Bearings, Seals, and Shaft Couplings Flashcards
7 cards from real CPM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Bearings, Seals, and Shaft Couplings flashcards as text
Parallel (offset) misalignment between two coupled shafts is best described as a condition where:
Answer: The shaft centerlines are parallel but displaced laterally from each other
Parallel misalignment means both shafts point in the same direction but their centerlines are offset, so they do not lie on the same axis.
Why is a cold alignment offset (intentional misalignment) sometimes introduced when aligning a pump-motor set at ambient temperature?
Answer: To account for thermal growth that shifts shaft centerlines once equipment reaches operating temperature
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.
A rigid coupling is the appropriate coupling choice when:
Answer: Both shafts are precisely aligned and must act as a single continuous shaft
Rigid couplings transmit torque without any flexibility; they require near-perfect alignment because they cannot tolerate misalignment without generating damaging stresses.
In the reverse dial indicator alignment method, dial indicators are positioned:
Answer: On brackets spanning the coupling with each indicator reading the opposite shaft
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.
A torque limiter (slip coupling) is used primarily to:
Answer: Protect machinery by slipping or disengaging when torque exceeds a preset limit
A torque limiter acts as a mechanical fuse, slipping or disengaging at a preset torque threshold to prevent overloads from damaging expensive machinery.
Maintaining the correct axial gap (end float) between coupled shaft ends is important primarily because:
Answer: It prevents axial thrust loads from being transferred between the two coupled machines
Proper end float allows each machine's shaft to expand thermally without pushing against the other shaft, preventing bearing overload and premature thrust failure.
Bracket sag in dial indicator shaft alignment refers to:
Answer: The downward deflection of the indicator bracket under its own weight, which introduces measurement error
Long unsupported indicator brackets deflect downward under gravity, causing a false reading that must be measured and subtracted from alignment data to get accurate results.