Detection of the Rotational Direction of a Shaft in Observer 9.1

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Dylan Welch
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Application Note Detection of the Rotational Direction of

1 Introduction In some applications, it is important to

mills, shovels and draglines, since defects are more

load. This kind of measurement can be complemented with

is, for example, operating at a certain load and

important during the collection of vibration measurement.

the time difference between two pulse measurements on a

In this case, when the difference is positive, e.g.

1 Application Note Detection of the Rotational Direction of a Shaft in Observer 9.1 Introduction In some applications, it is important to control data collection with respect to the direction of the shaft rotation. This information is crucial in applications like rolling mills, shovels and draglines, since defects are more visible in a vibration spectra when the machine is under load. This kind of measurement can be complemented with gating (see application note CM3175, Gating Set up in Observer 9.1) to be able to collect vibration data when the machine is, for example, operating at a certain load and rotational speed. A shovel loading a haul truck. A dragline in operation. Fig. 1. Example of machines where the rotational direction is important during the collection of vibration measurement. To measure the rotational direction, we are going to use the time difference between two pulse measurements on a disc (see fig. 2). In this case, when the difference is positive, e.g., pulse 2 is later than pulse 1, the direction is forward. When the difference is negative, e.g., pulse 1 is later than pulse 2, the direction is reverse. The result of the measurement can directly be used in a vibration measurement as a condition when to take the measurements.

Procedure Step 1: Install two tachometers for measuring the rotational speed and one trigger point on the rotating disc. The two tachometers shall be close to each other.

Step 2: Initiate an SKF Multilog IMx device and create two digital channels, and then create two measurement points for the rotational speed of the shaft. 1.

2 Procedure Step 1: Install two tachometers for measuring the rotational speed and one trigger point on the rotating disc. The two tachometers shall be close to each other. See the laboratory set up in fig. 2. The trigger point on the rotating disc Tacho 1 Tacho 2 The two "Tachometers" will detect the rotational direction of the shaft Fig. 2. Mounting of the tachometers and the trigger point on a grinding machine. Step 2: Initiate an SKF Multilog IMx device and create two digital channels, and then create two measurement points for the rotational speed of the shaft. 1. Digital channels: Go to the main menu, in fig. 3a, and choose "On-line", and then select "IMx/MasCon devices". The window in fig. 3b will be opened. Then click the Initiate button in the area called "Digital channels" to create the two digital channels in figs. 4a and 4b. These channels are called "Rot. speed 1" and "Rot. speed 2". Select "On-line" in the main menu and then "IMx/MasCon devices" to open the window in fig. 3b. Fan 1 Fig. 3a. Select "IMx/MasCon devices" in the drop down menu. 2

The "IMx/MasCon devices" window for set up of an IMx device and channels. Digital ch. 1 Digital ch. 2 1 pulse per rev.

3 IMx devices Analogue channels The created IMx-S device called "IMx_1" is highlighted Digital channels Press Initiate to create an IMx device Press Initiate to create a "Digital" channel for the rotational speed of the shaft Fig. 3b. The "IMx/MasCon devices" window for set up of an IMx device and channels. Digital ch. 1 Digital ch. 2 1 pulse per rev. 1 pulse per rev. Fig. 4a. Set up of digital channel 1 for the measurement point "Rot. Speed 1". Fig. 4b. Set up of digital channel 2 for the measurement point "Rot. Speed 2". 3

2. Create a "Speed (IMx)" measurement point for each "Digital channel" in figs. 4a and 4b. Right-click on the machine "Fan 1" in fig. 3a. A drop down list will be visible.

