completed by winding several turns around the wire or small stuff and tying the ends securely.
Hooks should be inspected at least once a month, but those used for heavy and continuous loading should be inspected more frequently. Attention must be given to the small radius fillets at the neck of the hooks for any deviation for the original inner arc. Additionally, each hook must be examined for small dents, cracks, sharp nicks, worn surfaces, or distortions. If any of these defects are present, the hook must be discarded.
Hooks normally fail by straightening. If any deviation of the inner arc of a hook is evident, it indicates that the hook has been overloaded. Evidence of overloading a hook is easy to detect, so it is customary to use a hook that is weaker than the chain it is attached to. Using this system, distortion of the hook will occur before the hook is overloaded. Any distorted, cracked, or badly worn hook is dangerous and should be discarded immediately.
The safe working load of a hook can be formulated by using the following rule of thumb:
SWL = 2/3 x D2 x 1 ton. D is the diameter (in inches) of the hook where the inside of the hook starts to arc (fig. 6-26).
Below is an example of the safe working capacity of a hook with a diameter of 5/8 inch:
Figure 6-26. - Hook diameter.
D2 = 5/8 X 5/8= 25/64
SWL = 2/3 x 25/64 x 1 ton= 25/96= 0.2604 ton
0.2604 ton x 2,000 pounds/ton= 520.8 pounds
In the metric system, the formula for the safe working load for hooks is as follows: SWL = .46 x D2 x 1 tonne
Below is an example of the safe working capacity of a hook having a diameter of 1.59 cm.
D = 1.59 cm
D2 = 2.52 cm2
SWL= .046 x 2.52 cm2 x 1 tome = .116 tonne
Shackles (fig. 6-27) should be used for loads too heavy for hooks to handle. They provide a useful way of attaching, hauling, and lifting a load without tying directly to the object with a line, wire rope, or chain. Additionally, they can be attached to wire rope, line, or chain.
Safe Working Load of Shackles
The formula for computing the safe working load for a shackle is as follows:
SWL = 3D2 x 1 ton
Figure 6-27. - Two types of shackles: A. Anchor; B. Chain.Continue Reading