There is always more than one way a load can be lifted with a sling, in many cases it is a matter of opinion, but there are also always some options that are better than others. Some hitches should not be used when lifting with a sling.
Of the three most common hitches: vertical hitch, basket hitch, and choker hitch, a single vertical hitch should not be used when lifting long loads, loose or bundled materials, and unbalanced loads, and a basket hitch should not be used on awkwardly shaped or unbalanced loads.
Take care when selecting a sling configuration, called a hitch, for the job at hand. A hitch that has worked for you in the past on one type of load may not work in the future on a different load. Often the results can be catastrophic, so always research and consider hitched carefully.
What Are The Three Most Common Hitches?
There are three basic hitches when it comes to rigging and lifting loads:
- A Vertical hitch
- A Basket hitch
- A Choker hitch
This is not an exhaustive list, but almost all rigging is based on the three hitches above.
A Vertical Hitch
A straight sling is fastened to a load at one end and the lifting device at the other end. In most cases, this is done with hooks but can also be done with looped slings or fastened chains.
A Basket Hitch
Two or more ‘legs’ made up of straight slings that pass through part of the load, with both ends attached to the lifting device, are used.
A Choker Hitch
Using a single straight sling, one end of the sling passes through the loop or eye of the other end, and the load is placed in the self-tightening or ‘choking’ loop that is created.
What Are The Correct Uses Of The Three Most Common Hitches?
To get the safest and best uses out of the different types of hitches, you first need to know the correct use of each. This will help you work out the best hitch for lifting the load.
The Correct Use For A Vertical Hitch
Even though this is the simplest hitch, it should only be used when lifting a load with a ready-made attachment point.
This is also the easiest hitch to calculate the lifting strength of the sling because there is no working load limit to calculate: the full capacity of the sling is the lifting limit.
Because there is only one point of contact for the hitch on the load, it may swivel when being lifted; for safety and better positioning when setting the load down, attach a tagline and control the movement of the load while it is in the air.
The Correct Use For A Basket Hitch
When used at a 90⁰ angle, this hitch is the strongest of the three hitches and is usually recommended for heavy loads.
This hitch can hold up to double the weight of a single vertical hitch. For every angle variance in the sling, you will need to calculate the load capacity based on a lifting chart.
To get the full benefit of a basket hitch, you may need to use a lifting bar or beam to achieve the 90⁰ angle of the legs. Depending on the size of the load, you may also need more than one sling to keep control of the load during the lift.
This hitch should only be used when the cling can pass through part of the load. There is too much potential for movement and slippage if a load is balanced inside a basket hitch. A shackle should also be connected to each sling leg.
Avoid using a basket hitch with awkwardly shaped or unbalanced loads. A choker hitch or combination of hitches is usually better for these.
The Correct Use For A Choker Hitch
A choker hitch’s ‘choking’ loop will hold loose and bundled loads better than straight or basket hitches.
This hitch is best used when lifting cylindrical loads and comes in several variants and configurations to further hold materials together. A choker hitch also works well for loads without a direct attachment point.
The angle of the choke point will determine the working load limit. Consult a lifting chart to see at which angle the weight of the load will be safe.
Note that a single choker hitch will never provide full 360⁰ contact with the load. Full 360⁰ contact can be achieved with a double wrap choke hitch.
Always ensure the choke point is on the sling body rather than the eye, fitting, splice, or tag.
Wherever possible, tie a composite load together with wire or a similarly strong binding before attaching a choker hitch. This will help stop the load’s composite parts from sliding in the hitch.
When and How To Use A Multi-Leg Sling
Occasionally a hitch that should not be used when lifting with a sling may work when used in a multi-leg sling configuration.
A multi-leg sling with more than one vertical hitch will work well if a load has multiple attachment points. The load will be more stable, and depending on the angle of the slings, the load limit may increase.
Multi-leg slings need to be the same length to be safe and effective. Also, be aware that if more than one type of sling is used, the working load rating of the weakest sling must be taken as the measurement baseline for determining the working load overall.
A multi-leg sling should never exceed an angle of 120⁰, and any one leg of a three-leg sling should never be greater than 45⁰ to the vertical.
How Does The Angle Of A Sling Affect The Working Load Limit?
The angle of the sling leg compared to the horizontal line of the crane or lifting device is known as the sling-to-load angle. The sling-to-load angle determines the:
- Sling workload limit
- The length of the sling is needed to lift the load. The longer the sling, the less the sling-to-load angle will be.
Note the following when you consider the length of a sling and the angle of the sling to the load:
- As the sling-to-load angle decreases, additional tension is placed on the sling and the hitch.
- Slings with a listed capacity to handle the full measured weight of a load will not hold the load when an angle is introduced to sling and hitch.
- At a 90⁰ angle, a single vertical hitch will hold 100% of the weight of the load. At a 30⁰ angle, the hitch will hold only 50% of the weight of the load. At a 10⁰ angle, the hitch will hold less than 18% of the weight of the load.
Of the three basic types of hitch: vertical, basket, and choker, there are some instances where one type of hitch should not be used, but rather one of the others would better suit the materials being lifted.
A single vertical hitch should not be used when lifting long loads, loose or bundled materials, and unbalanced loads, and a basket hitch should not be used on awkwardly shaped or unbalanced loads.
A double wrap choke hitch should be used in favor of a simple choker hitch when the load needs full 360⁰ contact. Always determine the best hitch for the load type and weight.