In industry, many couplings utilize an elastomeric insert or element. This type of coupling has many advantages, among them:
- Ease of replacement
- Ability to absorb torsional loading
- No need for lubrication
- Tolerant of slight amounts of misalignment
It is important to remember that even though these elastomer couplings can be tolerant of misalignment, the bearings and seals are not, and as such, precision alignment (normally closer than the coupling manufacturer recommends) is necessary. Even with excellent alignment, the coupling element will eventually need replacement.
So, when should the elastomer be replaced? While each manufacturer has good recommendations (read that little piece of paper they put in the box!), here are some good indications that is time to replace the element.
OBVIOUS SIGNS OF WEAR
Remember the most common reason for wear is misalignment. If wear is excessive, then the ability of the insert to transmit power is reduced.
On two piece coupling inserts (or one piece inserts in which the two halves are vulcanized together), you may notice a twist in the seam between the two halves. When this twist becomes excessive, the width of the coupling is decreased, which could result in a loss of tooth contact on the hubs.
When some elastomer couplings have run beyond there capacity to transmit power, you may see some of the “legs” of the insert gone, or see the metal jaws making direct contact. In these cases, the entire coupling should be replaced.
In most of these photos, coupling damage is obvious, so one may be led to believe these are extreme examples. But all damaged couplings in these photos were taken by VibrAlign trainers, while teaching training classes in the field. So, these types of failure do occur on a regular basis.
To minimize such failures:
- Make sure the proper insert is being used.
- Perform precision alignment-every time.
- Ensure proper installation and spacing.
- Inspect couplings on a regular basis.
- Replace them as needed.
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