Drilling rig equipped with structure and means for detecting moisture in material flow and detection method

Abstract

A structure (1) for detecting moisture in a material flow (20) during drilling, the structure (1) comprising a control unit (2), a data acquisition unit (3), and a sensor (4), the sensor comprising at least two probes (5), the at least two probes (5) being positioned in contact with the material flow and connected to a programmable voltage source and a programmable voltage receiver, the structure (1) being configured to: measure a ratio between a received voltage waveform and an applied voltage waveform at predetermined frequencies; determine a complex impedance between the at least two probes (5) for each of the predetermined frequencies based on the measured ratio; determine a pair of time-averaged values ​​of the determined complex impedance for each of the predetermined frequencies using the time window; determine a set of standard deviations based on the determined time-averaged values; and indicate that moisture has been detected if at least one of the standard deviations exceeds a threshold value.

Description

[Technical field]

[0001] The present invention relates to the mining sector, for example to the field of rock breaking and rock excavation, in particular to detecting moisture in a material flow during excavation. [Background technology]

[0002] Rock drilling and rock breaking are widely used today in many industries such as oil and gas, well drilling, mining, infrastructure construction and civil engineering. There are various drilling techniques, e.g. rotary-impact drilling and rotary drilling. The choice of drilling technique depends on the specific application, where the type of rock, drilling depth and borehole diameter are important.

[0003] When drilling rock masses, etc., a material flow occurs. The material flow may contain not only cut stone particles, but also dust and sand. Filters may be used to separate the cut stone particles, dust and / or sand from the air. If the material flow contains water, the particles and water may form a solidified layer on the filter, which requires frequent replacement of the filter. It is therefore effective to detect the moisture contained in the material flow during drilling. Automatic detection of moisture is essential for remote operation of the drilling unit.

[0004] US Patent US8076950B2 discloses a method for measuring the water conductivity and water volume fraction of a multi-component mixture of water and at least one additional liquid or gas in a pipe. The method is based on measuring the complex permittivity of the multi-component mixture, which is determined by measuring the wave phase constant of a plane electromagnetic wave propagating near the inner wall of the pipe. The measurement of the wave phase constant is based on measuring the phase difference between two receiving antennas in the pipe, which are placed at different distances from a third transmitting antenna. The phase measurements are performed at at least two frequencies in the range of 10 MHz to 10 GHz. However, this method is not applicable for applications where the water content is high to moderate and water contamination in the material flow is too low to affect the phase velocity in the medium in a detectable way.

[0005] To make matters worse, water bound to solid particles does not exhibit the usual dielectric behavior, which is expressed by values ​​of the dielectric constant on the order of 60 to 80. Bound water does not exhibit a dielectric constant larger than 2 to 5. Thus, phase measurements of bulk dielectric behavior are not very sensitive.

[0006] US Patent US7679375B2 discloses a method for detecting foreign objects in products. The method responds to sudden changes in the dielectric composition of the material flow. Measurements are made during propagation and are not used to calculate the dielectric function of the material, but are instead drawn with a Poincaré curve. This is to include the scattering signals of small objects. The aim of the method is to detect objects smaller than the wavelength of the radar signal used and objects with a lower dielectric function than their surroundings.

[0007] International Patent Publication WO 2006 / 052202 A1 relates to a method for measuring physical parameters such as temperature and density inside an object by determining its dielectric function. The method requires the coherent and simultaneous application of ultrasonic and microwave signals, with the alternative application of a microwave signal having such an effect that non-linear material properties become visible. It is therefore necessary that the density of the material is changed by the ultrasonic waves. Such an ultrasonic-induced density change requires an inelastic medium. The method is therefore not applicable to systems containing air.

[0008] International Patent Publication WO 02 / 18920 A1 discloses a method and apparatus for measuring the distribution of selected properties in a material, and in particular an apparatus for non-contact and non-destructive measurement of the spatial distribution of material properties such as density, moisture content and temperature by detecting electromagnetic radiation.

