Technical field

[001] The present invention relates to method of operating a sealing monitoring system in a sealing of a rotatable shaft, Invention relates also to a sealing moni toring system for a sealing in connection with a rotatable shaft comprising a flush ing liquid system, the sealing being arranged between a rotatable shaft and a seal housing.

Background art

[002] Invention relates to monitoring of mechanical seals in pumps or alike flow machines having a mechanical seal in its rotatable shaft. Mechanical seals are gaining more and more acceptance in various shaft sealing applications. The mechanical seals find use in various pumps, mixers and agitators. Mechanical seals are of relatively simple construction, they endure high temperatures and their maintenance and service is relatively easy. But, just like all kinds of seals, their lifetime is hard to predict. It is also quite impossible to perform any visual monitoring of the condition of the seal. Failure of such seals may cause consid- erable damages and extra costs. Therefore, prior art includes numerous docu ments that discuss the monitoring of the condition of a mechanical seal.

[003] EP3139072 A1 discloses an apparatus for monitoring one or more com ponents of a propulsion system of a watercraft. Plurality of sensors are arranged to a mechanical seal of a propeller shaft and information obtained by the sensors is sent to a controller which is configured to provide estimated residual life time of the mechanical seal device.

[004] WO2018210504 A1 discloses a mechanical seal having a rotary part and a non-rotary part, the rotary part having at least a rotary slide ring and a rotary slide ring carrier, and the non-rotary part having at least a non-rotary slide ring and a non-rotary slide ring carrier. The mechanical seal is provided with a cir cumferential groove in one of the rotary slide ring and the non-rotary slide ring and a sensor in communication with the mechanical seal.

[005] US 6065345 A discusses a method of monitoring the condition of a me chanical seal in an apparatus provided with a rotating part, in particular in a pump, which has a rotating shaft for the forwarding of a fluid. The sound emission of the seal is continually measured at discrete times in the operating state of the appa ratus and at least one statistical characteristic value is won from the acoustic signals. The goal in the above discussed patent is to monitor the sliding condition of the seal. In other words, if the seal is starting to run dry, i.e. the flushing is, for some reason, not working properly, the acoustic emission from the seal changes with the condition of the lubricating film.

[006] US 6360610 B1 discusses a system and a method that are particularly suited for monitoring the interface of two liquid lubricated mechanical seal faces. The system monitors an interface by using a wave source to produce an ultra sonic shear wave, directing the wave at the interface, detecting the wave after it interacts with the interface, and comparing the detected wave to predetermined wave characteristics. Based on the comparison, an alarm may be triggered.

[007] EP 1510698 B1 discloses a pump provided with a device for protecting the pump against dry running. The pump is provided with a sensor by means of which a filling level at a region of a mechanical seal is detected and starting of the pump can be prevented if liquid is not detected.

[008] It is also known as such to monitor mechanical seals making use of wire less monitoring systems. As an example of such it is referred to a publication MX 2011003615 A which discloses i.a. gathering lubrication information of a mechan ical sea and vibration information the device by means of a wireless data transfer system.

[009] However, there is still a need of further improve the reliability of the oper ation of a mechanical seal. [0010] An object of the invention is to provide a method of operating a sealing monitoring system in a mechanical sealing of a rotatable shaft, in which perfor mance is considerably improved compared to the prior art solutions.

[0011] It is also an object of the invention to provide a sealing monitoring system which is considerably improved compared to the prior art solutions.

Disclosure of the Invention

[0012] Objects of the invention can be met substantially as is disclosed in the independent claims and in the other claims describing more details of different embodiments of the invention.

[0013] According to invention, a method of operating a sealing monitoring sys tem in a sealing of a rotatable shaft comprising a sealing, provided with a flushing liquid system between a rotatable shaft and a stationary housing, a first liquid detector configured to detect presence of flushing liquid in the flushing liquid sys tem, which method comprises

detecting a first flushing liquid presence status in the flushing liquid system by means of the first liquid detector, and

a) in case the first flushing liquid presence status is affirmative, transmitting the first flushing liquid presence status to a further processing using a wireless data communication system with a first data transmission interval between the transmissions, and

b) in case the first flushing liquid presence status is negative, transmitting the first flushing liquid presence status to further processing using the wireless data communication system with a second data transmission interval being shorter than the first transmission interval between the transmissions.

