![]() How to calculate this stress factor or angle factor is explained later in this article. A wise rescuer however remains aware that despite having the two lines sharing the load, the snatch block itself will carry at least the full load of the pull. ![]() All rescue personnel who have winches in their inventory should have the equipment that’s needed and be capable of setting up a 2:1 mechanical advantage as described. With this running block rigging and “two moving lines to the load,” there is a 2:1 mechanical advantage gained. Rescuers should recognize this as a common and familiar rigging for a winch that results in the object-and the snatch block that’s attached to it-moving as the effort is applied from the winch. With this rigging, the return line runs parallel to the incoming line. The line then returns to an anchor point at the rescue truck near the winch. A running snatch block would be secured directly by strap or chain to the heavy object that must be moved. The wire rope line from the rescue truck’s winch travels out and goes around the pulley (sheave) of the snatch block, making a U-turn. Therefore, with a running block system, the snatch block must be attached to something that moves as the pulling effort from the winch is applied.Ĭonsider a disaster scene scenario where a heavy object must be moved horizontally using a winch rigging system to provide the pulling power. ( Note: Although the examples that are pictured in this column demonstrate the use of steel wire rope, the same rigging concepts and principles apply if a rescue team is winching using synthetic rope.) ![]() When rigged into a system, a snatch block can be arranged as a running block (also known as traveling block), where it physically moves as the pulling effort takes place (see Figure 1). As the snatch block name implies, opening the side plates allows the block to be easily inserted anywhere along the length of the wire rope. Although it actually is a class of lever, basically it is a wheel that has a grooved edge, called a sheave, or pulley, that’s mounted onto a unit that has sides that open to allow it to straddle the wire rope line of the winch. Task: The rescue team shall apply a snatch block tool in a rigging system, so the load on all components, including the snatch block, is maintained at or below their safe working load limit.Ī snatch block is a simple tool. Objective: Understand critical aspects of winching operations when using a snatch block tool in a rigging system Topic: Winching with a snatch block and components ![]()
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