Laboratory experimental research on multi-sensor monitoring of belt conveyor idlers – Phase 2

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Specialization: Transport Engineering and Logistics Report number: 2016.TEL.8038

Title: Laboratory experimental research on multi-sensor monitoring of belt conveyor idlers – Phase 2.

Author: V.R.Sikkes

Assignment: Research

Confidential: Yes, till September 2018

Initiator (university): Dr. ir. Y. Pang Initiator (company): TU Delft

Supervisor: Dr. ir. Y. Pang, MSc. X. Liu

Date: 27-9-2016

This report consists of 80 pages. It may only be reproduced literally and as a whole. For commercial purposes only with written authorization of Delft University of Technology. Requests for consult are only taken into consideration

Delft University of Technology

FACULTY MECHANICAL, MARITIME AND MATERIALS ENGINEERING

Department Marine and Transport Technology Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl

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Summary

This report is a continuation of the report written by E.W.L.A van Bodegom[1]. It will show some tests that were repeated in order to test the repeatability, but will go deeper into some problems and phenomena that were encountered during the experiments done by van Bodegom[1].

From van Bodegom's report, it is recognized that challenges remain with the IR sensors and with the sound measurement. Both challenges are researched in this report. Furthermore, some tests will be repeated in order to test the repeatability and a 37.4 Hz vibration frequency phenomenon is discussed and researched.

The main question for this research is: Which parameter is best applicable to detect idler roll failure? This question uses van Bodegom[1] and four sub questions in order to answer it. The four sub questions are:

1. Are the results from previous test repeatable? 2. Where does the 37.4 Hz phenomenon come from?

3. What is the influence of emissivity on measurements of temperature of idler rolls? 4. Can the measurement of acoustic emission be used to detect damaged rolls?

To answer the first sub questions, some of the tests done by Bodegom[1] were repeated. This was done under the same conditions and procedures as Bodegom did. This meant that the same weight was put on the rolls, as well as the same belt velocity as when van Bodegom did the experiments. The tested rolls were put in the same position and the data was collected at the same place. This gave data which could be compared to the previous data from van Bodegom[1].

The 37.4 Hz can be found in all the experiments done by van Bodegom[1] and also the repeated experiment done in this report showed the frequency. The frequency is calculated to occur at one type of defect roll and at one belt speed. But the frequency occurs in all the experiments. Because of this, it is probably not a frequency which can be linked to a specific roll defect. To exclude the effect of this phenomenon, the specific frequency had to be explained. The idea is that the frequency is a natural frequency of either the conveyor frame or the idler rolls. By hitting either the frame or a roll with a steel hammer, the natural frequency of these parts can be acquired. The exact frequency 37.4 Hz was not found. But a frequency of 38.5 Hz was found by hitting a roll. The experiments that were done excluded that the frequency came from the conveyor frame and suggest that the frequency comes from the rolls themselves. It is assumed that the belt has an influence on the frequency measurement of the roll when the belt is tensioned and running.

During the experiments done by van Bodegom[1], there were problems with the IR sensor and the IR camera when they were used to measure the temperature of shiny surfaces. This has to do with the emissivity of an object which can cause an IR sensor to give inaccurate temperature data. Several experiments were done in this report to find out to what extend the emissivity of a surface influences the measurement. This was done by heating up 3 identical idler roll shafts which have different surface treatments. One shaft was left with a polished surface, one shaft was painted with a heat resistant, mat finish paint and one shaft was immersed in salted water for five days and exposed to air for five days in order to rust the surface. The shafts were heated up with a hot air gun and their temperature was measured with three types of sensors, namely: a thermal couple, an IR sensor and an IR camera. The goal was to see how much difference there was the measured temperatures by the three sensors. In an ideal situation, the three sensors would give the same temperature.

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idler roll failure with sound. There is a device on the market which claims to detect defect and damaged rolls based on their sound emissions.

The setup used to measure sound in van Bodegom[1] was also used for this report, but the location of the microphones was changed in order to minimize the noise coming from the engine and maximizing the noise coming from the rolls. A sampling frequency of 30 kHz was used instead of 100 Hz which made it possible to pick up frequencies up to 15 kHz. In order to process the data, two GUI’s (Graphical User Interface) were developed and used to answer the question: Can the measurement of acoustic emission be used to detect damaged rolls? A Filter GUI and a Comparison GUI were made. With the Filter GUI, the user can see, filter and listen to the sound of one roll from one microphone. If needed, multiple filters can be applied and the sound can be played back at each step. With the Comparison GUI the user can see the frequency data from all the rolls at once that was captured by a single microphone. The user can then choose to plot the data of a healthy roll inside the plot of a damaged roll which makes it easier to compare the two sounds. The combination of these GUI’s made it possible to look for differences in sound with the Comparison GUI and then listen to that specific frequency band with the Filter GUI. One healthy roll and one set of damaged rolls were tested in order to find a frequency band which could be used to identify that roll as a damaged roll.

The conclusion of this report is a combination of the report done by van Bodegom[1] and the results from this report. The sub-questions were answered with data from the tests done for this report, but the main question took both reports into account.

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4.3IRCAMERA ... 31 4.4TEST SETUP ... 33 4.5DIFFERENT SHAFTS ... 37 4.6TESTS ... 37 4.7CONCLUSION ... 49 4.8RECOMMENDATIONS ... 49 5.SOUND EMISSIONS ... 51 5.1SKFDEVICE ... 51 5.2TEST SETUP ... 52 5.3GUI’S ... 54 5.4TESTS ... 62 5.5CONCLUSION ... 75 5.6RECOMMENDATIONS ... 75 6.CONCLUSION... 77 6.1REPEATABILITY ... 77 6.237.4HZ PHENOMENON ... 77 6.3EMISSIVITY ... 77 6.4SOUND EMISSIONS ... 77 6.5OVERALL CONCLUSION ... 78 BIBLIOGRAPHY ... 80

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1

Introduction

This report is a continuation of the research which was started by E.W.L.A van van Bodegom[1]. It will show some tests that were repeated in order to test the repeatability and will go deeper into some problems and phenomena that were encountered during the tests done by van Bodegom[1].

The focus of this report is still the same as van Bodegom[1], but with the knowledge gained from the results of the tests done by van Bodegom[1]. Further research is done in this report, which includes the problems and phenomena that were encountered by van Bodegom .

1.1 Short summary of report by van Bodegom[1]

The introduction given in van Bodegom[1] can also be used for this report, so a small summary will be given.

The idler roll plays an important role in a conveyor system. If one fails, the entire system needs to be shut down in order to repair it. If a belt needs to shut down, there is a less or no transport of product. A defect idler roll can also cause extra friction on the system which will make the energy consumption go up, or even damage the belt which is very costly.

In order to avoid these situations, maintenance is applied. Strategies often involve inspecting the rolls manually, which is very time consuming.