[0014] By means of the invention it is possible to obtain the information of status of the flushing liquid, and particularly possible failure of the sealing in a device provided with the rotatable shaft, even at remote or unmanned locations practi cally in real time, and over a long period of time due to the practise that the data transmission interval is changed based on the flushing liquid presence status and unnecessary energy consumption can be minimized. [0015] According to an embodiment of the invention the first liquid detector de tects the presence status of the liquid intermittently, and in the in case the first flushing liquid presence status is affirmative the first flushing liquid presence sta tus of the flushing liquid system is detected using a first detecting interval, and in the in case the first flushing liquid presence status is negative the first flushing liquid presence status of the flushing liquid system is detecting using a second detecting interval being shorter than the first detecting interval.

[0016] This way providing a break between the transmissions and/or when the interval between the transmissions is changed based on the presence of the flushing liquid the sealing monitoring system uses only minimal amount of energy and thus its independency is at high level.

[0017] According to an embodiment of the invention the first liquid detector de tects the presence status of the liquid continuously.

[0018] According to an embodiment of the invention in the in case the first flush ing liquid presence status is affirmative the wireless data communication system is set to idle between the data transmissions.

[0019] According to an embodiment of the invention in the in case the first flush ing liquid presence status is affirmative the first data transmission interval is more than one hour.

[0020] According to an embodiment of the invention in the in case the first flush ing liquid presence status is affirmative the first data transmission interval is more than 4 hours.

[0021] According to an embodiment of the invention in the in case the first flush ing liquid presence status is affirmative the first data transmission interval is infi nite. In this case the first flushing liquid presence status is transmitted to a further processing only in case the first flushing liquid presence status is negative again.

[0022] According to an embodiment of the invention in the in case the first flush ing liquid presence status is negative the second data transmission interval is less than 60 seconds. [0023] According to an embodiment of the invention the sealing monitoring sys tem is provided with a vibration sensor unit, and the method comprising detecting vibration information of the shaft of the device, and determining rotation status of the shaft from the vibration information and in in case the first flushing liquid pres ence status is affirmative transmitting the vibration information to further pro cessing using the first data transmission interval between the transmissions, in case the first flushing liquid presence status is negative transmitting the vibration information to further processing using the second data transmission interval be tween the transmissions.

[0024] According to an embodiment of the invention the sealing monitoring sys tem is provided with a vibration sensor unit, and the method comprising detecting vibration information of the shaft of the device, and determining rotation status of the shaft from the vibration information and in in case the first flushing liquid pres ence status is affirmative transmitting the vibration information to further pro cessing using the first data transmission interval between the transmissions, in case the first flushing liquid presence status is negative transmitting the vibration information to further processing using the second data transmission interval be tween the transmissions and decreasing interval of detecting vibration infor mation of the shaft of the device.

[0025] According to an embodiment of the invention the vibration information is used for determining if the shaft is rotating or not. In case the first flushing liquid presence status is negative, the vibration information is used for determining if the shaft is rotating or not and if the shaft is rotating the first flushing liquid pres ence status to further processing using the wireless data communication system with a second data transmission interval being shorter than the first transmission interval between the transmissions.

[0026] According to an embodiment of the invention, in case the first flushing liquid presence status is affirmative, transmitting the first flushing liquid presence status to a further processing using a wireless data communication system with a first data transmission interval between the transmissions, and detecting the transmission occurrence and in case the transmission occurrence cannot be pos itively confirmed, triggering an alarm signal. When the first data transmission in terval is stored or made available for use in a transmission receiving unit, the omission of transmission within the interval can be used to detect a problem in the transmission procedure. This way it is possible to actively monitor for exam ple charge of a battery providing power to the wireless data communication sys tem.

[0027] According to an embodiment of the invention the sealing monitoring sys tem is provided with a vibration sensor unit, and the method comprises detecting a start moment of the device and defining the first flushing liquid presence status at the start moment of the device, and in case the first flushing liquid presence status is negative, transmitting an anomaly message to further processing, the anomaly message comprising information that the sealing is running dry.

[0028] According to an embodiment of the invention the flushing liquid system comprises a node to which the first flushing liquid presence status is transmitted using a wireless data communication system and the first flushing liquid presence status is transmitted from the node further processing using the wireless data communication system. More generally all the sensors of the sealing monitoring system are arranged to communicate with the node which transmits the commu nicated data to further processing via the internet.

[0029] Invention relates also to a sealing monitoring system for a sealing in an apparatus comprising a rotatable shaft, a flushing liquid system, the sealing being arranged between the rotatable shaft and a housing, wherein the sealing moni toring system comprises a first liquid detector configured to detect presence of flushing liquid in the flushing liquid system, a data processing apparatus which is configured to receive data of the first liquid detector and a wireless data commu nication system in data transfer connection with the data processing apparatus, and wherein the data processing apparatus comprises

executable instructions to detect the first flushing liquid presence status of the flushing liquid system,

executable instructions to determine the first flushing liquid presence sta tus to be either affirmative when the presence of the flushing liquid in the flushing liquid system is detected, or negative when the presence of the flushing liquid in the flushing liquid system is not detected,

executable instructions to transmit the first flushing liquid presence status to further processing using the wireless data communication system with a first data transmission interval in case the flushing liquid presence status is affirma tive, and

executable instructions to transmit the first flushing liquid presence status to further processing using the wireless data communication system with a sec ond data transmission interval being shorter than the first transmission interval between the transmissions, in case the flushing liquid presence status is nega tive.