[0009] None of the above methods provide a practical solution for measuring low enough moisture content to prevent filter clogging. The small amounts of moisture involved do not allow for volumetric measurements of property changes. Also, natural changes in the volumetric properties of the material flow, such as changes in stone properties and density, will be much more pronounced than the presence of water. Therefore, improvements in this field are needed. Summary of the Invention

[0010] An objective of the embodiments described herein is to improve water detection performance in material flow during drilling, i.e. at least to achieve an alternative to known solutions in the art.

[0011] According to one aspect, the object is achieved by providing a structure adapted for detecting moisture in a material stream being drilled, the structure comprising a control unit, a data collection unit, and a sensor. The sensor has at least two probes. The at least two probes are arranged to contact the material stream and are connected to a programmable voltage source and a programmable voltage receiver. The structure is configured to measure a ratio of a received voltage to an applied voltage for a set of predetermined frequencies. The structure is further configured to determine a set of complex impedances between the at least two probes for each of the set of predetermined frequencies based on the measured ratio. The structure is further configured to determine a set of time average values ​​of the determined complex impedances for each of the predetermined frequencies using the time window. The structure is further configured to determine a set of standard deviations based on the determined time average values. The structure is configured to indicate that moisture has been detected if at least one of the standard deviations exceeds a threshold condition.

[0012] In accordance with another aspect, the above objects are also achieved by providing a method for detecting moisture in a material stream during drilling, the method comprising measuring a ratio of a received voltage waveform to an applied voltage waveform for a set of predetermined frequencies. The method further includes determining a complex impedance between at least two probes for each of a set of predetermined frequencies based on the measured ratio. The method further includes determining a set of time average values ​​of the determined complex impedance using a time window. The method further includes determining a set of standard deviations based on the determined time average values. The method further includes indicating that moisture has been detected if at least one of the standard deviations exceeds a threshold condition.

[0013] Additionally, a drilling rig is provided that includes a structure for detecting moisture in a material flow.

[0014] At least two probes are placed in contact with the material flow during drilling, and a ratio between the received voltage and the applied voltage is measured, whereby a complex impedance between the probes at each predetermined frequency can be directly determined based on the measured ratio. A set of time average values ​​of the determined complex impedances is then determined, and a set of standard deviations based on the determined time average values ​​is determined, whereby moisture can be indicated when at least one of the standard deviations exceeds a threshold condition. This improves and optimizes the detection of moisture in the material flow during drilling. The optimized and improved water detection reduces filter wear and reduces the frequency of filter replacement.

[0015] The result is a method and structure for detecting moisture in a material stream during drilling.

[0016] Further objects and advantages, as well as technical features, of the present invention will become apparent through the following description of one or several embodiments with reference to the accompanying drawings. It should be noted that the drawings are not necessarily drawn to scale and that dimensions of certain elements may be exaggerated for clarity. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a drilling rig having an exemplary structure disposed thereon for detecting moisture in a material flow during drilling; [Diagram 2] FIG. 1 is a schematic diagram of an exemplary structure for detecting moisture in a material stream while drilling; [Diagram 3] 1 is a flow chart illustrating a method for detecting moisture in a material flow while drilling. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The present invention will now be described in more detail with reference to the accompanying drawings, which show examples of embodiments, in which: The invention is not limited to the described embodiments, but is defined by the appended claims, in which like reference numerals generally refer to like elements.

[0019] 1 shows a schematic diagram of an embodiment of the present disclosure with a structure 1 adapted to detect moisture in a material flow during drilling, e.g. rock drilling. The structure 1 is placed in the material flow 20 of a drilling rig 10 before a filter 30, e.g. a material filter used to separate ashlar particles, dust and / or sand from air.

[0020] An arrangement 1 for detecting moisture in a material stream 20 being drilled is shown in Figure 2. The arrangement 1 comprises a control unit 2, a data acquisition unit 3 and a sensor 4. The arrangement 1 may also have a remote unit 6 for repeating a moisture detection indication to operators on the drilling rig.

