Guided wave radar level meter and method of operating guided wave radar level meter

Abstract

The present disclosure discloses a guided wave radar level meter and a method of operating a guided wave radar level meter. A guided wave radar level gauge (100) for determining a filling level of a product (102) contained in a tank (104) for high pressure applications, comprising: a transceiver (203), a probe (108), a reference reflector (110) and control circuitry (200) configured to: perform a distance measurement to determine a measured distance to the reference reflector; determining a first dielectric constant of the vapor in the canister based on the measured distance to the reference reflector and a reference distance to the reference reflector; acquiring the temperature or pressure of the vapor in the tank; determining a second dielectric constant of the vapor in the tank based on the acquired temperature or pressure; and comparing a difference between the first dielectric constant and the second dielectric constant of the vapor in the canister to a predetermined difference threshold.

Description

Technical Field

[0001] The present invention relates to a guided wave radar level meter and to a method for operating a guided wave radar level meter. In particular, the present invention is directed to a guided wave radar level meter for saturated steam applications. Background Art

[0002] Radar level gauge (RLG) systems are widely used to determine the fill level of a product contained in a tank. Radar level measurement is usually performed by means of a non-contact measurement in which an electromagnetic signal is radiated towards the product contained in the tank, or by means of a contact measurement in which the electromagnetic signal is guided towards and into the product by a probe acting as a waveguide, usually referred to as guided wave radar (GWR). The probe is usually arranged to extend vertically from the top of the tank towards the bottom of the tank.

[0003] The emitted electromagnetic signal is reflected at the surface of the product, and the reflected signal is received by a receiver or transceiver included in the radar level meter. Based on the emitted signal and the reflected signal, the distance to the surface of the product can be determined. More specifically, the distance to the surface of the product is usually determined based on the time between the emission of the electromagnetic signal and the reception of the reflection of the electromagnetic signal in the interface between the air in the tank and the product contained in the tank. In order to determine the actual filling level of the product, the distance from the reference position to the surface is determined based on the above-mentioned time (the so-called flight time) and the propagation speed of the electromagnetic signal.

[0004] Guided wave radar is particularly advantageous in high pressure saturated steam applications such as boiler drums, high pressure feedwater heaters and steam separators where high pressure and temperature as well as vibration and potential magnetite coating of metal parts can cause problems for other measurement technologies. Guided wave radar is used for direct level measurement and is completely independent of density and has no moving parts, which offers the advantages of lower maintenance costs and greater reliability.

[0005] An example implementation of guided wave radar for pressurized steam applications uses a reference reflector at a known position to be able to compensate for changes in operating conditions due to the vapor in the tank. However, the system requires calibration of the position of the reference reflector when commissioning the system or when replacing components of the system, and such calibration needs to be performed in an empty tank or at least in near-ambient conditions. Therefore, when changing components of the radar level gauge, processing in the tank may need to be interrupted.

[0006] It would therefore be desirable to provide an improved solution for providing accurate level measurement in high pressure saturated steam applications. Summary of the invention

[0007] In view of the above-mentioned and other disadvantages of the prior art, it is an object of the present invention to provide a radar level gauge with improved calibration and a method for determining the filling level of a product.

[0008] According to a first aspect of the present invention, there is provided a guided wave radar level meter for determining a filling level of a product contained in a tank for high pressure applications, comprising: a transceiver configured to provide a transmission signal and receive a reflection signal generated by reflection of the transmission signal at a surface of the product; a probe connected to the transceiver and configured to propagate the transmission signal toward the surface and return the reflection signal to the transceiver; a reference reflector arranged at a reference position on the probe; a control circuit system configured to determine the filling level based on the received reflection signal, wherein the control circuit system is further configured to: perform distance measurement to determine a measured distance to the reference reflector; determine a first dielectric constant of vapor in the tank based on the measured distance to the reference reflector and the reference distance to the reference reflector; obtain a temperature or pressure of the vapor in the tank; determine a second dielectric constant of the vapor in the tank based on the obtained temperature or pressure; and compare a difference between the first dielectric constant and the second dielectric constant of the vapor in the tank with a predetermined difference threshold.

