System and method for monitoring a steam trap

Abstract

A method of monitoring a steam trap, the method comprising: receiving, from an acoustic sensor, acoustic data indicative of the operation of the steam trap, each acoustic datum being associated with a corresponding time value; determining a plurality of spectral entropy values from the acoustic data, each spectral entropy value being associated with a corresponding time value; comparing a first spectral entropy value of the spectral entropy values to a first threshold value; and determining an operation mode of the steam trap at a time corresponding to the first spectral entropy value based at least partially on the comparison of the first spectral entropy value to the threshold value.

Description

[0001] System and Method for Monitoring a Steam Trap

[0002] Background

[0003] In industrial steam systems, condensate is formed during system operation when steam used for heating gives up its latent heat and condenses, condensate may also be formed due to heat loss in a steam distribution system. In order to discharge the condensate, steam traps may be coupled to the steam distribution systems. Steam traps act to discharge condensate from a system while preventing the escape of steam. However, as steam traps wear, steam may leak out through the steam trap.

[0004] Generally, it is desirable to monitor the activity of a steam trap in order to determine how a system is functioning. For example, wear of a steam trap may be determined, and a volume of condensate discharge or steam leakage may also be determined. Steam traps may also fail in an open position, constantly passing fluid, or in a closed position, where no fluid passes.

[0005] Summary of the Invention

[0006] According to a first aspect of the invention, there is provided a method of monitoring a steam trap, the method comprising: receiving, from an acoustic sensor, acoustic data indicative of the operation of the steam trap, each acoustic datum being associated with a corresponding time value; determining a plurality of spectral entropy values from the acoustic data, each spectral entropy value being associated with a corresponding time value; comparing a first spectral entropy value of the spectral entropy values to a first threshold value; and determining an operation mode of the steam trap at a time corresponding to the first spectral entropy value based at least partially on the comparison of the first spectral entropy value to the first threshold value.

[0007] The acoustic data may also be referred to as an acoustic signal, the acoustic signal containing information indicative of a plurality of acoustic signal values.

[0008] By determining the spectral entropy of the acoustic signal and basing a determination of an operation mode of a steam trap on the determined spectral entropy, a more reliable determination may be made as to the operation mode of the steam trap. Overall, the method involves the calculating of spectral entropy values from received acoustic data, and comparison of the spectral entropy values to one or more threshold values for determining how the steam trap is operating, i.e. whether the trap is closed, is leaking steam, is open or is transitioning, such as by a disc click.

[0009] The first threshold value may be a steam leakage threshold value, selected or calculated such that a spectral entropy value below the steam leakage threshold value is indicative of steam leakage of the steam trap. Therefore, the method may comprise determining that the steam trap is leaking steam based on a determination that the first spectral entropy value is less than the steam leakage threshold value. The determination may also be made based on further comparisons or a chronology of known events such as disc clicks. The method may comprise determining that the steam trap is passing condensate based on a determination that the first spectral entropy value is greater than the steam leakage threshold value

[0010] The first threshold value may be a background threshold value, selected or calculated such that a spectral entropy value below the background threshold value is indicative of the steam trap not passing fluid. Therefore, the method may comprise determining that the steam trap being closed and not passing fluid based on a determination that the first spectral entropy value is less than the background threshold value. The method may comprise comparing the first spectral entropy value to the background threshold value and comparing the first spectral entropy value to the steam leakage threshold value, and based on a determination that the spectral entropy is between the background threshold value and the steam leakage threshold value, may determine that the steam trap is leaking steam.

[0011] The first threshold value may be a valve actuation threshold value, selected or calculated such that a spectral entropy value above the valve actuation threshold value is indicative of the steam trap transitioning from a closed state to an open state or vice versa. Therefore, the method may comprise determining that a transition or disc click event has occurred based on a determination that the first spectral entropy value is greater than the valve transition threshold value.

