Requirements of good shaft alignment / good coupling setup
it should be easy to connect or disconnect the coupling.
it should transmit the full power from one shaft to other without losses.
it does allow some misalignment between the two adjacent shaft roation axis.
it is the goal to minimise the remaining misalignment in running operation to maximise power transmission and to maximise machine runtime (coupling and bearing and sealings lifetime).
it should have no projecting parts.
it is recommended to use manufacturer's alignment target values to set up the machine train to a defined non-zero alignment, due to the fact that later when the machine is at operation temperature the alignment condition is perfect
Tools to measure shaft axis alignment condition
it is possible to measure the alignment with dial gages or feeler gages using various mechanical setups.
it is recommended to take care of bracket sag, parallaxe error while reading the values.
it is very convenient to use laser shaft alignment technique to perform the alignment task within highest accuracy.
it is required to align the machine better, the laser shaft alignment tool can help to show the required moves at the feet positions.
Flexible coupling, Coupling maintenance and failure
Coupling maintenance is generally a simple matter, requiring a regularly scheduled inspection of each coupling. It consists of:
Performing visual inspections, checking for signs of wear or fatigue, and cleaning couplings regularly.
Checking and changing lubricant regularly if the coupling is lubricated. This maintenance is required annually for most couplings and more frequently for couplings in adverse environments or in demanding operating conditions.
Documenting the maintenance performed on each coupling, along with the date.
Even with proper maintenance, however, couplings can fail. Underlying reasons for failure, other than maintenance, include:
Improper installation
Poor coupling selection
Operation beyond design capabilities.
The only way to improve coupling life is to understand what caused the failure and to correct it prior to installing a new coupling. Some external signs that indicate potential coupling failure include:
Abnormal noise, such as screeching, squealing or chattering
Excessive vibration or wobble
Failed seals indicated by lubricant leakage or contamination.
Checking the coupling balance
Couplings are normally balanced at the factory prior to being shipped, but they occasionally go out of balance in operation. Balancing can be difficult and expensive, and is normally done only when operating tolerances are such that the effort and the expense are justified. The amount of coupling unbalance that can be tolerated by any system is dictated by the characteristics of the specific connected machines and can be determined by detailed analysis or experience.
