Advanced antenna protection for radars in level gauging and other applications

A level gauge includes at least one antenna configured to transmit wireless signals towards a material in a tank and to receive wireless signals reflected from the material in the tank. The level gauge also includes a housing having an outer portion, a raised rim within the outer portion, an angled portion that extends between the outer portion and the rim, and a concave portion within the rim. The concave portion forms a crater within the housing. The at least one antenna is configured to transmit and receive the wireless signals through the concave portion of the housing.

TECHNICAL FIELD

This disclosure relates generally to radar systems. More specifically, this disclosure relates to advanced antenna protection for radars in level gauging and other applications.

BACKGROUND

Processing facilities and other facilities routinely include tanks for storing liquid materials and other materials. For example, storage tanks are routinely used in tank farm facilities and other storage facilities to store oil or other materials. As another example, oil tankers and other transport vessels routinely include numerous tanks storing oil or other materials.

Often times, it is necessary or desirable to measure the amount of material stored in a tank. This may be useful, for example, during loading of material into the tank or unloading of material from the tank. As particular examples, “custody transfers” and “weights and measures of oil” often require highly accurate measurements from level gauging instruments installed on the roof of a tank. In bulk storage tanks, an error of one millimeter in a level reading can correspond to several cubic meters of volumetric error. This can result in losses of thousands of dollars for one or more parties.

Radar gauges are one type of non-contact level gauge used for the last several decades. Radar gauges typically transmit wireless signals towards a material in a tank and receive wireless signals reflected off the material in the tank. Unfortunately, radar measurements can be affected by multiple reflections inside a tank, such as reflections from the tank's walls, bottom, roof, and obstructions like agitators, ladders, and heat coils. Furthermore, the full capacity of a tank is often used for storage and transfer. For this reason, level measurements typically need to be constantly reliable even as the level of material approaches the bottom or roof of the tank, which can be difficult to achieve with conventional radar gauges.

One approach to solving these problems is to use narrow radar beams with smaller antennas. A smaller antenna can often fit into various nozzles of a tank, eliminating the costs associated with forming large “man-holes” in the tank. Moreover, narrower beams can avoid reflections from other objects in a tank. Therefore, millimeter-wave radars with ultra-wide bandwidths have been proposed. However, the material in a tank can be aggressive (such as highly corrosive), and the pressure inside the tank can be higher than atmospheric pressure. As a result, robust protection of sensitive level gauging equipment, such as millimeter-wave radars, can be very important for achieving high performance and lower cost.

SUMMARY

This disclosure provides advanced antenna protection for radars in level gauging and other applications.

In a first embodiment, a level gauge includes at least one antenna configured to transmit wireless signals towards a material in a tank and to receive wireless signals reflected from the material in the tank. The level gauge also includes a housing having an outer portion, a raised rim within the outer portion, an angled portion that extends between the outer portion and the rim, and a concave portion within the rim. The concave portion forms a crater within the housing. The at least one antenna is configured to transmit and receive the wireless signals through the concave portion of the housing

In a second embodiment, an apparatus includes a housing configured to protect one or more wireless components. The housing includes an outer portion, a raised rim within the outer portion, an angled portion that extends between the outer portion and the rim, and a concave portion within the rim. The concave portion forms a crater within the housing and is substantially transparent to wireless signals used by the one or more wireless components.

In a third embodiment, a method includes transmitting wireless signals towards a material in a tank through a housing and receiving wireless signals reflected from the material in the tank through the housing. The housing includes an outer portion, a raised rim within the outer portion, an angled portion that extends between the outer portion and the rim, and a concave portion within the rim. The concave portion forms a crater within the housing and is substantially transparent to the wireless signals.

DETAILED DESCRIPTION

FIGS. 1A and 1Billustrate example tank level measurement systems according to this disclosure. As shown inFIG. 1A, a system100is used in conjunction with a tank102that can store one or more materials104. The tank102generally represents any suitable structure for receiving and storing at least one liquid or other material. The tank102could, for example, represent an oil storage tank or a tank for storing other liquid(s) or other material(s). The tank102could also have any suitable shape and size. Further, the tank102could form part of a larger structure. The larger structure could represent any fixed or movable structure containing or associated with one or more tanks102, such as a movable tanker vessel, railcar, or truck or a fixed tank farm.

The system100includes a level gauge106on a roof of the tank102. The gauge106is used to measure the level of material104in the tank102. For example, an antenna in the gauge106transmits wireless signals towards the material104and receives reflected signals from the material104. The gauge106can then analyze the signals to determine the level of material104in the tank102. The gauge106includes any suitable structure for generating signals for wireless transmission towards material in a tank and receiving reflected signals from the material in the tank.

In some embodiments, the gauge106supports the use of wireless signals in the ultra-wideband (UWB) “millimeter wave” (MMW) range, which extends from about 30 GHz to about 300 GHz. With MMW frequency operation, the gauge's antenna can be miniaturized, such as to fit into a small nozzle in the roof of the tank102. The nozzle could facilitate access to the tank102. A UWB gauge106with a narrow beam width can solve various problems discussed above, such as interference caused by reflections from the tank's walls, bottom, roof, and obstructions like agitators, ladders, and heat coils. Moreover, this type of gauge106can be constantly reliable even as the level of material104approaches the bottom or roof of the tank102. In addition, this type of gauge106can be accurate even in the presence of interference from multiple closely-spaced objects in the tank102.