[0012] The determination of the operating mode may also be made based on further comparisons or a chronology of known events such as disc clicks which were classified by comparison of the first or other spectral entropy values to the first or other thresholds. The method may further comprise: in response to determining that the first spectral entropy value is greater than the first threshold value, calculating a difference between the first spectral entropy value and a second spectral entropy value; and comparing the calculated difference to a threshold difference value; and the determining of the operation mode of the steam trap at the time corresponding to the first spectral entropy value may be based at least partially on the comparison of the calculated difference to the threshold difference value. Since a high rate of change of spectral entropy is indicative of movement of solid parts within a steam trap, the difference between two spectral entropy values may provide further information regarding the function of a steam trap.

[0013] The threshold difference value may be a valve transition difference value, and the determining of the operation mode may be determining that the steam trap has transitioned from a closed to an open state at the time corresponding to the first spectral entropy value based at least partially on the determined difference being above the valve transition difference value. In this case, the first threshold value may be a steam leakage value or may be a background reference value. The valve transition may be movement of a disc within the steam trap, and the transition may be referred to as a disc click.

[0014] The second spectral entropy value may correspond to a time adjacent to the time corresponding to the first spectral entropy value. In this way, the change in spectral entropy may be determined over a small time period.

[0015] The method may further comprise, in response to the determination that a valve transition of the steam trap has occurred at the time corresponding to the first spectral entropy value, storing the first spectral entropy value as a valve transition threshold value. In this way, later valve transitions may be determined with improved computational efficiency.

[0016] The method may further comprise comparing a third spectral entropy value of the spectral entropy values to the valve transition threshold value, and determining that the steam trap is discharging condensate, at least partially based on the third spectral entropy value being lower than the valve transition threshold value. In this way, the later valve transitions and condensate discharge events may be determined without a comparison to adjacent spectral entropy values, thereby reducing computational intensity.

[0017] The method may further comprise comparing the third spectral entropy value to a third threshold value, and determining that the steam trap is discharging condensate, at least partially based on the second spectral entropy value being greater than the third threshold value. The third threshold value may be the background threshold value or the steam leakage threshold.

[0018] The third spectral entropy value may be any spectral entropy value corresponding to a time subsequent to a valve transition and the third threshold value may be a steam leakage value.

[0019] The plurality of spectral entropy values may be determined from the acoustic data based on the entire frequency range of the acoustic data. This may provide a more robust method that is more resistant to noise and thereby provides a more reliable indication of the mode of operation of the steam trap.

[0020] The method may further comprise determining the first, second and / or third threshold value(s) based on an orifice size of the steam trap and / or an upstream pressure of the stream trap. This may provide more repeatable analysis for a large number of steam traps with less computational effort.

[0021] The steam trap may be a thermodynamic steam trap.

[0022] The acoustic sensor may be a vibroacoustic and / or piezoelectric sensor.

[0023] The acoustic sensor may be arranged upstream of the steam trap.

[0024] The method may comprise comparing the first spectral entropy value, optionally a plurality of the spectral entropy values, further optionally all of the spectral entropy values, to one or more threshold values in order to determine an operation mode of the steam trap. The method described herein, and all variations thereof, may be repeated for a plurality of spectral entropy values and optionally for all spectral entropy values. According to a second aspect of the invention, there is provided a processor arranged to be coupled to an acoustic sensor, the processor being configured to carry out any method according to the first aspect.

[0025] According to a third aspect of the invention, there is provided a system for discharging condensate, the system comprising: a steam trap for discharging condensate, an acoustic sensor arranged to detect acoustic waves from the steam trap and to output acoustic data, and a processor according to the second aspect, the processor being arranged to receive the acoustic data from the acoustic sensor.

[0026] According to a fourth aspect of the invention, there is provided a computer-readable medium comprising instructions which, when executed by a suitable processor, cause the computer to carry out the method of the first aspect.

[0027] It is noted that the terms “first”, “second”, and “third” are not intended to indicate chronology, order or priority and are merely labels for distinguishing separate features of the invention. The presence of a “second” feature does not necessitate the presence of a “first” feature and the presence of a “third” feature does not necessitate the presence of a “first” or a “second” such feature.

[0028] It will also be understood that the method may be carried out at different sites and / or on different processors. For example, the acoustic data may be received and the spectral entropy may be determined locally to a steam trap. The spectral entropy may be transmitted to a remote site for comparison to thresholds and determination of the mode of operation of the steam trap.