[0030] According to an embodiment of the invention the first flushing liquid pres ence status, a second flushing liquid presence status and/or the vibration status is transferred to a remote data server, which makes it possible to utilize the data for various purposes.

[0031] According to an embodiment of the first liquid detector is configured to detect presence of flushing liquid intermittently and the data processing appa ratus comprises executable instructions to detect the first flushing liquid presence status using the first detecting interval in case the first flushing liquid presence status is affirmative, and executable instructions to detect the first flushing liquid presence status using a second detecting interval being shorter than the first de tecting interval in case the first flushing liquid presence status is negative.

According to an embodiment of the invention first liquid detector is configured to detect presence of flushing liquid continuously.

[0032] According to an embodiment of the invention the data processing appa ratus comprises executable instructions to set the wireless data communication system to idle between the transmissions.

[0033] According to an embodiment of the invention the data processing appa ratus comprises executable instructions to transmit the first flushing liquid pres ence status to further processing using the wireless data communication system with the first data transmission interval being more than one hour in case the flushing liquid presence status is affirmative. [0034] According to an embodiment of the invention the data processing appa ratus comprises executable instructions to transmit the first flushing liquid pres ence status with the first data transmission interval being more than 4 hours in case the flushing liquid presence status is affirmative.

[0035] According to an embodiment of the invention the data processing appa ratus comprises executable instructions to transmit the first flushing liquid pres ence status with the first data transmission interval being infinite in case the flush ing liquid presence status is affirmative.

[0036] According to an embodiment of the invention the data processing appa ratus comprises executable instructions to set the second data transmission in terval to less than 60 seconds.

[0037] According to an embodiment of the invention the sealing monitoring sys tem comprises a node which is configured to communicate with a gateway to the internet, and the first liquid detector is configured to communicate with the node. Advantageously the node is a standalone device off the mains power grid, which node is provided with dedicated power accumulator providing power to operate any power consumers in the node over a period of time more than 1 month.

[0038] According to an embodiment of the invention the sealing monitoring sys tem comprises a second liquid detector configured to detect presence of liquid outside the flushing liquid system and the second liquid detector is configured to communicate with the node and the node which is configured to communicate with a gateway to the internet and transfer the data obtained by the first liquid detector and the second liquid detector to the gateway.

[0039] According to an embodiment of the invention the sealing monitoring sys tem comprises a second liquid detector configured to detect presence of liquid outside the flushing liquid system, and the data processing apparatus is config ured to receive data of the second liquid detector, wherein the data processing apparatus further comprises

executable instructions to detect the second flushing liquid presence sta tus outside the flushing liquid system, executable instructions to determine the second flushing liquid presence status to be either affirmative when the presence of the flushing liquid out-side the flushing liquid system is detected, or negative when the presence of the flush ing liquid outside the flushing liquid system is not detected, and

executable instructions to transmit the second flushing liquid presence status to further processing using the wireless data communication system with the second data transmission interval in case the second flushing liquid presence status is affirmative.

[0040] A data processing apparatus is a computer processor that incorporates the functions of a central processing unit on one or more integrated circuits (IC). The data processing apparatus is a clock driven, register based, digital integrated circuit that accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output.

[0041] It is possible to obtain various advantageous effects and functionalities. For example the device provided with the seal can be monitored efficiently in remote places. The sealing monitoring system according to the invention makes it also possible provide multiple devices at even a remote site with efficient mon itoring in a straightforward and economical manner.

[0042] The exemplary embodiments of the invention presented in this patent ap plication are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. The novel features which are considered as charac teristic of the invention are set forth in particular in the appended claims.

[0043] The liquid detectors are known as such for a skilled person in the art. There are many principles known which may be used for detecting the presence of a liquid, which are based on making use occurrences of optical, ultrasonic, float, capacitance, radar or conductivity or resistance nature depending on the presence or absence of the liquid. Brief Description of Drawings

[0044] In the following, the invention will be described with reference to the ac companying exemplary, schematic drawings, in which

Figure 1 illustrates a sealing monitoring system for a mechanical sealing accord- ing to an embodiment of the invention,

Figure 2 illustrates a sealing monitoring system for a mechanical sealing accord ing to another embodiment of the invention,

Figure 3 illustrates a sealing monitoring system for a mechanical sealing accord ing to still another embodiment of the invention, Figure 4 illustrates a flowchart of a method according to an embodiment of the invention, and

Figure 5 illustrates a sealing monitoring system for a mechanical sealing accord ing to still another embodiment of the invention.