[0009] With the described radar level meter, it is possible to determine whether the measured position of the reference reflector corresponds to the calibrated position of the reference reflector, i.e. if the calibration is correct, it is not necessary to drain the tank. In other words, the control can be performed during operation of the tank. Thus, the described radar level meter can perform a verification test during operation, which both reduces the risk of erroneous level measurements and simplifies the replacement of components since the components in the radar level meter can be installed and the calibration performed without opening, depressurizing or draining the tank.

[0010] According to an example embodiment, the control circuit system is further configured to: determine that the difference between the first dielectric constant and the second dielectric constant is above a predetermined threshold; determine an updated position of the reference reflector based on the second dielectric constant; and set the reference position of the reference reflector to the updated position. Therefore, the calibrated position of the reference reflector can be automatically updated as needed in response to changes in conditions in the tank, ensuring that level measurement can be performed with the required accuracy.

[0011] According to an example embodiment, the control circuit system is further configured to: determine that the difference between the first dielectric constant and the second dielectric constant is above a predetermined threshold; and provide a notification to a user that the calibrated position of the reference reflector is incorrect. In some cases, it may be desirable to also notify the operator of the change in conditions in the tank that resulted in the incorrectly calibrated position of the reference reflector, as this may be an indication of a fault or the like that requires attention. For example, the notification may be provided in the form of a visual alarm or an audible alarm.

[0012] According to an example embodiment, the control circuit system is further configured to: determine that the difference between the first dielectric constant and the second dielectric constant is below a predetermined threshold; and provide a notification to the user that the calibrated position of the reference reflector is correct. Confirmation that the calibrated position of the reference reflector corresponds to the measured position serves as a verification check and validation that the calibration is correct, ensuring that the level measurement is reliable.

[0013] According to an example embodiment, the radar level gauge may further comprise a temperature sensor and / or a pressure sensor arranged in the tank to determine the temperature and / or pressure in the tank. Thus, both temperature sensing and pressure sensing may then be integrated in the radar level gauge system and controlled by the same measurement circuitry as that controlling the level measurement, thereby facilitating the integration of the inspection check in the radar level gauge system. However, the temperature and / or pressure may also be acquired from other sensors, or the temperature and / or pressure values ​​may be manually entered into the radar level gauge system for verification of the reference reflector position.

[0014] According to an example embodiment, the control circuitry is further configured to: obtain a pressure in the tank; and determine that the tank is pressurized when the pressure is above a first predetermined pressure threshold.

[0015] In addition, the control circuit system can also be configured to: obtain the pressure in the tank and the temperature in the tank; and when the pressure is higher than a second predetermined pressure threshold and the temperature is higher than a predetermined temperature threshold, determine that the tank includes saturated steam. Since the known relationship between temperature, gas pressure and dielectric constant is generally applicable to saturated steam, but not necessarily to unsaturated steam, it is desirable for the radar level gauge system to ensure that the tank is pressurized and contains saturated steam before determining the dielectric constant of the vapor in the tank based on temperature or pressure and before recalibrating the position of the reference reflector.

[0016] According to a second aspect of the present invention, there is provided a method for determining a dielectric constant in a guided wave radar level meter for determining a filling level of a product contained in a tank for high pressure applications, the radar level meter comprising: a transceiver configured to provide a transmission signal and receive a reflection signal generated by reflection of the transmission signal at a surface of the product; a probe connected to the transceiver and configured to propagate the transmission signal toward the surface and return the reflection signal to the transceiver; a reference reflector arranged at a reference position on the probe; a control circuit system configured to determine the filling level based on the received reflection signal, the method comprising the following operations performed by the control circuit system: performing a distance measurement to determine a measured distance to the reference reflector; determining a first dielectric constant of vapor in the tank based on the measured distance to the reference reflector and a reference distance to the reference reflector; obtaining a temperature or pressure of the vapor in the tank; determining a second dielectric constant of the vapor in the tank based on the obtained temperature or pressure; and comparing a difference between the first dielectric constant and the second dielectric constant of the vapor in the tank with a predetermined difference threshold.

