Cold Vulcanised (CV) bonding of pulley lagging has been used for many years primarily due to the convenience of application and the minimal investment required to set up.
It can also be done on site when unexpected lagging problems occur. When done properly CV application can provide an acceptable result for medium and light duty pulley applications however because this method does not provide reliable 100% rubber tear adhesion service life is often compromised.
Failure of CV bonding to provide rubber tear adhesion can result in lagging coming away from the pulley and also to corrosion of the pulley shell at the lagging joins with the resultant pitting leading to a de-rating of the pulley service capability due to the reduction in shell thickness. Photo #1 & 2. The cost for these problems in plant down time and pulley refurbishment is always substantial, and in the case of the de-bonding is many times the cost of the original lagging application.
Most people involved in pulley refurbishment and/or lagging replacement know that removal of CV lagging is pretty simple and can be done by applying tension to the end of a lagging strip with a forklift or overhead crane. This usually peels the lagging away from the pulley shell with little or no rubber tear.
Refer to Photo#3. This photo also shows significant pulley shell corrosion adjacent to the pulley edge – this is usually the result of poor adhesion between the lagging and pulley shell and can lead to complete debonding of the lagging and unplanned conveyor down time.
There are many reasons for the failure to obtain rubber tear adhesion with conventional CV bonding systems and lagging including:
- Use of adhesives, primers and lagging that have not been engineered by a single manufacturer to work together
- Lack of detailed OEM application specifications and work methods
- Poorly trained and supervised applicators
- Application in hostile (dirty, wet, humid) conditions
Elastotec has been working to address the first three of these causes of problems with CV bonding systems.