CRE Equipment and Tools Knowledge 3

Question 1

In infrared thermography, an electric motor shows a hot spot on one phase connection that is 25°C above the other two phases. This most likely indicates:

Accepted Answer

A loose or high-resistance electrical connection

Answer

Normal thermal gradient during operation

Answer

Bearing overheating

Answer

Stator core lamination fault

Question 2

Which tool measures the dynamic stiffness of a machine structure to identify resonance conditions?

Accepted Answer

Impact hammer with accelerometer (modal analysis)

Answer

Tachometer

Answer

Particle counter

Answer

Clamp-on ammeter

Question 3

An oil sample shows a ferrous particle count spike with large, chunky particles (>40 µm) on a ferrograph. This pattern is associated with:

Accepted Answer

Severe sliding or fatigue wear indicating imminent failure

Answer

Normal running-in wear

Answer

Water contamination

Answer

Additive precipitation

Question 4

A portable vibration balancer requires a trial weight run to determine which quantity?

Accepted Answer

The influence coefficient (sensitivity of vibration to added weight)

Answer

Bearing defect frequency

Answer

Oil film thickness

Answer

Rotor critical speed

Question 5

Acoustic emission (AE) testing is MOST advantageous compared to vibration analysis for detecting:

Accepted Answer

Low-speed bearing defects (<10 RPM)

Answer

Mass imbalance

Answer

Gear mesh harmonics

Answer

Shaft resonance

Question 6

When performing a pump performance test, cavitation is confirmed by observing:

Accepted Answer

Reduced head and flow with increased noise and vibration at random frequencies

Answer

Increased discharge pressure and reduced current draw

Answer

Stable performance curve with elevated temperature

Answer

Higher suction pressure than design

Question 7

A torque wrench calibration certificate shows a ±4% accuracy at full scale. When tightening a critical fastener to 100 Nm at 50% full scale, the actual torque uncertainty is approximately:

Accepted Answer

±8 Nm

Answer

±4 Nm

Answer

±2 Nm

Answer

±1 Nm