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Carryback as Fugitive Material

Material carryback often leads to belt mistracking and subsequent other problems and requires workers to perform hazardous manual cleanup.

Carryback refers to any material that remains attached to the conveyor belt past the discharge point. This material represents a significant fraction of all fugitive materials and can pose just as significant a risk for conveyor systems as transfer point spillage and other types of fugitive materials.

A head pulley showing a primary cleaner, secondary cleaner, and tertiary cleaner.
Typical belt-cleaning systems feature one or more scrapers mounted at or near the discharge (head) pulley to remove residual fines.

These problems present themselves as accumulations of fugitive material, leading to belt mistracking, shortened belt-life, premature component failures, and other problems that create conveyor downtime and expensive repairs. Dust from carryback can pose a risk for fire or explosion as well as slips, trips and falls. Sometimes this dust can also represent a serious health hazard to personnel.

Because carryback is unplanned, it can also manifest in a highly noticeable manner, potentially drawing negative attention from neighbors and regulatory agencies. No matter where it lands, carryback is a leading cause and indicator of conveyor inefficiencies.

Generally, conveyor belts attempt to reduce the incidence of carryback through the use of belt cleaning systems, blades designed to scrape off the fine material that remains adhered to the belt past the discharge point. These belt cleaners are generally designed to clean the belt as it passes around the head pulley.

Carryback is typically the belt’s cargo in its worst state. These particles are generally smaller in size with higher moisture than other conveyed materials, making them more adhesive. The process of conveying materials creates a small amount of vibration that serves to shake small particles and excess moisture down to the lowest levels of the belt, where it combines to create the materials responsible for carryback. When allowed to dry, this material can form a sort of crude cement that can prove difficult to remove, causing damage to the belt and equipment and potentially serving to clog transfer chutes.

Topics: Material Carryback & Belt Cleaning

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