Ceramic-Epoxy Pulley Lagging: What It Is and Why We Don’t Recommend It
1. What it is
Ceramic-Epoxy Pulley Lagging comes in 2 forms: ceramic beads embedded in an epoxy paste, and ceramic tiles bonded directly to the pulley shell with epoxy. Ceramic beads in an epoxy paste is a very quick to apply product, with little expertise required to do the application. Direct bonded ceramic tiles take much longer to apply, depending on the pulley size this can be a few days, as it is analogous to laying a mosaic down on a cylinder.
The marketed advantage of Ceramic Epoxy Pulley Lagging is that it can last a long time, with some cases of it even lasting as long as 20 years. Even in the rare cases where it does last so long, there are enormous cost implications to using it.
2. Why We Don’t Recommend It
2.1 Ceramic Epoxy Pulley Lagging is rigid and brittle which has major consequences.
Due to the rigidity of these products, if they are used on drive pulleys, they aggressively wear away the underside of the conveyor belt through a process called localised slippage – see our article on Rubber Backed Ceramic Lagging to learn why this happens. This wear is worsened by higher wrap angles and greater differences in tension between the top (T1) and return (T2) sides of the belt – normally higher wrap angles and a lower T2 are ideal for a conveyor system. The result is that the Ceramic Epoxy Pulley Lagging could last for up to 20 years (this is rare but not unheard of), but the conveyor belt has been replaced frequently which is an enormous cost and entirely avoidable. We have been on sites where this product has been installed on a drive pulley, and literally watched it rain rubber dust from the drive pulley. It is becoming commonplace for conveyor belt manufacturers to void the warranty on the conveyor belt if they find out this lagging has been used on the drive pulley.
Pulley shells are not rigid, they deflect and warp during normal operation and start-up of the conveyor system – this is normal, to be expected and is accounted for in the design of a pulley. Perfectly rigid pulley shells would be unnecessarily heavy and expensive. In order for any guarantee to be offered on Ceramic Epoxy Pulley Lagging, the installer would have to do a Finite Elements Analysis (FEA) on the particular pulley. The FEA would need to include any worn areas of the pulley shell, take into account the various operating stages of the particular conveyor (especially start-up with a loaded belt) to prove that the pulley deflects and warps within a range that the Ceramic Epoxy Pulley Lagging can handle. The consequences of this lagging coming off are dire. It can tear/rip the conveyor, damage scrapers, idlers, the pulley itself and other components in and around the conveyor.
Ceramic Epoxy Pulley Lagging even on a tail pulley has negative consequences for the belt and the lagging. Even on a well-maintained system with a decent plough in front of the tail pulley, stones and other material tend to fall and become trapped between the conveyor belt and pulley. Because the lagging is rigid, the conveyor belt alone is forced to conform to the trapped stones. This wears away the conveyor belt, often gouges rubber out of the underside of the conveyor belt or worse cuts the conveyor belt. The consequence for the Ceramic Epoxy Pulley Lagging is that is tends to chip and crack when this happens.
Handling and transporting pulleys that have been coated with Ceramic Epoxy Pulley Lagging is a challenge. The slightest bump causes the lagging to crack or pieces to fall off. With no built-in cushioning effect, its brittleness makes it fragile.
2.2 Ceramic Epoxy Pulley Lagging cannot handle moisture.
A common cause of failure of this lagging is that the epoxy bond does not protect the shell from moisture and therefore rust. When the shell begins to rust, patches of the lagging fall off and do so in an ever-accelerating manner, with all the consequences and risks that come with this rigid lagging falling off.
2.3 Ceramic Epoxy Pulley Lagging has a different Coefficient of Thermal Expansion to Steel.
This may seem like an unusual issue to raise, but because Ceramic Epoxy Pulley Lagging is rigid, the Coefficient of Thermal Expansion becomes critical for any application or environment where large differences in temperature are expected. Large temperature variances can cause the lagging to literally “pop off” the shell. Even rapid heating of the Pulley Lagging through belt slip (usually a jammed conveyor) can cause this – most laggings will be damaged by excessive heat, but none will cause the kind of damage that Ceramic Epoxy Pulley Lagging will.
2.4 Removal is difficult
Should the mine decide to remedy the situation and remove Ceramic Epoxy Pulley Lagging, the process can take days, and/or require blow-torches and chisels.
3. Conclusion
Ceramic Epoxy Pulley Lagging is just not worth it. The type of pulley lagging used should not have consequences and such high risks for the rest of the components in the conveyor system. Pulley Lagging is always less expensive than the Conveyor Belt and should never be prioritized over the life of the Conveyor Belt. As appealing as the idea is that a bucket of epoxy and ceramic beads or tiles is all that is needed to lag a Pulley, we strongly recommend that it should be avoided – don’t just take our word for it, ask for advice from the conveyor belt manufacturer and pulley manufacturer.