[0021] The material flow 20, which may also be referred to as drill cutting flow, drill flow or material backflow, is the return drill flow and has, for example, a gaseous component consisting mainly of air, a set of solid components consisting of sand, dust and stone particles, a set of liquid components in the presence of moisture and / or a set of dissolved components in said liquids.

[0022] The control unit 2 can be, for example, a controller such as a microcontroller, microprocessor, data logger unit, or other digital hardware configured to execute the methods herein. The control unit 2 has a display to show the status of the system and buttons connected for restarting or manually detecting the presence or absence of moisture. The data collection unit 3 can be, for example, a miniature signal generator.

[0023] The data collection unit 3 is completely electrically isolated from the probe 5. This is a requirement to avoid damage or destruction of the electronics in dry environments where the material flow 20 would electrostatically charge the sensor head. The structure 1 is therefore suitable for dielectric or piezoelectric rock types that are susceptible to charging effects and also to triboelectric charging effects.

[0024] Also, the voltage levels used may be of the order of 5V, well below the levels at which sparks or discharges may occur, and the structure 1 is therefore also suitable for use in potentially explosive environments, such as natural gas or coal mines.

[0025] The sensor 4, e.g. a probe holder, has a number of probes 5 which may be arranged in pairs. The probes 5 are arranged in contact with the material flow 20 and are connected to a programmable voltage source and a programmable voltage receiver.

[0026] The probe 5, for example a pair of probes 5, may be designed to provide between them the smallest possible capacitive gap and the longest possible resistive measurement line in the material flow 20. According to some embodiments, the probe 5 may be made of a metal. Common to all embodiments, the probe 5 may be at least partially conductive. The choice of metal may be made to provide a long lifetime of the probe 5 in the material flow 20.

[0027] A line with high resistive sensitivity will have a large absolute change in conductivity in the imaginary part of the complex impedance. A small capacitive gap along a long line will result in a large measurable capacitance. Thus, the absolute change in capacitance will be large. This property is particularly evident for curved shapes such as meander structures, Sierpinski curves, or Peano curves.

[0028] The structure 1 is configured to measure a ratio between the received voltage waveform and the applied voltage waveform for a set of pre-determined frequencies and to determine a set of complex impedances between at least two probes 5 for each of the pre-determined frequencies based on the measured ratio. The set of impedance values ​​is considered as coordinates in a high-dimensional Euclidean vector space. For example, N pre-determined frequencies lead to N complex coordinates consisting of 2N coordinate values. Thus, the measurements are described by points in the 2N-dimensional vector space. Because the space is treated as a Euclidean space, concepts such as distance and average value remain valid. The structure 1 is further configured to determine a set of time average values ​​of the determined complex impedances for each of the pre-determined frequencies using a time window and to determine a set of standard deviations based on the determined time average values. The structure 1 is further configured to indicate that moisture has been detected if at least one of the standard deviations exceeds a threshold condition. That is, the structure 1 is configured to have an indicator criterion that acts as a threshold condition when the distance of a local measurement point to the average value exceeds a pre-determined geometric shape.

[0029] According to some embodiments, each of the at least two probes 5 may have one or more heaters. One heater may be provided for each pair of probes 5. The heater may be externally controllable, for example, by turning it on and off, to stabilize the temperature at a predetermined value. The heater may be a resistor. As a typical resistor heater, a commercially available heater element for a 24V soldering iron may be used. Generally, a heating power of 200W to 500W may be sufficient.

[0030] The heater has two functions. First, the heater can be switched on as soon as the sensor 4 detects moisture. As soon as moisture is detected by a substantial change in the characteristics seen in the measured impedance series, this change will persist until the moisture dries or is otherwise removed by the material flow 20. During this time, no useful measurements can be made. This time is called the blind time. This time is typically in the range of a few seconds with no substantial interference with the operation of the drill. Nevertheless, in dry conditions it may be desirable to shorten the blind time or force a restart. This is done by activating the heater until the probe dries. · Another is that the heater can be switched on periodically to detect the presence of moisture in the conductive material stream 20 by indirect heat capacity measurement. In the presence of moisture, the measured impedance set will correlate with heater activity. In the absence of moisture, there is no correlation between the impedance set and heater status. Thus, the method self-calibrates for changes in drilled rock properties.

