lower liquid inlet and the air pressure sensor; at the initial moment, the two liquid inlets, one high and one low, set on the passive detection head 1 have the same air pressure when not in contact with the liquid surface; as the liquid level rises, a closed air plug is formed between the lower liquid inlet and the air pressure sensor, and the air pressure gradually increases until the higher liquid inlet also enters the liquid; after the two air pressure sensors output electrical characteristic values ​​to the pressure difference comparison circuit 2034 for subtraction, the difference shows a trend of gradually increasing until the pressure threshold set in the control unit is reached; the control unit controls the execution component to sound and light alarm.

[0062] The present invention is arranged on the sealing cover of the oil tanker. Specifically, a through hole is arranged on the sealing cover, and the present invention is inserted into the tank body of the oil tanker and measured after being fixed. In order to ensure the sealing performance, a sealing ring can be arranged for sealing.

[0063] The above description is only a preferred embodiment of the invention and is not intended to limit the invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the invention should be included in the protection scope of the invention.

Claims

1. A differential pressure controller for liquid level detection, used for measuring the liquid level of oil in a tank truck, comprising a passive detection head (1) for detecting the liquid level height, and a gas-to-electric converter (2) for receiving an output signal of the passive detection head (1); characterized in that: The passive detection head (1) comprises two liquid inlets, one higher and one lower than the liquid surface, which are isolated from each other; Among them, two liquid inlets, one high and one low, are respectively connected to two air pressure sensors for detecting the change data of the air pressure at the two liquid inlets, one high and one low; The passive detection head (1) comprises a lower shell (101) for immersion under the liquid surface, a straight tube (102) having one end connected to an end of the lower shell (101) away from the liquid surface, and a hose (103) having one end connected to the other end of the straight tube (102); wherein a low-position through hole (1A) is provided at an end of the lower shell (101) close to the liquid surface; and a high-position through hole (1B) is provided on the side wall of the lower shell (101); A protection component (104) is provided between the lower shell (101) and the straight tube (102); wherein the protection component (104) comprises a metal hose (1041) and a spring (1042) coaxially arranged inside the metal hose (1041); The gas-to-electric converter (2) comprises two gas pressure sensors and a control unit for receiving a difference between the two gas pressure sensors; when the difference between the electrical characteristic signals output by the two gas pressure sensors is greater than a threshold value set in the control unit, an alarm signal is issued; The gas-to-electric converter (2) further comprises a housing (201) for arranging the first air pressure sensor (2A) and the second air pressure sensor (2B), a filling body (202) arranged in the housing (201) for encapsulating the first air pressure sensor (2A) and the second air pressure sensor (2B), and a circuit board (203) for arranging the single-chip computer (2C); the other end of the hose (103) is in communication with the housing (201); The low-position through hole (1A) and the high-position through hole (1B) are connected to the detection ends of the first air pressure sensor (2A) and the second air pressure sensor (2B) in the housing (201) respectively after passing through the straight tube (102) and the hose (103) in sequence through the low-position connecting tube (1C) and the high-position connecting tube (1D); the signal output ends of the first air pressure sensor (2A) and the second air pressure sensor (2B) are electrically connected to the single-chip computer (2C); The metal hose (1041) is detachably connected to the lower shell (101) and the straight pipe (102); wherein the low-position connecting pipe (1C) and the high-position connecting pipe (1D) are both arranged inside the spring (1042); The differential pressure controller further comprises an explosion-proof housing (3); wherein the explosion-proof housing (3) comprises a housing (301); the circuit board (203) is detachably arranged in the housing (301); and the housing (301) is detachably connected to the outer shell (201).

2. A differential pressure controller for liquid level detection according to claim 1, characterized in that: The box body (301) is provided with a power hole (301A) for passing a power cord, a low-level indicator light (301B) for indicating that the liquid level is lower than the high-level through hole (1B), a high-level indicator light (301C) for indicating that the liquid level exceeds the high-level through hole (1B), and a sound alarm (301D) for alarming that the liquid level exceeds the high-level through hole (1B); The low-position indicator light (301B), the high-position indicator light (301C) and the sound alarm (301D) are all electrically connected to the single-chip computer (2C).

3. A differential pressure controller for liquid level detection according to claim 1, characterized in that: The circuit board (203) further comprises a filter circuit (2031), a voltage difference comparison circuit (2034), a differential amplifier circuit (2032) and a voltage follower (2033); The output ends of the first air pressure sensor (2A) and the second air pressure sensor (2B) are respectively connected to a filter circuit (2031) for filtering high-frequency interference signals, and then connected to a pressure difference comparison circuit (2034) for comparing the output signals of the first air pressure sensor (2A) and the second air pressure sensor (2B); the output end of the pressure difference comparison circuit (2034) is connected to a differential amplifier circuit (2032), and then connected to a voltage follower (2033) for voltage stabilization, and finally connected to a single-chip computer (2C).

4. A detection method of a differential pressure controller for liquid level detection as claimed in claim 1, characterized in that: After the passive detection head (1) is lowered into the oil tank, the electrical characteristic values ​​output by the two air pressure sensors are subtracted, and the difference is finally sent to the control unit; as the liquid level rises, the lower liquid inlet first contacts the liquid surface, so that a sealed air plug is formed between the lower liquid inlet and the air pressure sensor; at the initial moment, the two liquid inlets, one high and one low, provided on the passive detection head (1) have the same air pressure when not in contact with the liquid surface; as the liquid level rises, the air pressure formed between the lower liquid inlet and the air pressure sensor gradually increases until the higher liquid inlet also enters the liquid; the difference between the electrical characteristic values ​​output by the two air pressure sensors shows a trend of gradually increasing until the pressure threshold set in the control unit is reached; the control unit controls the actuator to sound and light alarms.

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