Container for pressurized liquid gas and liquid level measuring system

Abstract

According to the invention, a container (1) is provided for a pressurized liquid gas, such as LPG or LNG, having an opening (2) from the outside of the container (1) to the inside of the container and having a microwave level sensor (4) mounted on the outside of the container (1) and above the opening (2), the microwave level sensor is configured to emit microwave beams towards the interior of the container (1) and to receive microwave beams reflected from the surface of the liquid inside the container (1). A cover (3) which closes the opening (2) is arranged between the microwave level sensor (4) and the interior of the container (1), wherein the cover (3) is made of a plastic material through which at least part of the microwave beams can pass.

Description

Technical Field

[0001] The invention relates generally to the field of containers for storing liquid products and to a measuring device for determining and monitoring the filling level of a product stored in a container by means of a microwave transit time measurement method. More specifically, the subject of the invention is a container for pressurized liquid gas, such as LPG (liquefied petroleum gas) or LNG (liquefied natural gas), comprising a microwave level sensor. The invention also relates to a level measurement system. Background Art

[0002] Various devices are currently known for monitoring and measuring the filling level of a liquid medium in a container. These are, for example, mechanical float level indicators, magnetostrictive probes, ultrasonic sensors and radar (microwave) tank measuring instruments.

[0003] Each of these known devices has some disadvantages. Some of them have mechanically movable parts that may get stuck or not work accurately in low liquid level situations. Other devices are difficult to install or replace on the container because they require degassing of the tank or are expensive.

[0004] Known radar tank measuring instruments operate on the principle of the microwave transit time measurement method for determining the fill level in a container. The fill level of the medium in the container is determined based on the transit time of the measuring signal, which is the distance between the microwaves emitted via the antenna toward the surface of the medium and reflected on the surface of the medium and received by the transceiver.

[0005] These known measuring devices or their components are exposed to high pressures, since they require some components to be mounted inside the container / tank, or at least require through-holes in the tank in order to fit the sensors therein.

[0006] In order to protect the measuring electronics and the microwave signal coupling in the transmitter from high voltages and aggressive chemicals and to keep the radiation characteristics of the antenna constant, the sensor element or the sensitive element of the antenna is sealed outside the container (tank).

[0007] WO 2003 / 046491 A1 discloses an antenna for protecting level measurement from aggressive chemical media and high temperatures by at least partially filling with a dielectric material or a disk-shaped dielectric element.

[0008] WO 01 / 88488 A1 discloses a fill-level measuring device having an antenna, a hollow conductor, the hollow conductor coupled in the form of a circuit board, and an electrical conductor attached to the hollow conductor, which protrudes into the hollow conductor. Summary of the invention

[0009] The object of the present invention is to provide a simple and cost-effective solution for measuring the fill level of a liquid medium in a closed container, which solution eliminates the above-mentioned disadvantages.

[0010] According to a first aspect of the present invention, there is provided a container for pressurized liquid gas (such as LPG or LNG), the container having an opening leading from the outside of the container to the inside thereof, the opening being used for mounting a microwave level sensor on the outside of the container and above the opening, the microwave level sensor being configured to emit microwave beams toward the inside of the container and the microwave level sensor being configured to receive microwave beams reflected from the surface of the liquid in the container, and the container further comprising a cover closing the opening, wherein the cover is made of a plastic material that is transparent to at least a portion of the microwave beams.

[0011] Throughout the disclosure of the present invention, "a cover made of a material that is transparent to at least a portion of the microwave beam" means that the cover is made of the following material: the material allows at least a portion of the microwave beam emitted from the sensor to pass through the cover into the container and at least a portion of the microwave beam reflected from the surface of the liquid in the container to pass through the cover and return to the sensor.

[0012] In one embodiment, the opening is provided with a flange for mounting a level sensor, and the cover is mounted on the flange, preferably the cover is mounted on the top of the container.

[0013] In another embodiment, the cover is tightly sealed.

[0014] In another embodiment, the cover is made of a thermoformable plastic, a resin (raisin), or a composite-based polymer reinforced with a mineral or synthetic material.

[0015] In another embodiment, the cover is made of a plastic material having a coefficient of thermal expansion similar to that of the container within the operating temperature range of LPG or LNG.

[0016] In another embodiment, the cover is made of modified polyamide.

[0017] In another embodiment, the cover is made of polyaryletherketone, preferably the cover is made of polyetheretherketone.

[0018] In another embodiment, the cover is partially made of metal.

[0019] In another embodiment, the cover has a flat bottom surface or a convex spherical bottom surface.

