Lagging Selection is key to obtaining the best possible lagging performance and a recent visit to a pulley refurbishment facility emphasised this with three pulleys on the floor – two with cold bonded ceramic lagging and one with hot vulcanised ceramic lagging.
Lagging can be of good quality and application can be correct, but lagging can still fail and does. Everything seems right but the lagging still doesn’t perform to expectations. So why does this happen? It’s because the lagging selection is not right for the application.
Hot Vulcanised lagging application involves the chemical cross-linking of five reactive layers during the autoclave curing process. To achieve the desired 100% rubber tear adhesion all five layers must crosslink at the same time. Occasionally conditions can be created in the autoclave that prevent this happening, and result in non-uniform adhesion around the pulley circumference. This bulletin explains how these conditions occur and what needs to be done to eliminate this problem.
Spare pulleys are held so that in the event that an operational pulley requires replacement this can be done quickly and efficiently at the timing dictated by the mine maintenance personnel. The reason for changing a pulley broadly falls into two categories:
Catastrophic lagging failure due to debonding occurred within two weeks of installation and operation of the pulley, resulting in a shutdown of production, and necessitated a replacement of the pulley. Within only two weeks of service, this ceramic lagging was already experiencing loss of the ceramic tiles.