A shackle is a U-shaped, load-bearing connector designed with a removable pin to secure various rigging components. These devices are essential in numerous lifting, towing, pulling, and load-securing operations, allowing for connections between different types of slings, chains, or ropes. Shackle safety and proper use of shackles is crucial to prevent rigging failures, which can lead to property damage or serious injury.
This article will provide an overview shackle safety, various shackle designs, the different types of pins used for load securement, and the materials from which shackles are constructed. We’ll also touch on specialty shackles for unique applications and important safety considerations.
What Are the Different Types of Shackles?
Parts of a Shackle
To better understand how shackles work, let’s familiarize ourselves with their key components:
- Bow: The curved section of the shackle body, often called the bail or body. It is opposite the pin and supports the load.
- Ears: The part of the shackle body that holds the pin.
- Pin: A steel bolt that passes through the ears to secure the shackle.
- Shoulder: The part of the pin that makes contact with the shackle’s ears when the pin is fully engaged.
Always ensure that the shackle selected matches or exceeds the Working Load Limit (WLL) for your lifting application, and that it is compatible with the slings and other rigging components being used. This information can usually be found on the manufacturers website. Find the data sheet for the shackle you are using
Shackle Safety & Types: Anchor Shackles vs. Chain Shackles
The shape of the shackle’s bow determines its suitability for specific tasks.
Anchor Shackles (Bow Shackles)
Anchor shackles, also called bow shackles, have a larger, rounded “O” shape. This design allows them to accommodate side loading or multi-leg sling connections, making them versatile for various rigging tasks.
Safety Consideration: When using anchor shackles for side pulling, you must reduce the WLL based on the angle of deviation from in-line loading.
Chain Shackles (D Shackles)
Chain shackles, also referred to as D shackles, feature a narrower, D-shaped bow. These are designed for in-line tension only and should not be used for side loading. Side loading can cause the bow to twist or bend, compromising safety.
Safety Tip: Ensure that the center line of the load aligns with the center line of the shackle to prevent deformation. Never side load D Shackles!
Shackle Pin Types & Shackle Safety
Choosing the right pin type is essential for ensuring that the shackle functions safely in your specific rigging application.
Screw Pin Shackles
A screw pin shackle has a threaded pin that can be quickly connected or disconnected, making it ideal for temporary or “pick and place” rigging applications. However, screw pin shackles are not recommended for permanent setups.
Safety Tip: Always tighten the pin before each lift, as movement can cause the pin to unthread itself. Before placing tension on the load, back the pin off a quarter turn. This prevents the pin from being torqued during the lift, which makes removal of the pin after the lift difficult.
Bolt Pin Shackles
Bolt pin shackles feature a combination of a bolt, nut, and cotter pin, providing a secure and permanent connection. These are suitable for situations where the shackle may experience rotation or torque. Use Bolt type shackles in long-term installations.
Safety Tip: The nut and cotter pin eliminate the need for retightening, making bolt pin shackles a more reliable choice for applications involving rotational forces. Nut and cotter pin shackles are ideal for semi-permanent applications, where the shackle will be left in place for an extended period of time. Inspection of shackles and rigging tends to get overlooked in these applications. Inspect these shackles before each use. They are not ideal for applications where the shackle will be continually removed and reinstalled because the cotter pin and nut can be misplaced during operations. Only the manufacturers nut and cotter pin should be used for these shackles
Round Pin Shackles
Round pin shackles are secured with a cotter pin and are best suited for applications where the load is applied directly in-line, such as towing, tie-downs, and suspension work. These shackles are not recommended for overhead lifting or in multi-sling configurations.
Shackle Safety Tip: Avoid using round pin shackles in side-loading or multi-leg sling setups, as they may not provide adequate security for these situations. Dynamic loading can cause stress to the cotter pin. For this reason, round pin shackles are not as safe as screw pin or bolt shackles and are not commonly used in construction.
Specialty Shackles
In addition to standard anchor and chain shackles, there are specialized shackle designs for unique lifting and rigging needs.
Synthetic Sling Shackles
Synthetic sling shackles are designed with a wider bow to prevent bunching or pinching of synthetic slings like web slings or round slings. This design ensures that the sling’s full WLL is utilized and prevents damage to the material.
Wide Body Shackles
These shackles offer increased surface area and are typically used with high-capacity synthetic slings or wire rope slings. The larger bow radius prevents kinking and increases the service life of the sling by improving the D/d ratio.
Long Reach Shackles
Long reach shackles are used in applications where the lifting point is hard to access, such as during construction lifts or when handling thicker materials.
Sheet Pile Shackles
As the name suggests, sheet pile shackles are used for pulling sheet piling and are equipped with an easy-opening pin that remains attached to prevent loss during use.
Shackle Materials: Which to Choose?
Shackles are made from a variety of materials, each suited to different environments and load requirements.
- Carbon Steel Shackles: These shackles offer a design factor of 6:1 and are more ductile than alloy steel. They are available in all pin types and are commonly used for general lifting and rigging tasks.
- Alloy Steel Shackles: These shackles, with a design factor of 5:1, are stronger than carbon steel. Alloy steel allows for a higher WLL in a smaller design, making them ideal for high-stress applications.
- Galvanized Shackles: Coated with zinc oxide to resist rust, these shackles are well-suited for environments where corrosion is a concern, though they are less resistant to extreme conditions than stainless steel shackles.
- Stainless Steel Shackles: These offer the highest level of corrosion resistance, making them ideal for marine and chemical environments. However, they tend to be more expensive than galvanized or alloy steel options.
Shackle Safety: Side Loading and Working Load Limits
Certain types of shackles can handle side loading, but it’s essential to reduce the WLL accordingly. For example:
- 0° to 5°: No reduction in WLL.
- 6° to 45°: Reduce WLL by 30%.
- 46° to 90°: Reduce WLL by 50%.
- Over 90°: Side loading is not recommended; consult the manufacturer for guidance.
Safety Tip: When using shackles with multiple sling legs, ensure the sling legs rest against the shackle body and do not exceed a 120° angle, as this increases stress on the shackle. The WLL reductions mentioned above are examples. Consult the manufacturer of the shackle you are using to verify actual ratings for side loading applications.
Conclusion
Choose the right shackle for your rigging needs and also understand your load, sling configuration, and the type of shackle for the job. By partnering with a reputable supplier, you can select a shackle that meets the required Working Load Limit and offers the durability and safety features necessary for your lifts. Always perform regular inspections and adhere to safety guidelines to prevent failures and ensure safe lifting operations. As always, INSPECT YOUR EQUIPMENT before each use and document regular safety inspections in order to assist the team to track what is onsite and what the condition of the equipment is.