Van Bodegom[1] focused on testing the feasibility of multi sensing technologies for the condition monitoring of idler rolls. Which meant that different sensors were tested to see if they could distinguish a healthy roll from a defect or damaged roll by measuring the temperature, vibration and/or acoustic emission.

In his report, van Bodegom did experiments to find out which parameter (temperature, vibration or sound emissions) can best be used to detect idler roll failure. He did this by selecting several sensors which he used in the experiments. The experiments were done with a special setup which consisted of a (small) belt conveyor of which the top three idler rolls could be changed. The idler rolls used for the experiments were prepared with a specific fault or damage in them in order to test whether the damage could be picked up by the sensors.

These sensors were tested with multiple tests which had different characteristics. The weight/pressure on the rolls, the velocity of the belt, the angle of the trough and the duration of the test were characteristics that were changed between tests.

The same setup and idler rolls are used in this report, but different tests were done in order to continue the research.

1.2 Problems and phenomena in report by van Bodegom[1]

During the tests done by van Bodegom[1] some problems occurred.

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fact that the heat from the surrounding air is reflected, but also the heat from the object itself cannot be accurately ‘seen’ by the sensors. This problem is investigated in this report and a solution is presented. The sound data in van Bodegom[1] could not really be used to detect defect or damaged rolls. The data the microphones produced was often saturated and the sampling frequency was too low to pick up all the sound emissions. In this report, the sound measurement is completely changed in order to get more accurate data.

A phenomenon occurred during testing with the idler rolls in van Bodegom[1]. A 37.4 Hz frequency occurred in all the tests. This frequency was calculated to be caused by a defect or a certain belt speed but it should not occur in all the tests, which were done with different rolls and with different belt speeds. This report tries to find out where the frequency comes from.

1.3 Outline report

The goal of the report is roughly the same as in van Bodegom[1] and it is to find the best parameter to detect idler roll failure. But this report has learned from van Bodegom[1] and researched some of its suggestions.

The main question is:

 Which parameter is best applicable to detect idler roll failure? To answer the main question, some sub questions were formulated.

 Are the results from previous test repeatable? Chapter 2

 Where does the 37.4 Hz phenomenon come from? Chapter 3

 What is the influence of emissivity on the measurements of temperature of idler rolls? Chapter 4

 Can the measurement of acoustic emission be used to detect damaged rolls? Chapter 5

1.4 Methods, procedures

Chapter 1 through 6 in the report by van Bodegom[1] describes how the rolls were damaged and what kind of damage each roll has. The same rolls are used in the tests that were done for this report.

The testing procedures and methods to acquire and process the data stayed the same in all the tests that were done.

Because the experiments that needed to be done for this part of the research as very different from each other, each part of the research had a different procedure. To answer the first sub-question (Are the results from previous test repeatable?), some tests that were done by van Bodegom, were repeated to check whether the results would be similar to that of van Bodegom. The procedures for these tests were the same as when van Bodegom did them.

The 3.64 Hz frequency needed to be found in order to explain the phenomenon. The procedures were therefore quite simple. A test was donet, for example: hit the roll. And the data was checked to see if the frequency was clearly visible. If the frequency was not clearly visible, a different test needed to be done. The Influence of emissivity was tested with a different setup than with all the other tests. Three separate shafts were used in order to do the experiments. These shafts were put on a stand and heated up in order to measure the temperature with three different sensors. The heating process and the duration of the tests was the same for all tests done for this part. Only the surface of the shafts were different in order to test the emissivity factor.

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To test whether sound could be used to detect idler roll failure the test setup which was used to do the ‘normal’ test was altered slightly in order to get the correct data. What this meant will be explained in chapter 5. But again, the same rolls and sensors were used, as were used in all the previous tests. In order to check the data, special Matlab programs were made in order to ‘show’ the sound and to filter the sound in order to listen to different frequencies.

1.5 Sensors

The sensors that were used in the previous test are also used in the tests done for this report. Especially the IR camera and the microphones were used extensively. Further explanation of the usage of these sensors will be described in chapters 5 and 6 respectively.

As in the previous test, the most important sensors were: the thermocouple, IR sensor, IR camera (all 3 temperature sensors), the accelerometer (vibrations) and the microphones (sound). The microphones were discarded by Bodegom as a good sensor to identify damaged or defected rolls. But in this report, the microphones were used in a different setting where they did give accurate data.

Table 1. 1 Overview of sensors used

Type of sensor Range

Thermocouple -50 to 250 (°C)

Infrared Sensor 0 to 100 (°C)

Infrared Camera -10 to 150 (°C)

Accelerometer -2 to 2 (g)

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For more detailed information about the sensors used in the experiments, see van Bodegom[1] chapter 3 (p.9-p.18) and van Bodegom[1] appendix 2,3 and 4.

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2

Repeated tests

Several tests done by van Bodegom[1] were repeated to check whether the results would be the same. This means that the same test setup and procedures were used to do the tests

As it was shown in van Bodegom[1], four rolls were made with the same defects. This means that it could be possible that a B roll used in van Bodegom[1], is not the same B roll used for the repeated tests done in this report. This chapter tries to answer the question: Are the results from previous tests repeatable?

In order to answer this question, several tests done by van Bodegom[1], were repeated and the results are checked with the results from CH.7 in van Bodegom[1]

The repeated tests will be compared with respect to the temperature and vibration. Sound is not compared with the previous tests, because the sound data was completely saturated due to the placement of the microphones in [1]. This will be further explained in chapter 6

The lay-out of this chapter is as follows: First, the test that were repeated are presented in section 2.1 as well as the roll defects (2.2). The data from the repeated test is then shown (2.3 – 2.6). Discussion is presented in 2.7, after which the conclusions (2.8) and recommendations (2.9) will be given

2.1. Repeated tests

Table 2.1 Shows a list of tests that were repeated and compared to the same tests done by van Bodegom[1].

Table 2. 1 Summary of repeated laboratory idler experiments

Experiment schedule

Type of experiment Name Date Conditions Paragrap

h Load on all three rolls (kg) Belt velocity (m/s)

Defect roll experiment ShC2 21-12-15/23-12-15 285 1.82 2.3

ShC2 19-2-16/23-2-16 486 1.82 2.4

Trough_ShR1 29-2-16/3-3-16 536 1 2.5

Damaged roll

experiment

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2.2 Roll defects

The table with all the roll defects is presented below. This table was also used in van Bodegom[1].

