R 408.11827 Sheaves.

Rule 1827. (1) Sheave grooves shall be smooth and free from defects that could cause rope damage. (2) Sheaves carrying ropes that can be momentarily unloaded shall be provided with close fitting guards or other suitable devices to guide the rope back into the groove when the load is applied again. (3) Sheaves in the bottom block shall be equipped with close fitting guards that will prevent ropes from becoming fouled when the block is lying on the ground with ropes loose. (4) Pockets and flanges of sheaves used with hoist chains shall be of dimensions that the chain does not catch or bind during operation. (5) All running sheaves shall be equipped with means for lubrication.Permanently lubricated, sealed, or shielded bearings meet this requirement