[0029] Brief Description of the Drawings

[0030] Figure 1a shows a system according to the invention, the system comprising a steam trap in the closed position;

[0031] Figure 1 b shows the system of Figure 1a within the steam trap in the open position;

[0032] Figure 2 is a flowchart showing a method of operation of a steam trap; Figure 3a is a graph showing the amplitude against time of a sound recording of a steam trap;

[0033] Figure 3b is a first graph showing the spectral entropy against time of the sound recording of Figure 3a;

[0034] Figure 3c is a second graph showing the spectral entropy against time of the sound recording of Figure 3a; and

[0035] Figure 4 shows a method of monitoring a steam trap according to the invention.

[0036] Detailed Description

[0037] Figure 1 shows a system 10 for discharging fluid including condensate and for monitoring the discharged fluid.

[0038] The system 10 includes a thermodynamic steam trap 11 arranged to discharge condensate and to prevent the discharge of vapour. Typically, the condensate to be discharged is water and the vapour to be prevented from discharging is steam. However, different fluids may be used.

[0039] The system 10 has a steam trap 11 that is coupled, via an upstream pipe 12, to a steam system (not shown) for receiving fluid from the steam system. The steam trap 11 is coupled to a downstream discharge pipe 14 and is arranged to allow condensate to leave the steam system via the downstream discharge pipe 14.

[0040] The steam trap 11 has a strainer 16 that is arranged to prevent solid debris from passing into and fouling or blocking the steam trap 11. It will be understood that the strainer 16 is not essential and that a steam trap 11 may be provided that has no strainer 16. The steam trap is arranged to allow fluid to pass through the strainer 16 and then to enter a control chamber 20 via an inlet orifice 19. The control chamber 20 may contain steam or may contain condensate. The inlet orifice 19 may be closed periodically by a valve disc 18. As shown in Figure 1a, when the valve disc 18 is lowered, the valve disc 18 may close the inlet orifice 19, preventing the outlet of fluid from the steam system. Figure 1 b shows the system 10 where the valve disc 18 is raised so that the fluid may pass from the inlet pipe 12, pass through the control chamber 20 to a peripheral outlet 21 and be discharged via the discharge pipe 14.

[0041] The system 10 also comprises an acoustic sensor 22 that is coupled to a upstream pipe 12 and arranged to receive acoustic signals from the steam trap 11 . The acoustic sensor 22 may be a vibroacoustic sensor, a piezoelectric sensor, a piezoelectric vibroacoustic sensor, or may be any other form of microphone, vibration or acoustic sensor. The acoustic sensor 22 is arranged to receive the acoustic signals from the steam trap 11 and to provide data indicative of the acoustic signals, which are to be transferred to the processor 24 for analysis.

[0042] The acoustic sensor 22 may alternatively be coupled to other components of the system 10, such as to a casing of the steam trap 11 or to the discharge pipe 14.

[0043] The processor 24 may be arranged to process the data from the acoustic sensor 22 in order to provide an indication of a manner of operation of the steam trap 11. The method of processing is explained below with reference to Figures 3a, 3b and 4.

[0044] While the steam trap 11 shown in Figures 1a and 1 b is a thermodynamic steam trap, it will be understood that any steam trap may be used and that the steam trap may be mechanical, using a float valve, or thermostatic, using a bimetallic valve.

[0045] Figure 2 illustrates a method 50 of operation of the steam trap for allowing the discharge of condensate from the steam system while preventing the release of steam.

[0046] Condensate may build up in a steam system due to a cooling of the steam system while it is turned off or may accumulate on an inner surface of pipework due to heat transfer to the external environment. Discharge of the condensate may then be required for optimal functioning of the steam system.

[0047] At step 52, the steam trap is closed as shown in Figure 1a, with the disc covering the inlet orifice to prevent the flow of fluid through the steam trap. At this time, no fluid may be flowing through the steam trap, or steam may leak through the steam trap due to sub- optimal seating or sealing of the disc. At step 54, due to condensate flowing into the inlet orifice and moving the disc, the disc may be raised to open the inlet orifice and to allow fluid communication between the inlet orifice and the outlet orifice. The movement of the disc may involve the disc contacting an upper part of the steam trap, which may produce a sound known as a disc click.

