Shaft Alignment & Machinery Installation Flashcards

Which type of shaft misalignment produces high vibration predominantly in the axial direction at 1× and 2× running speed?

Answer: Angular misalignment

Angular misalignment causes the shaft ends to meet at an angle, generating strong axial forces that produce elevated 1× and 2× vibration in the axial direction.

What is the most common vibration frequency signature associated with parallel (offset) misalignment?

Answer: Dominant 2× radial vibration

Parallel misalignment typically produces a dominant 2× radial vibration component because the coupling must correct twice per revolution to accommodate the offset.

During a soft foot check, what is the maximum acceptable dial indicator reading before corrections must be made?

Answer: 0.002 inch (0.05 mm)

The industry-accepted threshold for soft foot is 0.002 inch (0.05 mm); readings above this value indicate the machine frame is distorted and must be corrected before alignment proceeds.

What is 'soft foot' in the context of machinery installation?

Answer: A condition where one or more machine feet do not make full contact with the baseplate when hold-down bolts are tightened

Soft foot occurs when tightening hold-down bolts causes the machine frame to distort because one or more feet do not sit flush on the baseplate, inducing internal stresses and misalignment.

Which alignment method mounts two dial indicators on the coupling hub of each machine and measures runout as the shafts are rotated together?

Answer: Reverse indicator method

The reverse indicator method places a dial indicator on each shaft pointing back toward the opposite machine, allowing both parallel and angular misalignment to be calculated simultaneously with high accuracy.

Thermal growth must be accounted for during precision shaft alignment because:

Answer: Machinery expands when it reaches operating temperature, shifting the shaft centerlines from their cold-aligned positions

As machines heat up to operating temperature, differential thermal expansion between the driver and driven machine changes shaft centerline positions, so cold alignment must include a thermal offset to achieve true alignment at running conditions.

What is the primary purpose of shims during machinery installation?

Answer: To adjust the vertical position of machine feet to achieve correct shaft alignment

Shims are precision metal spacers placed under machine feet to make fine vertical elevation adjustments that bring the shaft centerlines into proper alignment.