Table 2. 2 Roll defects

type of bearing

defect Code

Number

of rolls defect details

No defect A 4 No defect bearings installed

Outer race defect B 4 Scratch perpendicular on the direction of movement of the rolling elements. Scratch width 1 mm, depth 0.5 mm

Inner race defect C 4 Scratch perpendicular on the direction of movement of the rolling elements. Scratch width 1 mm, depth 0.5 mm

Rolling element

defect D 4

Damage on one of the rolling elements. Diameter 0.5 mm, depth 0.5 mm

Debris in

lubricant E 4

MICRON+MDA M4080 particles from ELEMENT SIX (size range 0.04-0.08 mm) in the lubrication oil (Shell Gadus S2 V220 2). The contamination level is around 5 vol. %

Radial

overloading F 4

Roll #1: application of 18kN load for 2 hours

Roll #2: application of 18kN load, roller failed within 2 hours Roll #3: application of 18kN load for 1/2 hours

Roll #4: application of 18kN load for 1/2 hours The tangential speed measured during the test is: 3.42 m/s (13Hz, 781 RPM)

‘Damaged’ G 3

Three different types of damaged bearings are installed. Roll G1: Bearing cover damaged using a hammer, visible damage on the bearing cover

Roll G2: Small hole through up to the bearing.

Roll G3: five holes drilled in the bearing. Broken cage and drilled holes filled with metal particles: mass (~30g) and size (~250µm)

No lubrication H 2 Not lubricate the new bearing

‘Damaged’ H 2

Two rolls H are damaged as follows:

Roll H2: five holes through bearing covers up to the bearing and cage destroyed

Roll H3: give holes through bearing covers up to bearing. The holes are filled with metal particles: mass (~15g) and size (~50µm)

Corroded

bearing I 4

Bearings placed in salty water or acid liquid for one week. Afterwards the bearings are exposed to air till corrosion can be observed on the bearing

Table 2.2 shows the different defects in all rolls. For rolls A, B, C and D there are frequencies that have been calculated which should be related to the defect. These calculated frequencies will be presented for each of the repeated tests.

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2.3 Repeated defect roll experiment 3

The first test that was repeated is the Defect roll experiment 2. The dimensions for this test are the same as Defect roll experiment 3 in van Bodegom[1]. The only difference is that van Bodegom[1] focused at the shaft end ShC1 and this test focused at the shaft end ShC2. This has no effect on the result because the brackets ShC1 and ShC2 can be considered as symmetrical.

As is van Bodegom[1], the temperature increase will be measured from the starting temperature of the first roll that is tested on that day.

Table 2. 3 Test conditions of Defect roll experiment 3

Type Condition

Left wing roll Center roll Right wing roll

Type of roll installed Roll G1 Defect rolls Roll A

Defect bearing installed at shaft end ShL1 ShC2 -

Load on rolls (kg) 79 115 91

Type of idler rolls used A-B-C-D-E-F-H-I

Belt speed (m/s) 1.82

Sample frequency (Hz) 100

Sample time (sec) 10

Sample interval (min) 0, 30, 60, 90, 120

Trough angle (°) 0

2.3.1 Temperature

Thermocouple

Table 2.4 presents the thermocouple data from the repeated test and the thermocouple data from the previous tests. The blue color indicates that the temperature from the repeated test is lower, the red color indicates that the temperature from the repeated test is higher than the previous tests.

Table 2. 4 Thermocouple data defect roll experiment 3

Defect roll experiment 3

Thermocouple (°C)

Roll Previous Repeated Difference

A 5.5 4.6 0.9 B 7 5.2 0.8 C 6.7 5.1 1.6 D 5.6 4.3 1.3 E 7 4.4 1.6 F 6.7 6 1.7 H 5.3 5 1.3 I 6.8 4.7 2.1 Average difference 1.4

What can be seen from table 2.4 is that the temperature increase is very similar, but it seems to be 1 degree lower.

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IR Sensor

Table 2.5 presents the infrared sensor data from the repeated test and the infrared sensor data from the previous test.

Table 2. 5 IR sensor data defect roll experiment 3

IR Sensor (°C)

A 4.7 3.3 1.4 B 5.7 4.2 1.5 C 5.8 6 0.8 D 4.9 3.7 1.2 E 5.7 8.7 2 F 5.9 6 0.9 H 5.4 2.8 2.6 I 6.6 4.1 2.5 Average difference 1.6

Note: In the tables, the blue color represents the fact that the temperature from the repeated test was lower than in the original tests and the red color represents the fact that the temperature from the repeated test was higher than in the original tests

From table 2.5 it can be seen that the difference regarding the temperature increase between the repeated and the previous test is slightly bigger than with the thermocouple. Similar to van Bodegom[1] is the fact that the healthy roll has the smallest temperature increase.

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IR Camera

Table 2.6 presents the infrared camera data from the repeated test and the infrared camera data from the previous test.

Table 2. 6 IR camera data defect roll experiment 3

IR Camera (°C)

A 4.7 4.4 0.3 B 6.1 6.1 0 C 6.7 8.1 0.4 D 4.3 5.7 1.4 E 5.4 9.3 2.9 F 5.2 7 0.8 H 4.9 6.3 1.4 I 5.8 6.3 0.5 Average difference 0.9

From table 2.6 the repeated test seem to have more of an increase in temperature, although the healthy roll stays the coldest.

2.3.2 Vibrations

Accelerometer

Table 2. 7 Calculated frequencies for a belt velocity of 1.82 m/s

Calculated defect frequencies for a belt velocity of 1.82 m/s:

Type of frequency: Color

representation:

Frequency and its harmonics (Hz):

Rotating frequency roll Green 4.3, 10.6, 14.9, 21.2, 25.5, 31.8, 36.1, 42.4, 46.7 Outer race defect Purple 18.7, 37.4

Inner race defect Magenta 29.1

Rolling element defect Yellow 23.5, 49 Plots and figures can be found in appendix 1

The colors next to the frequencies in table 2.7 are used in the frequency plots to indicate that a particular frequency is found within a 0.5 Hz margin of the calculated frequency.

The energy plots from van Bodegom[1] show a clear peak at 36.1 Hz. In the repeated test this clear peak was not visible from the data, see appendix 1 figure 1.4-1.14. Other frequencies seem to be stronger. This is true for both the X direction and the Y direction as can be seen in appendix 1 figure 1.4-1.14. As in van Bodegom[1] only roll A-D are checked for calculated frequencies. As said above, the 36.1 Hz frequency which was clearly the biggest peak does not show up as clearly in the 10 highest peaks. Most of the highest peaks can be traced back to the rotating of the roll. See table 2.6. In X direction, all 3 rolls didn’t show the frequencies that were calculated for their defects. The calculated frequencies occurred sometimes but were not corresponding to the defects and were not showing consistently. In Y

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rolls showed the frequency as well. This was also the case in van Bodegom[1]. There was no detection of defect by frequency.

As in van Bodegom[1], the energy plots from the idler frame sensor is shown as well, to see the correlation between the sensor on the roll and the sensor on the frame. The peaks in the repeated test as a bit clearer. But there are still al lot of frequencies which are strong as well. The only frequency which stands out in the idler frame, is the 37 Hz frequency. This is the same as in van Bodegom[1].