[0017] The effects and features of this second aspect of the invention are largely similar to those described above in conjunction with the first aspect of the invention.

[0018] Further features and advantages of the present invention will become apparent when studying the appended claims and the following description.The skilled person realizes that different features of the present invention can be combined to create embodiments other than those described in the following, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] These and other aspects of the present invention will now be described in more detail with reference to the accompanying drawings showing example embodiments of the invention, in which:

[0020] Figure 1 schematically illustrates an exemplary tank arrangement including a guided wave radar level gauge system according to an example embodiment;

[0021] Figure 2 is included in Figure 1 Schematic diagram of a measuring unit in a radar level gauge system;

[0022] Figure 3 schematically illustrates an exemplary tank arrangement including a guided wave radar level gauge system according to an example embodiment;

[0023] Figure 4 is a flow chart outlining the general steps of a method according to an example embodiment;

[0024] Figure 5 is a flow chart outlining the general steps of a method according to an example embodiment;

[0025] Figure 6 is a flowchart outlining the general steps of a method according to an example embodiment; and

[0026] Figure 7 is a flow chart outlining the general steps of a method according to an example embodiment. DETAILED DESCRIPTION

[0027] In this detailed description, various embodiments of the system and method according to the present invention are described primarily with reference to a guided wave radar level meter installed in a tank located on land. However, the described system and method are suitable for use in other fields such as marine applications. In addition, various embodiments of the present invention are discussed primarily with reference to a radar level meter system having a signal propagation device in the form of a probe and wireless communication capabilities.

[0028] It should be noted that this in no way limits the scope of the present invention, which also covers radar level gauge systems having another type of signal directing device, and radar level gauge systems configured for wired communication (e.g. using a 4mA to 20mA current loop and / or other wired means for communication).

[0029] Figure 1 An exemplary radar level gauge system 100 of the GWR (guided wave radar) type installed at a tank for high pressure applications is schematically shown. The radar level gauge system comprises: a measuring unit 106 configured to provide a transmission signal Tx and receive a reflection signal Rx resulting from reflection of the transmission signal at a surface 116 of the product; a probe 108 connected to the measuring unit 106 and configured to propagate the transmission signal toward the surface 116 and return the reflection signal to the measuring unit 106; a reference reflector 110 arranged at a reference position on the probe 108; and a measuring unit control circuit system arranged in the measuring unit 106 and configured to determine the filling level based on the received reflection signal.

[0030] The guided wave radar level gauge system 100 is installed to measure the filling level of the product 102 in the tank 104. In addition, the described radar level gauge system 100 is configured to determine the filling level of the product in the tank 104 in a high-pressure steam application, wherein the tank includes a liquid and a pressurized vapor 112. It is assumed here that the volume above the determined filling level includes saturated vapor 112. In the example shown, the probe 108 is arranged in a static tube 114 that is arranged separately from the tank 104. The probe 108 extends from the measuring unit 106 toward the product 102 in the static tube 114 and enters the product 102 in the static tube 114. The static tube 114 is connected to the tank so that the filling level of the tank 104 is the same as the filling level in the static tube 114, thereby enabling the filling level in the tank to be measured by measuring the level of the product in the static tube 114.

[0031] The fill level of the product 102 in the tank 104 can be determined by analyzing the transmitted signal directed by the probe 108 toward the surface 116 of the product 102 and the reflected signal traveling back from the surface 116. It should be noted that although a tank 104 containing a single product 102 is discussed herein, the distance along the probe to any material interface can be measured in a similar manner.

[0032] Now refer to Figure 2 The schematic block diagram in the Figure 1 Radar level gauge system 100 in FIG. Figure 2 The schematic block diagram in Figure 1 The measuring unit 106 of the exemplary radar level gauge system 100 in includes a measurement control circuit system 200 , which may also be referred to as a measurement control unit (MCU) 200 , a wireless communication control unit (WCU) 202 , a transceiver (Tx / Rx) 203 , a communication antenna 204 , and an energy storage device such as a battery 206 .