[0031] According to some embodiments, one of the at least two probes 5 may have one or more heaters, which may be adapted to be externally controlled to stabilize the temperature at a set of predetermined values. One of the at least two probes 5 may be referred to as an ambient probe and is left at an ambient temperature, which is assumed to be less than 100° C., and the other of the at least two probes 5 may be referred to as a heated probe and is heated to a temperature slightly greater than 100° C. Due to convection cooling, the temperature of the heated probe is lowered by the material flow 20 and may need to be constantly stabilized. A complex impedance may be measured at both probes 5. The ambient probe may produce a potential moisture contamination signal. The probe produces a dry signal in any situation at a temperature above 100° C. The ambient probe will eventually produce a moisture contamination signal. As long as the material flow 20 does not contain moisture, both responses will be equal within the reproducibility of the measurement. If the material flow 20 becomes moist, there will be a difference between them. By recording the difference between this pair of complex impedances, the presence of moisture can be detected in the first method. The first method can directly detect the presence of moisture without the need for time integration or averaging.

[0032] However, when subjected to particularly large amounts of moisture, the real part of the complex impedance pair can drop substantially for both the heated and ambient probes. As a result, both probes will exhibit blind times. However, the blind time for the heated probe will be significantly shorter compared to the blind time for the ambient probe. This difference in return slope can be used to detect the presence of moisture in a second way.

[0033] With this second method, it is possible to apply a heater to the ambient probe as well in order to reduce the blind time of the sensor. In this case, special care must be taken, since this additional heater can cause both probes 5 to be too hot, which can lead to a situation where moisture is not detected. It has proven more effective to accept the b-error, which is the detection of moisture when it is not present, rather than the a-error, which is the detection of moisture when it is present. These indirect heat capacity measurements allow self-calibration with a short time delay. Another advantage is that the temperature of the heated probe can be set, for example, to 125 °C, instead of 360 °C in the on-off case.

[0034] According to some embodiments, each of the at least two probes 5 may have one or more heaters, which are adapted to be controlled externally to monitor the heating current and / or the temperature. That is, the functionality of monitoring the current flowing through the heater and / or the temperature of the heater is added. The presence of moisture can be indicated by a dip in the real part of the difference pair between the heated and unheated electrode pairs, for example the pair of probes 5. At the same time, the heater current may increase significantly with a sudden intrusion of moisture. The evaporation of the moisture contained in the material stream 20 allows the heating probe to be cooled more efficiently. With an ambient probe pair, such an effect is not present. In addition to the peak in the heating current, the dip in the differential impedance is a clear indication of moisture under almost all circumstances. These indirect heat capacity measurements allow self-calibration with low b-error and short time delay. Another advantage is that the temperature of the heating probe can be set to, for example, 125°C, instead of 360°C in the on-off case.

[0035] According to some embodiments, the sensor 4 has at least three probes 5, each of the three probes 5 having one or more heaters. The heaters are adapted to be controlled externally to monitor the heating current and to measure the temperature. These probes 5 can be heated to different predefined temperatures. Using these embodiments, it is possible to limit the temperature below 100° C. The measurement can then no longer be based on the evaporation energy required, but simply on the cooling effect. By having a material flow 20 that is essentially and on average drier than the accumulated material on the probe 5, the accumulated material on the probe 5 is in evaporation equilibrium with the material flow 20. Thus, drying the probe cools it, which is done by directly measuring the temperature of the probe or indirectly by measuring the heating energy required to keep the temperature at a predefined level. Three temperature points are sufficient to establish the existence of evaporation equilibrium, since the relationship between the required heaters is a function of temperature.