2.4 Repeated defect roll experiment 5

The second repeated test, was the Defect 5 Table 2.8 test conditions Defect 5 roll experiment

Table 2. 8 Test conditions Defect 5 roll experiment

Type of roll installed Roll G3 Defect roll Roll A

Type of idler rolls used A-B-C-D-E-F-H-I

Belt speed (m/s) 1.82

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2.4.1 Temperature

Thermocouple

Table 2.9 presents the thermocouple data from the repeated test and the thermocouple data from the previous test

A 5.4 4.5 0.9 B 5.9 4.6 1.3 C 8.1 5.6 1.5 D 8.3 6.6 0.7 E 7 8.2 1.2 F 5.9 5.6 0.3 H 6.4 5.7 0.7 I 8 6.1 0.9 Average difference 0.9

Again, the repeated test values shown in table 2.9 seem to be similar than the previous test, but a degree lower. This time, the healthy roll stays colder than the defect rolls

IR Sensor

IR Sensor (°C)

A 6 3.8 1.2 B 5.3 5.2 0.1 C 8 6.5 0.5 D 6.7 6.9 0.2 E 7 23.3 16.3 F 5.6 5.9 0.3 H 5.8 4.8 1 I 6.4 6.2 0.2 Average difference 2.6

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The values shown in table 2.10 show that the IR sensor values are similar in the previous and the repeated test. Only roll E stands out with a 24 degree increase. This is caused by the fact that roll E has more clearance between the bracket and the shaft end. This was also found in van Bodegom[1](Page 65 and 68) The healthy roll stays colder than the defect rolls

IR Camera

IR Camera (°C)

A - 4 - B - 4.6 - C - 8.8 - D - 9 - E - 18.7 - F - 6.1 - H - 8.1 - I - 8.9 - Average difference -

For this test there was no data from van Bodegom[1] on the IR camera. In the repeated test it was possible to place the camera to see C2 and the data was recorded. This data shows that roll A stays the coldest, but it also shows roll E getting far hotter than all the other rolls. A fact that was also picked up by the IR sensor but was not picked up by the thermocouple.

2.4.2 Vibrations

Accelerometer

representation:

Rolling element defect Yellow 23.5, 49

Appendix 1 figure 1.19 shows the FFT Energy plots in X direction of all the rolls and they look very similar to the figures in van Bodegom[1]. Clear spikes are visible and other frequencies are clearly lower than the spikes.

The same as in van Bodegom[1], none of the calculated frequencies for the defects clearly shows up in the test with the according roll.

In the Y direction (Appendix 1 figure 1.24). The FFT Energy plots are very similar to that in van Bodegom[1]. Clear spikes are visible with other frequencies being low in energy.

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of 37 Hz. But it is within the 0.5 Hz margin. Because this frequency corresponds with and outer race defect which should only show in roll B, the frequency cannot be an indicator for the outer race defect. Again, the FFT plots from the idler frame are compared with the FFT of C2 and the 36.3 Hz frequency is clearly shown in the Y direction but not in the X direction. The vibrations in the X direction are lower than the vibrations in X direction on the rolls.

2.5 Repeated defect roll experiment 6

Table 2. 13 Test conditions Defect 6 roll experiment

Type of roll installed Roll G3 Roll G1 Defect roll

Defect bearing installed at shaft end ShL1 ShC1 ShR1

Type of idler Rolls used A-B-C-D-E-F-H-I

Belt Speed (m/s) 1

Trough angle (°) 12

2.5.1 Temperature

Thermocouple

A 3.1 2.8 1.3 B 4.2 2.2 2 C 4.6 3.1 1.5 D 4.4 2.5 1.9 E 5.5 3.6 1.9 F 4.9 3.4 1.5 H 4.2 2.6 2.6 I 5.1 2.2 2.9 Average difference 2.1

Table 2.14 shows a difference of a couple of degrees between the previous and the repeated test and the defect roll is not always hotter than the healthy roll.

IR Sensor

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IR Sensor (°C)

A 4 4,1 0.1 B 5,3 5 0.3 C 5,6 5,8 0.2 D 5,1 4,5 0.6 E 6,5 22,6 15.1 F 6,1 5,7 0.4 H 5 3,6 1.4 I 6,3 2,5 2.8 Average difference 2.9

Table 2.15 shows again that roll E becomes much hotter than the other defect rolls. This has been seen in the previous test as well, but it is not normal. Not all the E rolls got this hot. This can be seen in van Bodegom[1], where different E rolls were used and they did not all reach temperatures this high. The rest of the data from the repeated tests is very similar to the previous tests previous except roll H and I, which stay cold.

IR Camera

IR Camera (°C)

A 3.4 4 0.4 B 5 3.7 0.3 C 4.4 4.8 0.4 D 4.2 4.7 0.5 E 5.3 18.1 11.8 F 5.1 5.6 0.5 H 4.2 4.5 0.3 I 5.8 5.2 0.6 Average difference 1.9

In table 2.16 it can be seen that the previous and the repeated data is very similar, only roll E stands out. But this has happened in other tests as well.

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2.5.2 Vibrations

Accelerometer

Table 2. 17 Calculated frequencies for a belt velocity of 1 m/s

Calculated defect frequencies for a belt velocity of 1 m/s:

representation:

Rotating frequency roll Green 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48 Outer race defect Purple 10.4, 20.8, 31.2, 41.6

Inner race defect Magenta 15.1, 32.2, 48.3 Rolling element defect Yellow 12.6, 26.2, 40.8

In X direction (Appendix 1 figure 1.34), in the FFT Energy plots, the peaks are quite similar. This test does have some more high peaks. It looks like the 34 Hz that was found in van Bodegom[1] is also in this repeated test.

As in van Bodegom[1], the matrix values don’t correspond with the calculated frequencies for this speed. Again, the FFT Energy in Y direction is very similar as in van Bodegom[1]. (Appendix 1 figure 1.39) As in van Bodegom[1], the matrix values don’t correspond with the calculated frequencies for this speed in Y direction.

The idler frame plots show lower energies than were found in van Bodegom[1], but the peaks were very similar.

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2.6 Repeated damaged roll experiment 2

Table 2. 18 Test conditions Damaged 2 roll experiment

Type of roll installed Roll G2 Roll B Roll A

Belt Speed (m/s) 1.4

Trough angle (°) 0

2.6.1 Temperature

Thermocouple

Table 2. 19 Thermocouple data damaged roll experiment 2

Damaged roll experiment 2

G2 20.7 22.8 2.1

Average

difference 2.1

Because it was only 1 roll being tested, the comparison is very quick. Both rolls got far hotter than the defect rolls and the difference between bot test is 2,1 degrees. Which, looking at the total temperature increase is very similar.

IR Sensor

Table 2. 20 IR sensor data damaged roll experiment 2

IR Sensor (°C)

G2 16.3 25.1 8.8

Average

difference 8.8

The difference between the previous and the repeated test is quite big, 8,8 degrees. Bot rolls do get hotter than the defect rolls.

