Alignment and Levelling Flashcards

What is the rim and face method of shaft alignment?

Answer: Using dial indicators mounted on one shaft to read offset on the rim and angular misalignment on the face of the opposing coupling hub

The rim and face method uses a dial indicator reading on the rim (outside diameter) of the opposite coupling hub to measure offset misalignment, and another indicator on the face to measure angular misalignment.

When shimming a machine for alignment, what is the maximum recommended number of shims under one foot?

Answer: 3 to 5 shims

Best practice limits shim packs to 3-5 shims under each foot. Excessive shim stacking introduces compressibility and instability, which can create soft foot and allow the alignment to shift under load.

What is the reverse indicator method of shaft alignment?

Answer: Mounting dial indicators on each shaft to read the rim of the opposite shaft's coupling hub

The reverse indicator method mounts a dial indicator on each shaft that reads the rim of the opposite coupling hub. Both shafts are rotated together, and readings at four positions (12, 3, 6, 9 o'clock) are used to calculate offset and angularity.

What effect does angular misalignment have on a flexible coupling?

Answer: It causes axial vibration at 1× and 2× running speed

Angular misalignment causes cyclical axial displacement as the shafts rotate, producing vibration predominantly at 1× and 2× running speed in the axial direction. This accelerates coupling element wear and bearing fatigue.

Why are jackscrews (jacking bolts) important during alignment?

Answer: They allow precise, controlled horizontal positioning of the machine without hammering

Jackscrews provide controlled, fine adjustment of the machine's horizontal position during alignment. They allow the millwright to make precise movements without the unpredictability of hammering or prying the machine into position.

What is bore alignment used for?

Answer: Verifying the alignment of bearing bores along a long machine train or multi-bearing equipment

Bore alignment checks that the bearing bores along a long machine frame or multi-bearing equipment (such as a paper machine or turbine casing) are in proper alignment with each other using optical or laser methods.