Balancing Cost and Effectiveness
The success of an operation in minimizing carryback can be classified into various "Levels." These levels are determined by measuring the amount of carryback remaining on a specified area of belting, typically a square meter. In this context, Level 0 cleaning represents a baseline where more than 250 grams of material per square meter remain on the belt.
Level I cleaning allows 101 to 250 grams of carryback per square meter and is typically achieved with a single primary cleaner or a slab-style secondary cleaner.
Level II cleaning involves leaving 11 to 100 grams of material per square meter of belting. This level is often accomplished using a double or triple engineered cleaner system, which includes a pre-cleaner, secondary cleaner, and sometimes even a tertiary cleaner.
Level III cleaning aims to reduce carryback to levels between 0 and 10 grams per square meter. Systems achieving this performance typically involve belt-washing mechanisms with water-spray bars, multiple cleaning assemblies, and methods for removing excess moisture from the belt. These advanced systems offer superior cleaning performance but come at a higher initial purchase and maintenance cost.
As a company invests more in belt cleaners, the cost associated with cleaning up fugitive material (carryback released from the belt) generally decreases. The relationship between the purchase and maintenance of cleaning systems versus the savings from reduced cleanup expenses reaches a break-even point where the curves of Cleanup Cost and Belt-Cleaning System Investment and Maintenance Cost intersect.
In this economic analysis, the optimal point of benefit tends to be around or near Level II cleaning performance. Decreasing carryback levels or improving cleaning effectiveness impacts two interconnected costs: investment costs rise while cleanup costs decrease. While it's possible to nearly eliminate carryback, the investment required for such a system may exceed the cost savings from reduced cleanup expenses. Therefore, adding additional belt cleaners beyond a certain point, based solely on ROI calculations, may not be justified.
Multiple belt cleaning systems take into consideration the dynamics of the surface of the belt and nature of the material as it passes around the head pulley.
Similar cost-benefit analyses can be conducted for maintenance and adjustment of belt-cleaning systems. While regularly cleaning and re-tensioning the cleaning blades can enhance performance, there's a threshold where the labor costs of frequent adjustments outweigh the benefits gained.
This economic evaluation focuses solely on the financial benefits of belt-cleaning system improvements and does not consider factors such as health, safety, or community relations. The optimal balance between these elements, maintenance costs, and return on investment should be individually assessed and optimized for each plant.