Detailed Description of Drawings

[0045] Figure 1 depicts schematically a device 1 , or relevant parts of it, in which a shaft 14 is rotatably supported in a body 22, and a mechanical sealing 11 is arranged to the rotatably supported shaft 14. The shaft and the device is run by a motor 17 coupled to the shaft 14 so as to seal an inner side of the device from outer side of the device. In the embodiment of the figure 1 the seal 18 comprises a rotary part 24 and a non-rotary part 26. The rotary part 24 in the figure 1 com prises a retainer ring, a rotary slide ring carrier and a rotary slide ring 28. The rotary slide ring 18 is attached to an axial end of the rotary slide ring carrier. The non-rotary part 26 comprises a non-rotary slide ring carrier, a non-rotary slide ring 30 and a gland ring. The non-rotary slide ring 30 is attached to an end of the non-rotary slide ring carrier. The slide rings 28 and 30 are, when in use in the flow machine, in mechanical contact with one another. In addition to the compo nents shown in the figure 1 the mechanical sealing 11 may comprise O-rings, drive pins, set screws and bolts, but as they do not relate to explaining the pre sent invention they have not been discussed in any more detail. The contact sur face between the rotary slide ring 28 and the non-rotary slide ring 30 act as a primary seal of the mechanical sealing 18. The sealing 11 is described herein mainly for the purpose of understanding the sealing monitoring system 10 and it may be constructed in various manners.

[0046] The mechanical sealing 1 1 of the device 1 is provided with a flushing liq uid system 32. In the figure 1 the flushing liquid system 32 is shown generally as a partial conduit opening into the seal chamber 20 indicating the that flushing can be implemented in various ways known as such to a skilled person in the art. In some cases the flushing liquid can be for example process liquid which the de vice, such as a pump, is arranged to handle. The purpose of the flushing liquid system is circulate fluid to or from the seal chamber 20 in order to maintain proper lubrication, pressure, temperature, and solids management. The goal is to create an ideal work environment for the sealing 1 1 in order to minimize wear and fail ures, thus prolonging its useful life. Any liquid available and fitting to the purpose can be used as flushing liquid. The present invention is, naturally, applicable to for example double-acting mechanical seals, too. The mechanical seal 18 is used for sealing the shaft 14 of, for instance, a flow machine 16, e.g. a centrifugal pump, agitator, mixer or alike. The mechanical seal 18 is configured such that the interior of the flow machine, generally at the left hand side of the seal 18 in the figure 1 , is kept fluidly separate from the atmosphere, generally at the right hand side of the seal 18. The mechanical seal is positioned in a seal chamber 20 provided within a specific seal housing or within a casing cover 22 of the flow machine. The present invention is applicable also for other kinds of sealing in connection with rotatable shaft such as gland packing sealing.

[0047] The device 1 comprises a sealing monitoring system 10 which is arranged in connection with the sealing 11 of the device. The sealing monitoring system 10 comprises a first liquid detector 40 arranged in connection with the flushing liquid system 32. In the figure 1 the sealing 11 is a mechanical sealing which comprises a schematically and exemplarily illustrated single-acting mechanical seal 18 being arranged between the rotatable shaft 14 and a stationary seal housing 22. The sealing monitoring system 10 is configured to be suitable for detecting operation and condition of the mechanical sealing 1 1 comprising a flushing liquid system and the sealing. The first liquid detector 40 is configured to detect presence of flushing liquid in the flushing liquid system 32. In the figure 1 there is depicted that a first liquid detector 40 may be provided in either or both the seal chamber 20 itself and in a conduit opening into the seal chamber 20. This should be understood so that the actual location of the first liquid detector can vary depending on the case as long as it is located such that the presence status of the flushing liquid adjacent to the mechanical seal 18 can be detected or determined in reliable manner. The flushing liquid may be water based solu tion, advantageously water, in which case the liquid detector is a water detector.

