More from: shackles

Rigging 101: 3 Fundamental Questions about Shackles

Mytee Products carries a complete range of shackles as part of our rigging inventory. Customers use them to perform heavy lifts, particularly when loading unusual cargo onto flatbed trailers. We know how dangerous such lifts can be, which is why we do our best to encourage customers to adopt a safety-first mindset.

Where shackles are concerned, an important part of safety is thoroughly understanding what they are and how they work. There is not enough space in a single blog post to talk about shackles in detail, but we can offer a few basics. We have done so by way of three fundamental questions that we often hear from customers purchasing shackles for the first time.

 

What are the different kinds of shackles?

Shackles are defined by their shape and the pins they utilize. The purpose in classifying them this way stems from the fact that the shackle has two main paths through which energy travels: the main body and the pin.

In terms of shape, you are looking at anchor-style and chain-style shackles. The former is more circular in shape with the legs tapering toward the center of the shackle’s main body. The latter looks just like a chain link. For purposes of description, these kinds of shackles are sometimes referred to as D-shape shackles.

Pins can be either screw or bolt-type pins. A screw-type pin is just as its name suggests. It has a threaded end that is screwed into the opposite leg of the shackle after insertion. A bolt-type pin slips through both legs and is then secured by either a nut or cotter pin.

What are the biggest concerns when using shackles?

This question is usually born out of inexperience. It is a fair enough question and getting the right answers could mean the difference between a safe lift and an unnecessarily dangerous situation. From our perspective, here are the biggest concerns:

• Replacing manufacturer pins with generic bolts or unidentified pins. A replacement pin that is not strong enough can bend under load.
• Allowing shackles to be pulled at odd angles, thus allowing the legs to open. This could lead to a broken shackle.
• Mistakenly using deformed shackles or those with bent pins. Disaster awaits.
• Purposely forcing pins, or the shackles themselves, into position. This puts unnecessary stress on a shackle.
• Exceeding a 120° angle between multiple sling legs. This puts too much stress on sling and shackle alike.

Most of the concern over lifting with shackles relates to creating unsafe conditions by not using lifting equipment properly. The best way to avoid accidents is to thoroughly understand lifting principles and abide by all generally accepted safe lifting rules.

How often should shackles be inspected?

General guidelines say shackles should be inspected regularly. We prefer a more defined answer: inspect shackles prior to and after each lift. Shackles should be inspected for:

• pin hole elongation and wear
• any bending in the shackle body
• distortion, wear, fractures, or blemishes on pins
• pin straightness and seating
• any distortion in excess of 10% of a shackle’s original body shape.

It is always better to be safe than sorry where shackle inspections are concerned. Some normal wear and tear is expected over the life of a shackle, but wear and tear should not be enough to significantly alter the appearance or function of a shackle. The presence of any significant distortion is reason to discard a shackle.

We carry a variety of rigging equipment and supplies for your convenience. Please do not hesitate to ask if you have questions about our shackles, slings, etc.


Rigging Science: The Physics Behind the Block and Tackle

Mytee Products carries a full inventory of rigging supplies covering everything from blocks to turnbuckles and shackles. All of that is well and good, but sometimes it is helpful to understand the physics behind rigging principals. Understanding makes for safer lifts.

In light of that, we thought it might be interesting to discuss the physics behind the block and tackle principal. The block and tackle represents one of the easiest ways to lift extremely heavy loads with very little force. Block and tackle setups have been used for centuries by cultures all over the world.

The Block and Tackle Defined

A block and tackle isn’t a single piece of equipment. Instead, it is a particular kind of rigging set-up that includes multiple pulleys and some sort of means to lift the load – be it rope, wire, chain, etc. The most basic setup utilizes at least two pulleys with a rope or wire running between them.

The pulleys in a block and tackle system can be located close together or at a distance. Locations are chosen based on the nature of the lift. The pulleys on a crane might be close together while those in the warehouse rigging system are farther apart.

The Principle of Lifting Force

Physics dictates that a certain amount of force is required to lift a load off the ground. The heavier the load, the more force required. The lifting force has to be either equal to or greater than the weight of the load.

