ITMC Preventive Maintenance & Troubleshooting 2 — Questions and Answers
Question 1: A vibration analysis on a rotating shaft shows a dominant frequency at exactly 1x running speed. What is the most likely cause?
- Bearing defect
- Mass unbalance (Correct answer)
- Misalignment
- Looseness
Correct answer: Mass unbalance
A dominant vibration at 1x running speed (fundamental frequency) is the classic signature of mass unbalance in a rotating component.
Question 2: Which lubrication method is BEST suited for bearings operating at very high speeds?
- Grease packing
- Oil mist lubrication (Correct answer)
- Wick lubrication
- Splash lubrication
Correct answer: Oil mist lubrication
Oil mist lubrication delivers a fine aerosol of oil that minimizes churning losses and heat buildup, making it ideal for high-speed bearings.
Question 3: During a PM inspection, a technician finds a V-belt deflects more than the manufacturer's specification. What corrective action is required?
- Replace the belt immediately
- Increase belt tension (Correct answer)
- Decrease belt tension
- Lubricate the belt
Correct answer: Increase belt tension
Excessive deflection indicates the belt is too slack and must be tensioned to the manufacturer's specification to prevent slipping and premature wear.
Question 4: A hydraulic system is operating at lower pressure than its setpoint even though the pump is running. The FIRST component to inspect is:
- The hydraulic cylinder
- The pressure relief valve (Correct answer)
- The directional control valve
- The hydraulic filter
Correct answer: The pressure relief valve
A relief valve stuck open or set too low will bleed off pressure, causing the system to operate below setpoint.
Question 5: What does a trending increase in motor winding insulation resistance readings over several PM intervals indicate?
- Insulation is deteriorating
- Motor is operating normally
- Moisture contamination is increasing
- Insulation condition is improving (Correct answer)
Correct answer: Insulation condition is improving
Insulation resistance readings that trend upward over time indicate the insulation is drying out and improving in quality.
Question 6: A pump is experiencing cavitation. Which symptom is MOST characteristic?
- Smooth, quiet operation with low flow
- Rattling or crackling noise with erratic flow (Correct answer)
- High discharge pressure with vibration
- Overheating with no flow
Correct answer: Rattling or crackling noise with erratic flow
Cavitation produces a characteristic rattling or crackling sound caused by vapor bubble collapse, often accompanied by erratic flow and reduced performance.
Question 7: When performing a predictive maintenance thermographic scan, a hot spot is detected on one phase of a three-phase motor contactor. What does this indicate?
- Normal operating temperature differential
- A loose or high-resistance connection (Correct answer)
- The motor is overloaded
- The thermal camera needs recalibration
Correct answer: A loose or high-resistance connection
A hot spot on one phase of a contactor indicates a loose connection or high contact resistance causing localized resistive heating.
ITMC Preventive Maintenance & Troubleshooting 2
A vibration analysis on a rotating shaft shows a dominant frequency at exactly 1x running speed.
What is the most likely cause?