阅读说明：本技术 卫生级容器密封件 (Sanitary container closure ) 是由 哈坎·弗雷德里克松 比约恩·林德布拉德 米卡埃尔·埃里克松 于 2019-04-23 设计创作，主要内容包括：一种适于安装在容器的管嘴上的导波雷达物位计,包括：带有开口的附接套环,其被配置成与管嘴对准并通过环形夹持装置固定；以及传输线探头,其附接至探头连接器的外端部。GWR物位计还包括：环形密封衬垫,其被装配在套环开口中,该环形密封衬垫具有中心探头连接器延伸穿过的中心开口；以及定距套筒,其围绕探头连接器的外端部布置并且具有径向突出的套环部分,其中处理电路被配置成检测由已经穿过密封衬垫的中心开口并收集在紧邻地围绕径向突出的套环部分的环形空间中的容器内容物或冷凝物引起的阻抗变化。(A guided wave radar level gauge adapted to be mounted on a nozzle of a tank, comprising: an attachment collar with an opening configured to align with the nozzle and be secured by an annular clamping device; and a transmission line probe attached to an outer end of the probe connector. The GWR level gauge further comprises: an annular sealing gasket fitted in the collar opening, the annular sealing gasket having a central opening through which the central probe connector extends; and a distance sleeve disposed about an outer end of the probe connector and having a radially projecting collar portion, wherein the processing circuitry is configured to detect a change in impedance caused by container contents or condensate that has passed through the central opening of the seal gasket and collected in an annular space immediately surrounding the radially projecting collar portion.)

1. A guided wave radar level gauge for determining a filling level of a product in a tank, said level gauge being adapted to be mounted on a spout of the tank, said level gauge comprising:

a transceiver circuit configured to generate and transmit an electromagnetic transmission signal S_TAnd receiving an electromagnetic return signal S from said container_RThe electromagnetic return signal being caused by reflection from a surface of the article,

a transmission line probe electrically connected to the transceiver circuitry, the probe extending in use from the level gauge to the bottom of the tank and being adapted to enable the microwave transmit signal to propagate along the probe towards the product and return the electromagnetic return signal,

a processing circuit configured to determine a distance between a reference position and a surface of the item based on a relationship between the transmitted signal and the return signal,

an attachment collar having an opening configured to align with the nozzle and be secured by an annular clamping device, an

A coaxial probe connector comprising a central probe connector suspended in a dielectric sleeve mechanically fixed in the attachment collar, the central probe connector having an outer end extending outside the dielectric sleeve beyond the opening of the collar, wherein the probe is attached to the outer end of the probe connector,

the method is characterized in that:

an annular sealing gasket fitted in the opening of the collar, the annular sealing gasket having an outer periphery configured to be sandwiched between the attachment collar and the flange of the nozzle and a central opening through which the central probe connector extends, an

A distance sleeve arranged around an outer end of the probe connector, the distance sleeve having a radially projecting collar portion between the dielectric sleeve and the sealing pad such that when the probe is attached to the probe connector, an inner circumference of the sealing pad will be sandwiched between the axially projecting collar portion and an end of the probe,

wherein the processing circuitry is configured to detect a change in impedance caused by container contents or condensate that has passed through the central opening of the sealing liner and collected in an annular space immediately surrounding the radially projecting collar portion.

2. The metrology instrument of claim 1, wherein the ring clamp is a clamp.

3. Level gauge according to claim 1 or 2, wherein the attachment collar comprises:

the annular sealing surface is provided with a plurality of annular sealing surfaces,

an annular abutment surface located radially outside the sealing surface and configured to abut an outer periphery of a spout of the container, an

A ridge located radially outward of the abutment surface;

such that when the metering apparatus is mounted on the clamp flange of the nozzle of a container, the ridge encircles the outer periphery of the clamp flange, thereby ensuring radial alignment, the annular abutment surface abuts the outer periphery of the nozzle of the container to ensure a well-defined axial relationship, and the sealing liner is sandwiched between the sealing surface and the clamp flange.

4. A metering apparatus according to any one of the preceding claims wherein the flange of the nozzle is provided with an annular groove and wherein the sealing gasket comprises an annular projection configured to be received in the groove.

