433A Alignment and Levelling 1 — Questions and Answers
Question 1: What is the primary goal of precision shaft alignment?
- To make the shafts perfectly parallel
- To ensure the centerlines of two coupled shafts are collinear within tolerance (Correct answer)
- To eliminate all vibration in the system
- To reduce the cost of coupling replacement
Correct answer: To ensure the centerlines of two coupled shafts are collinear within tolerance
Precision shaft alignment aims to make the rotational centerlines of two coupled shafts collinear (sharing the same axis) within acceptable tolerances, minimizing forces on bearings, seals, and couplings.
Question 2: What are the two types of misalignment that must be corrected during shaft alignment?
- Vertical and horizontal
- Axial and radial
- Offset (parallel) and angular (Correct answer)
- Static and dynamic
Correct answer: Offset (parallel) and angular
Shaft misalignment is described in terms of offset (parallel) misalignment, where shaft centerlines are parallel but displaced, and angular misalignment, where shaft centerlines intersect at an angle.
Question 3: When using a precision level to level a baseplate, what does a reading of 0.001 inch per foot represent?
- The baseplate is perfectly level
- The baseplate rises 0.001 inch over a 12-inch span (Correct answer)
- The baseplate has 1% slope
- The baseplate is out of tolerance
Correct answer: The baseplate rises 0.001 inch over a 12-inch span
A reading of 0.001 inch per foot means there is a height difference of one thousandth of an inch for every twelve inches of horizontal distance across the baseplate surface.
Question 4: What is soft foot in the context of machinery alignment?
- A damaged machine foot
- A condition where one or more feet do not make full contact with the base when bolts are tightened (Correct answer)
- A foot made of soft material
- A foot that requires no shimming
Correct answer: A condition where one or more feet do not make full contact with the base when bolts are tightened
Soft foot occurs when one or more machine feet do not sit flat on the baseplate, causing the machine frame to distort when hold-down bolts are tightened. This distortion changes internal alignment and must be corrected before proceeding.
Question 5: In laser shaft alignment, what does the term 'coupling center' refer to?
- The physical center of the coupling housing
- The point where the flexible element is located, used as the reference for alignment corrections (Correct answer)
- The center bolt of the coupling
- The midpoint between the two machines
Correct answer: The point where the flexible element is located, used as the reference for alignment corrections
The coupling center is the point at or near the flexible element of the coupling, used as the reference point for calculating alignment corrections. Misalignment values are often referenced to this point.
Question 6: Why must thermal growth be accounted for during cold alignment of machinery?
- To prevent the baseplate from warping
- Because machines change position as they reach operating temperature, so cold offsets ensure alignment at running conditions (Correct answer)
- To protect the laser alignment tool from heat
- To reduce the time needed for alignment
Correct answer: Because machines change position as they reach operating temperature, so cold offsets ensure alignment at running conditions
Machines are typically aligned cold but operate hot. Thermal growth causes the machine housings to expand and shift position, so intentional cold offsets are applied to ensure the shafts are properly aligned at operating temperature.
433A Alignment and Levelling 1
What is the primary goal of precision shaft alignment?