27. (1) No pulley block shall be used in the processes unless the safe working load is clearly stamped upon it.
(2) The safe working load of a single-sheave block is to be taken as the maximum load that can safely be lifted by the block when the load is attached to a rope passing around the sheave of the block.
(3) In the case of a single-sheave block where the load is attached directly to the block instead of to a rope passing around the sheave, it is permissible to lift a load equal to twice the safe working load of the block as determined in subsection (2).
(4) Where a rigging arrangement plan is available on board, it is permissible to use single-sheave blocks in any position where the maximum “working load” or “resultant” is not more than double the safe working load or half the proof load of the block.
(5) Where no rigging arrangement plan is available on board, single-sheave blocks shall have a safe working load not less than the load being lifted or “hook load”.
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