5. A metering apparatus according to one of the preceding claims, wherein the sealing gasket is made of rubber.

6. A metering apparatus according to one of the preceding claims, wherein a gap is formed radially outside the sealing gasket.

Technical Field

The present invention relates to a Guided Wave Radar (GWR) level gauge mounted to a vessel nozzle through a sanitary vessel seal. The container closure may comprise a clip (also known as a tri-clip).

Background

Radar Level Gauges (RLGs) are suitable for measuring a filling level of a product, such as a process fluid, a particulate compound and other materials, contained in a container, such as a process container. In some applications, it is desirable to provide a satisfactory seal for the container on which the RLG is mounted. Such a seal is commonly referred to as a "process seal". The process seal may be provided by an annular sealing element, sometimes referred to as a gasket, sandwiched between the instrument and an annular opening, e.g., a container nozzle, on which the instrument is mounted.

In some cases, the RLG is mounted to the container spout by an annular coupling device, such as a clip (tri-clamp). U.S. patent 6,658,932 discloses a yoke mounted contactless (free-propagating) radar level gauge in which a PTFE process seal is fitted between the tank opening and the gauge housing. PTFE process seals may be radar signal transmissive.

Although not commercially available, it is desirable to provide a guided wave radar level gauge that can be mounted and sealed in a similar manner. A Guided Wave Radar (GWR) level gauge includes a transmission line probe extending from the level gauge to the bottom of a tank. In use, an electromagnetic signal is directed along the probe and reflected by an impedance transition caused by the surface of the article.

In the case of a GWR level gauge, the above mentioned sealing gasket needs to be ring-shaped with a central opening through which the transmission line probe of the level gauge can pass.

In some applications, for example in the food industry, any equipment in contact with the process needs to comply with health regulations, such as EHEDG (European Hygienic Engineering & Design Group). One requirement is that: any leakage past the container seal must be externally visible to enable detection and replacement of the liner. There is a constant effort to find improved solutions for such leak detection.

Disclosure of Invention

It is an object of the present invention to provide a sanitary process seal for a guided wave radar level gauge with improved leakage detection.

This and other objects are achieved by a guided wave radar level gauge for determining a filling level of a product in a tank, the level gauge being adapted to be mounted on a spout of the tank, the level gauge comprising: a transceiver circuit configured to generate and transmit an electromagnetic transmission signal S_TAnd receiving an electromagnetic return signal S from the container_RThe electromagnetic return signal is caused by reflection from a surface of the article; a transmission line probe electrically connected to the transceiver circuitry, the probe extending in use from the level gauge to the bottom of the tank and being adapted to enable a microwave transmit signal to propagate along the probe towards the product and return an electromagnetic return signal; processing circuitry configured to determine a distance between the reference location and the surface of the item based on a relationship between the transmitted signal and the return signal; an attachment collar having an opening configured to align with the nozzle and be secured by an annular clamping device; and a coaxial probe connector including a central probe connector suspended in a dielectric sleeve mechanically secured in an attachment collar, the central probe connector having an outer end extending outside the dielectric sleeve beyond the collar opening, wherein the probe is attached to the outer end of the probe connector. The GWR level gauge further comprises: an annular sealing gasket fitted in the collar opening, the annular sealing gasket having a grooveCausing a periphery sandwiched between the attachment collar and the flange of the nozzle and a central opening through which the central probe connector extends; and a distance sleeve arranged around an outer end of the probe connector, the distance sleeve having a radially projecting collar portion between the dielectric sleeve and the sealing gasket such that when the probe is attached to the probe connector, an inner circumference of the sealing gasket will be sandwiched between the axially projecting collar portion and the end of the probe, wherein the processing circuitry is configured to detect impedance changes caused by container contents or condensate that has passed through the central opening of the sealing gasket and collected in an annular space immediately surrounding the radially projecting collar portion.

