CAT III Activity Book PDF

Activity book Activity book CAT III Activity book Page 21 CONDITION MONITORING TECHNOLOGIES 1. What types of sound are we normally detecting when we employ ultrasound testing? a. Loud sound...

Activity book Activity book CAT III Activity book Page 21 CONDITION MONITORING TECHNOLOGIES 1. What types of sound are we normally detecting when we employ ultrasound testing? a. Loud sound b. High frequency sounds c. Low frequency sounds 2. How is ultrasound able to detect a lack of lubrication in a bearing? ____________________________________________________________________________________ ____________________________________________________________________________________ 3. Can ultrasound testing be used in combination with a vibration analysis program? a. No, it is unnecessary to do both b. Yes, ultrasound testing can be used to detect faults that vibration cannot detect 4. Name four fault conditions that can be detected by ultrasound testing: ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 5. Does a thermography camera measure temperature? a. Yes b. No 6. Does thermography provide an early warning (months in advance) of bearing wear? a. Yes b. No 7. Can thermography be used to provide an indication of an electrical short circuit? a. Yes b. No [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 22 CAT III Activity book 8. Is it important to be able to take an accurate temperature measurement? a. Yes - accuracy is always important b. No - a relative temperature reading can also be useful c. No - temperature is not important in thermography 9. Which environmental conditions should you avoid when performing infrared readings? ___________________________________________________________________________________ ___________________________________________________________________________________ 10. Which condition monitoring techniques can be used on electric motors? a. Thermography b. Oil/grease analysis c. Vibration analysis d. Motor current analysis e. All of the above 11. Which of the following fault conditions can be detected with motor current analysis? a. Damaged bearings b. Broken rotor bars c. Unbalanced power supply d. Mechanical unbalance 12. Name two types of faults that can be detected with motor circuit analysis: ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 13. What is the main benefit of performing oil analysis? a. Detecting the presence of wear in the machine b. Detecting whether the oil has the required properties necessary to lubricate the machine correctly c. Detecting whether misalignment is causing the oil to become hot d. Detecting whether the machine is running low on oil [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 23 14. Does standard oil analysis detect the large particles that are generated when wear occurs? a. Yes b. No 15. Approximately what size of particle can standard oil analysis detect? a. Up to 4 μm b. Up to 10 μm c. Up to 20 μm d. All sizes 16. Why is wear particle analysis important? a. Because it can tell you about the condition of the lubricant b. Because it can tell you if there is excessive wear in the machine c. All of the above 17. If you are performing standard oil analysis, is it necessary to perform wear particle analysis? a. Yes, you should always perform wear particle analysis b. Yes, but only if the application will benefit from wear particle analysis c. No, you can learn enough from oil analysis 18. On what type of machine component is wear particle testing essential? a. Motors with belt drives b. Centrifugal pumps c. Gearboxes d. Fans and blowers [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 24 CAT III Activity book SIGNAL PROCESSING Useful information: N N lines T = Ts × N = = = FS 2.56 × Fmax Fmax T = Time required to collect the waveform Ts = Time between each sample Fs = Sampling rate = Samples per second N = Number of samples (1024, 2048, 4096, etc.) Fmax Resolution = lines Bandwidth = Resolution × Window factor Window factor = 1 (no window/uniform/rectangular) or 1.5 (Hanning window) Separating frequency ≥ 2 x Bandwidth ≥ 2 x Resolution * Window Factor Required spectral lines ≥ 2 x Window factor x Fmax / Separating frequency Accuracy of frequency (at peak) = ± ½ x Resolution [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 25 1. Why can the integration process create a signal-to-noise problem? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 2. What is the difference between analog integration and digital integration? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 3. What precautions should be taken when testing low speed machines (below 3 Hz or 180 RPM)? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 4. Name three applications where one might use triggering (external signal to trigger a measurement or external tachometer signal for synchronization). ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 5. If the record length is 2 seconds, and there are 1024 samples in the time waveform, what is the Fmax? a. 200 Hz b. 400 Hz c. 800 Hz d. 1600 Hz [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 26 CAT III Activity book 6. If the Fmax is 10,000 Hz and a 1600 line spectrum, how long does it take to sample the vibration signal with one average only? a. 0.16 seconds b. 1.6 seconds c. 16 seconds d. 6.25 seconds 7. If the Fmax is 160 Hz, 3200 line spectrum, how long does it take to sample the vibration signal with 10 averages (no overlap)? a. 0.05 seconds b. 0.5 seconds c. 20 seconds d. 200 seconds 8. If the Fmax is 160 Hz, 3200 line spectrum, how long does it take to sample the vibration signal with 10 averages and 50% overlap? a. 100 seconds b. 110 seconds c. 200 seconds d. 20 seconds 9. A machine will generate key vibration signals of 100 Hz and 100.50 Hz, suggest an Fmax setting and corresponding lines of resolution setting to resolve these two frequencies (assume that a Hanning window will be used): ____________________________________________________________________________________ ____________________________________________________________________________________ 10. What is the difference between dynamic range and signal to noise ratio? ____________________________________________________________________________________ ____________________________________________________________________________________ 11. Name 5 common windows and their applications ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 27 12. Leakage is caused by: a. Noise in the time waveform b. A low sample rate c. Poorly shielded cables d. The signal does not begin and end at zero in the time record 13. Explain the benefits of overlap averaging? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 14. What factors should you consider when selecting the number of averages (for normal testing and linear averaging)? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 15. What are three applications for peak hold averaging? ____________________________________________________________________________________ ____________________________________________________________________________________ 16. What are 3 ways to deal with testing variable speed machines? ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 28 CAT III Activity book TIME WAVEFORM ANALYSIS 1. Name three fault conditions that can be diagnosed via time waveform analysis. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 2. Name four phenomena that can be observed in the time waveform. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 3. A 1500 RPM motor is driving a pump via a gearbox with 40 teeth on the input gear. What Fmax and LOR setting will allow one to see three harmonics of the gear mesh frequency in the spectrum and 5 rotations of the gear in the time waveform? ____________________________________________________________________________________ ____________________________________________________________________________________ 4. A 1500 RPM motor is driving a pump via a gearbox with 40 teeth on the input gear. What Fmax setting is required in order to be able to clearly see each tooth mesh in the time waveform? ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 29 5. What is the approximate frequency of the dominant event in this time waveform? a. 0.63 Hz b. 6.7 Hz c. 24.7 Hz d. Not enough information 6. Why is time waveform analysis so important when performing vibration analysis on gearboxes? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 7. Why is time waveform analysis useful when performing vibration analysis on rolling element bearings? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 30 CAT III Activity book 8. Why is time waveform analysis useful when a pump is cavitating? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ PHASE ANALYSIS 1. Name three reasons why the peak value of the vibration signal does not coincide perfectly with the passing of the point of greatest mass in the rotor by the sensor? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 2. Machine balancing: What would happen if we performed an ‘original run’, using an accelerometer (mounted in-line with the tachometer), and measured a vibration reading of 0.5 G's and a phase angle of 0° and then placed the trial weight opposite the tachometer (i.e. 180°)? (Assume a rigid rotor and a trial weight with enough mass to significantly affect the vibration reading.) a. The vibration level would decrease b. The vibration level would increase c. The vibration reading would not change d. Not enough information 3. What happens to the phase angle as a machine speed is increased towards the first critical speed? a. Nothing b. Nothing until the machine speed reaches the critical speed; then it shifts by 180° c. It decreases d. It increases 4. What is the difference between relative phase and absolute phase? ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 31 5. What are two benefits of relative phase? ____________________________________________________________________________________ ____________________________________________________________________________________ For the following questions the relative vibration levels can be interpreted as follows: High vibration: Low vibration: NOTE: For your own benefit, try to answer these questions before referring to the training manual 6. Which fault condition is indicated by the following bubble diagram? ___________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 32 CAT III Activity book 7. Which fault condition is indicated by the following bubble diagram? ___________________ 8. Which fault condition is indicated by the following bubble diagram? ___________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 33 9. Which fault condition is indicated by the following bubble diagram? ___________________ 10. Which fault condition is indicated by