[0020] In another embodiment, the container further includes: a microwave liquid level sensor and a mounting device, wherein the microwave liquid level sensor is mounted on the outside of the container and located above the opening, the microwave liquid level sensor being configured to transmit microwave beams toward the interior of the container and receive microwave beams reflected from the surface of the liquid in the container; the mounting device being configured to assemble and disassemble the microwave liquid level sensor to and from the container without removing the cover, wherein the cover closes the opening in the container and is located between the microwave liquid level sensor and the interior of the container.

[0021] In another embodiment, the microwave level sensor is configured for analyzing the received microwave beam using an algorithm, preferably an adaptive algorithm.

[0022] According to a second aspect of the present invention, there is also provided a liquid level measurement system, the liquid level measurement system comprising the above disclosed container and further comprising a data recording device.

[0023] In one embodiment, the liquid level measurement system further comprises a display, which is preferably an LCD display or an electronic paper display.

[0024] In another embodiment, the liquid level measurement system further comprises a power source, which is preferably a battery or a photovoltaic cell.

[0025] In yet another embodiment, the photovoltaic cell is a silicon-based cell or a perovskite-based cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will now be discussed in more detail with reference to the accompanying drawings, in which:

[0027] Figure 1 is an exploded view of a liquid level measurement system according to a preferred embodiment of the present invention.

[0028] Figure 2 It is a bottom side view of the cover.

[0029] Figure 3 It is the obstacle detection map measured by the level measurement system.

[0030] Figure 4 is an exploded side view of the level measurement system without the container. DETAILED DESCRIPTION

[0031] Tanks used to store fluids like gasoline and other flammable products are usually metal containers that are tightly sealed to not allow any vapor to leave the container and not allow any material to get in. Some flammable products are stored under pressure, which means that the pressure in the container is higher than the pressure outside the container.

[0032] Figure 1An exploded view of a level measurement system according to a preferred embodiment of the present invention is shown. A container 1 (only a partial view is shown) is a metal tank for storing pressurized liquid gas (such as LPG (liquefied petroleum gas) or LNG (liquefied natural gas)). Information about the amount of liquid stored is crucial and valuable as a gas. A sudden drop in gas level may also indicate a gas leak in a storage or delivery system. This is why the container 1 has an opening 2 (a through hole in the tank wall) leading from the outside of the container 1 to its inside. A microwave level sensor 4 is mounted on the outside of the container 1, above the opening 2. The microwave level sensor 4 emits a microwave beam toward the inside of the container 1 and receives a signal reflected back by the surface of the liquid. A portion of the emitted microwave beam passes through the cover, while the rest is reflected or scattered by the cover 3. The portion of the beam that passes through further travels toward the surface of the liquid, and again, a portion of the beam reflected from the surface passes through the cover 3 back to the sensor 4, and another portion of the beam penetrates the liquid toward the bottom of the container 1. After reaching the bottom, the portion of the microwave beam reflected from the bottom also returns toward the sensor 4.

[0033] By calculating the time difference or frequency difference between the emitted microwave beam and the microwave beam reflected back from the liquid surface in the container 1 and received by the microwave level sensor 4, one can estimate the level of the liquid. Based on this estimation, the fill level of the liquid can be determined. The microwave level sensor 4 can be configured and programmed to perform such an estimation.

[0034] In a preferred embodiment, the microwave level sensor 4 is capable of receiving all reflected beams (i.e., beams reflected from different surfaces including the gas surface) and selecting only the beam reflected from the surface of the liquid stored in the container 1 for measuring the level of the liquid. An algorithm for selecting the right beam may be used, such as an FFT (Fast Fourier Transform) signal analysis algorithm and / or an adaptive algorithm based on a machine learning algorithm. Figure 3 is a diagram showing two reflected beams that have been received and analyzed. The first beam with the larger amplitude is the beam reflected from the cover 3 itself. The second beam with the smaller amplitude is the beam reflected from the gas surface. The received beam pattern may be much more complex because there may be many more reflections and refractions of the beam.

[0035] As mentioned initially, the liquid stored in the container is flammable and chemically aggressive. Any direct contact with the microwave level sensor 4 can cause damage to the sensor or its components. In the worst case, it may even lead to ignition of the vapors caused by sparks generated by the electronics of the sensor. Therefore, the container 1 is provided with a cover 3 closing the opening 2 and sealing the container 1.