The present invention is based on the recognition that additional potential leakage points (along the probe) may arise when the GWR level gauge is mounted to the container nozzle in a hygienic manner (e.g. by a collar). If a potential leak is detected, the "internal" leakage along the probe can be used as an "early warning," i.e., an indication that the process seal may need to be replaced. Unfortunately, this "internal" leak is not readily available from the outside. However, the presence of any conductive fluid, such as liquid container contents or condensate, will result in a decrease in impedance that can be detected by analysis of the received radar signal. Any leakage through the central opening of the gasket can thus be reliably detected.

The general principle of detecting leakage along a probe of a GWR level gauge by detecting disturbances of a microwave signal is known per se, see for example US 9,217,659. However, the level gauge in US 9,217,659 differs greatly in design, and the purpose of leak detection is quite different from the present invention. In particular, there is no suggestion in US 9,217,659 to use the proposed leak detection as an early warning of a defective sealing cushion of a sanitary seal.

The annular clamp may be a collar, but may alternatively be some other type of annular clamping device configured to secure the attachment collar to the nozzle flange.

In one embodiment, the attachment collar comprises an annular sealing surface, an annular abutment surface located radially outward of the sealing surface and configured to abut an outer periphery of the container nozzle, and a ridge located radially outward of the abutment surface. By this design, when the metering apparatus is mounted on the collar flange of the container nozzle, the ridge surrounds the outer periphery of the collar flange, thereby ensuring radial alignment, the annular abutment surface abuts the periphery of the container nozzle to ensure a well-defined axial relationship and the sealing liner is clamped between the sealing surface and the collar flange.

By this design, there is no need forThe ring can complete the alignment and sealing, thereby enabling a more cost effective installation. In addition, compared with the conventionalSuch a design allows an improved tolerance chain in the axial direction compared to rings, since the axial position is determined only by the axial distance between the sealing surface and the abutment surface.

The spout flange may be provided with an annular groove facing away from the container, and the sealing liner may comprise an annular protrusion configured to be received in the groove. Such a groove usually forms part of a bayonet connection. By protruding into the groove, the gasket may provide improved sealing performance.

The sealing gasket is preferably made of a soft sealing material with sufficient hygienic properties, for example rubber or a softened plastic such as PTFE. Such materials typically have a greater thermal expansion than metals. For this reason, a gap may be formed in the radial direction outside the sealing gasket (between the gasket and the peripheral wall of the attachment collar) to allow thermal expansion of the gasket without impairing the sealing function.

Drawings

The present invention will be described in more detail with reference to the accompanying drawings, which show a currently preferred embodiment of the invention.

FIG. 1 is a schematic view of a guided wave radar level gauge according to a second embodiment of the present invention.

FIG. 2 is a perspective view of a mounting of a yoke of the radar level gauge.

Fig. 3 is a cross-sectional view of the clamp installation of the RLG of fig. 1.

Detailed Description

Embodiments of the present invention will be described herein with reference to a radar level gauge. However, it will be appreciated that the invention will be equally applicable to other metering instruments in which the attachment collar is sealingly mounted on the container nozzle by a clamping arrangement. For example, the present invention may be implemented in pressure gauges and ultrasonic meters.

In FIG. 1, a Radar Level Gauge (RLG)1 according to an embodiment of the present invention is schematically shown. Here, the RLG1 is mounted on a sanitary vessel 2 and is arranged to measure a process variable, for example the level L of an interface between two materials in the vessel 2. Typically, the first material is an item 4 stored in a container, for example a liquid such as milk or a solid such as a particulate compound, the second material is air or other atmosphere 5 in the container, and the interface is a surface 3 of the item 4. In some applications, the vessel is a very large metal vessel (on the order of ten meters in diameter).

The RLG1 circuitry comprises transceiver circuitry 6, processing circuitry 7 and an interface 8.

The transceiver circuit 6 is configured to generate and transmit an electromagnetic (microwave) transmit signal S_TAnd receiving an electromagnetic (microwave) return signal S_R. Transmitting signal S_TPropagating towards the surface 3 of the article 4 by the signal propagation device; the signal propagation device is here a guided wave probe 31 (see further details below). Electromagnetic return signal S_RCaused by reflections in the surface 3 and returned through the signal propagation means and fed back to the transceiver 6. The transceiver circuit 6 may be one functional unit capable of transmitting and receiving electromagnetic signals, or may be a system comprising separate transmitter and receiver units. The elements of the transceiver circuit 6 are typically implemented in hardware and form part of an integrated unit, commonly referred to as a microwave unit. For simplicity, the transceiver circuit is referred to as a "transceiver" in the following description.

