Free Millwright Precision Shaft Alignment Techniques Questions and Answers — Questions and Answers
Question 1: What is the first corrective step a millwright should take after discovering a 'soft foot' condition on a motor?
- Proceed with the alignment and compensate for the reading.
- Add or remove shims under the appropriate foot to eliminate the rock. (Correct answer)
- Tighten all the hold-down bolts to maximum torque.
- Replace the motor bearings.
Correct answer: Add or remove shims under the appropriate foot to eliminate the rock.
A soft foot creates a strain on the machine's frame, which can interfere with alignment readings. It must be corrected by adding or removing shims under the problem foot before proceeding with any alignment adjustments.
Question 2: When aligning a hot pump to a cold motor, what must be accounted for to achieve proper alignment under operating conditions?
- Shaft end float
- Coupling backlash
- Thermal growth of the pump (Correct answer)
- Initial starting torque
Correct answer: Thermal growth of the pump
Thermal growth causes machinery to expand as it heats up to operating temperature. This change in dimension, particularly vertical growth, must be calculated and compensated for during the cold alignment process.
Question 3: In the rim-and-face alignment method, which type of misalignment is primarily measured by the 'face' reading?
- Parallel offset misalignment
- Angular misalignment (Correct answer)
- Axial shaft float
- Torsional misalignment
Correct answer: Angular misalignment
The face reading is taken on the face of the coupling hub. Any variation in this reading as the shafts are rotated indicates that the shaft centerlines are not parallel, which is the definition of angular misalignment.
Question 4: Acceptable alignment tolerances are most dependent on which machine characteristic?
- Machine weight
- Coupling type
- Operating speed (RPM) (Correct answer)
- Baseplate material
Correct answer: Operating speed (RPM)
Higher rotational speeds require tighter alignment tolerances. The potential for destructive vibration increases significantly with speed, so machines operating at high RPMs must be aligned more precisely.
Question 5: When using the reverse dial indicator method, what does a Total Indicator Reading (TIR) of zero at both 12 and 6 o'clock on one shaft, while reading the other, indicate?
- Perfect angular alignment in the vertical plane.
- A severe soft foot condition.
- Perfect parallel alignment in the vertical plane. (Correct answer)
- The dial indicator is broken.
Correct answer: Perfect parallel alignment in the vertical plane.
The reverse dial indicator method measures parallel offset by reading the rim of the opposite coupling hub. If the readings at the top (12) and bottom (6) are the same (resulting in zero difference), it means the shafts are parallel in that plane.
Question 6: What is a primary advantage of using a laser alignment system over traditional dial indicator methods?
- They do not require the shafts to be rotated.
- They are not affected by thermal growth.
- They reduce calculation errors and eliminate indicator bracket sag. (Correct answer)
- They can be used without removing coupling guards.
Correct answer: They reduce calculation errors and eliminate indicator bracket sag.
Laser systems eliminate reading errors from indicator sag, are faster, and can calculate required shims and moves automatically. This significantly reduces the potential for human error and speeds up the alignment process.
Free Millwright Precision Shaft Alignment Techniques Questions and Answers
What is the first corrective step a millwright should take after discovering a 'soft foot' condition on a motor?