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IR Camera

Table 2. 21 IR camera data damaged roll experiment 2

IR Camera (°C)

G2 22.3 19.2 3.1

Average

difference 3.1

The difference that was seen with the IR sensor can also be seen in the IR camera data. Although the difference is not as big, 3.1 degrees. It is still quite a difference.

2.6.2 Vibrations

Accelerometer

representation:

Rotating frequency roll Green 3.1, 8.2, 12.3, 15.4, 20.5, 23.6, 28.7, 32.8, 35.9, 41, 44.1, 49.2

Outer race defect Purple 13.5, 29, 42.5 Inner race defect Magenta 22.6, 44.2 Rolling element defect Yellow 19.1, 38.2

The FFT plots are both (X and Y) similar to van Bodegom[1](Appendix 1 figure 1.48-1.53). There are no real spikes apart from one near 50 Hz. This spike is also found in the Idler frame sensor so it does not come from the roll.

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2.7 Results

Overall, the temperature results from the repeated test were similar to the previous tests.

More specifically, the data from the thermocouples were often 1 degree lower than those from the previous tests. The 1 degree difference in the thermocouple data could be explained by the fact that the starting temperature of the previous tests was lower than the starting temperature of the repeated tests. On the other hand, the 1 degree difference is within the accuracy of the sensor. The data from the thermocouples did show that the temperature increase of the healthy rolls was almost always smaller than the defect rolls, which was also described in van Bodegom[1].

The data from the infrared sensor was similar to the previous test. Although roll E was a big exception. But the fact that it happened in multiple test and the same sensor was used for other rolls as well, proved that the sensor was working correctly and that the big increase in temperature was caused by the specific E roll. It is possible that the roll E used in van Bodegom[1] is not the same roll E used in the repeated tests. Other than roll E the data mostly varied only 1 degree in both ways (hotter or colder than the previous data). The same reason as for the thermocouple could be used here, that the starting temperature was higher than when van Bodegom[1] did the tests. Another problem which the infrared sensors could have is that the shaft ends were too shiny and that the emissivity value was low. This will be explained in more detail in chapter 4. This problem was also mentioned in van Bodegom[1]. As in the thermocouple data, the healthy roll always stayed the coldest.

The data from the infrared camera was overall very similar to the previous tests. The difference was often less than 1 degree. Only in the Damaged roll test was the difference bigger, but this roll had a painted shaft end which solved the emissivity problem and could be the cause of the difference. The camera also had a problem with emissivity, but because the camera measures the temperature over a small area instead of a single spot, the camera had less problems with the emissivity of the shaft end. And again, roll E became much hotter than the other defect rolls.

As in the thermocouple and infrared data, the healthy roll always stayed the coldest.

The vibration test results from the repeated test overall were very similar to the previous test.

More specifically, as in van Bodegom[1], no calculated frequencies were found consistently in the results. The vibrations in the repeated test seemed to have more energy but the peaks were almost on the exact same spot.

2.8 Conclusion

To answer the question: Are the results from previous test repeatable?

Yes. The tests are repeatable and similar results can be found if the tests are done under the same conditions.

2.9 Recommendation

The temperature increase of the rolls were measured for these test. But the starting temperature of the rolls will have an influence on the outcome. A recommendation would be to test whether the maximum temperature of a roll is depended on its starting temperature. Will a defect roll become, for example, 30°C with a starting temperature of 20°C and as well with a starting temperature of 15°C.

If this is true, one would only need to measure the temperature of once to see if it is in need of replacement. This would be more practical then to measure over a period of time.

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3

The 37.4 Hz phenomenon

In van Bodegom[1] a phenomenon occurred which was not discussed in the report. A vibration around 37.4 Hz occurred in all the tests. This vibration was also measured in the repeated tests that were done for this report.

For some speeds and/or defects, this was a calculated frequency. But it also occurred in tests where this frequency was not calculated.

The frequency occurred in all tests and with all the rolls and could therefore not be caused by a defect of the rolls.

As a comparison, the figure below shows the frequency occurring during a test.

Figure 3.1 shows the frequency response of the F roll after 90 minutes under a load of 285 kg spread over all 3 rolls. The F roll was radial overloaded, and as can be seen in table 3.1 37.4 Hz is not expected to be seen on a roll with that defect,

In van Bodegom[1], a maximum deviation of 0.5 Hz was used in the detection of specific vibrations. That same rule will be applied in this report. A frequency of 37.4 ± 0.5 Hz needs to be found in order to explain the phenomenon.

Several test were done in order to find out where this phenomenon comes from. These tests and their results will be explained in this chapter.

First, the calculated frequencies are checked to see if the 37.4 Hz comes from the rolling of the roll or is caused by one of the defects (3.1.1).

Second, some tests are done to check whether 37.4 Hz is the natural frequency of the frame (3.1.2). The frame of the conveyor is large and heavy, so a low frequency like 37.4 Hz could come from the frame. Last, the rolls are hit in several directions to see if 37.4 Hz is the natural frequency of the roll itself (3.1.3). The rolls are identical apart from the defects, so the natural frequency is the same for all rolls, which could explain why the frequency occurs in all the tests.

After the tests, a conclusion will be drawn in section 3.2.

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3.1 Tests

3.1.1 Turning rolls

In van Bodegom[1], tables were presented that stated the frequencies that could occur because of the rotating of the rolls or defects in the roll. This was done for 3 different speeds. These tables are shown below.

Table 3. 1 Calculated defect frequencies for multiple belt velocities

Calculated defect frequencies for a belt velocity of 1 m/s:

representation:

Rotating frequency roll Green 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48 Outer race defect Purple 10.4, 20.8, 31.2, 41.6

Inner race defect Magenta 15.1, 32.2, 48.3 Rolling element defect Yellow 12.6, 26.2, 40.8 Calculated defect frequencies for a belt velocity of 1.4 m/s:

representation:

Rotating frequency roll Green 3.1, 8.2, 12.3, 15.4, 20.5, 23.6, 28.7, 32.8, 35.9, 41, 44.1, 49.2

Outer race defect Purple 13.5, 29, 42.5 Inner race defect Magenta 22.6, 44.2 Rolling element defect Yellow 19.1, 38.2 Calculated defect frequencies for a belt velocity of 1.82 m/s:

representation:

Rolling element defect Yellow 23.5, 49

As one can see, the 37.4 Hz frequency is calculated to occur during a test with a speed of 1.82 m/s and a roll with an outer race defect.

Apart from this where the frequency can be caused by a defect in the roll, the 37.4 Hz is not caused by the rotating of the rolls or a defect to the roll.

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3.1.2 Natural frequency of the conveyor frame

To check whether 37.4 is the natural frequency of the machine, the machine was hit with a steel hammer. This was done in multiple places and in multiple directions. The positions where the frame was hit are shown in figure 3.2 and marked with a red dot.