[0048] Subsequent to the disc click, at step 56, the steam trap may be in a stable, open state as shown in Figure 1b. In this state, condensate may flow under the disc between the inlet orifice and the outlet orifice. The condensate may fill the control chamber and a relatively equal pressure above and below the disc may maintain the disc in a raised position allowing condensate to be discharged.

[0049] As the condensate in the system is reduced, hotter condensate or steam may flow into the steam trap. When hot condensate flows through the gap under the disc, the gap may act as a venturi, where the pressure of the hot condensate reduces due to the speed of the flow. In this case, the pressure of the hot condensate may decrease to cause evaporation of the condensate, known as flash steam. As steam fills the control chamber, the pressure above the disc may increase above the pressure below the disc and the disc may therefore seal at step 58.

[0050] With the disc sealed at step 52, the steam in the control chamber may condense due to heat transfer to the environment, and the pressure in the control chamber may therefore reduce. The disc may therefore raise and a disc click may occur at step 54.

[0051] The steam trap may thereby operate cyclically to discharge condensate.

[0052] It will be understood that the present disclosure may also apply to other forms of steam trap known in the art such as thermostatic or mechanical steam traps that may operate by cyclic opening and closing of valves.

[0053] Figure 3a shows a graph 100 showing an acoustic signal received from a thermodynamic steam trap. The graph shows amplitude on the Y-axis and time on the X-axis. During a first time period 102, the steam trap is leaking steam, then a disc click, opening the steam trap, occurs at 104. After the disc click, the steam trap discharges condensate during a second time period 106. Figure 3b shows a second graph 110 showing a spectral entropy calculated based on the acoustic signal shown in Figure 3a. The graph 110 of Figure 3b illustrates spectral entropy (on the Y-axis) against time (on the X-axis). The graph 110 shows the same first time period 112, during which steam leaks through the steam trap, which has a low spectral entropy. Steam leakage in a steam trap is undesirable and occurs while the disc is covering the inlet orifice. If the disc were sealing the steam trap correctly, there would be a lower sound level and a lower spectral entropy at this time.

[0054] At a point in time 114b, the disc click occurs. The disc click is identifiable by a higher spectral entropy determined from the acoustic data. Subsequent to the disc click 114b, during the second time period 116, the spectral entropy is higher than during the steam leakage, but lower than the disc click.

[0055] Based on known heuristics and experiential evidence, thresholds 120, 122 have been determined for assessing spectral entropy of acoustic data received from steam traps. A spectral entropy difference value 118 has also been determined. It will be understood that the threshold values and difference value may be different for different steam traps and for steam traps operating with different upstream pressures.

[0056] A first threshold 120 is a background noise threshold. A spectral entropy below this threshold is indicative of only background noise being detected by an acoustic sensor, meaning that no fluid is passing through the steam trap. This may indicate a good level of sealing of the steam trap, so that an assessment may be made that the steam trap is not suffering from wear and does not require replacement.

[0057] A second threshold 122 is a steam leakage threshold. A spectral entropy below this threshold, and in particular between this threshold and the background noise threshold 120, is indicative of steam leakage through the steam trap. Since steam leakage is undesirable, this may indicate that the steam trap is not properly sealing, is suffering from wear, and may require replacement. Quantification of steam leakage may also allow a system operator to manage the connected steam system adequately.

[0058] Further, in order to determine a valve transition, such as by a disc click, a difference between two adjacent spectral entropy values 114a, 114b may be calculated. Where the spectral entropy of one point 114b is greater than a previous, adjacent spectral entropy value 114a by greater than a difference threshold 118, it may be determined that a valve transition has occurred. The difference threshold 118, which may be referred to as a valve transition difference threshold, may be determined based on heuristics and experiential or empirical data.

[0059] Considered alternatively, a valve transition threshold value may be determined dynamically for each spectral entropy value 114b as the sum of the valve transition difference value 118 and the preceding spectral entropy value 114a. A valve transition may be determined by comparison of the spectral entropy value 114b to a valve transition threshold value which is dynamically determined.

