When you are carrying out rigging jobs that involve shackles, it is very important to the right type of shackle for your application. With the right shackle, you can achieve your rigging goals in a safe and efficient manner and complete the job without incident.
1. What’s a shackle?
A shackle is a jaw or u shaped connecting link, which is designed to connect the lifting slings, wire rope, chain, and rope for a variety of rigging, lifting, pulling, and hoisting applications. The removable pin design is perfect for temporary lifting jobs or quick connect and disconnect.
2. What are the different types of shackles?
Let’s identify the different parts of a shackle first, you can refer to the below sketch to know terms like “body” and “pin”
Shackles come in a number of a wide variety of types, styles, sizes. It can be confusing to choose the right shackle for your rigging jobs, the shape of the shackle’s body is a major determinant of how it can be used, we just outline some of the basic differences between the most common types of shackles in this article.
chain shackle vs anchor shackle (bow shackle vs d shackle)
Anchor Shackles / Bow Shackles
The terms anchor shackles and bow shackles are both used interchangeably, feature a large rounded shape that increased area on the inside of the shackle body and allows them to take loads from many directions without developing significant side load. That makes them ideal for use with multiple-leg slings, connecting slings to load rings, and accommodating a wider strap.
Chain Shackles / D Shackles
Chain shackle is referred to as D shackle/Dee shackle, due to the “D” shape design body. “D” (chain) shackles are generally used to join two pieces rated for in-line tension, while bow (anchor) shackles are typically employed where more than one attachment has to be made to the body, for side and racking loads may twist or bend the chain shackle.
Shackle Pin Types: Screw pin shackles vs Bolt type shackles
The shackle pin types are the deciding factors on which shackle will work best for your application.
Screw pin shackles are suitable for quick-to-assemble to connect or disconnect the two-component items, for you can easily and quickly thread the pin insert through the ears and tighten it down. They can be used for little risk of the pin becoming unscrewed during the lifting operation and are not recommended for permanent or long-term installations.
Bolt type shackles are also referred as safety pin shackles, for the combination of a bolt/nut/cotter pin and the split retaining pin cannot unscrew in service, it is a more secure choice than screw pin shackle, and can be used in any application that uses a round pin or a screw pin.
The screw pin anchor shackle is used for static loads, side loading, and multi-leg directions, while bolt type anchor shackles for applications where there may be movement or remains connected for semi-permanent or long-term.
3. Shackle sizes and shackle materials you should know
Rigging shackles can vary from different types, sizes, and qualities in order to suit different rigging jobs. That’s why when it comes to choosing the right type of shackles, one must have adequate knowledge about the basic properties it possesses.
This article will discuss some main properties of the shackles, as well as how those parameters are interconnected to each other.
No matter small shackles or big shackles, always be aware that the diameter of the shackle pin is usually longer than the shackle body measurements, however, the key measurements given under any standard shackle sizes will be the diameter of the shackle body, not the shackle pin sizes. Following the picture show how to measure shackle length:
Due to varying shackle sizes, it might be clear that the shackle weights are different, normally, sizes or weights should not have more than a + or – 5% variance within standard shackle sizes(RR C 271 shackle, ASME b30 26 shackles), the most popular shackle sizes and dimensions currently available in the market are 3/4″, 5/8″, 1/2″, 1″, 3/8″ and 7/8″.
Lifting shackles are made on the basis of loading capacity, performance, and environmental applications, These factors are firstly determined by the raw materials, normally they can be divided into three types of shackles by materials, they are carbon steel shackles(mild or low-carbon steel), alloy steel shackles and stainless steel shackles(inox steel or inox). If you want to know more about rigging hardware materials, check out this useful article.
Carbon Steel Shackles
Our conventional shackles, with safety factor of 6:1 or 4:1, hot dipped galvanized or galvanized finish. Available in round pin, screw pin, bolt type.
Alloy Steel Shackles
Alloy steel shackles feature improved mechanical properties, making them more highly loading limited, fatigues, or can be used in some extreme conditions. Safety Factor of 5:1. Refer our Grade 80 alloy steel shackles, It can achieve an equivalent WLL as carbon shackles in but with smaller and lighter weight design.
Stainless Steel Shackles
Stainless steel shackles feature a chromium oxide film on their surfaces which creates high corrosion resistance, can be used in saltwater or chemical environments, are ideal for marine applications. Shackles made from stainless steel are typically more expensive than galvanized shackles.
Both stainless steel shackles and galvanized shackles can offer protection from rust and corrosion, but stainless steel shackles are better choices, for the galvanised shackles just add a thin layer of zinc oxide on the shackle body, while stainless steel shackles are natural to protect against rust and corrosion because stainless steels contain the element “molybdenum”, which can be especially used in extreme conditions or moisture or in a high chloride environment.
Shackle sizes and material are part of the main aspects of rigging shackles that affect its grade & price. By having a rough idea of them, you may easily choose the right shackles but the best way of getting these figures is by asking your manufacturer in the first place.
4. How the Shackle is produced?
Anchor shackle, snap shackle, chain shackles, tow shackle, recovery shackle, there are hundreds of types of shackles are the most commonly used in rigging applications, how are these rigging shackles produced? In this article, we will show you how to produce the shackles product.
Main Procedures include:
Cutting → Heating → Roll Forging → Punch Bending→Die Forging → Edge Cutting → Burr Removing→ Drilling, Tapping, Thread Rolling → Heat Treatment (Quenched & Tempered) → Shot Blasting → Surface Treatment → Inspection→ Packing
- Cutting: We use the cold cutting by 5000kN type shears to the whole round steel into pieces, no matter what size you want to produce such as 3/8 inch shackle, 1/2 inch shackle, 5/8 inch shackle, 3/4 inch shackle, or even 4 inch shackle, we should make sure the round steel pieces length is at least two times of shackles body length.
- Roll forging and punching bending are also the very important processes, for heating the shackle and hammering it into shape to creates the desired steel grain structure.
- In the process goes into making these shackles, dia forging and heat treatment steps are the key points, after dia forging, all load rated shackles structure has become more compact, and the plastic and mechanical properties of the shackle rating have been improved.
- Heat treatment also known as Quenched and Tempered, makes the shackles have a high fatigue resistance and allows the shackle body and pin to bend before breaking, not to brittle fracture, keep the load rating safe, keep the required temperature and time on auto-continuous heat treatment furnace, then you can get the high strength shackles featured 6times W.L.L
- Edge Cutting, Burr Removing, Drilling, Tapping, and Thread Rolling steps make the shackles surface more smooth, and prepare for the next process surface finishing.
- Surface treatment can offer excellent protection from rust and corrosion for rigging shackles, making them achieve and maintain high performance in harsh conditions of heat, cold and salt corrosion, etc
So in theory, it is very simple to manufacture the rigging shackles. However there are many more details that must be closely monitored and controlled, and this requires time and experienced personnel.
If you want to get more useful knowledge about producing the lifting shackles, you can contact us by email at [email protected]. We will be glad to share with you more useful information.