[0036] The cover 3 is made of plastic that can at least partially transmit microwaves. Preferably, the plastic is a synthetic polymer, a thermoplastic polymer such as polyaryletherketone (PAEK) or polyetheretherketone (PEEK), or a resin-based polymer. In some preferred embodiments, the cover 3 is made of a composite-based polymer reinforced by a mineral or synthetic material. The cover 3 must be as strong as the container 1 and must withstand the harsh conditions of the stored gas in the container 1. It must also withstand the harsh weather conditions outside the container. The container 1 shrinks and expands while filling, emptying and heating (e.g., being exposed to sunlight when stored outdoors) or cooling (e.g., when the pressurized gas stored inside is decompressed). The main function of the cover 3 is to seal the container and withstand mechanical stress in the same way as the container 1, while being at least partially through (half through) for microwaves. Partial through (half through) means that at least a portion of the microwave beam directed toward the cover 3 can pass through the cover 3.

[0037] The cover 3 is securely and tightly attached to the container 1, preferably by using screws, bolts, rivets, glue or pressed into the container 1. The attachment must be strong enough to maintain the pressure and temperature of the stored liquid.

[0038] In a preferred embodiment of the present invention, a container 1 suitable for pressurized liquid gas (such as LPG or LNG) is provided. The container 1 has an opening 2, and the container 1 has an opening 2 leading from the outside of the container 1 to the inside thereof, and the opening 2 is suitable for mounting a microwave level sensor 4 on the outside of the container 1, above the opening 2. The container 1 further includes a cover 3 closing the opening 2, wherein the cover 3 is made of a plastic material that can transmit (at least partially pass and / or semi-pass, meaning that at least a portion of the microwave beam directed to the cover 3 can pass) at least a portion of the microwave beam when the microwave beam is directed to the cover 3. The cover 3 is attached to the container 1, and in a preferred embodiment, the container 1 has a flange around the opening 2. The flange is a portion of the wall of the container 1, and the thickness of the portion around the opening 2 is greater than the thickness of the rest of the wall of the container 1. The flange can have a flat surface parallel to the ground on the upper side, which is suitable for attaching any kind of (mechanical, acoustic, microwave) level sensor or cover 3. In a preferred embodiment, the cover 3 is mounted on a flange for better leveling of the level sensor 4 when mounted to the cover 3. The flange is positioned on top of the container 1 for more accurate measurement. The flange for mounting the cover 3 and / or the level sensor 4 can be positioned in different positions. Moreover, the flange flat surface angle can vary.

[0039] The cover 3 is tightly sealed using a sealing element 6, such as a rubber O-ring, or any other method, such as bonding, pressing or screwing. The cover 3 is preferably made of a plastic material that has the ability to deform under high pressure and can adapt to the surface for sealing the connection.

[0040] Preferably, the cover 3 is made of a thermoformable plastic material to facilitate the manufacturing process using injection molding or 3D printing techniques. The cover may also be made of a resin or a composite material based polymer reinforced with a mineral or synthetic material.

[0041] In some embodiments, the cover 3 is partially made of metal, with a small portion of plastic material in the center forming a window-like structure. Metal parts reinforce the cover 3 in the outer parts or on the edges.

[0042] In one embodiment, the liquid level measurement system includes a microwave focusing element located on the side of the cover 3 facing the interior of the container 1 (preferably the bottom side). The cover focusing element constitutes a specially shaped bottom surface, which is suitable for shaping the microwaves generated by the sensor into a beam of a certain shape. For better measurement accuracy, containers of different shapes and different liquids may require beams of different shapes. The microwave beam propagating inside the metal container can be reflected, focused or scattered in a complex way, making it difficult to detect the reflected beam. Therefore, the accuracy of the measurement is very low. In a preferred embodiment, the focusing element has a convex spherical surface in the center. The convex spherical shape is preferably used for cylindrical metal containers filled with liquid gas (like LPG or CNG).

[0043] In another preferred embodiment, the cover 3 has a flat bottom surface. A flat surface is less likely to accumulate condensed gas or water droplets (liquid droplets) in one specific point. This makes the measurement more accurate.

[0044] In a preferred embodiment, the container 1 further includes a microwave level sensor 4, which is mounted on the outside of the container 1 above the opening 2. The microwave level sensor 4 is configured to transmit a microwave beam toward the inside of the container 1 and receive a beam reflected from the liquid surface. The microwave level sensor 4 also includes a mounting device configured to assemble and disassemble the microwave level sensor 4 to and from the container 1 without removing the cover 3. The microwave level sensor 4 is configured to receive all reflected and / or scattered beams and select beams reflected from the liquid surface.

[0045] The microwave level sensor 4 may be attached to the cover 3 by using screws, threads, bayonet mounts, press fits, magnets, glue or other means suitable for easily disconnecting the microwave level sensor 4 from the cover 3 .

[0046] The cover 5 is preferably used to protect the microwave level sensor 4 from external influences.

