Alignment and Levelling Flashcards

What is the purpose of dowel pins installed after alignment is complete?

Answer: To lock the machine's horizontal position so it can be returned to its aligned position after removal

Dowel pins are installed through the machine feet into the baseplate after final alignment to lock the machine's precise horizontal position. If the machine is removed for maintenance, the dowel pins allow it to be returned to its aligned position.

What does the term 'total indicated runout' (TIR) mean when checking a coupling hub?

Answer: The full range of indicator needle movement (maximum minus minimum reading) during one complete shaft rotation

TIR is the total range of the dial indicator reading — the difference between the maximum and minimum values recorded during one complete 360-degree shaft rotation. It represents the total eccentricity or wobble of the measured surface.

When performing a rough alignment using a straightedge and feeler gauges, what accuracy can typically be achieved?

Answer: Within 0.005 to 0.010 inch

Straightedge and feeler gauge methods can typically achieve rough alignment accuracy of 0.005 to 0.010 inches. This serves as a good starting point before using dial indicators or laser alignment for precision corrections.

What is induced soft foot?

Answer: Soft foot caused by external forces such as pipe strain or coupling lock-up that distort the machine frame

Induced soft foot is not caused by the machine foot or baseplate geometry but by external forces — such as pipe strain, conduit connections, or a locked-up coupling — that pull or push on the machine and distort its frame.

What role does the coupling gap play in shaft alignment?

Answer: It must be set to the manufacturer's specification to allow for thermal expansion and proper coupling function

The coupling gap (axial distance between coupling hubs) must be set per manufacturer specifications to allow for shaft thermal growth, prevent end-float contact, and ensure the flexible element functions properly within its design range.

Why is it important to rotate both shafts together when taking alignment readings?

Answer: To eliminate errors caused by coupling hub runout and surface irregularities

Rotating both shafts together (as a unit) eliminates errors from coupling hub eccentricity, surface finish variations, and mounting irregularities. If only one shaft rotates, these imperfections would be included in the misalignment readings.