[0036] According to some embodiments, the heater can be a resistive heater. As mentioned above, it becomes possible to monitor the current and / or temperature via the resistive heater. Here, the presence of moisture is indicated by a pair of dips in the real part of the difference between the heated and unheated probes 5. At the same time, a large increase in the heating current in the heated probes may occur. The heated probes are set to different temperatures, for example 40° C., 60° C. and 80° C., so that the increase in the required heating current may be proportional to the difference between the temperature of the material stream 20 and the set temperature. Having three probes 5 makes it possible to calculate a linear relationship of the required resistive heating current. During the resistance dip time, the measured data has several characteristics that allow for near perfect detection of moisture, as explained below. -The measured dip length will vary as the drying temperature depends on the set temperature. The coldest probe will show the longest dip and the hottest probe will show the shortest dip. Other dips, such as those due to non-uniformities in the material flow 20, do not have this statistical relevance and can therefore be excluded.

[0037] In the presence of a resistance dip, the heating currents of all three heaters can rise and deviate substantially from the previous linear relationship. Such an indirect heat capacity measurement allows self-calibration with little b-error and short time delay. Other advantages include the fact that the temperature of the heating probe can be set to a value below, for example, 100°C, no evaporation is required, and the chill effect is sufficient.

[0038] According to some embodiments, an alarm may be activated when moisture is detected, after which drilling may be stopped, either automatically or manually by an operator.

[0039] According to some optional embodiments, since paste, e.g., water-contaminated dust, may accumulate on the sensor 4, a power resistor, e.g., a resistive heater, may be placed in thermal contact with the probe 5, allowing heating of the probe 5, e.g., above 100° C. Heating may evaporate the moisture and facilitate returning the probe 5 to an operational state.

[0040] Also, according to some optional embodiments, since paste, i.e. water contaminated dust, may accumulate on the sensor 4, an ultrasonic exciter may be placed in mechanical contact with the probe 5 to more efficiently remove the dust. As used herein, the ultrasonic exciter is intended to prevent material accumulation and solidification of the material from obscuring the probe 5 from the material flow 20.

[0041] In one embodiment, the structure 1 comprises a programmable voltage waveform source and a programmable voltage waveform receiver, e.g. a controllable AC voltage source amplifier, as well as a control unit 2, which comprises an analog switch and an analog-to-digital converter allowing a comparison between a reference impedance and a measured impedance. These are configured to provide data of the complex impedance between a pair of probes 5. At a given time, exactly one pair of probes 5 is active. This complex impedance data is read by the control unit 2 and the required mean and standard deviation are calculated. The control unit 2 is configured to store the data for logging and improvement. The control unit 2 provides a communication channel by which the state of the system can be transmitted to a remote unit 6, which has a receiver for said communication and is equipped with means for displaying the setting state. The data can be transmitted in any known manner, e.g. wired or wireless.

[0042] The embodiments herein provide a fast response to detect moisture in the material stream 20. The response can be on the order of milliseconds. Another advantage of the embodiments herein is that the system performance is programmable. Another advantage of the embodiments herein is that the electronics used are simple and can be assembled from common off-the-shelf multi-sourced components.

[0043] An example of a method of how embodiments herein may be employed is described using the flow chart of FIG. 3. FIG. 3 illustrates an example of a method for detecting moisture in a material flow 20 during drilling. Several optional examples that may be used in this procedure are also described. The structure 1 comprises a control unit 2, a data acquisition unit 3, a sensor 4, and a drilling rig 10. The sensor 4 comprises at least two probes 5 arranged in contact with the material flow 20 and connected to a programmable, e.g. adjustable, voltage source and a coherent programmable, e.g. adjustable, voltage receiver, such that the complex resistance between the probes 5 can be measured.

[0044] Step 301 consists of measuring the ratio between the received voltage and the applied voltage for a set of predefined frequencies. This ratio is used to calculate the complex impedance. The predefined frequencies may be associated with wavelengths that are much larger than the distance between the probes 5. This has the advantage that radiation effects and interference are completely avoided. According to some embodiments, the predefined frequencies may be in the range of 0.1 kHz to 30 kHz. This interval may also be chosen for legal reasons. In such cases, the detection system is not considered a source of electromagnetic waves. Also, chip sets for impedance measurements in this frequency range are commercially available.

