From boats and ships to a variety of industrial lifting applications, shackles are the primary connecting device in a rigging system. When it comes to material handling, they are perfect for use with lifting slings and tow ropes.
Simply put, a shackle is nothing but a U-shaped piece of metal made from galvanized or stainless steel with a quick release clevis pin or bolt mechanism.
Like all other types of rigging hardware, shackles also require regular inspection and maintenance to ensure safe and efficient use. If you don’t inspect the shackles regularly, it can result in deadly accidents.
That’s why the American Society of Mechanical Engineers (ASME) has created standards for selection, use, and maintenance rigging hardware, with the B30.26 Rigging Hardware section focusing on shackles, among other lifting hardware.
In this post, we will take a look at the critical factors you should look for when visually inspecting shackles before every use.
1. Pin and Body Identifications or Markings
One of the first things you should check is pin and body identifications or markings. The ASME standards require every manufacturer to provide the necessary identifications and markings on the body and pin of each shackle.
- Body: The markings on the body tell you about the manufacturer (trademark or name), rated load limit, and the size of the shackle. These markings are forged, cast, or die-stamped on the body.
- Pin: The pin markings also tell you about the manufacturer and rated load limits, along with the grade and type of the material used to make it. They are also forged, cast, or die-stamped on the pin.
Before starting any material handling task, make sure to check the shackles for identifications and markings. If these markings are missing, you won’t be able to know the rated capacity of the shackle.
If the load you attach is more than the rated capacity, it can result in fatal accidents. So, if these specifications are missing or illegible, you should replace the shackle right away.
2. More Than 10% Damage to Original Shape
If any shackle is more than 10% worn out of its original shape, it is deemed unsafe for use. You can visually inspect each shackle before use to check if there is an elongation or wear of the shackle eye and pinholes. Elongation usually indicates that the shackles had been subject to overloading. If you see any of these signs, discard the shackle immediately.
3. Excessive Corrosion and Pitting
Pitting is a localized form of corrosion, commonly found in all metal shackles. Usually, pitting and corrosion take place if the shackles get exposed to moisture and oxygen for a longer period. The process of pitting produces small holes or cavities in the metal, making the shackles unsafe for lifting applications even within the rated load limits.
The threads of the screw pin and the grooves of the ears of a shackle are the most common areas for finding pitting and corrosion. The corrosion prevents the pin from fastening with the ears of the shackle properly, making it unsafe for use. So, check these areas carefully before each use. If you find any signs of pitting, remove the shackle from use immediately.
4. Other Deformations
Shackles are also susceptible to other forms of physical distortions, and may be bent, twisted, stretched, sagged, and cracked load-bearing components. These damages may become more prominent with age and excessive use. Make sure to check the body, the pin, and the pinholes carefully for these damages.
You should never try to repair bent, cracked, or twisted shackle components. The only safe option is to remove the damaged shackle from use.
5. Heat Damage
At the time of manufacturing, shackles are subject to heat treatment. The process of heat treatment involves using extreme chilling or heating temperatures to harden or soften the shackle material as per the desired requirements. This process plays a critical role in determining the elongation and duration of the shackles.
However, the flip side is that when the shackles get to heat in the field, the process can get reversed, distorting the shackles. A few signs may indicate potential heat damage. For example, blue or straw discoloration of the shackle material is normally a sign of heat damage.
Alternatively, when welding spatters, which are essentially molten dots of metal, fall on a shackle, their heat gets transmitted to the shackle immediately. This heat exchange can harm the physiological properties of a shackle. Make sure to check for these damages before each use.
How Frequently Should You Inspect the Shackles?
By law, regular inspection is necessary when it comes to material handling and rigging devices like shackles. You will need to perform the following three types of inspections to ensure safety and performance.
- Initial Inspection: You need to perform this inspection when you purchase new shackles or get old ones altered or repaired. Make sure to have an experienced and certified professional to make these inspections.
- Before Use Inspection: Every time you want to use a shackle, you need to inspect it visually. If you find any of the distortions that are mentioned herein, you need to replace those shackles immediately.
- Periodic Inventory Inspection: Apart from these, you need to check your inventory of shackles once every year. In this inspection, however, you will need to check factors like the frequency of shackle use, environmental conditions of the use, nature of the load, and duration of the use. All these factors affect the service life of each shackle.
Shackles play a critical role in various rigging and material handling applications across a wide range of industries. However, using shackles without a thorough safety check before each use can be dangerous. Hopefully, the above checklist will help you make sure that each shackle you are using is not only safe but also efficient.