[0048] The sealing monitoring system 10 according to the embodiment of the figure 1 comprises a body or a casing 12 which houses at least some of the components belonging to the sealing monitoring system 10. The casing together with its components can be referred to also as a node and therefore the reference number 12 is also used for denoting the node. The node may be provided with a predetermined sensor as is the case in the figure 1. The node 12 of the sealing monitoring system 10 comprises a wireless data communication system 36 by means of which the data generated by a data processing apparatus 34 provided in the node 12 and/or the sensors connected to the node 12 can be transmitted to further processing, such as to a data storage, a user console, a cloud service or a like. The data can be utilized for general monitoring of operation of the device 1 or sending process data, such as alerts etc. to a mobile device of an operator of the device 1. The node 12 is an independent unit which comprises at least the first liquid detector 40, the data processing apparatus 34. The node 12 is remov ably and firmly attached to the seal housing 22 of the device 1. The sealing mon itoring system 10 comprises data processing apparatus 34 or system such as a microprocessor or alike, which is configured to receive data from the first liquid detector 40, which comprises a sensor. The data processing apparatus 34 com prises executable computer program i.e. executable instructions which, when ex ecuted by the data processing apparatus, cause the sealing monitoring system 10 to carry out a method recited in any one of the appended method claims. [0049] The data processing apparatus 34 of the node 12 is configured to receive data from the first liquid detector 40 for determining the presence status of flush ing liquid. The wireless data communication system 36 is in data transfer con nection with the data processing apparatus 34 in the node 12. The wireless data communication system 36 makes it possible for the sealing monitoring system 10 to communicate wirelessly with auxiliary devices and this way provide com munication also to the internet. The sealing monitoring system 10 according to a preferred embodiment of the invention comprise a dedicated electric energy stor age 33, such as a battery or rechargeable accumulator. The energy storage 33 provides power for operating the components of and optionally connected to the sealing monitoring system 10. The electric storage 33 has a capacity of providing energy for operating the sealing monitoring system 10 over a time period of sev eral months without connection to a mains power source. Even if the energy stor age 33 is shown only some of the figures it is provided in the sealing monitoring system 10 shown in other figures as well. The data processing apparatus 34 comprises executable instructions to detect the first flushing liquid presence sta tus of the flushing liquid system 32, which may be performed using a first detect ing interval. Advantageously the computer program comprises executable in structions to determine data transmission interval of the node 12 which is used to forward the first flushing liquid presence status to further processing. The first data transmission interval is based on the first flushing liquid presence status. According to the invention the computer program comprises executable instruc tions to detect the first flushing liquid presence status of the flushing liquid system 32, and executable instructions to determine the first flushing liquid presence sta tus to be either affirmative when the presence of the flushing liquid in the flushing liquid system 32 is detected, or negative when the presence of the flushing liquid in the flushing liquid system 32 is not detected, and further executable instruc tions to transmit the first flushing liquid presence status to further processing us ing the wireless data communication system 36 with a first data transmission interval in case the flushing liquid presence status is affirmative, and executable instructions to transmit the first flushing liquid presence status to further pro cessing using the wireless data communication system 36 with a second data transmission interval being shorter than the first transmission interval between the transmissions, in case the flushing liquid presence status is negative. [0050] This way it is possible to operate the sealing monitoring system 10 such that in case the first flushing liquid presence status is affirmative the first flushing liquid presence status is transmitted to a further processing using a wireless data communication system 36 less frequently than in case the first flushing liquid presence status is negative which in turn save or decreases energy consumption of the node 12 and charging interval or changing interval of the energy storage 33 is increased.

[0051] In other words the computer program comprises executable instructions to determine transmission interval based on the first flushing liquid presence sta tus, such that the transmission interval is shorter in case the first flushing liquid presence status is negative i.e. the flushing liquid is not detected in the flushing liquid system 32. The node 12 is advantageously a standalone device which is advantageously provided with dedicated power source such as a battery or an accumulator 33. The node 12 being a standalone device is made possible by the energy storage 33 such as a battery or an accumulator.

[0052] According to an embodiment of the invention the executable instructions, when executed, set the second data transmission interval to be less than 60 sec onds. This way, in case the first flushing liquid presence status is negative, the status is updated frequently.

[0053] In order to minimize the energy consumption of the sealing monitoring system 10 advantageously the data processing apparatus comprises executable instructions to set the wireless data communication system 36 to idle between the transmissions. Thus, when the flushing liquid presence status is affirmative the status information is transmitted further only rarely, which further decreases energy consumption of the sealing monitoring system 10 and prolongs the avail able service period of the energy storage 33 (with one charge if rechargeable).

[0054] According to an aspect of the invention the data processing apparatus comprises executable instructions to transmit the first flushing liquid presence status to further processing using the wireless data communication system 36 with the first data transmission interval being more than one hour, in case the flushing liquid presence status is affirmative. [0055] According to a further aspect of the invention the data processing appa ratus comprises executable instructions to transmit the first flushing liquid pres ence status with the first data transmission interval being more than 4 hours.

