• Conveyor rolls must turn for the labyrinth seals to work correctly.
• The centrifugal and mechanical forces created when the labyrinth seals turn,  keeps solids out.
• When conveyors are idle:

• wet solids pack into poorly designed labyrinth seals;
• locking up rolls
• and as a result belts cut flat spots into rolls
• which in turn cut the belts, injuring workers and destroying careers