Lifting and rigging heavy items can cause lots of strain on your equipment and quickly become dangerous work. Using pulley mechanisms, like snatch blocks, allows you to increase the strength of your rope and reduce the amount of strain on different anchor points.
Used mostly for vehicle recovery situations, snatch blocks are a great tool to pull or hoist heavy items, as well as a variety of other applications. Read on to learn more about these devices and the different ways of using them.
What is a Snatch Block?
A snatch block, also known as a snatch pulley or snatch block pulley, is a particular type of heavy-duty pulley block that provides a strong and versatile mechanical advantage to lifting and rigging heavy items. They are typically used in vehicle recovery and work in conjunction with winches. However, they also work for other purposes like lifting and hoisting heavy objects, towing small vehicles, and clearing items out of roadways and other paths.
When configuring a pulley system to pull heavy items, a snatch block adds an additional component that offsets the anchor point. This allows you to pull in a three-point motion, changing the direction of the cable, reducing the amount of force needed, and making for a more efficient process.
Snatch Block vs. Wire Pulley
A common question asked is "what are snatch blocks, and how are they different from other wire pulleys?"
In essence, snatch blocks are heavy-duty pulleys in metal casings. However, the metal plate, sometimes called a "cheek plate," opens up for easier threading, or "reeving," of the wire rope. Pulleys do not have this capability, and require reeving the wire rope through the opening.
- Learn more about the difference between snatch blocks and wire pulleys.
Both of these mechanisms work the same way, and it really comes down to user preference, as well as what the situation requires.
Types of Snatch Blocks
There are three main types of snatch pulleys that come in many different variations and designs:
- Snatch Block w/ Hook End Fitting
- Snatch Block w/ Shackle End Fitting
- Swivel Snatch Pulleys
We at US Cargo Control offer different sizes, makes, and variations of these snatch pulleys, including Crosby® McKissick® Snatch Blocks.
How to Use a Snatch Block
Open the Metal Casing
This is done differently depending on the type of snatch block you have. Some require pulling a wire pin out of the sheave bolt, while others need to completely unscrew the sheave bolt to open up. Make sure you follow the directions on how to open up these mechanisms without completely disassembling them.
NOTE: Wire pulley do NOT open up.
Thread Wire Rope
Once opened up, then the next step is to thread the wire rope through, otherwise known as "reeving." Wrap the wire rope around the sheave a few times to secure it in place.
Close the Metal Casing
After settling the rope inside the sheave where you want it to be, seal up the metal casing by screwing the bolt back on or putting the pin back into place.
3 Common Ways to Use a Snatch Block
There are many different configurations and applications for using snatch blocks. The most common reasons are listed below:
1. Vehicle Recovery
Snatch blocks are often associated with vehicle recovery, where rescue trucks use these contraptions with winches and wire rope to increase the strength and allow for a smoother, easier recovery process. Rescue trucks attach the device to the vehicle via anchor shackle and pull the car out with its winch. Additionally, multiple snatch blocks will further increase the pulling power of the winch by adding a device to the rescue vehicle, itself.
Graphic from Ordealist.
For vehicles harder to reach directly, establish a firm anchor point, like a tree or a third vehicle, to redirect the pulling force and continue moving the vehicle in the intended direction. Use a tree saver strap or chain to wrap around the tree and connect the snatch block to.
Courtesy of Ordealist.
Some vehicles may be damaged or don't have a strong enough connection point. Using recovery straps or anchor shackles provides makeshift anchor points and access to the stuck vehicle.
- WATCH: Recovery Straps
Vehicles can also use snatch blocks for towing stuck or stranded vehicles along the road. They use a heavy-duty shackle that connects the device to the stuck vehicle and loop the wire rope through to the winch. This creates two parallel lines of taut wire rope used to pull the stuck vehicle.
3. Overhead Lifting & Hoisting
Lastly, snatch pulleys are used in lifting applications to increase the capacity of wire hoists. Cranes and other lifting equipment use a winch to pull their loads, and with the addition of snatch blocks, they reduce some of the tension when applied correctly.
- Use StraightPoint Load Monitoring Cells to better measure how much tension and weight your load has.
It should be addressed, but other smaller equipment with lifts or booms can use these devices. Ideally, these devices work for lifting items over short distances.
Safe Use of Snatch Blocks
No matter what you use snatch blocks for, make sure to use them correctly and within their rated capacities. Because so much force passes through them, it's crucial that you use the right kind of snatch pulley and have the right setup for the job. Here are some quick tips to follow:
- Choose a snatch block that has a rating of double the pull of the winch you'll use with it.
- Match the sheave size of the block to the diameter of the rope you'll be using with it.
- Check the working load limits (WLLs) of all materials you'll be using to prevent parts from damaging or breaking.
- Ensure your anchor point is solid enough to handle the imminent pressures of the job.
- Make sure the connection is secure for the snatch block as well as the pulley.
- Use orange cones, reflective safety vests, or other vehicle safety supplies if you are working in areas with oncoming or busy traffic.
Safety is of paramount importance at U.S. Cargo Control. Contact our experts if you have any questions about these products and how to set up a safe job.
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