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 can prevent this.
The resulting fault if alignment is not achieved within the demanded specifications is Shaft misalignment, which may be parallel, angular, or both.
Figure: Shaft misalignment.
There are some problems of shaft misalignment, such as:
Ø Lost production
Ø Leakage seals
Ø Increased vibration
Ø Higher energy consumption
Ø Bearing failure
Ø Shaft breakage
Ø Coupling wear
Ø Quality problems etc.
To prevent these problems shaft alignment is very necessary. It can be done by using shim, plane bar or dial indicators. In modern time dial indicators method is very popular because of its higher accuracy.
Shim is very thin plate which is used to get proper alignment. If pump shaft is in fixed height and the motor shaft is in misalignment, then shim is used for proper alignment. If the motor shaft is downward with respect to pump shaft, then shim is added to keep the both height same. Again if the motor shaft is upward with respect to pump shaft, then shim is removed from there to level the height at same.
At present time dial indicator methods are most popular. It gives more precious alignment. There are many types of dial indicator methods. Among them Mr. Shims dial indicator alignment method is familiar one.
Mr. Shim’s alignment system is designed for both Rim & Face and Reverse Dial methods of shaft alignment.
Reverse dial method Rim and Face method
Figure: The complete Reverse Dial, Rim& Face Precision Alignment System.