Q1. Name any five (5) effects of equipment failure.
Q2. a) Which condition monitoring method(s) is (are) most appropriate for monitoring the following conditions:
i. Resonance
ii. Misaligned machines
iii. Loose/corroded electrical connections
iv. Worn bearings
v. Mechanical looseness
vi. Unbalance of rotating parts
vii. Contamination of lubricant
b) There are four different maintenance philosophies. Which of them is the least effective and why?
Q3. Critical Question. This Critical question is mandatory. It should be answered and students are expected to get this question completely right to be assessed as competent with a score for this module.
Would the following vibrations be caused by a natural frequency or a forced frequency?
a) Pluck a guitar string
b) Misalignment between a motor and pump
c) A worn gear
d) Ringing of a bell
e) Machine tool chatter
Q4. Why vibrations are usually measured on the bearings of a machine?
Q5. a) You note high vibration levels at 1 x rpm on a machine in your plant. What are the probable causes and how can you distinguish between them?
b) What are the disadvantages of using hand-held probes for vibration monitoring?
Q6. a) An analyser is set to a maximum frequency of 80,000cpm. If the bandwidth is 200cpm/line, what would the resolution of the analyser be?
b) What is the advantage of using magnets for vibration sensor mounting? Why does the use of commercially available double adhesive tapes result in distorted measurements?
Q7. This question has two options. If you have the equipment specified in option A then you can perform the test/s required. However, if you don't have the necessary equipment then answer the question in Option B.
You are not required to complete both options!
Option A -
i. Use a phototachometer to measure the rotational speed of a given shaft. Validate the findings using a stroboscope.
ii. Record the measurements at different shaft speeds and repeat the same set of procedures for another shaft.
Option B -
i. What is a phototachometer and why would you use it to measure the rotational speed of a given shaft?
ii. What is a stroboscope and what are the benefits of using a stroboscope to validate the findings?
iii. Why would you record the measurements at different shaft speeds?
Q8. What are the basic requirements of a precision maintenance?
Q9. Discuss the root cause of breakdown.
Q10. How would you differentiate between the vibration signatures of parallel and angular misalignment?
Q11. A vibration analysis on an electric motor shows significant radial vibrations at 1x, 2x, 3x, 4x the running speed of the motor. A particularly predominant peak shows near 12,000 cpm. If the motor has 4 rotor bars and runs at 2940rpm what would you suspect the problem to be and how would you confirm your suspicions?
Q12. Distinguish between misalignment and unbalance.
Q13. List some of the maintenance actions that may affect balancing.
Q14. Which are the locations that are normally preferred for weight addition and removal in balancing?
Q15. What is centrifugal force with respect to unbalance? What is the formula used to determine centrifugal force?
Q16. What conditions should be met for taking up Two-plane balancing after Single-plane balancing was proven unsuccessful? What other important assumption is made in this method?
Q17. Why are overhung rotor configurations in pumps and fans difficult to balance?
Q18. Why do overhung rotors need to be balanced on or near resonance?
Q19. What are the four fundamental principles attached to the reverse-dial method? Also state the limitations of this method.
Q20. a) What is meant by shaft to shaft alignment?
b) Discuss the term coupling tolerance.
Q21. a) Briefly describe performance monitoring and how it can be used to monitor the condition of equipment.
b) With reference to machinery, what is TLC?
Q22. a) What are the three main aspects associated with an oil analysis program?
b) List three (3) advantages and three (3) disadvantages of thermographic imaging.
Q23. Critical Question. This Critical question is mandatory. It should be answered and students are expected to get this question completely right to be assessed as competent with a score for this module.
Plant/factories typically contain equipment that can be classified as critical, essential or general-purpose. List two (2) relevant factors under each classification that help catagorise the equipment.
Q24. You balanced a pump impeller by placing a 5 gram weight at a radius of 100 mm. The original vibration amplitude was 10 mm/s, and after adding the balancing weight, the vibration is 1 mm/s. The speed of the pump is 1500 rpm and the weight of the impeller is 3 kg.
a) Calculate the residual unbalance, the eccentricity and the balancing quality grade according to ISO balancing standard.
b) The stiffness of the pump's shaft is 80 kN/m. Calculate the natural frequency for the pump impeller on the shaft (ignore the weight of the shaft).
c) What is going to happen if the pump speed is increased to 1560 rpm?
Q25. Consider the small high-speed pump setup below (measurements in mm). This was one of three new pumps at a water wastewater plant. Alignment must be done on the system using the reverse method of alignment, especially since the pumps operate at a higher speed.
The following measurements were made (motor = dial indicator reading on indicator closest to motor, pump = dial indicator reading on indicator closest to pump):
Using these readings, suggest shims and left-right moves on the machine in order to align it.
