Alignment of Machinery

shaft alignment offset

shaft alignment offset

In mechanical and electrical engineering, there are hundreds of motors that drive machinery like pumps, fans, agitators, winches, and other rotating equipment. Diesel engines or turbines drive alternators.

Whenever some of the motors or driven machinery are dismantled or even when the machines are not running smoothly, alignment is done.

using feeler gauge to check shaft angular alignment

using feeler gauge to check shaft angular alignment

The purpose of alignment is to ensure that the centerline of the motor rotor shaft coincides exactly with the centerline of the driven machinery. Alignment is essential to ensure that the machine runs smoothly with minimum vibration.

Provided the two shafts are not bent crooked, the two alignments to be checked and adjusted are:

  • Offset alignment
  • Angular alignment
shaft offset alignment using a straight edge

shaft offset alignment using a straight edge

Rough alignment is usually sufficient, and can be done using straight edge ruler and feeler gages. However for precision alignment, the use of dial gauges with magnetic bases is recommended.

Offset Alignment

shaft offset alignment using straight edge

shaft offset alignment using straight edge

The radial alignment is checked using a straight edge ruler. By placing the ruler across the coupling halves at the top, bottom and both sides any gaps between the 2 coupling halves will indicate that the shaft is offset slightly. The misalignment can be corrected by shifting the motor or by putting shims to raise up the motor or driven machine.

Angular alignment

By inserting a feeler gauge between the coupling faces and rotate both coupling halves simultaneously we can check whether the shafts have any angular displacement between them. The feeler gauge readings at checked at four points on the shaft coupling. Again the alignment is corrected by shimming or shifting the machinery.

shaft angular alignment using feeler gauge

shaft angular alignment using feeler gauge

The motor and the driven machine should be bolted solidly to the base after finalizing the alignment positions of the equipment.