Patent Grant
11846535
This application claims priority to European Patent Application No. 19172814.6, filed on May 6, 2019, the content of which is hereby incorporated by reference in its entirety.
The present disclosure relates to a radar level gauge having a dielectric filling member arranged in an antenna arrangement of the radar level gauge, wherein the dielectric filling member comprises a sealing arrangement comprising a first and second sealing portions. The radar level gauge further comprises a structural reinforcement element arranged between the first and second sealing portions.
A radar level gauge (RLG) is conventionally used for measurements of a filling level of products such as process fluids, granular compounds and other materials contained in a tank. The RLG can, for example, comprise a transceiver, an antenna arrangement and processing circuit adapted for determining the filling level based on a relation between microwaves transmitted and received by the transceiver.
The RLG may further comprise a so-called dielectric filling member which is positioned in the cavity of the antenna arrangement. The dielectric filling member is arranged to protect the antenna arrangement from the thermal and chemical substances within the tank. The dielectric filling member also serves the purpose as a process seal for preventing tank content to be released to the outside ambient environment. The process seal is conventionally arranged between a portion of the tank and a portion of the antenna arrangement.
The dielectric filling member can however be exposed to relatively high under-pressure forces within the tank. This may cause the dielectric filling member to be forced towards the tank. There is thus a desire to modify the dielectric filling member for improving the resistance to such under-pressure forces.
It is an object of the present disclosure to describe a radar level gauge having an improved strength for sustaining the relatively high under-pressure forces obtainable in a tank.
According to a first aspect, this and other objects are achieved by a radar level gauge, for determining a process variable of a product in a tank using electromagnetic measuring signals, the radar level gauge comprising an antenna arrangement comprising an antenna mounting structure, the antenna arrangement being adapted to direct a microwave transmit signal toward the product and return reflections thereof from a surface of the product; a dielectric filling member arranged in the antenna arrangement, the dielectric filling member comprising a main body, and a sealing arrangement for preventing tank content from escaping into the outside environment, the sealing arrangement being arranged around a periphery of the main body and comprises a first sealing portion positioned between a portion of the antenna mounting structure and a portion of the tank, wherein a lower surface of the first sealing portion is arranged in abutment with the portion of the tank; and a structural reinforcement element arranged around a periphery of the main body, the structural reinforcement element being arranged in abutment with an upper surface of the first sealing portion such that, as seen in a microwave transmit signal direction, the first sealing portion is positioned above the portion of the tank and below the structural reinforcement element.
The dielectric filling member is intended to mean a sort of seal to protect the antenna arrangement against thermal and chemical impact from the content in the tank. Accordingly, the dielectric filling member should be formed by a dielectric filling material which is water repellent as well as resistant against the chemical substances provided in the tank. The dielectric filling material should also preferably not interfere with the operation of the RLG. According to a non-limiting example, the dielectric filling material may be formed by PTFE (polytetrafluoroethylene). Other alternatives are also conceivable, such as PFA (perfluoroalkoxy alkane) and FEP (fluorinated ethylene propylene). With regards to PTFE, this material can withstand relatively high temperatures, i.e. above 150 degrees C., which is preferable.
Furthermore, the structural reinforcement element should be understood as an element formed by a material having greater resistance to deformation in comparison to the material of the dielectric filling member. According to an example embodiment, the structural reinforcement element may be formed by a material having a stiffness coefficient higher than the stiffness coefficient of the sealing arrangement. The stiffness coefficient is here intended to mean the so-called Young's Modulus which is a measure of the deformation of a material at a specific load condition. According to an example embodiment, the structural reinforcement element may be formed by a metallic material. The metallic material may e.g. be steel.
Moreover, the wording “antenna mounting structure” is a structure that mounts the antenna arrangement to the tank. The antenna mounting structure may form an integral part with the remaining antenna arrangement, or may be arranged as a separate part connected to the antenna arrangement in a suitable manner, such as e.g. screw connected to the antenna arrangement, etc.
An advantage is that an improved seal is provided for preventing tank content from escaping into the outside environment. In detail, the structural reinforcement element will increase the stiffness of the sealing arrangement at the interconnection between the antenna mounting structure and the tank. Hereby, the dielectric filling member is less sensitive to under-pressure from the tank as the structural reinforcement element will prevent the dielectric filling member from being forced towards the inside of the tank. The use of the structural reinforcement element is particularly advantageous during relatively high temperatures when the material in the sealing arrangement tends to undesirable elastically deform. Hereby, the structural reinforcement element will prevent the dielectric filling member from deforming towards the tank. This will in turn improve the measurement quality of the RLG, since it can be assured that the dielectric filling member is maintained at the correct position in the antenna arrangement.
According to an example embodiment, the sealing arrangement may be integrally formed with the main body. The sealing arrangement and the main body may thus be formed in one piece and be of the same material.
According to an example embodiment, the sealing arrangement may further comprise a second sealing surface, the second sealing comprising an upper surface arranged in abutment with the portion of the antenna mounting structure and a lower surface arranged in abutment with the structural reinforcement element.
