Definition - What does Snatch Block mean?
Snatch Block, also known as Sheave or the Pulley, is a common lifting mechanism used on an oil rig to lift abnormally heavy objects. Snatch block is a part of the pulley system used in conjunction with a wire rope or another type of rigging rope, by looping the rope through the pulley (around the sheave) several times before hooking to the object. The force required diminishes proportionately with the amount of pulleys or “loops” used during the hoist.
Petropedia explains Snatch Block
Snatch Blocks are used to deflect a wire rope and can be supplied as Tail Board, with top hook suspension or as shackle suspended. They are often used when suspended from a hook for lifting equipment. A number of snatch blocks can be rigged multi-reeved to increase the capacity (SWL). The more times the wire line is reeved through a snatch block/crane block the greater the safe lifting capacity of the hoist or winch that is pulling the wire rope. This is why snatch blocks are reeved many times, so as to increase the capacity. On the negative side, every time the wireline is reeved the lifting speed is reduced by 50%.