What Are Snatch and Pulley Blocks and Where Are They Used?
A snatch block or pulley block is a simple tool and has two main uses:
- Single sheave models – used to redirect the path of a wire rope
- Multi sheave models – used to give mechanical advantage
What is a snatch or pulley block?
A snatch block is a heavy-duty sheave or pulley inside a forged steel casing. Typically, the sheave will run on either brass bushes or roller bearings. It is important to look at the loads, line speed and duty cycles of work before deciding on sheave bearing options. Some snatch blocks also offer grease zerks to help maintain the bearings, enabling long life and friction-free use.
They are primarily designed for lifting, slewing or slewing heavy goods when working as a pulley point that can redirect the course of a winch line.
As the snatch block’s name implies, the operator may open the side plates of the block, allowing the block to be easily inserted anywhere along the length of the wire rope, even if it is terminated at both ends. A pulley block is typically closed and any wire rope rigged into the system will have to be reeved.What are snatch block used for?
- With gin poles in cell tower or tower crane erection
- As a load multiplier on a marine mooring system allowing for greater pulling power but also control
- Vehicle recovery; used with 4x4; first responders
- Arborists use the tool to assist with lowering, lifting or dragging cut tree limbs
- To re-direct line path from a winch system or improve its pulling capacity by up to 100%
- To give mechanical advantage when lifting a load, such as a motor, or a multiplier block arrangement
When rigged into a system, a snatch block can be arranged as a running block (also known as a traveling block). This is where the block is attached to the load being moved; it moves with the load. In other applications the purchase block will be rigged to a fixed point and the item being moved or lifted will travel independently.
Snatch block safety
Snatch blocks can be dangerous if used incorrectly, so it’s important to know what you’re doing.
When used in conjunction with a winch, a huge amount of force passes through the snatch block. In fact, the pressure on the wire rope can be as much as twice that of the actual load being towed or moored.
If the load becomes too high and the block (or other rigging) fails, the resulting slingshot effect can be catastrophic.
With so much force resting on the snatch block, it’s imperative that the equipment is set up correctly and all components attached securely. This includes the anchor point itself; if the anchor point isn’t secure or can’t handle the pressure, this too could result in disaster.
Types of snatch block available on FAD Equipment Store