[0060] The valve transition may be via a disc click in the case of a thermodynamic steam trap, or a valve opening or closing in thermostatic or mechanical steam traps.

[0061] Alternatively, as shown in Figure 3c on graph 150, a third threshold 124, which is a valve transition threshold, such as a disc click threshold may be used for determining disc clicks. The valve transition threshold 124 may be determined based on a determined valve transition and may be equal to a spectral entropy value 114b that corresponds to a valve transition or may be determined as by multiplying the spectral entropy value 114b by a predetermined coefficient. A valve transition may be determined based on a spectral entropy being at or above the valve transition threshold 124.

[0062] The valve transition threshold 124 may alternatively be predetermined and based on calculated, experiential or empirical values for valve transitions and may be based on the size of the steam trap and / or an upstream pressure of the steam trap.

[0063] In order to determine a mode of operation of a steam trap, such as whether the steam trap is leaking steam or discharging condensate at a specific time, a spectral entropy value at that time may be compared to one or more of the above-described threshold values. In some cases, a single comparison may provide a strong indication of the mode of operation of the steam trap. A determination may also be made based on temperature data or events that are known to have occurred previously, such as a disc click or other valve transition. Alternatively, a comparison may be made to multiple threshold values to provide an indication of the mode of operation of the steam trap.

[0064] Figure 4 is a flowchart illustrating a method 200 of determining a mode of operation of the steam trap. At step 210, an audio signal, which may also be referred to as an acoustic signal, is received from an acoustic sensor coupled to the steam trap. The acoustic sensor may be arranged to receive soundwaves from the steam trap by being coupled to a pipe upstream of the steam trap. The audio signal may include a plurality of acoustic data at a plurality of corresponding time values.

[0065] At step 220, a spectral entropy of the audio signal is determined. The spectral entropy of each acoustic datum may be determined, or a subset of the acoustic data may be selected and the spectral entropy of each datum within the subset may be determined. The method for determining spectral entropy is well-known and comprises: determining a Fourier transform of the datum, determining a spectral power based on the Fourier transform, determining a normalised spectral power based on the spectral power, and determining the spectral entropy based on the spectral power and the normalised spectral power.

[0066] The spectral entropy may be determined without any frequency-based filtering step. Considered alternatively, the spectral entropy may be determined across the entire range of frequencies found in the acoustic signal. The full frequency range of the acoustic signal may be used for determining the spectral entropy. While alternative methods may calculate a spectral entropy for only a subset of the frequencies in the acoustic signal, it has been found that determining the spectral entropy based on the full frequency range of the acoustic signal may provide a more robust method of determining a mode of operation of a steam trap that is more resistant to background noise that may be detected.

[0067] Steps 215 and 225 may be performed simultaneously with steps 210 and 220, earlier than steps 210 and 220, or later than steps 210 and 220. At step 215, data regarding the steam trap to be monitored is received. The data may include an orifice size of the steam trap and an upstream pressure of the steam trap. The data may be input manually by a user or may be mined from a system, such as a digital twin, which contains the required data concerning the steam trap.

[0068] At step 225, spectral entropy thresholds are determined by the system based on the data received at step 215. The spectral entropy thresholds include the background reference value, which is based on an expected level of background noise and is determined to be lower than a spectral entropy of sound from steam leaking through the steam trap. The spectral entropy thresholds also include the steam leakage value, which is determined to be higher than the spectral entropy of noise caused by steam leaking through the steam trap and lower than the spectral entropy of noise caused by condensate being discharged through the steam trap.

[0069] The determined thresholds may also include a valve transition difference value, which is a difference between two adjacent spectral entropy values, above which a valve transition such as a disc click can be deemed to have occurred. Alternatively, an absolute spectral entropy valve transition threshold value may be determined as a spectral entropy value, above which a valve transition can be deemed to have occurred.

[0070] Alternatively, at step 225 the threshold values may be received by the system directly from a user, as opposed to being determined based on steam trap data. In this case, step 215 may be omitted. In some cases, where only limited data regarding the function of the steam trap is required, a subset of the thresholds may be determined. For example, if the only information required is whether the steam trap is leaking to allow steam to pass, only the background reference value may be determined. Alternatively, where temperature data related to the steam trap is available, fewer threshold values may be required for determining the mode of functioning of the steam trap.