the following bubble diagram? ___________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 34 CAT III Activity book 11. Which fault condition is indicated by the following bubble diagram? ___________________ 12. Which fault condition is indicated by the following bubble diagram? ___________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 35 SYSTEM DYNAMICS 1. Name three types of damping ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 2. Provide examples of damping in rotating machinery ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 3. In the following equation, what does ‘k’ represent? f (t )  kx  cv x  mx a. Stiffness b. Damping c. Mass 4. In the following equation, what does ‘cv’ represent? f (t )  kx  cv x  mx a. Stiffness b. Damping c. Mass 5. In the following equation, what does ‘m’ represent? f (t )  kx  cv x  mx a. Stiffness b. Damping c. Mass [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 36 CAT III Activity book 6. In the following equation, what does ‘x’ represent? f (t )  kx  cv x  mx a. Displacement b. Velocity c. Acceleration 7. In the following equation, what does ‘𝒙’ represent? f (t )  kx  cv x  mx a. Displacement b. Velocity c. Acceleration 8. In the following equation, what does ‘𝒙’ represent? f (t )  kx  cv x  mx a. Displacement b. Velocity c. Acceleration 9. If you performed a Bodé plot and you noticed that amplitude was high in a certain speed range but the phase did not change substantially, what would you conclude? a. There definitely is a resonance b. There definitely is NOT a resonance c. There probably is not a resonance [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 37 10. If you performed a run-down test (as shown below) and saw that the amplitude was high in a certain speed range and the phase did change by 180°, what would you conclude? a. There definitely is a resonance b. There definitely is NOT a resonance c. There probably is not a resonance 11. If you performed a rundown test and witnessed a Bodé plot as described in the previous question, and then repeated the test two weeks later to find that the natural frequency was higher than it was previously (but the amplitude at the natural frequency had not changed substantially), what would you conclude? a. The machine was running at a higher speed b. Bracing had been added to increase the stiffness c. Sandbags or some other form of weight was added to the machine d. Someone must have added damping to the machine 12. Based on the test data in question 10, would you say the machine was lightly damped or heavily damped? a. Lightly damped b. Heavily damped 13. If you noticed that the 1x vibration in a horizontally oriented motor was much higher (>4X higher) in the horizontal direction than the vertical direction, what would you conclude? a. The machine (or the structure supporting the machine) must have a resonance that causes it to vibrate in the horizontal direction b. The structure supporting the machine must be weak or loose in the horizontal direction. c. Either A or B could be correct. Additional tests would be required to distinguish between these two possible fault conditions. [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 38 CAT III Activity book 14. Is the following shape the first, second, or third bending mode? a. First bending mode b. Second bending mode c. Third bending mode 15. How many nodes does this mode shape have? a. 1 b. 2 c. 3 d. 4 16. How many anti-nodes does this mode shape have? a. 1 b. 2 c. 3 d. 4 [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 39 17. Is the value of zeta ζ marked by “A” more likely to be 0.05, 0.5 or 1.0? a. 0.05 b. 0.5 c. 1.0 OPERATING DEFLECTION SHAPES (ODS) 1. What method of data capture must you use if you wish to visualize the motion (deflection shape) at multiple frequencies (not just running speed)? ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 40 CAT III Activity book 2. What is the main difference between ODS and modal analysis? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 3. What are the primary reasons to perform an ODS test? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 4. When performing an ODS test with two accelerometers, what precautions should you take when selecting the location of the reference accelerometer? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 5. When performing an ODS test with two accelerometers, what precautions should you take when selecting the location of the ‘roving’ accelerometer? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 41 6. Can you perform an ODS test on a machine that is frequently changing speed and load? Explain your answer. a. Yes b. No ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 7. How does time-based ODS differ from frequency-based ODS? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ MODAL ANALYSIS 1. What does the coherence measurement tell you? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 2. When performing a modal test, what precautions should one take when selecting the location of the reference location? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 42 CAT III Activity book 3. When performing a modal test, what precautions should you take when selecting the location of the ‘roving’ accelerometer? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 4. What is the Frequency Response Function? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 5. Name two different ways to perform a modal analysis test. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 6. Describe the important characteristics of the hammer used in the impact test. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 43 7. Describe an important precaution that must be taken when impacting a structure (beyond not damaging the structure). ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 8. When performing a modal test with a force hammer, what plots does one typically want to look at for each test point? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ CORRECTING RESONANCES AND REDUCING VIBRATION 1. If it was determined that the speed of a machine coincided with a natural frequency, name four possible courses of action to deal with the situation. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 2. If it was determined that a structure had a natural frequency close to the running speed of the machine, and it was not possible to change the speed of the machine, what precautions would you take when designing your structural modifications? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 44 CAT III Activity book 3. Two different structures were tested and their Bodé plots are displayed below. Which structure has the highest ‘Q’? a. Machine 1 b. Machine 2 4. What is a tuned absorber? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 5. Why aren’t tuned absorbers well suited to machines that vary in speed? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 6. Why or when is isolation used? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 45 7. Are isolators designed so that their natural frequency is above, equal to, or below the running speed of the machine? a. Below machine running speed b. Equal to the running speed c. Above the running speed 8. When a machine is mounted on isolators or resilient mounts, what can happen when the machine starts up (or is run-down)? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 9. What issues have to be taken into account when specifying isolators? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 46 CAT III Activity book ROLLING ELEMENT BEARING ANALYSIS 1. With the inner race spinning, an inner race defect will typically produce a. A non-synchronous peak b. A non-synchronous peak with harmonics c. A non-synchronous peak with harmonics and shaft rate sidebands d. A sub synchronous peak 2. Name four root causes of rolling element bearing wear. ____________________________________________________________________________________ ____________________________________________________________________________________ 3. Describe the progression of rolling element bearing wear from the earliest stages up to failure in the ideal case ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 4. Describe the four recommendations made in the course regarding how to utilize demodulated data and how this relates to making repair recommendations. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 5. Describe the general patterns produced by the inner race, outer race and ball / roller faults. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 47 JOURNAL BEARING ANALYSIS 1. Does the voltage output of the non-contact eddy current (proximity) probe increase or decrease as the shaft is moved closer to the probe? a. Increase b. Decrease c. Will not change 2. What is the purpose of slow-roll subtraction (glitch removal)? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 3. Which measurement, A or B, represents an eccentricity ratio of 0.8 (approximately)? a. Measurement A b. Measurement B [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 48 CAT III Activity book 4. Given the following centerline diagram where would the center of the shaft normally be located when the machine is at rest? a. Position A b. Position B c. Position C d. Position D e. Position E 5. What is the difference between the ‘direct’ and ‘filtered’ signal? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 6. Describe the vibration precession of an orbit. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 49 7. When using a conventional data collector to perform orbit analysis, would you normally set your data collector to low resolution (e.g. 100 lines) or high resolution (e.g. 1600 lines)? a. Low resolution b. High resolution c. It is an orbit, it does not matter 8. What does a circular orbit indicate? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 9. What does it mean if the filtered orbit is heavily elliptical? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 10. What does it mean if the orbit is distorted or twisted? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 50 CAT III Activity book 11. List 5 common fault conditions in journal bearings. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ELECTRIC MOTORS 1. An eccentric stator (with an uneven stationary air gap) will produce... a. a high 1X peak at the motor running speed b. increased amplitude at twice line frequency c. harmonics of 1X with pole-pass sidebands d. sub synchronous vibration 2. An eccentric rotor (with a varying air gap) will produce... a. a high 1X peak at the motor running speed b. a peak at the rotor bar frequency with twice line-frequency sidebands c. increased amplitude at twice line frequency, with pole-pass sidebands d. harmonics of 1X with pole-pass sidebands 3. A cracked rotor bar will produce... a. a high 1X peak at the motor running speed b. a peak at the rotor bar frequency with twice line-frequency sidebands c. increased amplitude at twice line frequency, with pole-pass sidebands d. harmonics of 1X with pole-pass sidebands 4. Loose rotor bars will produce... a. a high 1X peak at the motor running speed b. a peak at the rotor bar frequency with twice line-frequency sidebands c. increased amplitude at twice line frequency, with pole-pass sidebands d. harmonics of 1X with pole-pass sidebands 5. In a motor running at 1740 RPM. What is the pole pass frequency? a. 60 RPM b. 120 RPM c. 120 Hz d. 240 RPM [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 51 GEARBOX ANALYSIS 1. What are the first 10 prime numbers? ____________________________________________________________________________________ ____________________________________________________________________________________ 2. If the input gear has 31 teeth and the output gear has 19 teeth, what are the common factors? a. 1 b. 1, 31 and 19 c. 1, 3, and 11 d. There are none – they are prime numbers 3. If the input gear has 30 teeth and the output gear has 18 teeth, what are the common factors? a. 1 b. 1, 2, 3 c. 1, 2, 5 d. 1, 2, 3, 5 4. If the input gear has 30 teeth and the output gear has 18 teeth, what is the gear assembly phase frequency (as a multiple of running speed)? a. 1X b. 5X c. 18X d. 30X 5. The input gear has 30 teeth and the output gear has 18 teeth. If one tooth is damaged on the gear with 18 teeth, how many teeth will eventually be damaged on each of the gears? a. All of them b. 9 on the 18 tooth gear and 15 on the 30 tooth gear c. 2 on the 18 tooth gear and 3 on the 30 tooth gear d. 3 on the 18 tooth gear and 5 on the 30 tooth gear 6. If the input gear has 30 teeth and the output gear has 18 teeth, what is the hunting tooth frequency (as a multiple of running speed)? a. 0.33X b. 0.11X c. 0.6X d. 30X [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 52 CAT III Activity book 7. If the input gear has 28 teeth and the output gear has 24 teeth, what is the product of the common prime factors? a. 2 b. 4 c. 12 d. 28 8. What are the three common configurations of a planetary gear? ____________________________________________________________________________________ ____________________________________________________________________________________ 9. What are some common vibration tests (include data formats) that are used for analyzing gearboxes? What technologies besides vibration analysis are useful? ____________________________________________________________________________________ ____________________________________________________________________________________ 10. If a worm gear has an input speed of 30 Hz and an output speed of 10 Hz and the worm wheel has 40 teeth, how many flights are there? a. 7.5 b. 13.3 c. 120 d. 0.75 11. If the Fmax was 4000 Hz, and the resolution was set to 800 lines, how many time samples would be acquired per tooth mesh if the input speed of the gearbox was 30 Hz and the pinion had 33 teeth? How many revolutions of the input gear would be present in the time waveform? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 53 BALANCING 1. If vibration readings indicated a high displacement vibration reading at 30° should you place the trial weight at 210°? a. Yes, that will balance the machine b. It depends whether the machine has a rigid or flexible rotor, and whether the machine is being operated anywhere near the natural frequency. c. No, it should be placed at 30° d. No it should be placed at 120° 2. If a rotor (supported by two bearings, one at each end) that normally turns at 1800 RPM weighed 90 kg and we had to place balance weights at a radius of 350 mm, which of the following available balance weights would you use as a trial weight? (Note: W is in grams) a. 4 kg b. 40 grams c. 4 grams d. 24 grams [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 54 CAT III Activity book 3. Explain what the ‘O’, ‘T’ and ‘O+T’ vectors represent. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 55 4. What is the magnitude of the sum of the following vectors: 4 mils at 60 degrees and 3 mils at 150 degrees ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 5. The original run is 4 mils at 60 degrees. A 1 ounce balance weight is added at 60 degrees. The trial run results in a vector of 3 mils @ 150 degrees. Calculate the final balance weight and angle. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 6. You need to place a balance weight of 10 grams at 30 degrees but you only have holes available at 0 degrees and 45 degrees. How much weight must be put in each of these holes? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com Page 56 CAT III Activity book DIAGNOSING MACHINE FAULTS 1. What is wrong with this machine? Please briefly explain why you have come to this conclusion. (Note that the L and R phase readings are axial readings taken on the left and the right of the shaft. The axial phase readings have been adjusted – as if they were all taken in the same direction.) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com CAT III Activity book Page 57 2. What is wrong with this machine? Please briefly explain why you have come to this conclusion. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ [email protected] Copyright ©2020 Mobius Institute www.mobiusinstitute.com This page left intentionally blank