What is Lagging in Conveyor Pulleys and How Does It Work?

Blog | November 16th, 2015

If you’re a heating engineer, then lagging is the insulating material that covers pipes and boilers. Alternatively, if you’re an engineer with pulley know-how and conveyor expertise, then the term describes a completely different component asset. It’s funny how a simple switch of professions can so alter the context of a single word. Anyway, when conveyor pulleys are lagged, they’re still being coated, but this coating is designed as a dynamic material, one that deals with the contact areas between the conveyor belt and the drum of the pulley.

Describing Pulley to Belt Energy Translation

The pulleys and motor-driven shafts of a conveyor system can be compared to the muscles and joints of a human body, though movement is restricted to a linear progression as directed by the radial turn of a series of horizontally-mounted rollers and pulleys. Some of these components are simple passive rollers, parts that add tension and direction to the system, but other pulleys incorporate drive mechanics. Regardless of this layout, the belt has to contact the pulleys as they turn. Note, the belt is technically rubbing against the rolled drum and not the shaft. This is a fine distinction but an important one when explaining lagging, because this drum is clothed in a blanket, one that exhibits essential grip characteristics, which is why the material is often fabricated from a tough rubber.

Drum Mechanics VS. Belt Friction

The friction coefficient between a belt, an endless loop of stout rubber, and the rolling conveyor pulleys can represent a substantial energy loss point unless a traction mechanism is incorporated between these two disparate assemblies. Imagine using a pulley system without a blanketing rubber coating. The pulley would rotate as designed, but there would be no traction between the underside of the belt and the exterior of the pulley drum. The lagging solution ensures the contact point between both the drum and the belt fully meshes. Full energy transmission can now take place across the system.

Conveyor Pulleys Need Tough Blankets

The lagged blanket doesn’t keep the pulley warm, but it does deliver mechanical efficiency. As such, the rubber blanketing has to be fabricated to the same standards as the belt material. The drum coating will therefore resist the abrasion effects generated by possible friction events, will maintain contact as guided by the tensioning subsystem, and must do all of this while delivering a low maintenance profile. Additionally, when maintenance issues do occur, it’s far more cost-effective to replace a slightly worn rubber coating rather than an expensive drive pulley.

A number of variants exist within the drum coating industry, replaceable coatings that are often compared to car tyres. They sport diamond-grip patterns, added channels for distributing friction, and a number of other optional extras.

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