[0071] At step 230, the determined spectral entropy values are compared to one or more of the determined threshold values. In the first instance, a spectral entropy value may be compared to the background reference value and, if it is greater than the background reference value, it may be compared to the steam leakage value. It will be understood that comparison of the spectral entropy value to the background reference value and the steam leakage value may occur in any order or simultaneously.

[0072] In the case that the spectral entropy value is determined to be less than the steam leakage value, and / or less than the background reference value, the method may move to step 240, indicating that the steam trap is not passing fluid, or to step 250, indicating that the steam trap is leaking steam. In both of steps 240 and 250, an output may be generated indicating the mode of functioning of the steam trap to a further program or sub-program or to a user. If it is determined that the spectral entropy value is greater than the steam leakage value, then the steam trap may be discharging condensate or may be undergoing a valve transition such as a disc click. In this case, at step 260, a difference may be calculated between the spectral entropy value and an adjacent spectral entropy value, which may be an immediately previous spectral entropy value, and the difference may be compared to the valve transition difference value.

[0073] It will also be understood that a difference between two adjacent spectral entropy values may be determined for all spectral entropy values. In this case, step 230 may be omitted or the relative positions of steps 230 and 260 in the method may be swapped. Further, where a valve transition is to be determined based on a threshold valve such as disc transition threshold value 124, step 260 may be omitted and step 230 may comprise a comparison of the spectral entropy value to a disc click threshold.

[0074] The method may move to step 270 if it is determined that the steam trap is discharging condensate. At step 270, an output may be generated indicating the mode of functioning of the steam trap is to discharge condensate. The output may be provided to a further program, to a sub-program or to a user.

[0075] Alternatively, if the difference is above the valve transition difference value (or, in alternative methods, the spectral entropy value is above the valve transition threshold value), the method may move to step 280 as it is determined that a valve transition has occurred. At step 280, the valve transition may be counted and the processor may increment a valve transition count by 1 for each valve transition that is determined to have occurred. The spectral entropy value may also be stored as the valve transition threshold value for comparison to other spectral entropy values. Further, an output may be generated indicating the mode of functioning of the steam trap.

[0076] By storing the spectral entropy value corresponding to the valve transition and the generation of a valve transition threshold, the difference calculated at step 260 may be replaced for analysis of subsequent data by a comparison to the valve transition threshold, or step 260 may be omitted and a comparison to the valve transition threshold may be included within step 230.

[0077] It will be understood that, in alternative methods, the comparisons of the spectral entropy to the thresholds may occur in a different order and that comparisons to some thresholds may be omitted. For instance, without comparison of a spectral entropy value to a background reference threshold it may be determined that the steam trap is discharging condensate after a valve transition. Further, it may also be determined that a valve transition has occurred if the steam trap has been leaking steam or not passing fluid and the spectral entropy then increases above the steam leakage value as the steam trap cannot begin discharging condensate after being closed without a disc click occurring.

[0078] Based on the determined steam trap operation modes, at step 290, further properties of the steam trap function may be determined. This is an optional step that may be performed to provide further data regarding the functioning of the steam system.

[0079] At step 290, a condensate discharge duration may be determined based on the number and / or timespan of spectral entropy values that are determined to be indicative of the steam trap discharging condensate.

[0080] A condensate discharge rate may also be determined based on the orifice size, upstream pressure, condensate discharge duration and the counted number of valve transitions. The condensate discharge rate may be determined as a mass flow rate of condensate, such as in units of kilograms per hour.

[0081] At step 290, a steam leakage duration may be determined based on the number and / or timespan of spectral entropy values that are determined to be indicative of the steam trap leaking steam.

[0082] A steam leakage rate may also be determined based on the orifice size, upstream pressure, steam leakage duration and the counted number of valve transition. The steam leakage discharge rate may be determined as a mass flow rate of steam, such as in unit of kilograms per hour.

[0083] While the majority of the above disclosure relates to thermodynamic steam traps having floating discs, it will be understood that the disclosure may also relate to mechanical or thermostatic steam traps. In this case, the valve transition may not be a disc click, but the disclosure relating to discharge of condensate, leakage of steam, and the situation of no fluid passing through the steam trap may apply analogously.