As shown inFIG. 1A, the gauge106includes a cover108that protects the antenna and other components of the gauge106from the environment within the tank102. Conventional systems cannot easily protect the front of an MMW antenna lens under harsh environmental conditions without significantly degrading the performance of the radar. As described in more detail below, the gauge106includes the protective cover108, which is generally described as having a “volcano cone” shape. Among other things, this protective cover108provides robustness against chemical liquids and vapors in the tank102, provides a mechanism against water condensation on a surface of the antenna, and provides reliable high performance. As such, this protective cover108can be used with UWB level gauges or other devices operating in the MMW range without significantly interfering with the operation of those devices.

FIG. 1Billustrates another example system150that uses the level gauge106with the protective cover108. In this example, the level gauge106is mounted on a trunk152that extends above the tank102. The trunk152provides access to an interior of the tank102while maintaining the level gauge106in a position above the roof of the tank102. As a particular example, the trunk152can be used on a transport vessel to hold the level gauge106above the deck of the vessel to help keep water off the gauge106, as well as to avoid direct contact with material inside the tank.

AlthoughFIGS. 1A and 1Billustrate examples of tank level measurement systems100and150, various changes may be made toFIGS. 1A and 1B. For example, each system could include any number of tanks, level gauges, and other components. Also, the functional division shown in each figure is for illustration only. Various components in each figure could be omitted, combined, or further subdivided and additional components could be added according to particular needs. As a particular example, the signal processing functionality described as being performed by the level gauge106could be performed by a processing system outside of and coupled to the level gauge106. In addition,FIGS. 1A and 1Billustrates example ways in which the level gauge106could be used. However, the level gauge106could be used in other ways.

FIGS. 2A through 4illustrate example level gauges with advanced antenna protection in a level gauging system according to this disclosure.FIGS. 2A and 2Billustrate one possible implementation of a level gauge200with advanced antenna protection. In particular,FIG. 2Aillustrates a bottom view of the gauge200, andFIG. 2Billustrates a cross-sectional view of the gauge200through a center of the gauge200inFIG. 2A. The gauge200could, for example, form at least part of the level gauge106in the systems100,150ofFIGS. 1A and 1B.

As shown inFIGS. 2A and 2B, the gauge200includes a lower housing202. The lower housing202helps to encase internal components of the gauge200, separating the internal components from the environment within a tank102. In this example, the lower housing202includes an outer annular region204, which here is generally flat on top and on bottom. Note, however, that the top and bottom surfaces of the outer annular region204could have other shapes. For instance, the top of the outer annular region204could be shaped to conform to the inner surface of the tank102, and the bottom of the outer annular region204could have any other desired shape. The outer annular region204here includes various openings205that allow the lower housing202to be bolted or otherwise secured against another structure. As particular examples, the lower housing202could be secured against the top of a tank102, an upper housing, or other structure to form an air-tight seal against the contents of the tank102.

The lower housing202also includes an angled annular region206that extends from the outer annular region204to a raised annular rim208. The angled annular region206in this example has generally straight sides, and the raised annular rim208is rounded. Of course, the sides of the angled annular region206need not be straight, and the raised annular rim208could have any other suitable shape.

In addition, the lower housing202includes a central area210. The central area210is concave and arches inward towards internal components of the level gauge200. As a result, the annular rim208is raised with respect to both the outer annular region204and the central area210. The central area210is transparent or substantially transparent to wireless signals used by the level gauge200to determine the level of material in a tank. The remaining portions of the housing202could be substantially or completely reflective or absorptive of the wireless signals.

The gauge200in this example is said to represent a “volcano cone” structure. This is because the outer surface of the housing202extends from the outer annular region204to the raised annular rim208before falling back into a “crater” in the form of the concave central area210.

The annular regions204-208are formed from one or more metals or other material(s) that can withstand the environment inside a tank102, such as stainless steel. Also, the concave central area210is formed from a polymer or other material(s) that can withstand the environment inside a tank102without significantly interfering with operation of the gauge200, such as a polytetrafluorethylene (PTFE) layer. In particular embodiments, the PTFE layer could be about 82 mm wide and about 9 mm-9.5 mm thick with a radius of curvature of about 60 mm-61 mm. The PTFE material is substantially inert against a variety of different chemical erosions.

Because the central area210is concave, substantially all of the water or other liquids that condense on the central area210flows away from the central area210towards the rim208. As a result, the gauge200is able to effectively cope with condensation effects. Also, the concave central area210can be sealed to other portions of the housing202, forming an air-tight seal against the contents of the tank102that is able to withstand an elevated pressure within the tank102. As a specific example, the PTFE layer described above could withstand a pressure of at least several bars, such as about three bars (three times normal atmospheric pressure). Note that the concave central area210can be connected to the other portions of the housing202in any suitable manner, such as with an annular structure211that uses bolts or other mechanism to secure the concave central area210and push the concave central area210into the other portions of the housing202. In addition, the concave central area210can have little if any effect on the wireless signals used by the level gauge200. For instance, the PTFE layer could at most have only a minor influence on the accuracy of a UWB MMW radar.

