Snatch block

The reel should be set up on a substantial horizontal axis, so that it is free to rotate as the rope is pulled off, and the rope will not rub against derrick members or other obstructions while being pulled over the crown. A snatch block with a suitable size sheave should be used to hold the rope away from such obstructions. 

FIGURE 9.1 Different kinds of snatch blocks and wire rope blocks (courtesy of the Bechtel Corporation). 

There are three types of blocks snatch, wire rope, and crane block. Figure 9.1 shows variations of the snatch block and wire rope block. A typical wire rope block is shown in Figure 9.2. 

A snatch block is an intermittent service block that jerks or snatches the load over small distances. It is characterized by a side-opening plate that facilitates threading wire rope through the block. 

FIGURE 9.4 Rope angle as a variable of snatch block loads (courtesy of the Bechtel Cotporation). 

Snatch blocks are either single or double sheave blocks manufactured with a shackle eye, hook, and swivel end fittings. Snatch blocks are mostly applied for altering the direction of the pull on a line. The stress on a snatch block varies with the angle between the lead and load line. When the two lines are parallel, 2,000 lbs on the lead line added to the 1,000 lbs on each load line result in a load of 4,000 lbs on the block. Table 9.1 shows the multiplication factors for snatch block loads. Figure 9.4 illustrates the rope angle as a variable of snatch block loads. 

Latest developments in the field snatch up and rename an older setup electrolysis block and cooling are integrated into the bottom of the chemical reaction vessel (Single Vessel Technology) [4, p. 533 37]. 

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