GB2550541A

GB2550541A - Monitoring device

Info

Publication number: GB2550541A
Application number: GB1605642.6A
Authority: GB
Inventors: Newby Ian; Raymond Smiddy John
Original assignee: AES Engineering Ltd
Current assignee: AES Engineering Ltd
Priority date: 2015-12-10
Filing date: 2016-04-01
Publication date: 2017-11-29
Also published as: GB201521740D0

Abstract

A condition monitor 1 for monitoring vibration of a structure or machine comprises an enclosure 3; at least one vibration sensor within the enclosure; a processor located within the enclosure, the processor connected to the at least one sensor for analysing signals produced therefrom; data storage within the enclosure for buffering data prior to wireless transfer; means for mounting the monitor to the structure or machine; and a wireless transmitter. The mounting may be achieved by one or two magnets integral to the monitor, the magnets having a curved mating surface for contact with the structure or machine. The vibration sensors may comprise two or more bi-axial sensors, providing simultaneous measurements over three axes. The monitor may determine faults using an algorithm that evaluates parameters including vibration amplitude, number of harmonics, total signal level, and noise floor level. The monitor may also comprise a temperature sensor for monitoring temperature.

Description

Monitoring Device

Field of the Invention

The invention relates to monitoring devices for monitoring the condition of machinery through vibration and/or temperature readings.

Background of the Invention

Machinery, especially machinery with moving parts, can, over time, develop problems during operation. This may be due to misalignment of parts, wear on parts or other issues, which may subsequently lead to further problems and failure.

Condition based maintenance (CBM), or condition monitoring (CM) is the detection of symptoms through the measurement of one or more parameters which may be indicative of a fault condition, either by an increase or decrease in the overall measured value, or by some other change to a characteristic value such as root-mean-square value (r.m.s.), peak value (pk), frequency component amplitude, pattern and/or distribution, etc.

Vibration monitoring (VM) is a particular technique used in condition monitoring. Vibration is the mechanical movement of a machine or asset which may be periodic (regular) or random and contains characteristic symptoms of a wide range of machine faults, including: unbalance, misalignment, poor bearing lubrication, gear faults, motor winding & rotor faults, bearing damage, etc. It is particularly effective for monitoring rotating and reciprocating machines. Vibration monitoring utilises vibration sensors or transducers to detect the vibration signal. The vibration signal may then be conditioned, filtered and processed using analysis instrumentation and software.

Common sources of poor vibration measurements, which limit the efficiency of CM arrangements, include poor sensor contact, faulty attachment, operator error, cable faults, ground loop, transducer fault, instrument fault, low instrument voltage and/or change of probe/magnet.

Various transducers are available for detecting vibrations in machinery and one particular system uses a portable digital assistant (PDA) which connects to a sensor device using a cable to download the information. The information can then be uploaded to a web-based server from the PDA. One of the problems with such an arrangement is that a user needs clear access to the device in order to upload information via a cable. Additionally, one not trained to interrogate the device is unlikely to identify any issues that may occur during use of the machines. Therefore, a problem may go unnoticed until a trained user is able to attend the site, interrogate the device and interpret the information collected. Furthermore, where a user needs access to the device, it may not be possible to locate the device in a position in which an efficient and effective reading may be taken, thereby limiting the use of the device.

For accurate sampling and diagnostics to be achieved traditionally three vibration readings are taken. In the case of the monitoring of the bearings of a motor, readings would typically be taken at both ends of the motor as close to the bearings as possible, each reading indicating different potential faults. These three readings are commonly:- 1. Horizontal, where the accelerometer is in line radially with the mountings which can indicate imbalance in the machine, radial mis-alignment, and/or looseness 2. Vertical perpendicular to the mountings which can indicate bearing defects or failure 3. Axial, in line with the motor shaft which can indicate angular misalignment or thrust bearing problems