The processing circuit 7 may comprise a combination of analog processing implemented in hardware and digital processing implemented in software modules stored in a memory and executed by an embedded processor. The present invention is not limited to this particular implementation and any implementation found suitable for achieving the functionality described herein is contemplated.

The processing circuit 7 is configured to process the transmission signal S_TAnd a return signal S_RProcessing is performed to determine the distance between a reference position at the top of the container (e.g. a passage between the outside and the inside of the container) and the surface 3. This processing typically includes generating a container signal or "echo curve" that includes a plurality of peaks representing echoes from the interior of the container. One of these peaks represents the echo from the surface 3. Based on the determined distance to the surface 3, commonly referred to as the empty space (ullage), and the known dimensions of the container 2, a process variable, such as the filling level L of the container, may be determined.

The interface 8 is configured to enable the transfer of the measurement values to the outside of the RLG and optionally for the power supply of the RLG. For example, the interface 8 may be a two-wire control loop 9, such as a 4mA to 20mA loop. Interface 8 may also include a serial data bus to enable communication using a digital communication protocol. Examples of digital protocols that may be used include HART, Modbus, Profibus, and Foundation Fieldbus (Foundation Fieldbus). The interface 8 may also be a wireless interface using for example wireless HART, in which case the RLG is provided with some kind of internal energy storage, e.g. a battery, which may be solar powered.

According to one measurement principle, the transmission signal is a continuous signal (frequency modulated continuous wave, FMCW) with a varying frequency. An FMCW-based RLG will emit a radar scan with a gradually changing frequency and mix (homodyne mixing) the received signal with the original signal to form a frequency domain container signal. Typically, the operating frequency range of an FMCW radar is centered at 6Ghz or 26Ghz with a bandwidth of 1GHz or several GHz.

According to another measurement principle, the transmitted signal is a series of different pulses with a duration in the order of ns and a repetition frequency in the order of MHz. In a process known as Time Domain Reflectometry (TDR), the return signal is sampled with the original pulse sequence in a sample and hold circuit to form a time domain container signal.

The transmitted signal may also be some combination of FMCW and pulsed signals. For example, a principle called a multi-frequency pulse wave (MFPW) has been proposed.

The circuits 6, 7, 8 are housed in a housing sometimes referred to as a Measurement Unit (MU) 10. The Measuring Unit (MU)10 is mounted on a container connection, here an annular attachment collar 12 made of a metallic material, typically steel, adapted to be securely fitted to a nozzle 13 of the container 2 by means of an annular clamping means 15, here a collar. The attachment collar 12 is adapted to provide a (preferably pressure-tight) passage for the electromagnetic signal through the top of the container, which connects the transceiver circuitry 6 with the signal propagation means.

In fig. 1, RLG1 is a Guided Wave Radar (GWR), and the signal propagation means is a probe 31 extending from RLG1 to the bottom of the vessel 2. The probe 31 may be, for example, a coaxial wire probe, a twin wire probe or a single wire probe (also referred to as a surface waveguide). Electromagnetic waves transmitted along the probe 31 will be reflected by any interface 3 between the materials in the vessel and the reflection will be transmitted back to the transceiver 6.

The probe 31 is attached to a coaxial probe connection comprising a central probe connector 32 suspended by a dielectric sleeve 33 arranged in the neck of the housing 10.

Fig. 2 shows in a perspective view in more detail how the ring clamp 15 secures the RLG1 to the container nozzle 13, where the container nozzle 13 has a collar-like flange 14.

Here, the ring clamp 15 has two substantially semicircular elements 15a, 15b, the elements 15a, 15b being held together by two bolts 16 acting in a tangential direction. In other examples, the ring clamp is divided into more than two sections, for example, three sections that together form an annular ring. Additionally, one or more of the segments may be joined by a hinge rather than a bolt. For example, in the example shown, one of the bolts 16 may be replaced by a hinge.

