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

A localized hot spot on one phase connection compared to balanced phases indicates increased contact resistance from a loose or corroded connection.

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

Impact hammer testing excites the structure across a frequency range and, combined with an accelerometer, generates a frequency response function revealing resonances.

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

Large ferrous particles (>40 µm) with severe morphology indicate heavy wear modes such as adhesive or fatigue spalling, signaling impending failure.

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

The trial weight run measures how the vibration vector changes per unit of added mass, establishing the influence coefficient for calculating the correction weight.

Question 5

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

Accepted Answer

Low-speed bearing defects (<10 RPM)

Answer

Acoustic emission is highly sensitive to stress wave events regardless of speed, making it superior for detecting defects in very slow-rotating bearings where vibration amplitudes are too low.

(CRE) Certified Reliability Engineer Practice Test

(CRE) Certified Reliability Engineer Practice Test

CRE Equipment and Tools Knowledge 3