Due to the number of readings potentially required on a site the time per reading can be limited affecting the accuracy of the readings. Furthermore, the cost of the condition monitoring program can be expensive. AES Engineering patent application No. WO2013/175162 discloses a device which can allow remote sensing to be possible thereby allowing effective readings to be taken. However it is limited to taking one reading per device thereby requiring multiple remote sensors to be fitted to the asset in the orientations listed above. This means it can be costly to implement and evaluate the data reducing the thoroughness of coverage of assets on a site. Furthermore, when used remotely, due to the amount of data storage being finite (often being limited to 50 readings before downloading is required) it is necessary to compromise on either the frequency of readings taken or frequency of downloading of data. Battery life is again finite and so can also be a limiting factor as the indication means, such as light emitting diodes, can reduce the time that the device can be left on the asset before it requires removing and recharging due to the power drawn from the battery being higher. Both of these factors therefore mean that a compromise is necessary between the frequency of readings, downloads or the level of visual indication and this compromise potentially reduces the quality of readings taken and increases the amount of labour and investment in devices which is required.

Statement of the Invention

According to the present invention, there is provided a condition monitor for monitoring vibration and/or temperature of a piece of equipment and/or a structure, the monitor comprising:-an enclosure; at least one vibration sensor located within the enclosure; a processor located within the enclosure and being connected to the or at least one of said sensors for analysing signals produced therefrom; means located in the enclosure for buffering the analysed signals prior to wifi transfer; a power source connected to the processor and located in or in close proximity to the monitor; and means for mounting the monitor on the piece of equipment or the structure and a wireless transmitter for external communication to a wireless receiver.

Accordingly, the present invention separates data acquisition and sensor from an external device for receiving the date and displaying/processing the data.

Preferably, the buffering means is capable of storing a multiple of analysed signals, each set of signals typically reaching the buffering means at a different time.

The remote receiver can be, for instance, a personal digital assistant (PDA), a tablet or other remote storage device.

Preferably, the monitor includes a mounting plate.

Preferably, the monitor includes an integral magnet.

The provision of an integral magnet assists in achieving consistent alignment, particularly axial alignment, when the monitor is located on a surface of the piece of equipment and/or the structure.

Preferably the magnet has a mating surface, which makes contact with the surface of the piece of equipment and/or the structure, which is curved. By providing a magnet with a curved surface, a better “magnetic purchase” is achieved. Furthermore the height of the unit can be reduced and a more powerful magnet can be used.

Preferably, the magnet is provided with two spaced apart mating surfaces, each being curved.

Preferably, there is provided within the enclosure two or more bi-axial vibration sensors. These sensors are used to obtain simultaneous readings along three axes, each over the same high frequency range. In addition, an external sensor may be connected to the monitor to enable simultaneous readings to be taken along four axes. The external sensor can be of any suitable type.

Preferably,, the monitor is provided with means for determining the nature of any fault in the piece of equipment and/or the structure. The fault identifying means may be located within the enclosure or in a remote receiver of signals from the monitor.

Determination of the nature of the fault is a process which hitherto has been carried out manually by careful examination of the analysed signals. Since there may be as many as fifty different possible faults, this process is not only difficult but subject to human error. In this aspect of the present invention, the analysed signals are subjected to processing using an algorithm designed to further analyse the signals to the extent that the particular fault can be identified and its identity displayed to the user so that appropriate action be taken.

The fault identifying means may act to extract a number of parameters from the time signature or frequency domain and evaluate these against other parameters from the same of different directions. These parameters can include: amplitude at running frequency; number of harmonics; the overall signal level; and the noise floor level. Each of the symptoms may be given a weighting and, if the evaluation succeeds, the symptoms weighting is added to the faults weighting to give an overall likelihood. A weighting can be negative, as well as positive, to reduce the overall likelihood.

Preferably the monitor is arranged to take simultaneous readings along three axes t provide data for fault detection.

The present invention also provides a method for monitoring vibration and/or temperature of a piece of equipment and/or a structure, the method comprising mounting a monitor of the invention on a piece of equipment or a structure, using the monitor to sense vibrations and produce signals relating thereto and analysing the signals to produce data, buffering the data within the monitor and transmitting the data to a remote location.