[0045] In step 302, the impedance is measured using a programmable sinusoidal voltage source, for example by coherent detection using the applied and received voltages. Using coherent detection, it is possible to calculate the real and imaginary parts of the complex impedance of the sensor 4 with the probes 5. The real part of the complex impedance is the conductivity, the imaginary part is the inductance and the capacitance. By adjusting the measurement frequency at predetermined intervals, it is possible to generate a spectrum of the complex impedance versus frequency. This spectrum is used to detect the presence of moisture. Thus, based on the measured ratio between the received and applied voltages, for each of the predefined frequencies, the complex impedance between at least two probes 5 is determined.

[0046] Step 303 consists of determining a set of time average values ​​of the determined complex impedance using a time window. Thus, without calculating further material parameters such as the dielectric function, a suitable time average value of the determined complex impedance is determined, for example calculated, using the time window. A suitable time average value allows the setting of an average value on the scale of several seconds, during which the material flow 20 can be assumed to be constant. For example, measurements around 20 kHz to 30 kHz allow 10,000 measurements per second. Using a frequency of, for example, 16 steps, it is possible to measure about 1,000 sets of impedance per second. Typically, 500 to 1,000 sets of measurements are integrated to obtain a stable average value. The presence of moisture appears in bursts, and the transition between the final dry and wet state occurs within milliseconds, generating deviations over 10 to 15 samples. Therefore, an average value integrated over more than 10 to 15 samples is acceptable. Integration over too long a time period can lead to the system being sensitive to material changes in the material flow 20. This occurs at the second level. In terms of samples, it is generally not advisable to integrate over more than 10,000 samples. This average is constantly calculated and updated.

[0047] The measurement parameter is the instantaneous deviation of the average value of the last few sets of measured impedance from the time average value obtained by averaging the previous set of measured impedances over a long span. If the calculation of the average value is considered as a low pass filter with a predefined integration time, the difference of two low pass filters can be used as the measurement parameter. The filters have different integration times. The integration time of the short fast filter is determined by the noise of the measurement system and is usually integrated over 2-5 samples. The integration time of the longer slow filter is determined by two requirements. It should be longer than the time for which typical impedance changes due to moisture are reported (usually 10-15 samples) and shorter than the time for which typical material flow parameters change (usually 1000-10000 samples).

[0048] Step 304 involves determining a set of standard deviations based on the determined time averages and the same time window. The standard deviations are constantly determined and updated. The deviation information is used to adapt threshold conditions at which the averages from the previous step 303 are considered significant. In a typical setup, instantaneous changes of more than 1.5 to 3 standard deviations are considered significant for moisture detection.

[0049] Step 305 consists in indicating that moisture has been detected if at least one of the standard deviations exceeds a threshold condition. A strong deviation in the direction of decreasing absolute impedance value indicates that there is a trace of moisture. This effect is due to the conductivity of moisture in the material flow 20. Generally, moisture in such a situation is all contaminated with salt. For the standard deviation obtained above, a coefficient is predefined, usually around 1.5 to 3.0, which is used to determine the threshold condition of the measured parameter. If the measured parameter is above this threshold in the direction of decreasing impedance, it indicates that moisture has been detected. If moisture is detected, an alarm is activated and the excavation can be stopped automatically or manually by the operator.

[0050] By following the above method, moisture detection during drilling can be demonstrated in an enhanced and more efficient manner. For clarity, it should be understood that the steps are repeated multiple times. Since the method is performed continuously during drilling, the repetition of steps is normal.

[0051] According to some embodiments, each of the at least two probes 5 may comprise one or more heaters. The heaters may be resistors and there may be one per pair of probes 5. The heaters may be adapted to be externally controllable, e.g. on / off, to stabilise the temperature at a predefined value.

[0052] According to some embodiments, one of the at least two probes 5 may comprise one or more heaters, said heaters being adapted to be externally controlled in order to stabilise the temperature at a set of predetermined values.

[0053] According to some embodiments, each of the at least two probes 5 may comprise one or more heaters, which may be adapted to be externally controlled to monitor the heating current and / or temperature, i.e. additional functionality is added to monitor the current flowing through the heater and / or the heater temperature.