The accelerometers were left on the positions they were when the ‘normal’ tests where done with the machine running. Specific places of these sensors are explained in van Bodegom[1](Ch.4 figure 3.6 p.22 and Ch.5 p.32-33)

The procedure for these test was as follows. The Labview program records for 10 seconds when the program is activated. The hit takes place within these 10 seconds.

Table 3.2 shows where the frame was hit and in what direction. The direction that is stated in the table means the direction seen from the accelerometer that is placed on the rolls. The X direction can be seen as the direction the belt travels. The Y direction is the direction gravity works in and the Z direction is from left to right. (The only sensor that can really measure this, is the one mounted on the idler frame itself).

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The frame and later the rolls were hit with a big steel wrench

Table 3. 2 Frame tests

Test Place Direction Comments

1 Frame near Roll R X The frame here means the big frame of the machine itself, not the frame where the rolls sit in

2 _{Frame near Roll R} _Y

3 _{Frame near Roll R} _Z

4 Idler frame near roll L No Tension on belt

The belt was still resting on the rolls

5 Idler frame near roll L belt lifted off frame loose

The belt was lifted up from the rolls and the idler frame was loose on its brackets

6 Machine running Measurements were taken during normal running and right after the machine was stopped

7 Machine stopping

The frequency responses that were measured from these hits will be shown below. Just as in van Bodegom[1], the energy of the frequencies will be plotted. Figure 3.1 shows how the peak looks like during a normal test. If a peak like this is found in one of the tests, the 37.4 Hz frequency can be explained.

Figure 3.4 shows the hit in the time domain. This shows the frame is hit only once.

Figure 3. 4 Time-domain plot of a single hit on the frame

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Figure 3.5 shows the first 3 hits that were recorded. These hits were executed on the conveyor frame, not on the idler frame. The Hit in X direction was done very close to the R roll. The hit in Y direction was executed right next to to the idler frame. The hit on in Z direction was executed on the end of the frame. The red dots in figure 3.5 indicate the positions of the hits on the frame.

From these tests, there is not much vibration in the frame from 1 hit. This could be, because the impact is to small or that the frame did not present high enough level of vibration. The hits on the frame might have been too soft, but hits that were any harder would have damaged the frame.

Figure 3.6 shows the two hits that were subjected on the idler frame. The first hit (left) was done on the idler frame without any tension on the belt, but the belt was still on the rolls and the idler frame was tightly connected to the frame. The second hit (right) was done with the belt lifted off and the idler frame loose from the frame. This meant that the bolts which connected the idler frame to the conveyor frame were loosend.

There are more vibrations than when the big frame was hit, but still no single peak is clearly visible The next test was to see if stopping the machine would induce the frequency.

Figure 3. 6 Left: Test 4; Right: Test 5

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Figure 3.8 shows 2 graphs, the left shows the frequencies with the machine running, the belt tensioned and the rolls in place. The right picture shows the frequencies right after the machine is stopped. The idea was that, if the frequency came from the frame, it would resonate right after the machine stopped. It is clear that this was not the case.

As can be seen in the pictures above, there is no reason to claim that 37.4 Hz is the natural frequency of the conveyor frame itself.

The steel hammer which was used might not have been big enough to induce a vibration big enough. But in order to do that, the machine would have been damaged. As the 37.4 Hz frequency occurs during normal running, it was assumed that if the vibration came from the machine, it could have been induced by a hit from a human.

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3.1.3 Natural frequency of the rolls

To test if the frequency was the natural frequency of the idler rolls, the belt was lifted so the tension and weight of the belt was off the rolls.

In order to test if 37.4 Hz is the natural frequency of the roll, the roll was hit with a steel hammer in multiple directions and places

Again, the direction stated below in the table is as follows. The Y direction is with the direction of gravity. The X direction is from the front of the roll to the back (or the other way around).

Table 3. 3 Roll tests

Test Roll Direction

1 C roll X 2 R roll Y 3 L1 X 4 Y 5 Separate roll X 6 Y

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Figure 3.9 shows the C and R roll being hit. This was done with the belt lifted off. The idler frame was firmly connected to the frame. There is still not much visible, although there is more vibration from the rolls than from the frame. There is also a small peak near 50 Hz. It is not near to the 37.4 Hz frequency, but it is a peak which indicates that the frequency could come from the roll.

Next, the L roll was hit very near to the L1 sensor.

Figure 3.10 shows the L roll being hit in 2 directions. This is the first test were a clear peak is visible. The peak is at 39.2 which is not within the 37.4±0.5 Hz margin as stated in the beginning of this chapter. But it does show a clear peak in the area the peak needs to be, so the next test was done with a separate roll.

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The frame had the same mounts for the rolls as the idler frame in the test setup. The advantage of this setup was the fact that there was enough space to get a good hit.

The result from figure 3.12 was that a frequency was found close to the 37.4 Hz (38.5 Hz)

This shows that the 37.4 Hz could be the natural frequency, although the exact frequency was not found. The last tests show that a clear peak is formed when the roll is hit separately or when the hit takes place near a sensor. This gives the hypothesis that the 37.4 Hz frequency is the natural frequency of the roll. There are a couple of potential reasons why the 37.4 Hz frequency was not found.

- The belt and the idler frame have a big damping effect. Which is why no specific frequency stood out in the tests with one hit.

- The belt has an influence on the natural frequency of the idler roll, caused by the tension of the belt on the rolls.

3.2 Conclusion

The exact frequency of 37.4 Hz has not been found except in the results of the ‘normal’ tests. However a frequency very close has been found in the vibrations of the idler rolls themselves.

In addition, it has been shown that the 37.4 Hz frequency is not caused by the rotating of the rolls and it is not the natural frequency of the conveyor frame.

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4

The influence of emissivity

One of the conclusions of van Bodegom[1] was that temperature was a good indicator to monitor an idler roll. van Bodegom[1] suggested that the IR Camera, was the best and easiest way to measure the temperature of the idler rolls.

The drawback of an infrared camera is that it is influenced by light and the surface material that it measures. This chapter will investigate emissivity and discuss the test that were done in order to estimate the consequences of emissivity on an IR camera.

The goal of these tests was to answer the question: What is the influence of emissivity on the measurements of temperature of idler rolls?

In the following tests, the camera is tested on different surfaces to see how much the emissivity of different surfaces influences the temperature readings from the camera.

In an ideal situation, all types of sensors would give the same temperature. During testing, it was tried to get the same temperature from all sensors. Although this was not the goal, it did show how much emissivity influenced the data.

This chapter will first give an introduction to the problem with low emissivity surfaces (4.1) and then explain what emissivity is and what it does in the camera (4.2). The camera and how it was used will then be explained in 4.2. In 4.4, the testing setup is explained and in the 4.5 the shafts are shown. After which test 1 (4.5.1) test 2 (4.5.2) and test 3 (4.5.3) are discussed. The conclusion (4.7) and recommendations (4.8) are discussed last.

