Shaft alignment is the process to align

Alignment

Alignment may refer to:* Alignment , secondary evidence used to associate features such as postholes* Alignment , in Israel from 1965 to 1992...

 two or more shafts

Driveshaft

A drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...

 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

Stress (physics)

In continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...

 on the shafts and will almost certainly result in excessive wear and 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 coupling

Disc coupling

Disc coupling: by definition, transmits torque from a driving to a driven bolt tangentially on a common bolt circle. Torque is transmitted between the bolts through a series of thin, stainless steel discs assembled in a pack...

s can prevent this. Tools used to achieve alignment may be mechanical or optical, like the Laser shaft alignment

Laser shaft alignment

When two machines are connected together through a shaft Coupling, every effort must be made to eliminate misalignment of those shafts which can lead to damage or wasteful loss of energy. Lasers are highly accurate and easy to use in aligning objects...

method.

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.

The resulting fault if alignment is not achieved within the demanded specifications is shaft misalignment, which may be parallel, angular, or both. Misalignment can cause increased vibration and loads on the machine parts for which they have not been designed (i.e. improper operation).

Types of misalignment

There are two types of misalignment: parallel and angular misalignment. With parallel misalignment, the center lines 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:

• 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.

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

• 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.