30 C.F.R. § 56.14111 – Slusher, backlash guards and securing.

(a) When persons are exposed to slushing operations, the slushers shall be equipped with rollers and drum covers and anchored securely before slushing operations are started.
(b) Slushers rated over 10 horsepower shall be equipped with backlash guards, unless the equipment operator is otherwise protected.
(c) This standard does not apply to air tuggers of 10 horsepower or less that have only one cable and one drum.