[0054] According to some embodiments, the sensor 4 comprises at least three probes 5, each of the three probes 5 having one or more heaters adapted to be externally controlled to monitor the heater current and to measure the temperature.

[0055] The heater described above may be a resistor, and one heater may be provided for each pair of probes 5 .

[0056] The foregoing description and accompanying drawings set forth non-limiting examples of the methods and structures taught herein. As such, the structures and techniques taught herein are not limited by the foregoing description and accompanying drawings. Instead, embodiments herein are limited only by the following claims and their equivalents.

Claims

1. A structure (1) for detecting moisture in a particulate material flow (20) during drilling, comprising: The structure (1) comprises a control unit (2), a data collection unit (3), and a sensor (4), The sensor comprises at least two probes (5), The at least two probes (5) are arranged in contact with the particulate material flow (20) and are connected to a programmable voltage source and a programmable voltage receiver; The structure (1) is Measure the ratio of the received voltage waveform to the applied voltage waveform at a preset frequency, determining a complex impedance between the at least two probes (5) for each of the predetermined frequencies based on the measured ratio; - determining pairs of time-averaged values ​​of the determined complex impedance for each of the predetermined frequencies using a time window; determining a set of standard deviations based on the determined time average values; and If at least one of the standard deviations exceeds a threshold, this indicates that moisture has been detected. It is configured as follows: A structure characterized by:

2. Each of the at least two probes (5) is provided with one or more heaters; The heater is adapted to be externally controlled to stabilize the temperature at a predetermined value.

2. The structure of claim 1.

3. One of the at least two probes (5) is equipped with a heater; The heater is adapted to be externally controlled to stabilize the temperature at a predetermined value.

2. The structure of claim 1.

4. Each of the at least two probes (5) is provided with one or more heaters; The heater current and / or heater temperature are adapted to be externally controlled to monitor the current and / or temperature.

2. The structure of claim 1.

5. The sensor (4) comprises three probes (5), Each of the three probes (5) is equipped with one or more heaters and adapted to externally control the resistive heating current and / or heater temperature for monitoring the current and / or temperature.

2. The structure of claim 1.

6. The predetermined frequency is in the range of 0.1 kHz to 30 kHz. The structure according to any one of claims 1 to 5.

7. The probe (5) is made of metal. The structure according to any one of claims 1 to 6.

8. A drilling rig (10) comprising a structure (1) according to any one of claims 1 to 7.

9. 1. A method for detecting water in a particulate material flow (20) during drilling, comprising: - measuring (301) the ratio between the received voltage waveform and the applied voltage waveform for a set of pre-determined frequencies; - determining (302) a complex impedance between at least two probes (5) for each of the predetermined frequencies based on the measured ratio; - determining (303) a set of time average values ​​of the determined complex impedance using a time window; - determining (304) a set of standard deviations based on the determined time average values; and indicating that moisture has been detected if at least one of the standard deviations exceeds a threshold condition (305); The method according to claim 1, further comprising:

10. Each of the at least two probes (5) is provided with one or more heaters; The heater is externally controlled to stabilize the temperature at a predetermined value.

10. The method of claim 9.

11. One of the at least two probes (5) is equipped with one or more heaters; The heater is externally controlled to stabilize the temperature at a predetermined value.

10. The method of claim 9.

12. Each of the at least two probes (5) is provided with one or more heaters; The heating current and / or the heating temperature are controlled externally to monitor the current and / or the temperature.

10. The method of claim 9.

13. The sensor (4) comprises three probes (5), Each of the three probes (5) has one or more heaters; The heater current and / or heater temperature are externally controlled to monitor the current and / or temperature.

10. The method of claim 9.

14. The predetermined frequency is within the range of 0.1 kHz to 30 kHz. Method according to any one of claims 9 to 13.

15. The probe (5) is made of metal. The method according to any one of claims 9 to 14.

16. The method of any one of claims 9 to 15, carried out on a drilling rig (10).

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