433A Mechanical Drives and Bearings 4

Question 1

What is the purpose of crowning on a conveyor pulley?

Accepted Answer

To track and center the belt on the pulley

Answer

A crowned (slightly larger diameter at center) pulley causes the belt to self-center by creating a tracking force. The belt naturally migrates toward the highest point of the crown.

Question 2

When coupling two shafts with a jaw coupling, what is the purpose of the elastomeric spider insert?

Accepted Answer

To provide electrical insulation and absorb shock and vibration

Answer

The elastomeric spider insert in a jaw coupling provides electrical isolation between shafts, absorbs shock loads and vibration, and accommodates minor misalignment while transmitting torque.

Question 3

What condition is indicated by a blue discoloration on a bearing race?

Accepted Answer

Overheating has occurred

Answer

Blue or straw-colored discoloration on bearing races indicates that the bearing has been subjected to excessive heat, typically above 200°C. This overheating compromises the bearing's hardness and load capacity.

Question 4

In a chain drive system, what is the effect of excessive chain sag on the slack side?

Accepted Answer

Chain whip causing vibration and accelerated wear

Answer

Excessive chain sag on the slack side causes chain whip — a whipping motion that generates vibration, increases dynamic loads on sprockets and shafts, accelerates wear, and can cause the chain to jump off the sprockets.

Question 5

What is the purpose of a shaft seal (oil seal) adjacent to a bearing?

Accepted Answer

To retain lubricant and exclude contaminants from the bearing

Answer

Shaft seals serve the dual purpose of retaining lubricant within the bearing housing and preventing external contaminants such as dirt, moisture, and process materials from entering and damaging the bearing.

Red Seal Millwright 433A Practice Test

Red Seal Millwright 433A Practice Test

433A Mechanical Drives and Bearings 4