The level gauge200in this example also includes a control unit212, a transceiver214, an antenna216, and an antenna lens218. The level gauge200transmits wireless signals towards the material104in the tank102and receives wireless signals reflected off the material104in the tank102. The signals are then analyzed to determine the material level. In this example, the transceiver214generates signals for wireless transmission via the antenna216, and the transceiver214processes signals received wirelessly by the antenna216. The antenna216transmits and receives the wireless signals. The antenna lens218focuses wireless signals being transmitted into a narrower beam width. The control unit212controls the transmission of the wireless signals and analyzes the signals to determine the material level.

The control unit212includes any suitable structure for controlling the transmission of wireless signals for identifying a material level in a tank and possibly analyzing signals to identify the material level in the tank. The transceiver214includes any suitable structure for transmitting and receiving wireless signals, such as a UWB MMW transceiver. Note that while shown as a single unit, the transceiver214could include a transmitter and a separate receiver. The antenna216includes any suitable structure for transmitting and receiving wireless signals, such as a radio frequency (RF) antenna. Note that while a single antenna216is shown, multiple antennas could be used, such as a transmit antenna and a receive antenna. The antenna lens218includes any suitable structure for focusing wireless signals.

FIG. 3illustrates an example lower housing302of a level gauge. As shown inFIG. 3, the lower housing302includes an outer annular region304, an angled annular region306, and a raised annular rim308. The annular regions304-308can be formed from at least one metal or other material(s). The lower housing302also includes a concave central area310, which can be formed from PTFE or other material(s). As can be seen here, the concave central area310is sealed to the raised annular rim308, which can help prevent material inside a tank102from reaching sensitive internal components of a level gauge.

FIG. 4illustrates an example level gauge400having both a lower housing402and an upper housing404. The lower housing402is similar to the housings202,302described above. The upper housing404covers internal components406of the level gauge400, such as a control unit, transceiver, antenna, and antenna lens. The upper housing404therefore provides protection to the internal components406of the level gauge400, such as protection from the ambient environment outside of a tank102.

AlthoughFIGS. 2A through 4illustrate examples of level gauges with advanced antenna protection in a level gauging system, various changes may be made toFIGS. 2A through 4. For example, as shown inFIGS. 2A through 4, the lower housings202,302,402have the “volcano cone” shape since the sides of their angled annular regions are angled upward towards a crater formed by their concave central areas. Note, however, that the phrase “volcano cone” does not require that a housing's angled sides would form a perfect cone but for the presence of the housing's concave central area. While shown as circular rings, the various annular regions in each housing could have any suitable circular or non-circular shape as needed or desired. Similarly, while shown as circular discs, the various concave central regions in each housing could have any suitable circular or non-circular shape as needed or desired. Also, each of the components shown inFIGS. 2A through 4could have any suitable size and dimensions.

FIG. 5illustrates an example method500for level gauging according to this disclosure. As shown inFIG. 5, active components of a level gauge are mounted on a tank at step502, an upper housing is mounted over the active components at step504, and a lower housing is mounted under the active components at step506. The active components can include, for example, the control unit, transceiver, antenna, and antenna lens of the level gauge. In particular embodiments, at least the antenna is sized to fit within a small nozzle in the roof of the tank. Mounting the upper and lower housings could include securing the housings on opposite sides of the roof or trunk of the tank and possibly to each other. Note that these three steps may occur individually or collectively (in any order or combination).

Wireless signals are generated and a narrow beam is transmitted through the lower housing at step508. This could include, for example, the transceiver214generating electrical signals that are converted by the antenna216into wireless signals. This could also include the antenna lens218focusing the wireless signals into a narrow beam. Note that any suitable wireless signals could be used, such as signals in the UWB MMW range. Wireless signals reflected from material in the tank are received through the lower housing at step510. This could include, for example, the transceiver214receiving and processing electrical signals created by the antenna216upon receipt of the reflected signals. The signals are analyzed to determine a level of the material in the tank at step512. Any suitable analysis operations could be used here, such as time of flight calculations.

During operation of the level gauge, the active components of the level gauge are protected by the housings from the tank environment at step514. This could include, for example, one or both housings preventing material stored inside the tank from contacting the active components.

Note that because narrow beams are used, this can help to reduce or eliminate interference caused by reflections from the tank's walls, bottom, roof, and obstructions like agitators, ladders, and heat coils. Also, the level gauge can provide reliable operation regardless of whether the material level is close to the top or bottom of the tank. In addition, the lower housing can protect the level gauge's other components from corrosive or other materials, reduce or eliminate condensation problems, and withstand elevated pressures inside the tank.

AlthoughFIG. 5illustrates one example of a method500for level gauging, various changes may be made toFIG. 5. For example, while shown as a series of steps, various steps inFIG. 5may overlap, occur in parallel, occur in a different order, or occur multiple times.