Mechanical Systems Installation & Repair Flashcards

When performing a reverse dial indicator alignment, a reading of +0.020 in. at the bottom of the coupling hub (zeroed at top) indicates what offset at that plane?

Answer: 0.010 in.

Rim readings show twice the actual offset, so a 0.020 in. TIR equals 0.010 in. of offset.

A soft foot condition on a motor is best detected by which method?

Answer: Loosening one hold-down bolt at a time while indicating foot movement

Loosening each bolt with an indicator on that foot reveals movement greater than about 0.002 in., which signals soft foot.

What is the primary purpose of grouting a pump baseplate?

Answer: Provide a rigid, uniform load transfer between the baseplate and foundation

Grout fills voids to create full contact and rigid support, reducing vibration and distortion.

When installing a bearing with an interference fit on a shaft using induction heating, what is the generally recommended maximum bearing temperature?

Answer: 250°F (120°C)

Most manufacturers limit heating to about 250°F (120°C) to avoid altering the bearing steel's hardness.

A centrifugal pump is making a crackling, gravel-like noise at the suction and showing reduced head. What is the most likely cause?

Answer: Cavitation due to insufficient NPSH available

Cavitation occurs when NPSHa falls below NPSHr, forming and collapsing vapor bubbles that sound like gravel.

On a V-belt drive, what is the proper method to check belt tension?

Answer: Measure the force required to deflect the belt a set distance at the span midpoint

The force-deflection method, typically 1/64 in. per inch of span, gives the correct tension.

What is the main reason for replacing all belts on a multi-belt V-drive at the same time rather than just the broken one?

Answer: Mixed new and stretched belts share the load unevenly

Old belts are stretched, so new belts carry most of the load and fail prematurely; matched sets prevent this.