If you have a big job in which you need to do some heavy lifting, do you know which lifting sling would be best for the job? First, one must take into account the weight, size, dimensions and shape of the item being lifted. Then, what will be used to do the lifting? A crane? A hoist? Some other lifting device? Once you have these planned, you need to consider which lifting device would be the best. We will look at the different choices available to suit your needs.
Which Lifting Sling Should I Use?
Slings can be made of different materials. Wire rope, chain or synthetic? Which one is best for the job and why? We will look at the different types and attachments to help you make an informed decision.
Wire rope slings are the most versatile of the lifting slings. Multiple strands of several steel wires wrapped around a steel or fiber core, provide a strength and versatility that is unmatched in chains and nylon ropes. They provide strength, flexibility and are lighter in weight than chain slings. Unfortunately they are not repairable when damaged, they have a low strength to weight ratio and can be susceptible to corrosion. They are, however, resistant to abrasion, fatigue and corrosion
Nylon slings are lightweight, extremely flexible and easy to work with. They are fairly inexpensive, come in a variety of sizes and are easily replaced if necessary. These slings are the best choice when lifting or moving delicate equipment or highly finished pieces. They are strong enough to lift heavy loads, but the materials are soft enough to protect valuable loads from being scratched or crushed. As some synthetic slings are fire resistant, they can be used around explosives.
WIre rope and synthetic slings can snug up around the load, but when it comes to durability and strength, the chains are the toughest and most dependable of the lifting slings. They have the power to withstand harsh temperatures that wire ropes and nylon ropes do not. They are the best choice in the most extreme weather and for the heavy-duty loads. Their fortitude comes from their flexible design.
Heavy machine shops and foundries count on their strength for repetitive lifting in challenging conditions that would destroy wire rope or nylon slings. Wire rope and nylon slings would need to be disposed of in these circumstances, but if a chain sling is ever damaged, it can be repaired quite easily and can be re-certified and can go on working hard for you.
Do I have a Balanced Lift?
Before making any decisions on lifting sling configurations, you need to make sure you have a balanced lift. In order to do that, you need to consider the following:
- The weight of the object
- The object’s center of gravity
- How many attachment points
- What type of hitch is needed
- Sling angle geometry
- The reach of the lifting device
- Height restrictions
- Fitting requirements
- Weather conditions
Once this is complete, you need to choose a lifting sling, but which one? We will look at each one so you will be confident in your decision on which one will be best for your application.
Now we will look at the slings themselves. There are four basic sling configurations:
- Basket Hitch
- Choker Hitch
- Multiple Leg
Vertical hitches, sometimes called straight hitches and can be made from wire rope, chain, or nylon. This hitch has an eye on each end, one eye connects to the lifting device, the eye on the opposite end connects to the device to be lifted. The load being lifted must be a balanced load and a tagline should be used to minimize rotation.
It’s important that the load being lifted by a basket hitch is balanced as well. When using a double basket hitch, you must distribute the load equally between slings. The basket sling runs beneath the load and the eyes at both ends are attached to the lifting hook.
To better balance the load and get a better grip, a double wrap basket hitch may be used. When using this sling, wrap the sling twice around the load and remember to not overlap the the sling underneath the load. Make sure it stays in position during the move.
For the basket hitch to work at full capacity, the legs must be at a vertical 90°. When used in this fashion, they have twice the lifting capability of a vertical sling. Lifting capacity is reduced when the sling angle is less than 90°.
Choker hitches are used when you need more load control because they can be used to tighten a sling down so it can be held securely and controlled more easily. To use a choker hitch, wrap the length around the load then pass one eye though the other then connect it to the lifting apparatus. Using a choker hitch reduces the capacity to only 10-15% of what a single leg hitch can lift. When the angle of the choke is less 120°, it can reduce the lifting capacity to 40% of the vertical hitch capacity.
Choker hitches must only be used on balanced loads because the sling never makes full contact with the load.
Bridle slings (multiple leg assemblies)
Bridle sling assemblies are made with two, three, or four legs. Having multiple legs provides extra strength and stability to the lift. Multiple straight legs are attached to a master link attached to the hoist. The legs are connected to the attachment points or fixed lifting lugs on the load to be lifted. When using multiple leg slings The sling hook must be positioned over the center of the load.
A single leg sling is a vertical hitch. The more legs that are used, the more weight they can hold. Each time another leg is added, the stability is improved as long as the leg lengths are equal, the center of gravity is in the middle of the load and the master link is directly over the center of gravity. Bridle assemblies can also have adjustable leg lengths to provide control and to help level unbalanced loads.
Lifting slings can be used in a variety of circumstances, from lifting walls to put on buildings to placing a giant sculpture on a high terrace, to transporting live animals. The sling you choose will depend on the job at hand and Silver State Wire Rope has them all! If you have any questions, give the professionals at Silver State Wire Rope a call today and see what they can do for you!