Preferably, the structural reinforcement element is here positioned between the first and second sealing portions such that, as seen in the microwave transmit signal direction, the first sealing portion is positioned below the structural reinforcement element and the second sealing portion is positioned above the structural reinforcement element. An advantage is that improved sealing towards the antenna mounting structure can be achieved.
According to an example embodiment, the main body may have a substantially conical portion, the first and second sealing portions each being arranged as a respective annular flange extending radially from a base portion of the conical portion.
Furthermore, and according to an example embodiment, the structural reinforcement element may be sandwiched between the first and second sealing portions.
According to an example embodiment, the sealing arrangement may comprise a circumferentially arranged cavity portion formed by sintering an outer end portion of the second sealing portion to the first sealing portion, the structural reinforcement element being arranged in the circumferentially arranged cavity portion.
Hereby, the structural reinforcement element is encapsulated within the circumferentially arranged cavity portion.
According to an example embodiment, the structural reinforcement element may comprise a plurality of through holes extending in the direction between the first and second sealing portions, the first and second sealing portions being connected to each other at the plurality of through holes by sintering the first and second sealing portions to each other.
Hereby, the structural reinforcement element will be well integrated between the first and second sealing portions.
The wording sintering should be understood to mean a process where two elements, i.e. the first and second sealing portions, are integrated by pressing them against each other and heating them without melting.
According to an example embodiment, the structural reinforcement element may comprise a first and a second element portion connected to each other around the main body.
An advantage is that the structural reinforcement element is relatively easy to assemble to the sealing arrangement. According to an example embodiment, the first and second element portions may be formed in a semicircular shape.
The first and second element portions are preferably attached to each other and, according to example embodiment, the first element portion may therefore preferably comprise a protrusion and the second element portion may comprise an indentation, wherein the protrusion is connected to the indentation when connecting the structural reinforcement element around the main body. Using a protrusion and indentation will enable for a so-called snap fit connection between the first and second element portions which will attach the two parts to each other when being arranged at the “correct” position. Hence, no additional connecting element is required.
According to an example embodiment, the structural reinforcement element may comprise at least two layers of reinforcement elements as seen in the microwave transmit signal direction.
Hereby, each layer can be formed by a relatively thin sheet of material. Also, the layers can be arranged to overlap at joints between two of the above described semicircular shaped element portions. Also, the at least two layers of reinforcement elements may preferably be attached to each other. Such attachment may, for example, be realized by a protruding portion of the first layer of material connecting with an indentation of the second layer of material. According to an example embodiment, one of the at least two layers of reinforcement elements may comprise a lip portion and the other one of the at least two layers of reinforcement elements comprises a notch portion for attachment to the lip portion.
Hereby, a snap-fit connection is provided between the layers of reinforcement elements. Thus, no additional attachment element is required, and the layers will be connected to each other when connecting the reinforcement element to the dielectric filling member.
According to an example embodiment, and as indicated above, the main body may be formed by a polymer material. The polymer material may, according to an example embodiment, be a fluoropolymer, preferably PTFE.
The present disclosure will be described in more detail with reference to the appended drawings, showing currently preferred embodiments of the radar level gauge, where:
With reference to
The RLG 100 comprises an antenna arrangement 114 comprising a transceiver circuitry 106, processing circuitry 108 and a signal/power interface 110 connected and powered by a battery 107, which are all illustrated very schematically in
The tank connection 112 is adapted to provide a passage (sometimes pressure sealed) for electromagnetic signals through the wall of the tank, which passage connects the transceiver circuitry 106 with the antenna arrangement 114, for allowing signals to propagate into the tank.
The antenna arrangement 114 further comprises a directional antenna 120 with a waveguide section 122 and a horn section 124. The horn section 124 is here formed by the tank connection 112, but may also be a separate part attached to the tank connection 112, e.g. by means of e.g. a threaded fitting.
The transceiver circuitry 106 is configured to generate and transmit an electromagnetic (microwave) transmit signal ST and receive an electromagnetic (microwave) return signal SR. A coupling arrangement, such as a probe (not shown), is arranged to couple the transmit signal from the transceiver circuitry 106 into the waveguide section 122.
The transceiver circuitry 106 may be a unit capable of transmitting and receiving electromagnetic signals, or may be arranged as a system comprising separate transmitter and receiver units. The elements of the transceiver circuitry 106 are typically implemented in hardware, and form part of an integrated unit normally referred to as a microwave unit. For simplicity, the transceiver circuitry is referred to as the “transceiver” in the following description.
The processing circuitry 108 is configured to determine the distance between a reference position at the top of the tank (such as the passage between the outside and the inside of the tank) and the surface of the tank content by analyzing the transmit signal ST and the return signal SR. The processing typically includes generation of a tank signal or “echo curve”, including a plurality of peaks representing echoes from the interior of the tank. One of the peaks represents an echo from the surface of the tank content. Based on the determined distance to the surface, generally referred to as ullage, and known dimensions of the tank 102, a process variable such as the filling level L of the tank can be determined.
