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.
In most cases, these maintenance steps should be sufficient to keep couplings working smoothly and to enable them to reach their full service life. 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. Every failed coupling provides some evidence about what caused the failure. Some failures can be seen readily, while others require some investigation.
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
In addition, examination of damaged parts helps provide an explanation of what caused the failure:
|Excessive torque loading due to improper coupling selection or system changes|
|Hardened rubber due to chemical contamination |
|Improper installation |
Possibly due to improper hub size selection
Improper size selection coupled with overload
|Excessive torsional vibration or loading. In properly installed couplings, torque is carried by contact friction between coupling surfaces rather than by the bolts. Excessive vibration can loosen bolts, causing torque to be applied to bolts. |
|Lack of maintenance |
Internal signs of failure must be investigated when the equipment simply stops running and there is no external evidence.
|Improper coupling alignment |
|Sludge contamination reduces lubricant flow, which can cause premature failure |
|Sludge contamination reduced coupling flexibility, leading to fatigue failure |
|Improper lubrication |
|Improper lubrication or lubricant contamination |