[0033] like Figure 2 As schematically shown in FIG. 1 , the MCU 200 controls the transceiver 203 to generate, transmit and receive electromagnetic signals. The transmit signal reaches the probe 108 through the feedthrough, and the receive signal reaches the transceiver 203 from the probe 108 through the feedthrough.

[0034] The MCU 200 determines the filling level of the product 102 in the tank 104 and provides a value indicating the filling level from the MCU 200 via the WCU 202 to an external device such as a control center through the communication antenna 204. The radar level gauge system 100 may advantageously be configured according to the so-called WirelessHART communication protocol (IEC 620691).

[0035] Although the measuring unit 106 is shown as including an energy storage device (battery 206) and is shown as including means for allowing wireless communication (e.g., WCU 202 and communication antenna 204), it should be understood that both power supply and communication may be provided in different manners, such as via a communication line (e.g., a 4mA to 20mA line).

[0036] The local energy storage 206 does not necessarily have to include (only) a battery, but may alternatively or in combination include a capacitor or a supercapacitor.

[0037] In addition, the measurement control unit (MCU) 200 may be more generally referred to as a control circuit system 200, and the control circuit system 200 may include a microprocessor, a microcontroller, a programmable digital signal processor, or another programmable device. The control circuit system may also include or alternatively include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. In the case where the control circuit system includes a programmable device such as a microprocessor, a microcontroller, or a programmable digital signal processor mentioned above, the processor may also include a computer executable code that controls the operation of the programmable device.

[0038] Figure 3 A signal is schematically shown detecting echoes generated by a level measurement using a radar level gauge system. The dashed line represents the uncorrected measurement signal and the solid line represents the calibration signal using a correctly calibrated reference reflector. The echoes in the signal indicate changes in impedance along the length of the probe 108 in the material surrounding the probe or in the probe 108 itself.

[0039] The first and largest echo 300 seen from the direction of the measuring unit 106 is the same for both the calibrated and the uncalibrated measurements, identifying the transition from the measuring unit 106 to the tube 114 .

[0040] The following echoes 302, 304 represent echoes from the reference reflector 110. It should be noted here that the reference reflector 110 can be configured in many different ways, for example depending on the type of probe used. The reference reflector 110 can, for example, vary in length, and for a single probe, the reference reflector 110 can be configured as a change in the diameter of the probe 108, wherein the transition of the probe 108 from a larger diameter to a smaller diameter generates a reference echo. The reference reflector 108 can also include a separate reflector element attached to the probe 108.

[0041] The lower reference reflector echo 302 of the two reference reflector echoes represents an echo 302 from a measured and uncalibrated signal, and the upper reference reflector echo 304 represents an echo for a calibrated signal.

[0042] Similarly, in the next two echoes at the location of the surface 116 of the product, the lower echo 306 of the two surface echoes shows the echo 306 from the measured and uncalibrated signal and the upper echo 308 represents the actual filling level for a correctly calibrated signal.

[0043] The reason for the erroneous echo position in the measurement is due to the fact that the dielectric constant of the vapor 112 in the tube is different from that of air, and the propagation speed of the signal depends on the dielectric constant of the material surrounding the probe. In particular, the dielectric constant in the vapor 112 is higher than that in air, giving erroneous results if the initial assumption is made that the dielectric constant of the environment surrounding the probe is equal to 1. The dielectric constant of pressurized vapor increases with increasing pressure and temperature, which also results in increasing errors in the uncalibrated signal.

[0044] By knowing the actual physical position of the reference reflector 110, and thus knowing the distance from the measuring unit 106 to the reference reflector, the measured signal can be calibrated and the correct filling level can be determined. This also makes it possible to determine the dielectric constant of the vapor in the tank based on the distance between the uncalibrated echo 302 and the actual position of the reference reflector 110.

