Increased Adhesion to the Pulley Shell
A significant cause of ceramic lagging failure is lifting of the lagging edge due to corrosion occuring at the lagging pulley interface. This is more likely to occur in pulleys operating in wet environments and is mainly seen on Cold Vulcanised Ceramic Lagging (CVCL) applications. The cause is the low and uneven levels of adhesion found between the rubber end pieces and the pulley shell.
Photo above top right shows a pulley shell after removal of the CVCL. A pattern of the CVCL adhesive can be seen (light grey areas) that has remained on the pulley shell when the lagging has been removed. This pattern matches the lagging areas with no ceramic tiles and inclucdes the recessed cutting sipes and the rubber areas between tile segments.
When CVCL is applied the application of pressure to the lagging to produce the bond is done via a rubber hammer. The result is very short duration of pressure (<1 second), uneven application of pressure ( not every part of the lagging can be guaranteed to be hammered) and minimal or no pressure along the recessed cutting sipes (these are supposed to be pressurised with astitching wheel but often this does not occur). The uneven adhesion provides a way for moisture to work between the lagging and the pulley shell and the edge joint is the place where this occurs. The increased and more uniform adhesion provided by the Hot Vulcanised Ceramic Lagging (HVCL) and also the Direct Bond Ceramic Lagging (DBCL) will prevent lifting of the lagging at the edge of the pulleys. Additionally for the HVCL the pulley shell end and end discs can be sealed in a layer of rubber that is also bonded to the lagging. This seals the lagging/pulley shell joint and eliminates the possibility of lagging failure due to edge lifting/debonding.