Brief Description of the Drawings

The accompanying drawings are as follows:-

Figure 1 is a perspective view (front and one side) of a monitor in accordance with the present invention;

Figure 2 is a side elevation of the monitor of Figurel;

Figure 3 is a further perspective view (other side and rear) of the monitor of Figure 1; Figure 4 is a longitudinal section of the monitor of Figure 1;

Figure 5 is a view showing internal components of the monitor of Figure 1;

Figure 6 is a further view showing internal components of the monitor of Figure 1; Figure 7 is a detailed internal view of part of the monitor of Figure 1;

Figure 8 is a further detailed view of another part of the monitor of Figure 1;

Figure 9 is a perspective view (on two sides and top) of a magnet base attachment for the monitor of Figure 1;

Figure 10 is a perspective view (other two sides and bottom) of the magnet base attachment shown in Figure 9;

Figure 11 illustrates the monitor of Figure 1 and the engagement of its magnet with curved surfaces;

Figure 12 is perspective view of a magnet base attachment for the monitor of Figure 1 and showing its screw fixing;

Figure 13 illustrates the ability of the monitor in Figure 1 to make good contact with a range curved surfaces; and

Figure 14 illustrates the positioning of the monitor of Figure 1 on a curved surface having a relatively large diameter.

Detailed Description of the Invention

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings.

Referring to Figures 1 to 3 of the accompanying drawings, a condition monitor 1 in accordance with the present invention comprises a housing 3 which has an elongated main body portion 5 and, at the front end of portion 5, a downwardly extending portion 7. Housing 3 includes two parts, an upper part 9 and a lower part II.

Referring to Figures 4 and 5, the downwardly extending portion 7 of monitor 1 includes a downwardly facing recess 13 within which is accommodated a magnet assembly 15 comprising a centrally located magnet 17 and leg members 19 which extend down opposed sides of magnet 17 and, beyond magnet 17, to a position exterior of recess 13. Each leg member 19 is of approximately L-shape (viewed on one side) and the bottom edge 21 is curved from the outside of the leg member in a direction inwardly and upwardly as illustrated.

As shown in Figures 1,2,3 and 5, there is bonded to magnet assembly 15 a magnet base attachment 23 for enabling the monitor 1 to be securely attached, using screw fixing 25, to a piece of equipment or a structure to be monitored.

Located adjacent the front of housing 3 and within downwardly extending portion 7 is a temperature sensor 24 which is located above an infra-red transparent window 26.

Referring to Figures 5 to 8 of the accompanying drawings, the interior of housing 3 of monitor 1 accommodates a battery 27 located on a circuit board 29.

Screws 31, one located at each corner of the device, extend between upper portion 9 and lower portion 11 of monitor 1.

Located within a recess located in the top of monitor 1 is non-contact on/off switch 31 which also incorporates a Bluetooth aerial. Extending downwardly from the underside of switch 31 is connector 33 from which wires 35 (not shown in full) extend to circuit board 29.

Positioned rearwardly from the above-mentioned recess accommodating switch 31 is a port 37 within which is located a connector 39 to which may be connected an external sensor and/or means for charging battery 27.

Located below circuit board 29 and above battery assembly 19 is a micro-electro-mechanical system (MEMs) module 41 in the form an accelerometer. MEMs sensor module 41 includes a MEMs sensor 43 which is arranged within housing 3 of monitor 1 so as to be able to detect vibrations as measured along three directions indicated as X, Y and Z in Figure 7. The principle directions, however, are along the X and Y axes and vibrations detected along the Z axis are not used. Accordingly, only signals corresponding to vibrations along the X and Y axis are transmitted via wires 45 (not shown in full) to the circuit board 29. Referring in particular to Figure 8, there is shown the positioning of a further MEMs sensor module 47 which includes a MEMs sensor 49 arranged at right angles to the orientation of MEMs sensor 43. In this orientation sensor 49 has its greatest sensitivity in the Z direction and data collected along this direction is fed from sensor 49 via wires 51 (not shown in full) to circuit board 29.

As a result, accurate data in the X, Y and Z directions are transmitted from sensors 43 and 49 to circuit board 29. Located on circuit board 29 (but not separately shown) is a processor for analysing this data and for feeding the subsequent analysed signals to a buffer (it is also not separately shown). From the buffer the analysed signals may be rapidly transmitted via the above mentioned Bluetooth aerial to a remotely located PDA which can display either analysed signals, in a form suitable for manual assessment, or an indication of a particular fault(s) if one has been detected by the sensors. The processing of the analysed signals to result in the identification of one or more faults may be carried out by processing means located on the circuit board or by the PDA. In either case, an algorithm is utilised to relate the analysed signals to one or more identifiable faults. Depending on the nature and severity of the fault, appropriate action may be undertaken to deal with the situation.