[0045] However, in some cases, the physical position of the reference reflector 110 may be unknown, or it may be desirable to verify that the assumed position of the reference reflector 110 is correct. If a component of the radar level gauge has been replaced or reinstalled, or if information has been lost for other reasons, the position of the reference reflector 110 may be unknown or at least unverified, for example. In such cases, it is advantageous to be able to determine the position of the reference reflector 110 without having to drain and depressurize the tank to perform measurements in ambient air with a dielectric constant equal to 1.

[0046] The determination of the conditions in the tank, and thereby the position of the reference reflector, may be performed by the systems and methods of the present disclosure.

[0047] A requirement for performing the measurement is that the reference reflector is located above the filling level of the tank. By comparing the signs of the echo signals, it can be verified that the position of the reference reflector is above the filling level, wherein the reference reflector is configured to provide a negative echo and the surface provides a positive echo. By observing the corresponding positions of the first positive echo and the first negative echo seen from the start of the probe, it can be determined whether the reflector is above or below the filling level.

[0048] An example method for determining the dielectric constant in a guided wave radar level gauge is performed by the control circuitry 200 of the radar level gauge system 100 and will be further referenced. Figure 4 To describe, Figure 4is a flow chart outlining the steps of the method.

[0049] The method includes performing 400 a distance measurement by the control circuit system 200 to determine a measured distance to the reference reflector 110. The distance to the reference reflector 110 may be determined during a level measurement, wherein different echoes in the reflection signal may be distinguished and the distance from the measuring unit 106 to the reference reflector 110 and to the surface 116 may be determined. Figure 3 , the reference reflector echo 302 below shows the measured signal.

[0050] Next, a first dielectric constant ε1 of the vapor in the tank may be determined 402 based on the measured distance to the reference reflector 110 and the known reference distance to the reference reflector 110. The difference between the measured distance and the reference distance indicates that the dielectric constant of the vapor surrounding the probe is different from 1, and since the relationship between the dielectric constant and the propagation velocity along the line is known, the first dielectric constant ε1 may be determined.

[0051] The next step includes obtaining the temperature T or pressure P of the vapor in the tank 404. Figure 3 In the example embodiment shown, the radar level gauge system 100 further comprises a temperature sensor 310 and a pressure sensor 312, which are arranged in the tank 104 to determine the temperature and / or pressure in the tank 104. It is sufficient to know one of the temperature and the pressure, because the relationship between the temperature, the pressure and the dielectric constant in the pressurized tank is known, where it can be assumed that the steam is saturated water vapor. Thus, the temperature or the pressure can be measured continuously or intermittently to provide input to the radar level gauge system 100.

[0052] The current temperature or pressure in the tank may also be manually input into the radar level gauge system 100 by an operator based on readings from a separate temperature sensor or pressure sensor.

[0053] Once the temperature and / or pressure has been determined, a second dielectric constant ε2 of the vapor in the tank 406 can be determined based on the acquired temperature or pressure, for example, by using the values ​​given in Table 1 below describing the relationship between temperature, pressure, and dielectric constant for saturated water vapor. Although the present specification describes the relationship between temperature, pressure, and dielectric constant for saturated water vapor, the same general principles can be used for saturated vapors of other materials. In addition, in addition to using tabulated values, an analytical expression describing the relationship between temperature, pressure, and dielectric constant can also be used. Such an analytical expression can be derived, for example, by curve fitting of measured values, by simulation and modeling, or by theoretical calculation.

[0054]

[0055]

[0056] Table 1. Error distance with varying temperature and pressure without vapor compensation

[0057] When the first dielectric constant ε1 and the second dielectric constant ε2 have been determined, the difference between the first dielectric constant and the second dielectric constant of the vapor in the tank is compared with a predetermined difference threshold 408. The difference threshold may be, for example, a percentage of the measured value, or may be an absolute value that may be set for a given implementation of the radar level gauge system. The predetermined threshold may be, for example, 4% of the dielectric constant calculated from the distance measurement.

[0058] Once the difference between ε1 and ε2 has been determined, further action can be taken depending on the results of the comparison and depending on the requirements for the specific application.