4.1 Introduction

The emissivity of a surface plays a big role when infrared sensors, which include the infrared camera, are used to measure the temperature of objects with a polished surface. It can influence the measurement in such a way that the data given by the sensor is not accurate and will (often) be interpreted as a higher temperature than the object is in reality.

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Figure 4.1 shows two images of the same roll but at 2 different times. The camera was pointed at the shaft end of the idler roll. The images show a clear difference in temperature, which is shown with different colors.

This shaft end often has a polished surface, which can give problems if the temperature is measured with an IR Camera. This will be explained and shown later in this chapter.

4.2 Emissivity and the IR Camera

Emissivity or emittance is a property of an object. Depending on the surface (polished or mat finish), the object emits more or less of its heat. If an object emits all its heat, it’s considered a black body. If an object has a polished surface, it will only emit a portion of its heat. The emissivity of an object is defined as a ratio between the emitted energy and the maximum possible (black body) emitted energy of that same body[2][3].

‘All objects reflect, transmit and emit energy. Only the emitted energy indicates the temperature of the object. When IR thermometers measure the surface temperature they sense all three kinds of energy; therefore, all thermometers have to be adjusted to read emitted energy only. Measuring errors are often caused by IR energy being reflected by light sources.’[4]

For the camera, this causes incorrect measurements. For a correct measurement, the camera only needs to ‘see’ the emitted energy. This is not problem for black body object since they only emit energy and don’t reflect energy. But if the object has a low emissivity, such as the polished shafts that were used in these tests (ε≈0.3), the camera also ‘sees’ the reflected temperature that is

coming from the object. This reflected energy can come from a light source or from the temperature of the surrounding air.

The camera which was used for these test had an emissivity setting in which the user could change the ε value, the default setting was ε=0.95 (gray body). With this setting, the camera can take into account that the surface it measures is reflective and change its formula which calculated the temperature from the energy the sensor ‘sees’[5].

During testing it became clear that it was very difficult to get the correct setting to correctly measure the polished shaft ends. This will be discussed later in this chapter.

Figure 4. 2 Illustration of reflected, transmitted and emitted energy (4).

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4.3 IR Camera

The focus of these tests will be on the measurements taken by the camera. The other sensors that were used will be explained later in this chapter.

The camera that was used was Flir AX8, the same camera that is used and explained in van Bodegom[1].

Figure 4. 3 Flir AX8, IR camera used for this research Table 4. 1 IR camera properties

Specification: Value:

Infrared resolution (pixels) 80 x 60 Thermal sensitivity (°C) < 0.10 @ +30°C

Camera focus Fixed

Measurement range (°C) -10 to 150

Accuracy (°C) ± 2

Ambient temperature range (°C) 0 to 50

Vibration (g) 2

Emissivity Adjustable

(Default = 0.95)

As mentioned in van Bodegom[1], this camera gives an image in which the thermal image and the visual image are combined into one image.

Because of this feature, the camera can be easily pointed in the right direction and it’s easier to check where the hotspots are.

The biggest advantage of the IR Camera is that it can show the temperature distribution. This has been mentioned in van Bodegom[1]. But during the tests with this camera, it became very clear how the measurement is influenced by the surface.

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In the figure above, it is clear to see that according to the thermal image of the camera, the 2 objects have different temperatures. The object are not the same, but they have the same uniform temperature (They had been laying in the same room for days before this picture was taken). The camera sees the polished surface (right object) as a hotter object than the object without a polished surface (Left object, surface is that of normal steel).

Within the interface of the camera, the user can define multiple spots from which the camera gives the temperature. The user can also define multiple boxes from which the camera gives the maximum, minimum and average temperature. This was very useful during testing with the camera, but also during testing with the idler rolls. With the rolls, a box was situated around the entire roll to know where the roll was at his hottest. And with the testing of the camera, the box would make sure the maximum value was measured, even if the position changed over time, due to the spots that were mentioned above. This feature was used in the following way during the tests. The camera was aimed at the shaft end and 2 boxes were used to measure the temperature. 1 box (box 1) enclosed the entire shaft end with the sensors. And 1 box (box 2) only captured the surface of the shaft end without the sensors in the box.

Figure 4. 6 Screenshot of IR Camera with measurement boxes and 1 measurement point.

This was useful to determine the temperature of the shaft as will be explained in 4.5.1

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4.4 Test setup

The testing setup consisted, other than the camera, of 2 other sensors, hardware to read out all the data and a hot air gun to heat up the shafts.

4.4.1 Hot air gun

As mentioned, the hot air gun was used to heat up the shafts during testing.

Figure 4. 7 Steinel HL 1800 E, hot air gun

Figure 4.7 shows the hot air gun which was used, a Steinel HL 1800 E

Table 4. 2 Hot air gun properties

The hot air gun would be placed near the shaft in order to heat it up. The air gun has multiple heat settings, but only 1 was used for all tests. The air gun blows out air of approximately 100°C. With this temperature, the shaft would become around 80°C.

Temperature range (°C) 50 to 600

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4.4.2 Sensors

Two other sensors were used in the testing of the camera. Namely a thermal couple and an IR sensor. Both these sensors are mentioned and used in van Bodegom[1].

Table 4. 3 Thermocouple properties

Table 4. 4 IR Sensor properties

Measurement range (°C) 0 to 100

Ambient temperature range (°C) 0 to 70 Field of view (distance:spot ratio) 2:1

Minimum spot diameter (mm) 3

Accuracy (°C) ± 1

Maximum Vibration shock (g) 100

Measurement range (°C) -50 to 250

Accuracy (°C) 1

Figure 4. 8 Thermocouple

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These sensors both measure a single point. The thermocouple is the only of the 3 sensor which is physically attached to the shaft and the IR sensor is put close to the surface of the shaft.

4.4.3 DAQ + Labview + Screenshots

The data from the thermocouple and the IR sensor was collected with a DAQ(Data Acquisition Device) and were processed by Labview, a program that works with the DAQ. Both the DAQ and Labview are explained and used in van Bodegom[1]

The data from the IR camera was collected by making screenshots of the interface and copying the data from the screen.

Figure 4. 10 Screenshot data collection, IR Camera interface + Labview

4.4.4 Overall setup

Together with the shafts, the sensors and the heat gun. The setup consisted of a stand to rest the shafts on and a cardboard box to block out the light.

The stand was used to rest the shaft on, but also to attach the sensor to.

The stand itself only touched the shaft on 4 small points, so the heat would not ‘leak’ away trough the stand.

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The cardboard box is place over the entire setup to block out the light. In earlier tests, it became clear that light has a big influence on polished and reflecting surfaces.

Figure 4. 11 Left: Shaft with sensors; Right: Shaft touching shaft

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4.5 Different shafts

In these tests, 3 shaft were use which were identical to each other apart from the fact that on 1 shaft end, they had a different surface.

