CPM Bearings, Seals, and Shaft Couplings 3

Question 1

Parallel (offset) misalignment between two coupled shafts is best described as a condition where:

Accepted Answer

The shaft centerlines are parallel but displaced laterally from each other

Answer

Parallel misalignment means both shafts point in the same direction but their centerlines are offset, so they do not lie on the same axis.

Question 2

Why is a cold alignment offset (intentional misalignment) sometimes introduced when aligning a pump-motor set at ambient temperature?

Accepted Answer

To account for thermal growth that shifts shaft centerlines once equipment reaches operating temperature

Answer

Equipment grows axially and radially as it heats up; an engineered cold offset ensures the shafts reach true alignment only after thermal equilibrium is achieved.

Question 3

A rigid coupling is the appropriate coupling choice when:

Accepted Answer

Both shafts are precisely aligned and must act as a single continuous shaft

Answer

Rigid couplings transmit torque without any flexibility; they require near-perfect alignment because they cannot tolerate misalignment without generating damaging stresses.

Question 4

In the reverse dial indicator alignment method, dial indicators are positioned:

Accepted Answer

On brackets spanning the coupling with each indicator reading the opposite shaft

Answer

The reverse indicator method uses two dial indicators mounted on opposing brackets so each indicator reads the shaft it is NOT mounted on, enabling simultaneous correction calculations for both machines.

Question 5

A torque limiter (slip coupling) is used primarily to:

Accepted Answer

Protect machinery by slipping or disengaging when torque exceeds a preset limit

Answer

A torque limiter acts as a mechanical fuse, slipping or disengaging at a preset torque threshold to prevent overloads from damaging expensive machinery.

CPM - Certified Plant Mechanic Practice Test

CPM - Certified Plant Mechanic Practice Test

CPM Bearings, Seals, and Shaft Couplings 3