[0056] According to a further aspect of the invention the data processing appa ratus comprises executable instructions to transmit the first flushing liquid pres ence status with the first data transmission interval being infinite. In other words according to this aspect in the case where the flushing liquid presence status is affirmative the computer program in the data processing apparatus 34 comprises executable instructions to never transmit or not to transmit - the first flushing liquid presence status, until the flushing liquid presence status is changed to neg ative. In this embodiment the data transmission is self-activating such the com puter program in the data processing apparatus 34 comprises executable instruc tions to detect the first flushing liquid presence status in the flushing liquid system by means of the first liquid detector, and if the first flushing liquid presence status is turned to negative (no liquid status detected), to commence transmission of the first flushing liquid presence status to further processing and to keep trans mitting using the wireless data communication system 36 with a data transmis sion interval of less than 60 seconds. This way the information of lack of flushing liquid is obtained without undue delay and the service period of the energy stor age 33 is simultaneously obtained.

[0057] The first liquid detector 40 may be configured or constructed to detect presence of flushing liquid intermittently. In such case the data processing appa ratus 34 of the node 12 comprises executable instructions to detect the first flush ing liquid presence status using the first detecting interval in case the first flushing liquid presence status is affirmative, and executable instructions to detect the first flushing liquid presence status using a second detecting interval being shorter than the first detecting interval in case the first flushing liquid presence status is negative. In other words the presence of the liquid is detected more often if, based on the signal of the liquid detector, there is not liquid present in the flushing liquid system 32. The first detecting interval is thus adopted when the first flushing liquid presence status is affirmative. [0058] A sealing monitoring system 10 according to an embodiment of the inven tion first liquid detector 40 is configured to detect presence of flushing liquid con tinuously.

[0059] Figure 2 shows schematically an embodiment of the invention according to which the sealing monitoring system 10 shown in the figure 1 has an additional, optional feature which brings about an additional functionality to the device 1 and the sealing monitoring system 10. Namely, the sealing monitoring system 10 comprises the first liquid detector 40 as is disclosed in the figure 1 and addition ally a second liquid detector 41. The second liquid detector 41 is configured to detect presence of liquid outside the flushing liquid system 32. As can be seen in the figure 2 the second liquid detector 41 is arranged in a vicinity of an opening 13 for the shaft 14 in the housing 22 of the device 1. According the embodiment of the figure 2 the data processing apparatus 34 in the node 12 is configured to receive data of the second liquid detector 41 as well, such that the data pro cessing apparatus comprises executable instructions to detect the second flush ing liquid presence status outside the flushing liquid system by means of the sec ond liquid detector 41. The data processing apparatus comprises executable in structions to determine the second flushing liquid presence status to be either affirmative when the presence of the flushing liquid outside the flushing liquid system is detected, or negative when the presence of the flushing liquid outside the flushing liquid system is not detected, and executable instructions to transmit the second flushing liquid presence status to further processing using the wire less data communication system 36 with the second data transmission interval in case the second flushing liquid presence status is affirmative. If the second flushing liquid presence status is affirmative there is a leak in the sealing and the data transmission interval is at least shorter than the first data transmission inter val. In the figure 2 the second liquid detector 41 is mechanically connected i.e. wired, in data transfer communication to the common data processing apparatus 34 and the wireless data communication system 36 with the first liquid detector 40 in the node 12. The second liquid detector 41 may be also provided with a wireless data communication system 36, as is depicted in the figure 3 by means of which the data transfer communication with the node 12 is accomplished in wireless manner. [0060] The sealing monitoring system 10 according to the invention can be em ployed to any mechanical sealing of a rotatable shaft, and operated by practic ing at least the following steps. Firstly a sealing 11 , which is provided with a flushing liquid system 32, is arranged between a rotatable shaft and a station ary housing 22. The mechanical sealing 11 is provided with a first liquid detec tor 40 and the first liquid detector 40 is configured to detect presence of flushing liquid in the flushing liquid system 32. With a reference to the figure 4 showing a flowchart of a method according to the invention using an intermittently prac ticed liquid detection, the sealing monitoring system 10 is operated after each start 100 of the device 1 by a procedure controlled by execution of the com puter program in the data processing apparatus 34. At first the first flushing liq uid presence status in the flushing liquid system 32 is detected 104 by means of the first liquid detector 40, and subsequently in the step 108 is it deduced whether the first flushing liquid presence status is affirmative or negative i.e. if the liquid is detected or not .