Figure 4.13 shows the 3 different shaft which were used in the tests. The left shaft has the original surface, which is polished. The shaft in the middle has 1 shaft end painted with mat finish heat resistant black paint. And the right shaft was left in salted water for 4 days and left in the open air for 4 days in order to rust 1 of the shaft ends.

4.6 Tests

To meet the goal, several test were done. The first test were done without the cardboard box and with the same settings for all 3 shafts. The second and third test were done with the cardboard box, but with different emissivity settings.

The procedure for these test was the same. The shaft was at room temperature and was put on the stand. The sensors and heating gun were placed in the same spot and the setting on the heating gun was the same for all test. Each test took 2 hours which gave the shaft enough time to reach a steady temperature. Labview logged the data every minute and a special program made a screenshot every minute so the data from the camera could be read from the screenshots after the test was complete. The test took 2 hours at which point the heat gun was shut down.

The goal of the tests and the setup was not to get the shaft equally hot. So variations in temperature between tests have no influence on the outcome. Variations between sensors during the same test are important and have an influence on the outcome.

4.6.1 Test 1

The first test was done with the IR camera on the same setting for all 3 shafts. The camera was left on the default setting which had an emissivity setting of 0.94.

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The setup is shown below.

This setup was used for all tests, the only difference is the cardboard box that is put over the setup in Test 2 and Test 3

Screenshot from the beginning and the end of the test are shown below.

Figure 4. 14 Test setup 1

Figure 4. 15 Left: Polished T=0; Right: Polished T=120

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0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 ₁₀ ₁₂ ₁₄ ₁₆ ₁₈ ₂₀ ₂₂ ₂₄ ₂₆ ₂₈ ₃₀ ₃₂ ₃₄ ₃₆ ₃₈ ₄₀ ₄₂ ₄₄ ₄₆ ₄₈ ₅₀ ₅₂ ₅₄ ₅₆ ₅₈ ₆₀ ₆₂ ₆₄ ₆₆ ₆₈ ₇₀ ₇₂ ₇₄ ₇₆ ₇₈ ₈₀ ₈₂ ₈₄ ₈₆ ₈₈ ₉₀ ₉₂ ₉₄ ₉₆ ₉₈ 100 102 104 106 108 110 112 114 116 118 120 Te mp era tu re (° C) Polished-B2-Max Rusted-TC Painted-TC Painted-B2-Max Polished-TC Rusted-B2-Max Painted-IR Rusted-IR Polished-IR

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The data from the first test and all the other screenshots that were taken can be found in APENDIX??. The graphs makes it easier to see the difference between the sensors

In the graph, only the values from the camera, IR sensor and the max value of box 2 are shown. This is done because box 2 doesn’t incorporate the sensors and the max value will be the value the user would want to know. If the camera reads the temperature correctly, the min and max value should be almost the same. This was done for this and all other tests done for this chapter.

From the data from the first test, several conclusions can be drawn.

The camera has problems reading the temperature of the polished shaft. If one looks at the maximum temperature of box 2, it does not get close to the temperature the thermocouple gives (an average difference of 32.2 °C in the last 10 min.). But if one look at the max temperature of box 1 and also the position of this spot. The temperature comes very close to the thermocouple temperature (an average difference of 4.1 °C in the last 10 min.). The spot where the maximum temperature is read is right on the thermocouple. The thermocouple itself is painted red and is not polished or shiny. This suggest that one only needs to stick something on a shiny object which in itself is not shiny and the temperature can be read correctly. This is what has been tested with the painted shaft.

If one looks at the painted shaft, all 3 sensors give almost exactly the same temperature. Any difference is quite steady and can be appointed to an offset in the sensors. The average difference between the max value of Box2 and the thermocouple is 0.5°C

The rusted shaft test did quite good as well, the IR sensor and IR camera have the same temperatures (an average difference of 0.2 °C in the last 10 min.). But in this case, the thermocouple is a few degreed under the other 2 sensors and it fluctuates a little. This can be caused by the rust on the shaft end. Because the rust is not nice and even like the paint is, the thermocouple can’t make 100% contact with the surface, so the measurement is a bit off.

Figure 4.19 illustrates the thermocouple making contact with an even smooth surface (left red cube) and with an uneven surface (right red cube). The thermocouple can’t get enough contact to make a good measurement on an uneven surface.

4.6.2 Test 2

The second set of tests was done with a cardboard box over the setup. And during the test, the emissivity setting was changed in order to get the temperature the same as the other sensors. The value of this setting will be shown in the graphs from each test. This test was only done with the polished shaft and the rusted shaft because the first test with the painted shaft proved that a thin layer of paint can solves the problem with emissivity.

Figure 4. 19 Illustration of contact area/surface between thermocouple and polished/rusted surface

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Figure 4. 20 Screenshot visual of test setup seen by IR Camera

Figure 4.20 shows that there is no light on the shaft end and that the measurement boxes measure the part that is in the dark.

Figure 4. 21 Left: Polished T=0; Right: Polished T=120

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0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 10 20 30 40 50 60 70 80 90 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 Em is siv ity Te m p era tu re ( °C) Time (min) TC B2-Max IR Emmisivity

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0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 10 20 30 40 50 60 70 80 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 Em is sitiv ity Te m p era tu re ( °C) Time (min) TC B2-Max IR Emmisivity

Laboratory experimental research on multi-sensor monitoring of belt conveyor idlers – Phase 2

Summary

Contents

1

Introduction

1.1 Short summary of report by van Bodegom[1]

1.2 Problems and phenomena in report by van Bodegom[1]

1.3 Outline report

1.4 Methods, procedures

1.5 Sensors

2

Repeated tests

2.1. Repeated tests

2.2 Roll defects

2.3 Repeated defect roll experiment 3

2.3.1

Temperature

2.3.2

Vibrations

2.4

Repeated defect roll experiment 5

2.4.1

Temperature

2.4.2

Vibrations

2.5

Repeated defect roll experiment 6

2.5.1

Temperature

2.5.2

Vibrations

2.6 Repeated damaged roll experiment 2

2.6.1

Temperature

2.6.2

Vibrations

2.7 Results

2.8

Conclusion

2.9

Recommendation

3

The 37.4 Hz phenomenon

3.1 Tests

3.1.1

Turning rolls

3.1.2

Natural frequency of the conveyor frame

3.1.3

Natural frequency of the rolls

3.2 Conclusion

4

The influence of emissivity

4.1 Introduction

4.2 Emissivity and the IR Camera

4.3 IR Camera

4.4 Test setup

4.4.1

Hot air gun

4.4.2

Sensors

4.4.3

DAQ + Labview + Screenshots

4.4.4

Overall setup

4.5 Different shafts

4.6 Tests

4.6.1

Test 1

4.6.2

Test 2