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A shackle refers to a steel connector in a U-shape that features holes drilled into the ends to receive a removable pin or bolt. Typically, shackles are used for connecting slings or loads to winches or crane blocks. They are an essential, powerful, and indispensable piece of material handling equipment. The "bow" of the shackle refers to the U-shaped body of the shackle.
At first glance, a shackle may appear to be a simple and unremarkable piece of equipment. When envisioning a construction site, we typically think of towering cranes and steel structures, not a seemingly insignificant shackle. However, despite its unassuming appearance, shackles play a crucial role in material handling equipment. Without them, cranes would be unable to lift and steel structures would remain grounded, rendering the construction site essentially useless.
Shackles play a crucial role in rigging, lifting, and material handling operations as they are incredibly versatile and important equipment used to connect different lifting equipment to the load. Despite their seemingly simple design, shackles can weigh anywhere from an ounce to over four tons and can lift loads exceeding 1,500 metric tons.
Shackles have a wide range of applications across various industries, including:
Transportation
Construction
Land-based energy
Marine
Offshore energy
Entertainment
Power and utilities
Cargo handling
Agriculture
Forestry
Oil and gas
Infrastructure
Towing
Mining
Familiarize Yourself with Shackles.
Using and handling shackles appropriately is crucial to maximize their potential. Now, let's examine several varieties of shackles:
Remotely operated vehicle (ROV) shackles
Shackles designed for underwater operations are essential in the subsea industry. They come in standard colors that make them highly visible to ROV operators and are equipped with specialized handles to accommodate different robotic grips.
Theatrical shackles
The shackles are designed with a black finish to blend in with the stage surroundings, ensuring dependable strength behind the scenes without drawing attention away from the on-stage action.
Anchor shackles
Anchor shackles, when utilized properly, allow for the collection of single or multiple leg slings in the bow, making them highly versatile and widely used across various material handling applications.
Wide body shackles
Wide body shackles are a type of anchor shackle with a broader bow cross-section, offering several benefits for heavy lifting operations. The wider shape provides a significant increase in sling bearing surface, eliminating the need for a thimble. Moreover, it boosts the usable sling strength, resulting in a longer lifespan of wire rope slings.
Chain shackles (Dee shackles)
Their construction allows for effective transportation of goods, especially in tight lifting spaces. Despite the term "chain shackle," this shackle variety is mainly employed in conjunction with wire rope slings that have a single leg and diverse attachment locations.
Round pin shackles
Round pin shackles are suitable for use in tie-down, towing, suspension, and lifting operations where the weight is applied solely in a straight line. However, it's crucial to avoid employing them in rigging situations where multiple sling legs need to be gathered or where there's a risk of side loading.
Screw pin shackles
These shackles find their use in pick-and-place tasks. Bolt-type shackles are recommended for permanent or long-term installations. Screw pin shackles, on the other hand, are appropriate for applications that involve side-loading situations. It's important to note that reduced working load limits are necessary for such cases. Moreover, during service, avoid rotating the screw pin using live lines, such as a choker application.
Bolt-type shackles
These shackles are versatile and can be employed in any situation where round pin or screw pin shackles are utilized. However, they are particularly suggested for permanent or long-term installations and in cases where the load may slide on the shackle pin, causing it to rotate. Bolt-type shackles have an additional securement system that utilizes a nut and cotter, eliminating the need to tighten the pin before each lift or movement of load.
Shackle Application
The correct usage of shackles is crucial in any material handling scenario. Here are some of the most frequently observed shackle application best practices. Although these are good general guidelines, it's always recommended to consult the manufacturer for a complete set of application recommendations and training protocols.
For permanent or long-term connections, utilize bolt-type shackles exclusively.
Avoid exposing shackles to forces that exceed their working load limit.
Before each lift, ensure that screw pins are tightened and fully engaged.
If a shackle is intended for a cotter pin, it should be used and maintained as such.
Ensure that the applied load is centered in the bow to prevent side loading.
Do not apply multiple sling legs to the pin.
Conduct regular inspections on shackles for any damage caused by excessive heat, deformation, wear, modifications, cracks, nicks, or gouges.
Shackle Inspection
Regular inspections of shackles are essential to verify their suitability for continued use. In case any of the defects listed below are identified, shackles must be taken out of service. It is worth noting that ASME B30.26 and the manufacturer's guidelines offer additional details on these defects, which include but are not restricted to:
Incomplete shackle pin engagement
Wear or metal loss that exceeds 10% of the shackle bow’s or pin’s original dimension
Evidence of heat or weld spatter
Excessive pitting or corrosion
Any signs of deformation
Any signs of cracks, nicks and gouges
20% or more of the threads are damaged
Evidence of modification of any kind
Missing or illegible manufacturing identification
ID and Application
To ensure the appropriate application of shackles, it is crucial to use the suitable type and size of shackle. It is advisable to inspect the bow of the shackle closely for details such as the working load limit, size, traceability code, and the manufacturer's name or trademark. Additionally, one should not overlook examining the pin or bolt for the manufacturer's name or trademark, grade, material type, or load rating.
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