4 2. Create a "Speed (IMx)" measurement point for each "Digital channel" in figs. 4a and 4b. Right-click on the machine "Fan 1" in fig. 3a. A drop down list will be visible. Then click on the option "Add" and select "Meas. Point" to view the window called "New meas. point" in fig. 6. Select the measurement point called "Speed", which is marked with a green circle. The window in fig. 5a will then be opened. Add an IMx device and the earlier created digital channel "Rot. speed 1". In this case, an IMx-S unit called "IMx_1" was selected. Repeat the procedure for the second measurement point called "Rot. speed 2." Note: See Step 5 to learn about which of the digital channels in the IMx that can be used for this application. The measurement point for measuring the rotation of the shaft is called "Speed (IMx)" Add an IMx device and a Digital channel for the rotational speed (ch. 1) Rot. speed 1 Fig. 5a. Set up of the rotational speed of the shaft on digital channel 1. Point type Speed (IMx) Add the same IMx device and a second Digital channel for the rotational speed (ch. 2) Rot. speed 2 Fig. 5b. Set up of the rotational speed of the shaft on digital channel 2. 4

Step 3: Create and configure a "Time difference" measurement point (in red) to calculate the time difference between the two trig pulses from the tachometers

Time difference (IMx) measurement point Rot. Speed 1 Rot. Speed 2 The two measurement points for the rotational speed in figs.

5 Step 3: Create and configure a "Time difference" measurement point (in red) to calculate the time difference between the two trig pulses from the tachometers (see figs. 6 and 7). Vibration and Time waveform measurement Trend based measurement points Fig. 6. Select the "Time difference" measurement point. Time difference (IMx) measurement point Rot. Speed 1 Rot. Speed 2 The two measurement points for the rotational speed in figs. 5a and 5b have been added to the "Time difference" measurement point. Fig. 7. Configuration of the "Time difference (IMx)" measurement point for the "Detection of the rotational direction of the shaft. 5

Step 4: A Dynamic vibration measurement point has to be created to be able to trend the time difference, see fig. 6. For this purpose, a vibration sensor has to be selected on the machine.

6 Step 4: A Dynamic vibration measurement point has to be created to be able to trend the time difference, see fig. 6. For this purpose, a vibration sensor has to be selected on the machine. This can be any vibration sensor on the machine. In this case, the dynamic measurement point Motor NDE was selected on the machine Fan 1 (see fig. 8). In the "Simultaneous measurements" section on the Acquisition tab (in blue), one of the "Rotational speed points needs to be selected as a Speed meas. It doesn t matter which one you select. In this case, the Speed measurement point called Rotational speed 1 was selected (see fig. 9). In the "Simultaneous measurements", a process point called Direction of rotational direction of the shaft has to be selected as a Process meas. in the "Simultaneous measurements". These two settings are marked with a red box in fig. 9. See also the necessary settings for the "Active range" on the Operating and Storage Conditions tab (in green) in fig. 10. In the example in fig. 10, the measurement data are only collected when the operating conditions are met. If the rotational direction point is included in the conditions, the collection of data will only take place in one of the directions. Note: If the data also needs to be collected in the other direction, a second vibration measurement point must be created. The vibration measurement point Motor NDE! Fig. 8. Create a vibration measurement point. 6

Select a vibration point on your machine, and also select one of the rotational speed measurement points, plus the process measurement point, which in this case is called Direction of rotational

7 Select a vibration point on your machine, and also select one of the rotational speed measurement points, plus the process measurement point, which in this case is called Direction of rotational direction of the shaft! A frequency range and number of lines must be selected for the vibration spectra, even if it is not used for this application. The "Rotational speed 1" is selected as a simultaneous measurement, together with the "Process meas." called "Detection of rotational direction of shaft". Fig. 9. A vibration point is created for configuring of the "Active range" settings on the "Time difference" measurement point on the "Operating and Storage Conditions" tab". 7

8 In this case, the direction of rotation is counter clockwise, but if we configure as +2 to 0, the direction of the rotation would be in the clockwise direction. In this case, data is collected in the speed range of 800 to 1100 RPM. Fig. 10. An example of a condition when data is collected on the machine. 8

