Tag: chain sling

Understanding Chain Slings: Why Do Only 3 of 4 Chain Legs Take the Load?

Understanding Chain Slings: Why Do Only 3 of 4 Chain Legs Take the Load?

Randy, an Instrument Technician in the energy industry and recent safety webinar attendee, asks:

“Why do only 3 of 4 chain sling legs take the load?”

Peter Cooke, Columbus McKinnon Training Manager and Safety Webinar Presenter, answers:

understanding chain slings
When using a chain to build a sling, tolerances for chain can make the legs slightly longer or shorter than one another. Because of this, the National Association of Chain Manufacturers (NACM) agreed to only count 3 of the 4 legs of a quad sling to be rated the same. When you first lift the load off the ground the legs that are under tension will stay under tension, so it is important for the rigger to visually see how many legs are loaded before lifting the load off the ground.

To do this, tension up the legs, but do not let the load leave the ground. Safely approach the sling being sure to stay out of the path of tension. You can then quickly check the legs by shacking them slightly. Although you may find all four legs are taking the load, only three are used for calculating the max working load limit of the sling.

It is important to always check the manufacturer’s load charts and safety information prior to making any lift. You must be qualified to lift the load you are rigging.

Want to learn more?

View our Safety Webinar on How to Size Your Chain Slings.
View our blogs on chain sling inspection.

Peter Cooke
Peter Cooke is a Training Manager specializing in Rigging & Load Securement for Columbus McKinnon Corporation.
A Chain Sling Question from the Mining Industry

A Chain Sling Question from the Mining Industry

Chain Inspection photoHere is a question from Adam, a mobile crane operator working in the mining industry, who regards proper rigging equipment and practices as a major safety priority:

“We have a 1-inch GR80 chain sling, 30 feet in length that is around ten years old and in good condition, although there is inner link wear throughout the sling at its bearing points. The narrowest measurement in link diameter at any point was .945″, which is well away from removal criteria. No components in the sling show any evidence of a stretch condition, and the sling has not been subjected to overload to the best of our knowledge, though I cannot guarantee that.

“The reach of the sling is approximately four inches longer than its tag indicates. According to my calculations, this stretch is due to the contact wear in each link. The chain moves freely and there is no binding or restriction of movement. Is this legitimate? If so, does the tag need to be replaced or modified to indicate its current length? Our inspections have always been completed by a company assigned employee.”

Response from Peter Cooke, training manager:

Thank you for reaching out to us. For your reference, I have included a section on alloy rigging chain inspection from our Columbus McKinnon rigging catalog here. Be sure to do a link-by-link inspection and follow the rejection criteria from OSHA 1910.184 and ASME B30.9. Be sure there are no stretched links. Reference the “Allowable Chain Wear Allowance tables” from the manufacturer and ASME B30.9.

Not knowing your exact configuration, I will use a standard DOS 1-inch grade 80 x 30’ reach sling as an example. If we just isolated the chain (taking out the master link, coupling links and hooks) you have approximately 106 links of chain. If you determined the minimum thickness to be 0.945” at the bearing points, that is approx. 0.055” of wear from the nominal dimension. 1” grade 80 chain has a pitch length of approx. 3.07” (dimension from the top inner link radius to the lower inner link radius) Let’s assume that wear occurred at both ends of the chain link. The pitch length would increase by 0.11”. Over the entire chain length you could see an increase in reach of approx. 11.66” (0.11” x 106 = 11.66”)

As long as there are no stretched links or deformation this would be acceptable. There is no rejection criteria for reach other than stretch. Wear is not stretch.

There is also no statement in 1910.184 and ASME B30.9 to replace the tag in this event with the correct reach.

A good practice would be to retag the sling with the current reach. The new tag would be considered a repair so your company’s name or initials would have to be on the tag. A load test would not be required. Lastly, lubricating the chain is an excellent way to minimize wear.

Peter Cooke
Peter Cooke is a Training Manager specializing in Rigging & Load Securement for Columbus McKinnon Corporation.
Advantages of Lifting with Chain Slings vs. Synthetic Slings

Advantages of Lifting with Chain Slings vs. Synthetic Slings

OLYMPUS DIGITAL CAMERA

Overhead Lifting Slings are generally used in conjunction with a crane, powered hoist, manual or lever hoist or some type of lifting device. There are numerous types of materials used for building overhead lifting slings – each with specific advantages and disadvantages – including:

  • Chain
  • Wire rope
  • Synthetics
  • Metal mesh.

Understand the Application Before You Spec a Sling
Before you select a sling it is important to fully understand the application and gather specific information on how the sling will be used. When choosing a sling, you must know the weight, center of gravity, number of attachment points for a balanced lift, sling angles, reach, upper and lower fittings and ambient conditions. Communicate or obtain as much background information as you can about the load being lifted, then decide what type of sling works best. This will help ensure you choose the right sling material and configuration for the task at hand.

Alloy Steel Chain: Recommended by ASME, NACM & OHSA
When using chain slings, the American Society of Mechanical Engineers (ASME), the National Association of Chain Manufacturers (NACM), and the Occupational Safety & Health Administration (OSHA) recommend only the use of alloy steel chain for overhead lifting. Grades 63, 80 and 100 are the alloy steel chains used throughout the industry. They contain elements that give them their unique strength, abrasion resistance, durability and toughness. Per ASTM Standards, alloy chain slings must have the ability to elongate at least 20% when overloaded in order to have a visual indicator to the rigger that the sling is overloaded. Once any stretch is discovered, the chain sling must be removed from service. Synthetics do not have any such indicators as standard.

