Patent Application
20160109329
The present invention concerns a method, system and computer program product for processing data obtained from a condition monitoring system, such a condition monitoring system for predicting the residual life of a component, such as a bearing, i.e. for predicting when it is necessary or desirable to service, replace or refurbish (re-manufacture) the component.
Condition monitoring is the process of determining the condition of machinery while in operation. Condition monitoring enables the repair of problem components prior to failure and not only helps plant personnel reduce the possibility of catastrophic failure, but also allows them to order parts in advance, schedule manpower, and plan other repairs during downtime.
Components such as rolling-element bearings are often used in critical applications, wherein their failure in service would result in significant commercial loss to the end-user. It is therefore important to be able to predict the residual life of such a bearing, in order to plan intervention in a way that avoids failure in service, while minimizing the losses that may arise from taking the machinery in question out of service to replace the bearing.
The residual life of a rolling-element bearing is generally determined by fatigue of the operating surfaces as a result of repeated stresses in operational use. Fatigue failure of a rolling element bearing results from progressive flaking or pitting of the surfaces of the rolling elements and of the surfaces of the corresponding bearing races. The flaking and pitting may cause seizure of one or more of the rolling elements, which in turn may generate excessive heat, pressure and friction.
Bearings are selected for a specific application on the basis of a calculated or predicted residual life expectancy compatible with the expected type of service in the application in which they will be used. However, this type of life prediction is considered inadequate for the purpose of maintenance planning for several reasons.
One reason is that the actual operation conditions may be quite different from the nominal conditions. Another reason is that a bearing's residual life may be radically compromised by short-duration events or unplanned events, such as overloads, lubrication failures, installation errors, etc. Yet another reason is that, even if nominal operating conditions are accurately reproduced in service, the inherently random character of the fatigue process may give rise to large statistical variations in the actual residual life of substantially identical bearings.
In order to improve maintenance planning, it is common practice to monitor the values of physical quantities related to vibrations and temperature to which a component, such as a bearing, is subjected in operational use, so as to be able to detect the first signs of impending failure.
In a condition monitoring system data dynamic signal data is obtained in the form of a time waveform (i.e. a graph of a varying quantity against time which usually consists of many samples) from at least one sensor. These time waveforms are usually transmitted and displayed to an analyst. This can however result in long transmission and display times and the data can be difficult to display or interpret. The transmission, display, storage and interpretation of such data can require a significant amount of energy, time and expertise, and consequently decreases the rate at which measurements and analyses can be made.
There are condition monitoring systems using vibration level sensors in which only the “overall amplitudes” (i.e. the total amount of vibration occurring in a selected frequency range) of a particular signal are transmitted or displayed. However, such transmitted or displayed data has limited value since it provides no information about the nature of a signal. Additionally, no further information can be post-processed from the transmitted or displayed overall amplitude values.
An object of the invention is to provide an improved method for processing data obtained from a condition monitoring system.
This object is achieved by a method comprising the steps of obtaining dynamic (demodulated) Acoustic Emission (AE) signal data in the form of a time waveform from at least one sensor, extracting a maximum or minimum or mean value of the time waveform and counts of crossing predetermined threshold values, and transmitting or displaying or storing the extracted values and the number of counts instead of the dynamic signal time waveform data.
Such a statistical demodulation method avoids the need to transmit and/or display and/or store the whole time waveform since only certain values extracted therefrom are transmitted and/or displayed and/or stored. The method thereby reduces the amount of data that needs to be transmitted, displayed and/or stored. Transmission, display and data processing times will therefore be shorter, less energy will be required for transmission, display and processing, and memory storage requirements will be substantially lower, which consequently results in extending the sensor battery life, or reducing the sensor battery size or power generation requirement.
A user will consequently be more quickly warned of deterioration in the condition of a component being monitored and poor installation or poor operating practices, such as misalignment, imbalance, high vibration, lack of lubrication and contamination in the lubricant, etc., which would reduce the residual life of the component if left uncorrected, will be more quickly identified
According to an embodiment of the invention the step of extracting values from the time waveform is carried out using Discrete Wavelet Transform (DWT), Continuous Wavelet Transform (CWT) or another time domain analysis.
According to an embodiment of the invention the counts of crossing predetermined threshold values are any of the following: periodic events or amplitudes.
According to an embodiment of the invention the at least one sensor is arranged to obtain data concerning at least one of the following: vibration, vibration enveloping, acoustic emission (AE), acoustic emission enveloping (AEE), load, temperature, rolling contact force/stress, high frequency stress waves, lubricant condition, rolling surface damage, operating speed, load carried, lubrication conditions, humidity, exposure to moisture or ionic fluids, exposure to mechanical shocks, corrosion, fatigue damage, wear.
According to another embodiment of the invention the extracted values and the number of counts are transmitted wirelessly over a wireless communication network.
According to a further embodiment of the invention the method is carried out once the whole of the time waveform has been acquired (which requires more memory). Alternatively, the method is carried out continuously as the time waveform is acquired, for example as sections of the time waveform are acquired in an FIFO buffer (which requires less memory but a faster processor).
According to an embodiment of the invention the method comprises the step of storing the extracted values and the number of counts electronically in a database.
According to another embodiment of the invention the condition monitoring system is arranged to monitor at least one bearing, such as a rolling element bearing. The rolling bearing may be any one of a cylindrical roller bearing, a spherical roller bearing, a toroidal roller bearing, a taper roller bearing, a conical roller bearing or a needle roller bearing.
The present invention also concerns a computer program product that comprises a computer program containing computer program code means arranged to cause a computer or a processor to execute the steps of a method according to any of the embodiments of the invention, stored on a computer-readable medium or a carrier wave.