The processing circuitry 108 may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The processing circuit may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where the processing circuitry 108 includes a programmable device such as the microprocessor, microcontroller or programmable digital signal processor mentioned above, the processor may further include computer executable code that controls operation of the programmable device. The interface 110 is configured to allow communication of a measurement value externally of the RLG and optionally for power supply of the RLG.
In use, the transmit signal ST generated by the transceiver is coupled into the waveguide section 122, allowed to propagate to the horn section 124 and then emitted into the tank. The transmit signal ST propagates towards the surface of the tank content 104 and the electromagnetic return signal SR is caused by a reflection in the surface. The return signal is returned by the antenna 120, allowed to propagate through the waveguide section and is coupled back to the transceiver by the coupling arrangement.
Furthermore, the RLG comprises a dielectric filling member 200. The dielectric filling member 200 is microwave transmissive and arranged at least partly in a cavity 130 formed by the waveguide section 122 and the horn section 124 of the antenna 120. The dielectric filling member 200 is arranged to protect the antenna 120 from the chemical substances as well as the thermal impact from the content within the tank 102. According to an example embodiment, and as will be referred to in the following, the dielectric filling member 200 is preferably made by a polymer material, more preferably PTFE. The PTFE material is chemically resistant and water repellant, which is advantageous in the environment of the tank. PTFE is also advantageous for its temperature resistance properties.
Moreover, the dielectric filling member 200 comprises a main body 202 having a substantially conical shape adapted to fit in the horn section 124 of the antenna 120. A base 204 of the conically shaped main body 202, i.e. the surface facing the interior of the tank, may have a convex shape in order to shape the radar beam of emitted waves in a beneficial manner, and also promote dripping of condensate formed on the filling member.
The dielectric filling member 200 further comprises a sealing arrangement 210 for preventing tank content from escaping into the outside environment. The sealing arrangement 210 is arranged between the antenna mounting structure 116 and the portion 118 of the tank 102. The sealing arrangement 210 is arranged around a periphery of the main body 202 and is preferably formed by the same material as the main body for being integrally formed with the main body 202.
According to the example depicted in
Moreover, the RLG also comprises a structural reinforcement element 300 arranged between the first 214 and second 212 sealing portions. In detail, the structural reinforcement element 300 is arranged in abutment with an upper surface 211 of the first sealing portion 214 and arranged in abutment with a lower surface 215 of the second sealing portion 212. Thus, the structural reinforcement element 300 is sandwiched between the first 214 and second 212 sealing portions at an opening formed by the first 214 and second 212 sealing portions. Detailed example embodiments of the structural reinforcement element 300 will be described further below with reference to
By positioning a structural reinforcement element 300 in the sealing arrangement 210 between the first 214 and second 212 sealing portions, the stiffness of the sealing arrangement 210 is improved and the dielectric filling member 200 will be more sustainable against under-pressure from the tank 102. The sealing arrangement 210 will also be less sensitive to high temperatures as the coefficient of thermal expansion of the structural reinforcement element 300 is preferably equal to, or lower than the coefficient of thermal expansion of the first and second sealing portions.
Reference is now made to
According to an example, and as depicted in the embodiment of
Turning to
During manufacturing, the dielectric filling member 200 is preferably formed together with the first sealing portion 214. The structural reinforcement element 300 is positioned on the upper surface 211 of the first sealing portion 214, preferably in a recess or the like formed by the first sealing portion 214. Forming of a recess is not necessary but illustrated merely as an example embodiment. The second sealing portion 212 is thereafter provided to the dielectric filling member 200 by sintering the second sealing portion 212 to the dielectric member 200 as well as to the first sealing portion 214. The cavity portion 235 is thus forming an enclosed portion of the sealing arrangement 210.
The sealing arrangement 210 depicted in
To describe the structural reinforcement element 300 in further detail, reference is made to
Moreover, the third 306 and fourth 308 element portions are connected to each other in a similar manner as the connection between the first 302 and second 304 element portions. Hence, also the third 306 and fourth 308 element portions are provided with protrusions 303 and indentations 305.
The first 302 and second 304 element portions form a first layer 310 of reinforcement elements, while the third 306 and fourth 308 element portions form a second layer 312 of reinforcement elements. As is depicted in
With reference to
The end surface portion 307′ of the semicircular first element portion 302′ preferably comprises a thickness that is thinner than the thickness of the remaining first element portion 302′. Similarly, the end surface portion 309′ of the semicircular second element portion 304′ preferably comprises a thickness that is thinner than the thickness of the remaining second element portion 304′. As depicted in
To describe the structural reinforcement element 300″ according to a still further example embodiment, reference is made to
During assembly of the structural reinforcement element 300″ in
Reference is finally made to
As depicted in
Although the structural reinforcement element 300′″ is depicted as a one-piece element in
The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the shape and form of the structurally reinforced element may be different than the illustrated examples, depending on the exact application. The plurality of through holes 360″′ may, for example, be of different shape and size. Also, the first and second sealing portions may be different in shape and design compared to the illustrated examples. Moreover, the structural reinforcement element 300 depicted in
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| 19172814 | May 2019 | EP | regional |
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| Number | Date | Country | |
|---|---|---|---|
| 20200355534 A1 | Nov 2020 | US |
