Leakage detection system and method

1. A method of detecting leakage from a tank containing a product, using a radar level gauge system comprising a transceiver, a propagation device coupled to the transceiver, and processing circuitry coupled to the transceiver, the method comprising the steps of:

performing a sequence of monitoring operations, each monitoring operation including the steps of:

generating, by the transceiver, an electromagnetic transmit signal exhibiting a time-varying frequency;

propagating, by the propagation device, the transmit signal towards a surface of the product in the tank;

returning, by the propagation device, an electromagnetic reflection signal resulting from reflection of the transmit signal at the surface back towards the transceiver;

receiving, by the transceiver, the reflection signal;

forming, by the transceiver, an intermediate frequency signal for the present monitoring operation based on the transmit signal and the reflection signal;

determining, by the processing circuitry, a phase of the intermediate frequency signal for the present monitoring operation;

determining, based on the phase of the intermediate frequency signal for the present monitoring operation and the phase of the intermediate frequency signal associated with at least one previous monitoring operation in the sequence of monitoring operations, a measure indicative of a present rate of change of the phase of the intermediate frequency signals for the sequence of monitoring operations;

comparing the measure indicative of the present rate of change of the phase with a predefined threshold value; and

determining a presence of leakage based on the comparison; and

providing, when it is determined that leakage is present, a signal indicative of detected leakage,

wherein the present rate of change is determined only based on the present monitoring operation, and previous monitoring operations carried out less than five minutes before the present monitoring operation.

2. The method according to claim 1 , wherein:

the method further comprises the step of repeatedly acquiring a measure indicative of a rate of change of a temperature at the tank.

3. The method according to claim 2 , wherein the determination of the presence of leakage is additionally based on the rate of change of the temperature at the tank.

4. The method according to claim 3 , wherein the determination of the presence of leakage is additionally based on the rate of change of the temperature at the tank as a function of time.

5. The method according to claim 1 , wherein the determination of the presence of leakage is additionally based on the phase of the intermediate signal as a function of time, or the rate of change of the phase of the intermediate signal as a function of time.

6. The method according to claim 1 , wherein the monitoring operations are carried out with an average frequency of at least one monitoring operation per second.

7. A leakage detection system, for detecting leakage from a tank containing a product, the leakage detection system comprising:

a propagation device for propagating an electromagnetic transmit signal towards a surface of the product in the tank, and returning an electromagnetic reflection signal resulting from reflection of the transmit signal at the surface of the product;

a transceiver coupled to the propagation device for generating and providing to the propagation device the transmit signal exhibiting a time-varying frequency, receiving the reflection signal, and mixing the transmit signal and the reflection signal to form an intermediate frequency signal; and

processing circuitry, coupled to the transceiver, and configured to:

determine a phase of the intermediate frequency signal formed by the transceiver;

determine, based on the phase of the intermediate frequency signal for a present monitoring operation and the phase of the intermediate frequency signal associated with at least one previous monitoring operation, a measure indicative of a present rate of change of the phase of the intermediate frequency signals for a sequence of monitoring operations;

compare the measure indicative of the present rate of change of the phase with a predefined threshold value;

determine a presence of leakage based on the comparison; and

provide, when it is determined that leakage is present, a signal indicative of detected leakage,

wherein the processing circuitry is configured to determine the present rate of change only based on the present monitoring operation, and previous monitoring operations carried out less than five minutes before the present monitoring operation.

8. The leakage detection system according to claim 7 , wherein:

the leakage detection system further comprises a temperature sensor; and

the processing circuitry is configured to repeatedly acquire a measure indicative of a rate of change of a temperature at the tank.

9. The leakage detection system according to claim 8 , wherein the processing circuitry is configured to determine the presence of leakage additionally based on the rate of change of the temperature at the tank.

10. The leakage detection system according to claim 9 , wherein the processing circuitry is configured to determine the presence of leakage is additionally based on the rate of change of the temperature at the tank as a function of time.

11. The leakage detection system according to claim 1 , wherein the processing circuitry is configured to determine the presence of leakage additionally based on the phase of the intermediate signal as a function of time, and/or the rate of change of the phase of the intermediate signal as a function of time.

12. The leakage detection system according to claim 7 , wherein the processing circuitry is configured to control the leakage detection system to carry out monitoring operations with an average frequency of at least one monitoring operation per second.