A seal is a spare part used in various machinery, including pellet mills, to prevent leakage of fluids (such as oil or grease) and contaminants (like dust or debris) from entering or escaping critical areas of the machine. In a pellet mill, seals protect bearings, rollers, and shafts from contaminants such as dust, moisture, and dirt. This is especially important in environments where raw materials like biomass, sawdust, or feed are processed.