[0061] In case the first flushing liquid presence status is affirmative Y, in the step 110 the first flushing liquid presence status is transmitted to a further pro cessing using a wireless data communication system 36 with a first data trans mission interval. Now, since the liquid is present, the situation is normal and the first data transmission interval can be set or maintained to be substantially long, or in some cases the data transmission may be totally omitted until the first flushing liquid status is detected to be negative. According to an embodiment of the invention the first data transmission interval is more than one hour, advanta geously even more than 4 hours. In some cases the first data transmission in terval is infinite, meaning that data transmission is halted if the first flushing liq uid presence status is affirmative. This procedure reduces energy consumption of the device considerably, since mere liquid detection consumes only minimal amount of energy. Next the control is returned to the step 104 such that the first flushing liquid presence status in the flushing liquid system 32 is detected again.

[0062] Optionally, in order to decrease energy consumption of the sealing mon itoring system, according to an embodiment of the invention the wireless data communication system 36 can be set to idle between each data transmission. [0063] In case it is deducted in the step 108 that the first flushing liquid pres ence status negative N i.e. the liquid is not detected, in the step 112 the first flushing liquid presence status is immediately transmitted to a further pro cessing using the wireless data communication system 36. Advantageously in the step 1 12 the wireless data communication system 36 is set to transmit the first flushing liquid presence status with a second data transmission interval which is shorter than the first data transmission interval, which second data transmission interval is advantageously less than 60 seconds.

[0064] Now turning back to the figure 3 the mechanical sealing may be pro vided with a second liquid detector 41 outside the mechanical sealing housing as in the figure 2, but the second liquid detector 41 further comprising a wire less data communication system 36 by means of which the data generated by the data processing apparatus 34 of the first liquid detector 40 can be transmit ted via the node 12 to further processing, such as to a data storage, a user con sole, a cloud service or a like. Also the second liquid detector 41 comprises a dedicated electric energy storage 33, such as a battery or rechargeable accu mulator. The energy storage 33 provides power for operating second liquid de tector 41. The electric storage 33 comprises a capacity of providing energy for operating second liquid detector 41 over a time period of several months.

[0065] The data can be utilized for general monitoring of operation of the de vice 1 or sending process data, such as alerts etc. to a mobile device of an op erator. The second liquid detector 41 is configured to detect presence of flush ing liquid outside the flushing liquid system, and a second flushing liquid pres ence status outside the flushing liquid system is detected by means of the sec ond liquid detector 41. In case the second flushing liquid presence status is af firmative, the second flushing liquid presence status to a further processing. In case the first flushing liquid presence status is affirmative and the second flush ing liquid presence status is affirmative it is known that the mechanical sealing is leaking.

[0066] The second liquid detector 41 comprises dedicated data processing ap paratus or system, such as a microprocessor 34 or alike, which is configured to control the operation of the second liquid detector 41 and its data communication to the node 12. The second liquid detector 41 is advantageously a standalone device which is advantageously provided with dedicated power source such as a battery or an accumulator. In the embodiment of figure 3 the second liquid de tector is operated such that the second flushing liquid presence status outside the flushing liquid system 32 is detected by means of the second liquid detector 40, and in case the second flushing liquid presence status is negative, the second flushing liquid presence status is transmitted to a further processing using a wire less data communication system 36 with the first data transmission interval be tween the transmissions, and in case the first flushing liquid presence status is affirmative, the second flushing liquid presence status is transmitted to further processing using the wireless data communication system 36 with the second data transmission interval being shorter than the first transmission interval be tween the transmissions. The second flushing liquid presence status is transmit ted to a further processing via the node 12.

[0067] Figure 5 shows schematically an advantageous embodiment of the inven tion according which compared to the sealing monitoring system 10 shown in the figure 1 has additional features and elements which brings about an additional functionalities to the device 1 and the sealing monitoring system 10. The sealing monitoring system 10 according to the embodiment of the figure 5 comprises the first liquid detector 40 configured to detect presence of liquid inside the flushing liquid system 32, an optional second liquid detector 41 configured to detect pres ence of liquid outside the flushing liquid system 32 and further a vibration sensor unit 43. The first and the second liquid detector comprise a dedicated data pro cessing apparatus or system 34 , such as a microprocessor or alike, which is configured to control the operation of the first 40, and respectively the second liquid detector 41 and their data communication. The vibration sensor unit 43 is configured to detect the vibration intermittently and the vibration is detected using the first detecting interval in case the first flushing liquid presence status is af firmative, and the vibration is detected using a second detecting interval being shorter than the first detecting interval in case the first flushing liquid presence status is negative. The detection interval used for detecting the vibration need not to be identical to the first or the second interval used for detecting the first or the second flushing liquid presence status. [0068] When the sealing monitoring system 10 is provided with the first and the second liquid detector 40, 41 the system can be operated such that when the liquid detection system results in a decision that the first flushing liquid presence status and the second flushing liquid presence status are both affirmative at the same time, it can be concluded that operation, for example dry operation, has caused a failure to the sealing. This information can be used to trigger a trans mission of an alarm signal.

