Know what hardware to use, how to use it, and how its working load limits (WLL) compare with the
rope or chain used with it.
All fittings must be of adequate strength for the application. Only forged alloy steel load-rated hardware
should be used for overhead lifting. Load-rated hardware is stamped with its WLL (Figure 1).
Inspect hardware regularly and before each lift. Telltale signs include:
– wear
– cracks
– severe corrosion
– deformation/bends
– mismatched parts
– obvious damage.
Hoisting Hooks
• Should be equipped with safety catches (except for sorting or grab hooks).
• Should be forged alloy steel with WLL stamped or marked on the saddle.
• Should be loaded at the middle of the hook. Applying the load to the tip will load the hook eccentrically and reduce the safe working load considerably.
• Should be inspected regularly and often. Look for wear, cracks, corrosion, and tw isting – especially at the tip – and check throat for signs of opening up (Figure 2).
Safety Tip
Whenever two or more ropes are to be placed over a hook, use a shackle to reduce wear and tear
on thimble eyes.
Shackles
• Available in various types (Figure 3).
• For hoisting, should be manufactured of forged alloy steel.
• Do not replace shackle pins with bolts (Figure 4). Pins are designed and manufactured to match shackle capacity.
• Check for wear, distortion, and opening up (Figure 5). Check crown regularly for wear. Discard shackles noticeably worn at the crown.
• Do not use a shackle where it will be pulled or loaded at an angle. This severely reduces its capacity and opens up the legs (Figure6).
• Do not use screw pin shackles if the pin can roll under load and unscrew (Figure 7).
Snatch Blocks
• A single or multi-sheave block that opens on one side so a rope can be slipped over the sheave rather than threaded through the block (Figure 8).
• Available with hook, shackle, eye, and swivel end fittings.
• Normally used wh en it’s necessary to change the direction of pull on a line. Stress on the snatch block varies tremendously with the angle between the lead and load lines. With both lines parallel, 1000 pounds on the lead line results in 2000 pounds on the block, hook, and anchorage. As the angle between the lines increases, the stress is reduced (Figure 9).
• To determine the load on block, hook, and anchorage, multiply the pull on the lead line or the weight of the load being lifted by a suitable factor from the table in Fllowing and add 10% for sheave friction.
Turnbuckles
• Can be supplied with eye end fittings, hook end fittings, jaw end fittings, stub end fittings, and any combination of these (Figure 10).
• Rated loads are based on the outside diameter of the threaded portion of the end fitting and on the type of end fitting. Jaw, eye, and stub types are rated equally; hook types are rated lower.
• Should be weldless alloy steel.
• When turnbuckles are exposed to vibration, lock frames to end fittings. This will prevent turning and loosening. Use wire or manufacturer-supplied lock nuts to prevent turning (Figure 11).
• When tightening a turnbuckle, do not apply, more torque than you would to a bolt of equal size.
• Inspect turnbuckles frequently for cracks in end fittings (especially at the neck of the shank), deformed en d fittin gs, deformed and bent rods and bodies, cracks and bends around the internally threaded portion, and signs of thread damage.
Table 2 gives the working load limits for turnbuckles based on the diameter of the shank.
Note how the use of hook end fittings reduces capacity.
Figure 12 shows the areas of a turnbuckle that require special attention during inspection.
Hoisting Tips
• Never wrap a wire rope sling completely around a hook. The tight radius will damage the sling.
• Make sure the load is balanced in the hook. Eccentric loading can reduce capacity dangerously
(Figure 13 ).
• Never point-load a hook unless it is designed and rated for such use. Point-loading can cut capacity by more than half.
• Never wrap the crane hoist rope around the load. Attach the load to the crane hook by slings or other rigging devices.
• Avoid bending wire rope slings near attached fittings or at eye sections.
• Understand the effect of pull angle on beam load (Figure14 ).