The present invention further concerns a system for processing data obtained from a condition monitoring system comprising at least one sensor arranged to provide dynamic (demodulated) Acoustic Emission (AE) signal data in the form of a time waveform from the at least one sensor. The system comprises a processing unit arranged to extract a maximum or minimum or mean value of the time waveform and counts of crossing predetermined threshold values, and transmission means arranged to transmit or display or store the extracted values and the number of counts instead of the dynamic signal time waveform data.
According to an embodiment of the invention the counts of crossing predetermined threshold values are any of the following: periodic events or amplitudes.
According to another embodiment of the invention the system comprises transmitting means arranged to transmit the extracted values and the number of counts wirelessly over a wireless communication network.
According to a further embodiment of the invention the processing unit is arranged to extract the values once the whole of the time waveform has been acquired. Alternatively, the processing unit is arranged to extract the values continuously as the time waveform is acquired.
According to an embodiment of the invention the system comprises storage means for storing the extracted values and the number of counts electronically in a database. The system may comprise a prediction unit configured to predict the residual life of a component such as a bearing, using the stored data or the extracted values and the number of counts.
According to another embodiment of the invention the condition monitoring system is arranged to monitor at least one bearing, such as a rolling element bearing.
It should be noted that the method, computer program and system according to the present invention may be used to monitor at least one component, such as a bearing during the component's manufacture, after the component's manufacture and before the component's use, during the component's use, during a period when the component is not in use and/or during the transportation of the component. A complete history log of a component may thereby be created. Accordingly, as a result of having condition status and/or residual life data accumulated over the component's life, starting with its very manufacturing all the way up to the present, a more accurate prediction can be made regarding the residual life of an individual component at any point in its life-cycle. An analyst or end user may be notified of relevant facts including the time at which it is advisable to replace or refurbish the component.
The method, system and computer program product according to the present invention may be used to monitor at least one component, such as a bearing, used in automotive, aerospace, railroad, mining, wind, marine, metal producing and other machine applications which require high wear resistance and/or increased fatigue and tensile strength.
The present invention will hereinafter be further explained by means of non-limiting examples with reference to the appended figures where;
It should be noted that the drawings have not been drawn to scale and that the dimensions of certain features have been exaggerated for the sake of clarity.
Furthermore, any feature of one embodiment of the invention can be combined with any other feature of any other embodiment of the invention as long as there is no conflict.
The inner ring and/or outer ring of a bearing 12, which can be monitored using a system or method according to an embodiment of the invention, may be of any size and have any load-carrying capacity. An inner ring and/or an outer ring may for example have a diameter up to a few metres and a load-carrying capacity up to many thousands of tonnes.
The system 10 in the illustrated embodiment comprises a processing unit 16 arranged to extract a maximum or minimum or mean value of the time waveform and counts of crossing predetermined threshold values. The system 10 also comprises transmission means 18 arranged to transmit the extracted values and the number of counts to a display means 20 and/or a device 22 used by a user or analyst and/or a database 24 where the extracted values and the number of counts may be electronically recorded. Data may be transmitted to and from the sensors 14, and to and from the processing means 16 in a wired or wireless (26) manner over a wireless communication network.
The database 20 may be maintained by the manufacturer of the bearings 12. The residual life data gathered in the database 20 for a whole batch of bearings 12 enables the manufacturer to extract further information, e.g., about relationships between types or environments of usage versus rates of change of residual life, so as to further improve the service to the end-user.
The system 10 may also comprise a prediction unit (not shown) configured to predict the residual life of each bearing 12 using the recorded data in the database 24 and a mathematical residual life predication model.
It should be noted that not all of the components of the system 10 necessarily need to be located in the vicinity of the bearings 12. For example, the database 24 and/or user device 22 may located at a remote location and communicate with at least one data processing unit 16 located in the same or a different place to the bearings 12 by means of a server for example.
It should also be noted that the at least one data processing unit 16, the transmission means 18 and/or the database 24 need not necessarily be separate units but may be combined in any suitable manner. For example a personal computer may be used to carry out a method concerning the present invention.
The extracted values and the number of counts may be transmitted wirelessly over a wireless network, in a wired manner, or in a combination of wired and wireless manners. The extracted values and the number of counts may then be analysed or processed further to obtain condition status information concerning the at least one component being monitored and/or to understand the nature of the original time waveform and any defect(s) associated with it and the severity thereof.
The extracted values and the number of counts may be used to make a prediction of the residual life of a bearing 12. Once such a prediction has been made, it may be displayed on display means 20, and/or sent to a user device 22, bearing manufacturer, database 20 and/or another prediction unit. Notification of when it is advisable to service, replace or refurbish one or more bearings 12 being monitored by the system 10 may be made in any suitable manner, such as via a communication network, via an e-mail or telephone call, a letter, facsimile, alarm signal, or a visiting representative of the manufacturer.
The prediction of the residual life of a bearing 12 may be used to inform a user of when he/she should replace the bearing 12. Intervention to replace the bearing 12 is justified, when the cost of intervention (including labour, material and loss of, for example, plant output) is justified by the reduction in the risk cost implicit in continued operation. The risk cost may be calculated as the product of the probability of failure in service on the one hand, and the financial penalty arising from such failure in service, on the other hand.
Further modifications of the invention within the scope of the claims would be apparent to a skilled person. Even though the described embodiments are directed to a method, system and computer program product for monitoring at least one component such as a bearing, such a method, system and computer program product may be used for monitoring and optionally predicting the residual life of another component of rotating machinery, such as a gear wheel.
This is a United States National Stage Application claiming the benefit of International Application Number PCT/EP2013/057177 filed on 5 Apr. 2013 (05.04.2013), which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/057177 | 4/5/2013 | WO | 00 |
