Shackles are versatile, load-bearing tools with removable
pins to secure or hold objects in place. They act as connectors for slings,
chains, ropes, or rope chains. As the pins are removable, the shackles are an
essential accessory for various lifting, rigging, towing, pulling, and hoisting
applications.
Shackles come in a variety of shapes and sizes. Sadly, their
simple construction often leads to widespread incorrect use. Using incorrect
shackles for a specific application can pose a safety risk when operating huge
machinery or heavy payloads. This post will explore six different types of
shackles you should know about.
Different Types of Shackles
Shackles typically have two main components, which define
their classification: the body and the pin. The body generally is horse-shoe
shaped or sharp-U shaped, and the pin runs through both ends of the loop. The
fasteners can be threaded or part threaded.
1. Classification By Body Type
Most shackles come in two main configurations: D shackles
and Bow shackles.
- D Shackles
A D shackle, also called a chain shackle, has a narrow body forming a D-shape.
It resembles a standard chain loop or link. The D-shackle is designed for
in-line tension and can hold more weight than a bow shackle of the same size.
Chain shackles are among the most common types and are ideal
for a wide range of everyday applications. Shackles are perfect for straight,
in-line lifting applications in an industrial setting.
It's essential to note that a D shackle can only be used for
perpendicular loading and shouldn't be side-loaded. Its shape makes the body susceptible
to twisting or bending when side-loaded. The center line of the D shackle
should coincide with the centerline of the payload when in use.
The D shackle can be closed using a clevis-type or threaded
pin. It's also available as galvanized steel, stainless steel, or various forms
of alloy steel. A chain shackle from alloy steel typically has a higher working
load limit than other materials.
Bow Shackles
A bow shackle, also called an anchor shackle, has a large,
rounded œO shaped body. The wide-flared bow shape allows the shackle to be
side-loaded at an angle. Anchor shackles typically take up more room and have a
lower working load limit than D shakes of a similar size.
Bow shackles can withstand far-reaching load straps than
narrow D shackles, supporting multi-sling leg connections. However, the
load-rated capacity decreases depending on the load angle.
- At 0° load angle, the bow shackle can carry 100% of its
maximum working load limit.
- At a 45° load angle, the anchor shackle can only hold 70%
of its maximum working load limit.
- At a 90° load angle, the bow shackle can only support 505
of its maximum working load limit.
2. Classification By Pin Type
The type of pin used to lock a bow or D shackle should
provide a secure connection without adding friction to the payload attachment.
The most popular types of pins are the screw, rounded and bolt-type.
3. Screw-Pin Shackles
Screw-pin shackles use a threaded pin that runs across the
ears of the body and is tightened down. They are easy to assemble and remove
and are ideally used for temporary or short-term installations.
Screw-pin shackles can be used for side-loading, but the
load weight reduces depending on the angle. You may need to remember to
retighten the pin with each use, as the screw pin is prone to unthread itself.
If you work in an environment with too much vibration, a wire mousing can
secure the pin to the lugs.
4. Bolt-Type Shackles
Bolt-pin shackles are popular for permanent installations
and have a bolt, nut, and cotter pin between the body's ears. The pins remain
secure even when subjected to torque or rotation. The cotter pin plus the
tightening nut eliminates the need to retighten the pin each time you wish to
use the shackle. Bolt-type shackles can be used in all applications using a
screw or rounded pin.
5. Round-Pin Shackles
Round pin shackles have an unthreaded pin secured with a
cotter pin. The shackles are perfect for applications where the pin is
subjected to twisting or torque.
Round pin shackles are popular in tie-down, suspension, or
towing applications. They are also used in in-line applications. Round pins
aren't suitable for overhead lifting operations with multiple slight
attachments or side loading.
6. Specialty Shackles
Some applications require specialized shackles adapted to
meet the payload demands or the work environment. This makes them more suitable
for specialist applications than standard shackles. Examples of specialty shackles
include:
Piling Shackles: typically used in the construction industry
and are used to secure piling sheets reading for piling into the ground.
Trawling Shackles: are tailored for marine environments and
are common in trawl doors and attaching trawl nets.
Wide Mouth Lifting Shackles: have a wider mouth opening and
allow fitting of larger harnesses and carry heavier loads.
ROV Shackles: are tailored for marine environments and
remotely operated vehicles used in subsea lifting operations.
Final Thoughts
Shackles are essential load-bearing fittings that help
secure loads in domestic and industrial settings. Understanding the different
types of shackles can help you pick the right one for your application. Always
ensure that the shackle you use meets or exceeds the load limit for your
payload.