[0069] The vibration sensor unit 43 comprises e.g. one or more acceleration sen sors configured to detect vibration of the device 1 in one or more directions. As can be seen in the figure 5 the second liquid detector 41 is arranged in a vicinity of an opening 13 for the shaft 14 arranged in the housing 22 of the machine for detecting liquid possible leaked through the sealing 18. The vibration sensor unit 43 is firmly attached to the body 22 of the device 1 such that the vibration of the device 1 can be determined when the device is running.

[0070] The sealing monitoring system 10 comprises a node 12 into which, in this embodiment of the invention, the vibration sensor unit 43 is arranged. The node 12 is also provided with a data processing apparatus 34 which has the executa ble instructions to control the operation of the node 12 such that the method de fined in the appended method claims can be implemented into practice. The first liquid detector 40 and the second liquid detector 41 are configured into wireless data transmission communication with the node 12. The node 12 is configured to function as a centralized data transmission link between the first liquid detector 40 and a gateway 50 to the internet 100, and the second liquid detector and the gateway 50 to the internet 100 for connecting the sealing monitoring system 10 to the internet 100 in centralized manner. The data processing apparatus 34 of the node 12 comprises executable instructions to relay data from the first liquid detector 40 and the second liquid detector 41 to the internet 100 and further to a predetermined destination for further processing the data.

[0071] According the embodiment of the figure 5 the data processing apparatus 34 of the node 12 is configured to receive data of the first liquid detector 41 and to receive data of the optional second liquid detector 41 , such that the data pro cessing apparatus comprises executable instructions to detect the first flushing liquid presence status inside the flushing liquid system, by means of the first liquid detector 40. In addition to detecting the first flushing liquid presence status, the sealing monitoring system 10 is configured to read and process data from the vibration sensor unit 43. The data of vibration signal is used for determining a whether the device 1 is running or not. That can be detected by using either time domain or frequency domain of the vibration signal, obtained for example the Fast Fourier Transform (FFT). According to an embodiment of the invention the time stamp of the moment of start of the device 1 is detected by analysis of the data of vibration signal and the first flushing liquid presence status is detected at the moment of start of the device 1. This way it is possible to check and/or confirm that the flushing liquid system is operating at the moment of start of the device 1.

[0072] In the sealing monitoring system 10 disclosed in the figure 5 the first liquid detector 40 is operated such that the first flushing liquid presence status inside the flushing liquid system 32 is detected by means of the first liquid detector 40. In case the first flushing liquid presence status is affirmative, the first flushing liquid presence status is transmitted to a further processing using a wireless data communication system 36 with the first data transmission interval between the transmissions, and in case the first flushing liquid presence status is negative, the first flushing liquid presence status is transmitted to further processing using the wireless data communication system 36 with the second data transmission interval being shorter than the first transmission interval. The first flushing liquid presence status is transmitted to a further processing via the node 12.

[0073] In turn, the second liquid detector 41 is operated such that the second flushing liquid presence status outside the flushing liquid system 32 is detected by means of the second liquid detector 41. In case the second flushing liquid presence status is negative, the second flushing liquid presence status is trans mitted to a further processing using a wireless data communication system 36 with the first data transmission interval between the transmissions, and in case the first flushing liquid presence status is affirmative, the second flushing liquid presence status is transmitted to further processing using the wireless data com munication system 36 with the second data transmission interval being shorter than the first transmission interval between the transmissions. The second flush ing liquid presence status is transmitted to a further processing also via the node 12. [0074] The transmission interval of the data, including the vibration information the first flushing liquid presence status and/or the second flushing liquid presence status, from the node 12 to further processing is determined advantageously by means of flushing liquid presence status in the following manner. The transmis- sion interval for the data is longer i.e. the first transmission interval used when either the first flushing liquid presence status is affirmative or the second flushing liquid presence status is negative, and the transmission interval for the data is shorter i.e. the second transmission interval used when either the first flushing liquid presence status is negative or the second flushing liquid presence status is affirmative.

[0075] Even if not shown in the figures the data processing apparatus and the wireless data communication system 36 may be integrated into a one data pro cessing unit. The wireless transmitting means like Bluetooth, Wi-Fi or generally radio frequency transmitting means, just to name a few optional means without any intention to limit the invention to the listed alternatives.

[0076] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred em bodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the in vention, as defined in the appended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodi ment when such combination is technically feasible.