Millwright Certification Lubrication Systems and Practices 2

Question 1

What is the purpose of a bearing isolator (labyrinth seal) used at bearing housings?

Accepted Answer

To retain grease inside the bearing and exclude contamination without contact friction

Answer

Bearing isolators use a non-contact labyrinth design to keep lubricant in and contaminants out without the wear associated with lip seals.

Question 2

In a forced (pressure) lubrication system, the oil pump is typically driven by:

Accepted Answer

The main machine shaft, an electric motor, or a hydraulic motor

Answer

Forced lubrication system pumps can be shaft-driven, motor-driven, or hydraulically driven depending on the machine design.

Question 3

What does ISO VG 68 indicate about a lubricating oil?

Accepted Answer

The oil has a kinematic viscosity of approximately 68 cSt at 40°C

Answer

ISO VG (Viscosity Grade) 68 specifies a midpoint kinematic viscosity of 68 cSt at 40°C, with a tolerance band of ±10%.

Question 4

Which condition indicates that lubricating oil should be changed immediately?

Accepted Answer

Oil appears dark or has a strong burnt smell and high acid number

Answer

Dark color, burnt odor, and elevated acid number (TAN) indicate oxidation and thermal degradation, meaning the oil has lost its protective properties.

Question 5

A centralized automatic grease system is most beneficial for:

Accepted Answer

Multiple lubrication points that are difficult to access or require frequent greasing

Answer

Centralized systems deliver precise grease quantities automatically to many points simultaneously, improving reliability and safety where manual access is difficult or frequent.

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Millwright Certification Lubrication Systems and Practices 2