[0059] Figure 5 is a flow chart describing the steps of a method according to an example embodiment. The described method also includes determining 500 that the difference between the first dielectric constant and the second dielectric constant is above a predetermined threshold, for example if ε2 deviates from ε1 by more than 4%. This can be regarded as an indication that the calibrated position of the reference reflector 110 is incorrect, and then an updated position of the reference reflector 108 can be determined 502 based on the second dielectric constant ε2 representing the actual conditions in the tank. The reference position of the reference reflector 110 is then set 504 to the updated position, thereby updating the reference position of the reference reflector 110.

[0060] Figure 6 1 is a flow chart describing the steps of a method according to an example embodiment, the method comprising: determining 500 that a difference between a first dielectric constant ε1 and a second dielectric constant ε2 is above a predetermined threshold; and providing 602 a notification to a user that the calibrated position of the reference reflector 110 is incorrect. It will then be up to the user to determine how to handle the deviation between the dielectric constants. In some cases, the cause of the deviation is known, and it may not be desirable to automatically update the reference position of the reference reflector 110.

[0061] Figure 7 is a flow chart describing steps of a method according to an example embodiment, the method further comprising: determining 600 that a difference between the first dielectric constant and the second dielectric constant is below a predetermined threshold; and providing 508 a notification to a user that the calibrated position of the reference reflector 110 is correct.

[0062] In some applications it is assumed that the tank contains saturated steam when the measurement is performed.Verification that the tank contains saturated steam may also be given by an operator.

[0063] However, it is also possible to verify that the tank comprises saturated steam by comparing the temperature and / or the pressure in the tank with corresponding temperature thresholds and / or pressure thresholds. Figure 7 An example implementation of the method is schematically shown, wherein the method further comprises acquiring 700 a pressure in the tank, and determining 702 that the tank is pressurized when the pressure is above a first predetermined pressure threshold. The first predetermined pressure threshold may be selected such that it may be determined whether the tank is pressurized, or whether the tank is open and at ambient pressure.

[0064] The method may also include obtaining a pressure in the tank 700 and obtaining a temperature in the tank 706; and when determining 704 that the pressure is above a second predetermined pressure threshold and then determining 708 that the temperature is above a predetermined temperature threshold, determining 710 that the tank includes saturated steam. Thresholds for temperature and pressure may be determined based on known properties of saturated steam in a pressurized tank.

[0065] Thus, the described method provides a verification test procedure in which the correct calibration of the reference reflector position can be verified. In particular, the verification test checks that the dielectric constant obtained from the lookup table and based on the measured temperature and / or pressure corresponds to the dielectric constant according to the measured distance to the reference reflector. The verification test can be configured to be performed automatically or manually and it provides verification that the level measurement is correct and that the level measurement is also correctly calibrated in case of changing conditions in the tank.

[0066] Although the invention has been described with reference to specific exemplary embodiments thereof, many different changes, modifications, etc. will become apparent to those skilled in the art. In addition, it should be noted that parts of the systems and methods may be omitted, interchanged, or arranged in various ways, while the systems and methods are still capable of performing the functions of the invention.

[0067] Additionally, variations to the disclosed embodiments may be understood and effected by the skilled person in practicing the claimed invention, based on a study of the drawings, the present disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A guided wave radar level meter (100) for determining a filling level of a product (102) contained in a tank (104) for high pressure applications, comprising: a transceiver (203) configured to provide a transmission signal and receive a reflection signal resulting from reflection of the transmission signal at a surface of the product; a probe (108) connected to the transceiver and configured to propagate the transmitted signal toward the surface and return the reflected signal to the transceiver; a reference reflector (110) arranged at a reference position on the probe; A control circuit system (200) is configured to determine the filling level based on the received reflected signal, wherein the control circuit system is further configured to: performing a distance measurement to determine a measured distance to the reference reflector; determining a first dielectric constant of vapor in the canister based on the measured distance to the reference reflector and a reference distance to the reference reflector; obtaining the temperature or pressure of the vapor in the tank; determining a second dielectric constant of the vapor in the tank based on the acquired temperature or pressure; and A difference between the first dielectric constant and the second dielectric constant of vapor in the canister is compared to a predetermined difference threshold.