Tapered slots 17 in the clamp elements 15a and 15b engage with the outer rim 18 of the attachment collar 12 and the outer rim 19 of the container nozzle 13. When the clamp 15 is fixed by tightening the bolts 16, the annular clamp 15 ensures a fixed position of the annular opening of the attachment collar 12 relative to the annular opening of the container nozzle 13. A sealing gasket (not shown in fig. 2) is sandwiched between the rim 18 of the attachment collar 12 and the rim 19 of the nozzle 13. The liner is made of a material approved for sanitary applications, such as rubber or a softened plastic such as PTFE.

Fig. 3 illustrates in more detail the attachment of the contactless RLG of fig. 1 according to an embodiment of the invention.

The attachment collar 12 of the RLG housing is formed with an annular sealing surface 61, the annular sealing surface 61 being surrounded by an annular abutment surface 62. Both the sealing surface 61 and the abutment surface 62 extend substantially in a plane perpendicular to the axial direction a. The abutment surface 62 is axially displaced towards the nozzle 13, i.e. the abutment surface 62 is positioned axially distally relative to the housing 10. When the attachment collar 12 is mounted on the nozzle 13, the abutment surface 62 will thus be in contact with the flange 14 and rest on the flange 14. This ensures a predetermined axial distance d between the flange surface 14a and the sealing surface 61.

Radially outward of and around the abutment surface 62 is a ridge 63 extending axially towards the nozzle 13. The ridge 63 may be continuous, but may alternatively be formed of discrete portions. When the nozzle 12 abuts the abutment surface 62, the flange 14 is received within the ridge 63 such that the ridge 63 will surround the flange 14 and secure it in a radial position.

The outer periphery 64a of the rubber packing 64 is sandwiched between the surface 14a of the flange 14 and the sealing surface 61. The outer periphery 64a of the gasket 64 has a thickness to ensure a satisfactory seal when it is compressed to a predetermined distance d. The gasket 64 also has an annular projection 65, the annular projection 65 being formed to be received by the annular groove 14b in the bail flange 14.

At normal temperature, the diameter of the gasket 64 is smaller than the area defined by the inner surface 12a of the attachment collar 12, shown by the gap 68 in fig. 3. This enables the gasket 64 to thermally expand at elevated temperatures without compromising the seal.

The rubber gasket 64 is annular in shape and is provided with a central opening 66 that allows the central probe connector 32 to extend therethrough. A metal sleeve 67 is disposed around the center connector 32 on the RLG side of the liner 64. The sleeve 67 has a base in the form of a radially projecting collar portion 67a which contacts the sleeve of the probe connector and a neck portion 67b which extends axially along the central connector 32. When the probe 31 is attached to the central connector 32 (typically by a threaded connection), the inner periphery 64b of the liner 64 is sandwiched between the collar portion 67a of the sleeve and the upper (RLG-facing) surface 31a of the probe 31. The neck portion 67b ensures a predefined distance d' between the surface 31a and the base 67 a. The inner periphery 64b of the gasket 64 has a thickness to ensure a satisfactory seal when it is compressed to the predetermined distance d'.

Due to the thickness of the collar portion 67a, the gasket 64 cannot contact the lower surface of the dielectric sleeve 33 immediately adjacent to the collar portion 67 a. Instead, an annular space 70 will be formed around the collar portion 67 a. Any leakage of product or condensate from the interior of the container through the central opening 66 of the liner 64 will collect in this space 70.

In use, any conductive liquid collected in the space 70 will cause a decrease in impedance, and electromagnetic signals propagating along the center conductor 32 through the opening 66 will be affected by such impedance changes. According to the invention, the processing circuit 7 is configured to detect any such impedance change. The details of such a determination will be understood by those skilled in the art.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. Rather, many modifications and variations are possible within the scope of the appended claims, which generally relate to the combination of GWR with sanitary-grade process seals and early warning leak detection based on radar signal interference. For example, the details of level sensing may differ from those discussed above. Furthermore, the physical design may be of any type compatible with GWR level gauges.