[0047] In another embodiment of the present invention, the liquid level measurement system includes a data logging device. The data logging device generally includes a microprocessor unit having a data storage element and a CPU unit programmed for liquid level calculation, storage information and / or communication. In a preferred embodiment, the microwave liquid level sensor 4 is communicatively connected to other data processing units via a radio communication device or a cable connection. This includes Internet communication via cable infrastructure or radio (such as WI-FI, GSM, Bluetooth, etc.).

[0048] In some embodiments, the level measurement system further comprises a display, preferably an LCD display or an electronic paper display, adapted to present information about at least the level of the liquid in the container.

[0049] The level measurement system may comprise a power source, preferably a battery or a photovoltaic cell, wherein the photovoltaic cell is a silicon-based cell or a perovskite-based cell.

[0050] In another preferred embodiment, the liquid level measurement system is configured to process information about the received signal inside the container. The signal is processed using advanced signal processing methods (such as Fast Fourie's Transformant, etc.) for measuring other liquid parameters (such as composition, purity, temperature, density, rheology). In another embodiment, the liquid level measurement system is configured to measure the parameters of the vapor above the liquid surface.

[0051] The microwave level sensor 4 according to the present invention uses a tank level measurement method based on radar technology. The radar system provides a high-precision, low-power solution and is quickly and easily installed on the tank without interfering with the tank structure. The radio band operation is not subject to interference from noise, dust, color or direct or indirect light. The sensor operates at a frequency of 60GHz and provides a few millimeters of accuracy within a distance of up to 5 meters.

[0052] Radar measurement technology can penetrate plastic obstacles and provide accurate level measurement with sensors located outside the tank. The sensor must be located on the top of the tank. Example sensor response and detection of possible obstacles and liquid levels.

Claims

1. A container (1) for pressurized liquid gas, such as LPG or LNG, the container (1) having an opening (2) leading from the outside of the container (1) to the inside of the container (1), the opening (2) being used for mounting a microwave level sensor (4) on the outside of the container (1) and above the opening (2), and the microwave level sensor (4) being configured to emit a microwave beam toward the inside of the container (1) and receive the microwave beam reflected from the surface of the liquid inside the container (1), characterized in that The container (1) further comprises a cover (3) for closing the opening (2), wherein the cover (3) is made of a plastic material that is transparent to at least a portion of the microwave beam.

2. The container according to claim 1, wherein The opening (2) is provided with a flange for mounting a liquid level sensor, and the cover (3) is mounted on the flange, preferably the cover (3) is mounted on the top of the container (1).

3. The container according to claim 1 or 2, wherein: The cover (3) is tightly sealed.

4. A container according to any one of the preceding claims 1 to 3, wherein: The cover (3) is made of thermoformable plastic, resin or composite material based polymer reinforced with mineral or synthetic materials.

5. A container according to any one of the preceding claims 1 to 4, wherein: The cover (3) is made of a plastic material having a thermal expansion coefficient similar to that of the container (1) within the operating temperature range of LPG or LNG.

6. The container according to any one of claims 1 to 5, wherein The cover (3) is made of modified polyamide.

7. The container according to any one of claims 1 to 5, wherein The cover (3) is made of polyaryletherketone (PAEK), preferably the cover (3) is made of polyetheretherketone (PEEK).

8. The container according to any one of claims 1 to 7, wherein The cover (3) is partially made of metal.

9. The container according to any one of claims 1 to 8, wherein The cover (3) has a flat bottom surface or a convex spherical bottom surface.

10. A container according to any one of the preceding claims 1 to 9, wherein: The container further comprises: a microwave liquid level sensor (4) and a mounting device, wherein the microwave liquid level sensor (4) is mounted on the outside of the container (1) and located above the opening (2), and the microwave liquid level sensor (4) is configured to emit a microwave beam toward the inside of the container (1) and receive the microwave beam reflected from the surface of the liquid inside the container (1), and the mounting device is configured to be used for assembling the microwave liquid level sensor (4) to and disassembling the microwave liquid level sensor (4) from the container (1) without removing the cover (3), wherein the cover (3) closes the opening (2) in the container (1), and the cover (3) is located between the microwave liquid level sensor (4) and the inside of the container (1).

11. The container according to claim 10, wherein The microwave level sensor (4) is configured to analyze the received microwave beam using an algorithm, preferably an adaptive algorithm.

12. A level measurement system comprising a container (1) according to any one of the preceding claims 1 to 11 and further comprising a data logging device.

13. The system according to claim 12, wherein: The liquid level measurement system further comprises a display, which is preferably an LCD display or an electronic paper display.

14. The system according to claim 12 or 13, wherein: The liquid level measurement system further comprises a power source, which is preferably a battery or a photovoltaic cell.

15. The system of claim 14, wherein: The photovoltaic cell is a silicon-based cell or a perovskite-based cell.

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