Claims

CLAIMS1. A method of monitoring a steam trap, the method comprising: receiving, from an acoustic sensor, acoustic data indicative of the operation of the steam trap, each acoustic datum being associated with a corresponding time value; determining a plurality of spectral entropy values from the acoustic data, each spectral entropy value being associated with a corresponding time value; comparing a first spectral entropy value of the spectral entropy values to a first threshold value; and determining an operation mode of the steam trap at a time corresponding to the first spectral entropy value based at least partially on the comparison of the first spectral entropy value to the threshold value.

2. The method of claim 1 , wherein the first threshold value is a steam leakage value, and wherein the determining of the operation mode is determining that the steam trap is leaking steam at the time corresponding to the first spectral entropy value based on the first spectral entropy value being less than the steam leakage value.

3. The method of claim 1 , wherein the first threshold value is a background reference value, and wherein the determining of the operation mode is determining that the steam trap is not passing fluid at the time corresponding to the first spectral entropy value based on the first spectral entropy value being less than the background reference value.

4. The method of claim 1 or 2, further comprising: comparing the first spectral entropy value to a second threshold value, and wherein the determining of the operation mode is determining an operation mode of the steam trap at the time corresponding to the first spectral entropy value based on the comparisons of the first spectral entropy value to the first threshold value and the second threshold value.

5. The method of claim 4, wherein the second threshold value is a background reference value, andwherein the determining of the operation mode is determining that the steam trap is leaking steam at the time corresponding to the first spectral entropy value based on the first spectral entropy value being greater than the background reference value.

6. The method of claim 1, further comprising: in response to the first spectral entropy value being greater than the first threshold value, calculating a difference between the first spectral entropy values and a second spectral entropy value; and comparing the calculated difference to a threshold difference value; and wherein the determining of the operation mode of the steam trap at the time corresponding to the first spectral entropy value is based at least partially on the comparison of the calculated difference to the threshold difference value.

7. The method of claim 6, wherein the threshold difference value is a valve transition difference value, and wherein the determining of the operation mode is determining that a valve transition of the steam trap has occurred at the time corresponding to the first spectral entropy value based at least partially on the determined difference being above the valve transition difference value.

8. The method of claim 7, wherein the first threshold value is the steam leakage value.

9. The method of claim 7 or 8, wherein the second spectral entropy value corresponds to a time adjacent to the time corresponding to the first spectral entropy value.

10. The method of any one of claims 6 to 9, further comprising, in response to the determination that a valve transition of the steam trap has occurred at the time corresponding to the first spectral entropy value, storing the first spectral entropy value as a valve transition value.

11. The method of claim 10, further comprising comparing a third spectral entropy value of the spectral entropy values to the valve transition value, and determining that the steam trap is discharging condensate, at least partially based on the third spectral entropy value being lower than the valve transition value.

12. The method of claim 11, further comprising comparing the third spectral entropy value to a third threshold value, and determining that the steam trap is discharging condensate, at least partially based on the second spectral entropy value being greater than the third threshold value.

13. The method of claim 12, wherein the third threshold value is the same as the first threshold value.

14. The method of any preceding claim, wherein the plurality of spectral entropy values are determined from the acoustic data based on the entire frequency range of the acoustic data.

15. The method of any preceding claim, further comprising determining the first, second and / or third threshold value(s) based on an orifice size of the steam trap and / or an upstream pressure of the stream trap.

16. The method of any preceding claim, wherein the steam trap is a thermodynamic steam trap.

17. The method of any preceding claim, wherein the acoustic sensor is a vibroacoustic sensor.

18. The method of any preceding claim, wherein the acoustic sensor is arranged upstream of the steam trap.

19. A processor arranged to be coupled to an acoustic sensor, the processor being arranged to carry out the method of any preceding claim.

20. A system for discharging condensate, the system comprising: a steam trap for discharging condensate, an acoustic sensor arranged to detect acoustic waves from the steam trap and to output acoustic data, and the processor of claim 19, the processor being arranged to receive the acoustic data from the acoustic sensor.

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