9 Step 5: Configure the hardware (HW) settings on the I/O board in the IMx-S device, for the sensor in fig. 2. In table 1, this sensor is called Tacho 2-wire. The digital inputs 1 to 4 (Dig 1 to Dig 4) can be configured via the DIP switches on the I/O board. The DIP switches for the sensors must be set according to table 1. The sensor that was used in fig. 2 is marked with a red box in table 1. This digital sensor input is called Tacho 2-wire. The digital inputs 5 to 8 are non-configurable inputs. They are only used for externally powered sensors, with a pulse level of 12 to 24 V; see the black box in table 2. Note: The shape of the signal has to be a square wave. The DIP switches on the I/O board for Digital inputs 1-4 are marked with a red box. DIG 1-4 Digital input 1-4 Digital input 5-8/RS485 Dig1 A 49 Dig1 B Digital channels 1-4 Internally powered by the IMx device. Dig1 O Dig2 A Dig2 B Dig2 O Dig3 A Dig3 B Dig3 O Dig4 A Dig4 B Dig4 O Dig5 A 61 Digital channels 5-8 Externally powered! No DIP switches exist. Dig5 B Dig6 A Dig6 B Dig7 A Dig7 B Dig8 A Dig8 B N.C. RS485 A RS485 B GND Fig. 11. The digital inputs 1-8 on the IMx-S I/O board. 9

10 Signal Tacho 2-wire (24 V internally powered, max 30 ma) Tacho 3-wire NPN (24 V internally powered, max 30 ma) Tacho 3-wire PNP (24 V internally powered, max 30 ma) Pulse V (external power) Pulse TTL (external power) + N.C. Terminal Brown (+24 V) Black (Signal) Blue (0 V) Brown (+24 V) Black (Signal) Blue (0 V) + N.C. N.C. + A B 0 A B 0 A B 0 A B 0 A B 0 DIP Settings position: Tacho 2-wire was the selected sensor in fig. 2. Table 1. The IMx terminal list for the internally powered Digital inputs 1-4 DIP switch setting for digital sensors. Signal Pulse V (external power + Terminal A B Table 2. The IMx terminal list for the externally powered Digital inputs 5 to 8. Note: Please also refer to the SKF Multilog IMx-S User Manual if needed. 10

11 Step 6: There is a positive and a negative time difference for this type of measurement (see fig. 12). For the set up in this example, a positive time difference corresponds to a clockwise direction of the shaft, and a negative time difference corresponds to a counter clockwise direction of the shaft. NOTE. This observation of the rotational direction needs to be done by the person who set up the system. When you start up the system, you need to make a note which direction corresponds to the + or sign in the trend. In this case, the rotational direction of the shaft has a positive (+) time difference between the two trig pulses in fig. 2. In the opposite direction, the time difference has negative ( ) time difference between the two trig pulses. Fig. 12. The trend diagram for the time difference measurement point. 11

12 Seals Mechatronics Bearings and housings Services Lubrication systems The Power of Knowledge Engineering Combining products, people, and applicationspecific knowledge, SKF delivers innovative solutions to equipment manufacturers and production facilities in every major industry worldwide. Having expert ise in multiple competence areas supports SKF Life Cycle Management, a proven approach to improv ing equipment reliability, optimizing operational and energy efficiency and reducing total cost of ownership. These competence areas include bearings and units, seals, lubrication systems, mecha tronics, and a wide range of services, from 3-D computer modelling to cloud-based condition monitoring and asset management services. SKF s global footprint provides SKF customers with uniform quality standards and worldwide product availability. Our local presence provides direct access to the experience, knowledge and ingenuity of SKF people. Please contact: SKF Condition Monitoring Center Luleå Aurorum 30 SE Luleå Sweden Tel: +46 (0) Fax: +46 (0) Web: SKF are registered trademarks of the SKF Group. All other trademarks are the property of their respective owners. SKF Group 2014 The contents of this publication are the copyright of the publisher and may not be reproduced (even extracts) unless prior written permission is granted. Every care has been taken to ensure the accuracy of the information contained in this publication but no liability can be accepted for any loss or damage whether direct, indirect or consequential arising out of the use of the information contained herein. PUB CM3190/1 EN June 2014

Machine Diagnostics in Observer 9 Private Rules

Machine Diagnostics in Observer 9 Private Rules Application Note Machine Diagnostics in SKF @ptitude Observer 9 Private Rules Introduction When analysing a vibration frequency spectrum, it can be a difficult task to find out which machine part causes