Referring to Figures 9 and 10 of the accompanying drawings, there is illustrated a magnet base attachment which is also shown in Figures 1 to 4 bonded to the bottom surfaces of leg members 19 of magnet assembly 15.

Base attachment 23 is a substantially rectangular tablet having upwardly extending integral protuberances 53 and 55 between which is located a central hole 57 extending through the body of the attachment.

Protuberances 53, 55 are sized and shaped to fit within the space between lower portions leg members 19. With the contacting surfaces of base attachment 23 bonded to mating surfaces of leg members 19 and with fixing screw 25 held captive with its head 59 (see Figure 4 and 12) located between leg members 19, the shank 61 of fixing screw 25 may be in screw threaded engaged with the piece of equipment and/or structure being monitored.

Base 23 is provide with grooves 63 on its underside in order to aid with adhesion.

Monitor 1 may, instead of being permanently or semi-permanently attached to the piece of equipment and/or structure to be monitored, be used in an entirely non-secure contact mode of operation. In this case the monitor is used without the above described base attachment. Referring to Figures 11, 13 and 14, monitor 1 is shown in contact with surfaces of difference curvatures. Figure 11 illustrates the position of monitor 1 on a surface having a curvature equivalent to 20mm diameter. It can be seen that contact between this surface and the curved surfaces of leg members 19 is at innermost positions of leg members 19. By contrast, and as illustrated in Figure 14, the monitor 1 is shown in contact with a surface with the equivalent of a 2,000 mm diameter and in this case it is the outer portions of the curved parts of leg members 19 that contact this surface. The range of surfaces which can be effectively contacted by the monitor via its curved leg members 19 is typically 20 to 2,000mm, this range of curvatures being illustrated, in particular, Figure 13.

Claims

1. A condition monitor for monitoring vibration and/or temperature of a piece of equipment and/or a structure, the monitor comprising:- an enclosure; at least one vibration sensor located within the enclosure; a processor located within the enclosure and being connected to the or at least one of said sensors for analysing signals produced therefrom; means located in the enclosure for buffering the analysed signals prior to wifi transfer; a power source connected to the processor and located in or in close proximity to the monitor; and means for mounting the monitor on the piece of equipment or the structure and a wireless transmitter for external communication to a wireless receiver.

2. A monitor according to Claim 1, wherein the buffering means is capable of storing a multiple of analysed signals prior to their transmission to a remote receiver.

3. A monitor according to any of Clams 2, wherein the remote receiver is a personal digital assistant or a tablet.

4. A monitor according the any of the preceding claims, wherein the monitor includes a mounting plate.

5. A monitor according the any of the preceding claims, wherein the monitor includes an integral magnet.

6. A monitor according to Claim 5, wherein the magnet has a mating surface for contact with the surface of the piece of equipment and/or the structure.

7. A monitor according to Claim 6, wherein the mating surface is curved.

8. A monitor according to Claim 7, wherein the curvature of the surface of the magnet varies over the mating surface.

9. A monitor according to any of Claims 5 to 8, wherein the magnet is provided with two spaced apart mating surfaces, each of which is curved.

10. A monitor according to any of the preceding claims, wherein two or more bi-axial vibration senses are provided within the enclosure.

11. A monitor according to any of the preceding claims, wherein the monitor is provided with means for determining the nature of a fault in the piece of equipment and/or structure.

12. A monitor according to Claim 11, wherein the fault identifying means are allocated within the enclosure.

13. A monitor according to Claim 11, wherein the fault identifying means are located in a remote receiver of signals from the monitor.

14. A monitor according to any of Claims 10 to 13, wherein the fault identifying means includes an algorithm capable of identifying a particular fault.

15. A condition monitor for monitoring vibration and/or temperature of a piece of equipment and/or a structure, the monitor being substantially as described with reference to the accompanying drawings.

16. A method for monitoring vibration and/or temperature of a piece of equipment and/or a structure, the method comprising, mounting a monitor as claimed in any of the preceding claims on a piece of equipment or a structure, using the monitor to sense vibrations and produce signals relating thereto and analysing the signals to produce data, buffering the data within the monitor and transmitting the data to a remote location.