Shackles are U-shaped pieces of metal with a pin along the non-curved side. Shackles are used to lift, secure and rig heavy loads, where they act as the final link in a connection chain or sling setup.
Shackles are advantageous if wanting to make a robust physical connection between the load-lifting device (typically a hoist hook or sling) and the payload that needs to be moved or supported.
Regardless of the type of shackle you’re using, they will always consist of two main components: the body and the pin. The body can have the anchor shape (Bow type) or a chain shape (Dee type). Each body shape can be used with a screw pin or a bolt-type pin. The bolt-type pin in particular is used to ensure safety and that the shackle pin won’t become loose under load or in applications involving vibration or movement.
WHAT ARE SHACKLES USED FOR?
Shackles are used in a variety of industrial and commercial settings.
Just like carabiners, the primary function of a lifting shackle is to provide a strong and durable connection between two points, that can be opened and closed as required to either allow or prevent disconnection. They are most often used in conjunction with other lifting equipment and accessories such as wire rope, synthetic slings and webbing. In these sorts of roles, shackles offer a reliable, secure and strong point of attachment between the sling or other lifting device and the payload in question.
DIFFERENTIATING BETWEEN A DEE AND BOW SHACKLE
D-shackles also referred to as ‘Dee-shackles’, are narrow shackles shaped like a loop of chain. They are usually closed with a threaded pin or a clevis-type pin, and they’re generally seen as suitable choices for moderate to heavy loads that are being lifted in line. Among the many different types of D-shackles available from suppliers and manufacturers today, the most common materials you’ll see listed in catalogues include stainless steel D-shackles, zinc-plated or galvanised, and various forms of alloy steel D-shackles.
They’re among the most common types of shackles found in a huge range of everyday scenarios, and the majority of other shackle types are essentially variations on the basic D-shape version.
For side loads, in which the lifting being done is not completely vertical, D-shackles are not recommended as they can start to twist or bend if enough force is applied.
A Bow Shackle is an ‘O’ shaped metal link which is closed by a bolt. Similar to an Anchor Shackle, the rounded design of both shackles allows Bow Shackles to take loads from many directions without developing a side load.
Bow shackles can also accommodate far wider lifting straps than the narrower D-shackle variants. They can also be used to recover vehicles as they cater to most vehicle weights available.
The trade-off for such advantages is a lower overall weight tolerance than an equivalent gauge D-shackle, provided the lifting is done strictly inline for the latter.
Shackles are quite straightforward pieces of equipment and relatively easy to use in most applications. The trick is to know which kind of shackle and the shackle size, is best suited to which kind of job.
Shackles are often listed for sale by size and frequently the product information might include pin size as well. It’s important to keep appropriate sizing (i.e. material thickness) as well as the working load limit in mind when planning and making a shackle purchase.
SAFETY, INSPECTION AND MAINTENANCE FOR SHACKLE USE.
Because shackles are so often used for critical and intensive lifting and rigging applications, it’s extremely important to make sure you follow some basic safety checks and upkeep rules in order to guarantee more consistent levels of performance over time.
Shackles should be inspected regularly for any signs of general wear, tear and fatigue. Potential points of damage or failure for all shackle types can occur in the body, the pin, or in the eye or pin holes, and it’s important to monitor these areas especially closely over the working lifetime of all shackles.
In particular, inspect shackles carefully for any signs of bending, warping or stretching, which may indicate that the shackle is not coping sufficiently well with the load forces being placed on it. Bent shackles tend to be a sign of excessive side-loading forces, which can ultimately lead to catastrophic failure (particularly of D-shackles), while distorted or fractured pins should be replaced immediately. Even if a pin remains entirely intact, it may not seat properly in the shackle if it’s even slightly warped from its original shape, which dramatically increases the risk of loosening under load. Shackle pins should never be forced or hammered into place if they’re reluctant to seat properly, and must never be replaced with a stand-in piece of hardware that wasn’t designed explicitly for that purpose and shackle type.