Advantages of Chain slings versus Synthetic slings

Durability:

  • Resists impact, cuts and abrasions
  • Resistant to chemicals and UV radiation
  • Can be used in oily or dirty environments
  • Can be used at higher temperatures range -40oF thru 400oF with not reduction of WLL (synthetic slings can be used in temperatures no higher than 194oF)
  • Minimum elongation when lifting or tensioning
  • Long service life compared to synthetic slings

Versatility:

  • Easily adjustable (synthetic slings cannot be adjusted and therefore are often used incorrectly)
  • Can be constructed in the field

Inspection & Maintenance:

  • Easy to inspect
  • Completely reparable (cannot repair load bearing fibers in synthetic slings)

139 Years of Chain & Forging Know-How
Columbus McKinnon’s chain manufacturing roots date back to the 1800’s. We hold patents for chain and chain link design as well as the chain manufacturing processes, which help ensure our chain is the strongest and most reliable chain on the market today. We also invented the first alloy chain in 1933 – the forerunner to our industry-changing Herc-Alloy® 800 and 100 chains. In addition to chain, we also manufacture a variety of dual-rated hooks, links, sub-assemblies and other attachments that complement our chain offering.

For additional information on the safe and proper use of chain slings, check out our Safety Webinar on Chain Sling Inspection.

Henry Brozyna
Henry Brozyna is a Product Trainer specializing in Rigging & Load Securement for Columbus McKinnon Corporation.
Sling Selection & Working Load Limits: What You Need to Know

Sling Selection & Working Load Limits: What You Need to Know

Chain slings are a combination of chain, hooks, rings and other attachments used primarily for overhead lifting applications. Slingssling selection are often used in conjunction with cranes and other lifting devices and allow riggers to create custom configurations to lift loads depending on the needs of that specific application.

Standard chain sling configurations consist of chain branches that are affixed on one end to a master link or ring with some type of attachment. When building a sling, ASME, NACM and OSHA recommend that only alloy steel chain is used. Columbus McKinnon’s Herc-Alloy chain, available in Grades 80 and 100, is made of superior triple alloy steel and is a strong and durable option for building chain slings.

All chain slings should come with a metal identification tag that is affixed to the chain. The tag should include the following information: sling size, reach, working load limit, serial number, manufacturer name, grade of sling and number of branches.

Proper Chain Sling Selection

When choosing a chain sling there are a few things to consider:

  1. Weight and configuration of the load(s) to be lifted
  2. Type of chain sling required, according to weight and configuration
  3. Size of the body chain according to the working load limits. Be sure to take into consideration the effect of the required angle (see information below).
  4. Reach required to give the desired angle. This is measured from the upper bearing surface of the master link to the bearing surface of the lower attachment.
  5. The share of load on pick points and location of the center of gravity

What Determines a Sling’s Working Load Limit?

The working load limit indicates the maximum load that should be applied to the sling and should never be exceeded during use to ensure operator safety.
Sling working load limits are determined by the following:

  • Type of hitch
  • Material strength
  • Design factor
  • Diameter of curvature (D/d)
  • Angle of loading

The working load limit of a sling can also be affected by the conditions the sling is used in. For example, rapidly applying a load can produce dangerous overloading conditions. Also, the twisting and knotting of links or sling components can decrease a sling’s working load limit. Environmental conditions, such as elevated temperatures, can affect the working load limit of a sling as well.

Since slings are most often used at an angle, let’s review an example of how angle of loading affects a sling’s working load limit. In the diagram below, the percentages shown represent the maximum working load limit of the sling when used at the designated angle. In some instances the working load limit of the chain is reduced to 50%!

For example: One 3/8″ Grade 80 double sling used at 90˚ would have a working load limit of 2 times the working load of a 3/8″ Grade 80 single or 2 x 7, 100 lbs. = 14,200 lbs.

The same double sling used at 35º would have a maximum working load limit of 57% of 14,200 lbs. or .57 x 14,200 lbs. = 8,094 lbs.

sling selection

For another example of how the angle of use can affect the working load limit of a chain sling, check out this past blog post: What is the working load limit of a 2 legged chain sling?

Want to learn more? View our Safety Webinar on Chain Sling Inspection

Tim Lewis
Tim Lewis is a Business Development Manager at Columbus McKinnon Corporation.
Is it Possible to Mix Chain Grades on a Sling?

Is it Possible to Mix Chain Grades on a Sling?

mixing chain gradesBen from Chicago asked the following question about mixing chain grades:

Is it possible to mix grade 80 chain and grade 100 components on a sling assembly?

Peter answers:

In simple terms, yes –  BUT the assembly can only be rated at the grade 80 WLL.  Here is an example:  A sling is made with grade 100 chain and the hooks used for the sling are grade 80. This sling would need to have a tag with a grade 80 working load limit (WLL) of the weakest component.

For your reference I have provided the following applicable standards:

ASME B30.9, 9-1.5.7

When components of a sling have a lower rated load than the alloy chain with
which it is being used, the sling shall be identified with a rated load consistent
with the lowest load rating of any of the components.

OSHA 1910.184(e)(2)(i)

Hooks, rings, oblong links, pear shaped links, welded or mechanical coupling
links or other attachments shall have a rated capacity at least equal to that of
the alloy steel chain with which they are used or the sling shall not be used
in excess of the rated capacity of the weakest component.

Peter Cooke
Peter Cooke is a Training Manager specializing in Rigging & Load Securement for Columbus McKinnon Corporation.