For example, imagine you are lifting a 200-pound load using a single pulley and a 200 ft. rope. You have to apply a minimum of 200 pounds of force in order to get the load off the ground. All 200 pounds will be carried by that single pulley. Also note that the amount of force you need is inversely related to the length of your rope.

If your rope is 100 feet long, more force will be required. The opposite is true if your rope is longer than 200 feet. What does this tell you? It tells you that a longer rope and more pulleys should require less lifting force from you.

Sharing the Load among Blocks

Remember that a block and tackle system utilizes multiple pulleys (or blocks) for lifting. Each of those blocks takes some of the weight of the load. So once again, let us assume a 200-pound load and two blocks in your system. Each block carries half the weight, or 100 pounds. Using the same 200-foot rope now means you only have to apply 100 pounds of lifting force instead of 200.

Introduce a third block into the system and you reduce the total weight carried by each block yet again. Instead of 100 pounds per block, you are now in the neighborhood of 70 pounds.

In theory, you can continue adding blocks and lengthening the rope to make your load even easier to lift. In practice though, there is a tipping point. Additional blocks and longer rope create resistance. Make your block and tackle system too big and the amount of resistance in the system could make it impossible to lift the load anyway. So there is a balance between distributing the weight and minimizing resistance.

Distributing the Load

The simplest way to understand the physics of a block and tackle system is to understand that each block in the system takes part of the load. It is all about load distribution. Greater distribution means less lifting force to get a load off the ground. That’s about it in a nutshell.


Safe Lifting Practices with Slings and Shackles

There are times when forklifts, pallets, and loading ramps are not sufficient for moving cargo around. That’s when you need slings and shackles. Lifting a load with slings and shackles also involves some sort of boom, be it from a boom truck or crane. Needless to say that there are a whole host of safety considerations when engaging in this sort of lifting operation.

The Occupational Safety and Health Administration (OSHA) has issued its own guidelines dealing with safe lifting practices. They mention a number of very specific things having to do with slings and shackles. For the benefit of our readers, we have summarized OSHA guidelines below. You can go to the OSHA website and search ‘safe lifting practices’ for more details.

Choosing the Right Kind of Sling

OSHA’s guidance begins with a discussion about choosing the right kind of sling. They discuss slings made from chain, wire rope, fiber rope, and synthetic webbing. The needs of most of our customers are sufficiently met with webbing slings. However, it is always important to assess each load before choosing the right sling for the lift.

OSHA recommends synthetic web slings when practical due to their strength, convenience, shock absorbency, temperature resistance, and safety. Synthetic webbing slings should be used with caution when dealing with acids and other corrosive substances. They should never be used when they show signs of excessive wear, elongation, or distortion.

The Four Points of Safe Lifting

The OSHA guidance goes on to discuss how to lift safely using four points of reference. Those four points are as follows:

1. Size, Weight, and Center of Gravity

The safest way to lift with a sling is to ensure that the hook is located directly over the center of gravity. Slight variations are workable but getting too far off center can cause big problems. The heavier the weight and the larger the size, the more critical center of gravity is.

2. Lift Angle and Number of Legs

A lift angle is formed between each sling leg and its horizontal line. The smaller that angle is, the more stress is put on the sling legs. It is important to know this angle in relation to the amount of weight being lifted. Smaller angles dictate less weight per lift. Larger angles can tolerate heavier loads.

3. Sling Load Limit

Just like webbing straps and chains used to tie down cargo, slings have working load limits. Each sling has a rated capacity calculated by considering the type and size of the sling and the type of hook being used. It is critical that operators know the rated capacity of their slings before attempting a lift. Manufacturers generally mark slings at the factory.

4. Usage, Care, and Handling

OSHA’s fourth point of reference for safe lifting involves the proper usage, care, and handling of slings and shackles. Their guidance suggests that a history of improper usage increases the risk of accidents with every subsequent lift. In simple terms, bad habits are hard to break.

For each lift, proper care and handling of slings is essential. Slings should be cared for to prevent even minor damage. They should be inspected prior to and following every lift. And they should always be used according to manufacturer instructions and OSHA guidelines.

This concludes our basic summary of OSHA guidelines for safe lifting with slings and shackles. If you ever have a question about safe lifting practices, find the answer before you attempt a lift. Remember that lifting with slings and shackles is always dangerous no matter how many safety precautions you take.