CMRT CMRT Mechanical Systems and Alignment 1 — Questions and Answers
Question 1: What is shaft alignment and why is it critical to equipment reliability?
- Balancing the rotating mass so centrifugal forces cancel out
- Positioning two shafts so their rotational centerlines are collinear, minimizing vibration and bearing loads (Correct answer)
- Verifying that shaft keys and keyways are properly fitted
- Ensuring the shaft is perfectly round and free of taper
Correct answer: Positioning two shafts so their rotational centerlines are collinear, minimizing vibration and bearing loads
Shaft alignment ensures that connected shaft centerlines are collinear, which reduces vibration, bearing and seal loads, and energy consumption, directly extending equipment life.
Question 2: What are the two primary types of shaft misalignment?
- Static misalignment and dynamic misalignment
- Angular misalignment and parallel (offset) misalignment (Correct answer)
- Horizontal misalignment and axial misalignment
- Radial misalignment and torsional misalignment
Correct answer: Angular misalignment and parallel (offset) misalignment
The two primary types of shaft misalignment are angular misalignment (shafts at an angle) and parallel (offset) misalignment (shaft centerlines are parallel but offset from each other).
Question 3: What is 'soft foot' in machinery alignment, and why must it be corrected before performing alignment?
- A condition where the machine feet are made of soft metal that deforms under torque
- A condition where one or more machine feet do not make solid contact with the base, causing frame distortion when bolts are tightened (Correct answer)
- A term for insufficient bolt preload on machine mounting hardware
- A measurement error caused by temperature fluctuations during alignment
Correct answer: A condition where one or more machine feet do not make solid contact with the base, causing frame distortion when bolts are tightened
Soft foot occurs when one or more machine feet do not uniformly contact the baseplate, causing the machine frame to distort when hold-down bolts are tightened and making accurate alignment impossible.
Question 4: Which type of coupling is most tolerant of shaft misalignment while still transmitting torque?
- Rigid (sleeve) coupling
- Jaw (spider) coupling
- Flexible elastomeric coupling (Correct answer)
- Disc coupling
Correct answer: Flexible elastomeric coupling
Flexible elastomeric couplings accommodate angular, parallel, and axial misalignment through the deformation of a rubber or polyurethane element while transmitting torque.
Question 5: What is the purpose of using shims under machine feet during precision alignment?
- To increase the height of the machine for better access during maintenance
- To make fine vertical position corrections and eliminate soft foot conditions (Correct answer)
- To absorb vibration from the machine and prevent transmission to the foundation
- To replace worn or corroded base plate surfaces
Correct answer: To make fine vertical position corrections and eliminate soft foot conditions
Shims are thin metal plates inserted under machine feet to make precise vertical height adjustments needed to achieve correct shaft alignment and eliminate soft foot.
Question 6: What alignment measurement tool provides the highest accuracy for modern industrial shaft alignment?
- Dial indicators mounted on a bracket straddling the coupling
- Laser alignment system with rotating targets (Correct answer)
- Straightedge and feeler gauge
- Optical tooling scope and target
Correct answer: Laser alignment system with rotating targets
Laser alignment systems provide the highest accuracy and ease of use by projecting laser beams between shaft-mounted targets and computing misalignment values and correction moves automatically.
CMRT CMRT Mechanical Systems and Alignment 1
What is shaft alignment and why is it critical to equipment reliability?