2. The radar level meter according to claim 1, wherein: The control circuit system is also configured to: determining that the difference between the first dielectric constant and the second dielectric constant is above the predetermined threshold; determining an updated position of the reference reflector based on the second dielectric constant; and The reference position of the reference reflector is set to the updated position.

3. The radar level meter according to claim 1, wherein: The control circuitry is also configured to: determine that the difference between the first dielectric constant and the second dielectric constant is above the predetermined threshold; and provide a notification to a user that the calibrated position of the reference reflector is incorrect.

4. The radar level meter according to claim 1, wherein: The control circuitry is also configured to: determine that the difference between the first dielectric constant and the second dielectric constant is below the predetermined threshold; and provide notification to a user that the calibrated position of the reference reflector is correct.

5. The radar level gauge according to any of the preceding claims, further comprising a temperature sensor (310) and / or a pressure sensor (312) arranged in the tank to determine the temperature and / or pressure in the tank.

6. The radar level gauge according to any one of the preceding claims, wherein The control circuit system is also configured to: obtain a pressure in the tank; and determine that the tank is pressurized when the pressure is above a first predetermined pressure threshold.

7. The radar level gauge according to any one of the preceding claims, wherein The control circuit system is also configured to: obtain a pressure in the tank and a temperature in the tank; and determine that the tank includes saturated steam when the pressure is above a second predetermined pressure threshold and the temperature is above a predetermined temperature threshold.

8. A method of determining a dielectric constant in a guided wave radar level gauge (100) for determining a filling level of a product (102) contained in a tank (104) for high pressure applications, the radar level gauge comprising: a transceiver (203) configured to provide a transmission signal and receive a reflection signal resulting from reflection of the transmission signal at a surface of the product; a probe (108) connected to the transceiver and configured to propagate the transmitted signal toward the surface and return the reflected signal to the transceiver; a reference reflector (110) arranged at a reference position on the probe; as well as A control circuit system (200) is configured to determine the filling level based on the received reflection signal, the method comprising the following operations performed by the control circuit system: performing (400) a distance measurement to determine a measured distance to the reference reflector; determining (402) a first dielectric constant of vapor in the tank based on the measured distance to the reference reflector and a reference distance to the reference reflector; obtaining (404) the temperature or pressure of the vapor in the tank; determining (406) a second dielectric constant of the vapor in the tank based on the acquired temperature or pressure; and A difference between the first dielectric constant and the second dielectric constant of vapor in the canister is compared to a predetermined difference threshold (408).

9. The method according to claim 8, further comprising: determining (500) that the difference between the first dielectric constant and the second dielectric constant is above the predetermined threshold; determining (502) an updated position of the reference reflector based on the second dielectric constant; as well as The reference position of the reference reflector is set (504) to the updated position.

10. The method according to claim 8, further comprising: determining (500) that the difference between the first dielectric constant and the second dielectric constant is above the predetermined threshold; as well as A notification is provided (602) to a user that the calibrated position of the reference reflector is incorrect.

11. The method according to claim 8, further comprising: determining (600) that the difference between the first dielectric constant and the second dielectric constant is below the predetermined threshold; as well as Notification is provided (508) to the user that the calibrated position of the reference reflector is correct.

12. The method according to any one of claims 8 to 11, further comprising: obtaining (700) the pressure in the tank; as well as When the pressure is above a first predetermined pressure threshold, it is determined ( 702 ) that the tank is pressurized.

13. The method according to any one of claims 8 to 12, further comprising: obtaining the pressure in the tank (700) and obtaining the temperature in the tank (706); as well as When the pressure is above a second predetermined pressure threshold and the temperature is above a predetermined temperature threshold, it is determined (710) that the tank includes saturated steam.

14. A computer program product comprising program code for performing the method according to any one of claims 8 to 13 when executed by control circuitry.

15. A non-transitory computer-readable storage medium comprising instructions which, when executed by control circuitry, cause processing circuitry to perform the method of any one of claims 8 to 13.

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