Shaft alignment


Shaft alignment

Shaft alignment is the process to align two or more shafts with each other to within a tolerated margin. It is an absolute requirement for machinery before the machinery is put in service.

When a driver like an electric motor or a turbine is coupled to a pump, a generator, or any other piece of equipment, it is essential that the shafts of the two pieces are aligned. Any misalignment between the two increases the stress on the shafts and will almost certainly result in premature breakdown of the equipment. This can be very costly. When the equipment is down, production might be down. Also bearings or mechanical seals may be damaged and need to be replaced. A proper shaft alignment or the use of disc couplings can prevent this.

Before such a shaft alignment can be done, it is also essential that the foundations for the driver and the driven piece are designed and installed correctly. If that is the case, than shaft alignment can be started.Following is a step by step procedure for the so called reverse dial indicator alignment.

Types of Misalignment

There are two types of misalignment, parallel and angular misalignment.With parallel misalignment, the centerlines of both shafts are parallel but they are offset.With angular misalignment, the shafts are at an angle to each other.

The parallel misalignment can be further divided up in horizontal and vertical misalignment.Horizontal misalignment is misalignment of the shafts in the horizontal plane and vertical misalignment is misalignment of the shafts in the vertical plane.

Similar, angular misalignment can be divided up in horizontal and vertical misalignment.

Parallel horizontal misalignment is where the motor shaft is moved horizontally away from the pump shaft, but both shafts are still in the same horizontal plane and parallel.

Parallel vertical misalignment is where the motor shaft is moved vertically away from the pump shaft, but both shafts are still in the same vertical plane and parallel.

Angular horizontal misalignment is where the motor shaft is under an angle with the pump shaft but both shafts are still in the same horizontal plane.

Angular vertical misalignment is where the motor shaft is under an angle with the pump shaft but both shafts are still in the same vertical plane.

Errors of alignment can be caused by parallel misalignment, angular misalignment or a combination of the two.


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