What is D/d Ratio & Why is this Critical for Lifting Slings?

What effect does D/d Ratio have on lifting slings and their sling capacities?

You may wonder what D/d ratio is and what purpose it serves when lifting loads with different types of slings. After all, it can be confusing as there are multiple factors you have to take under consideration such as knowing the weight of the load, the sling’s working load limit (WLL), and the load’s center of gravity.

Identifying the D/d ratio when using any type of sling for a lift is critical, because if the lifting sling tightly bends over too much during the lift – the sling will get damaged. This could then lead to unsafe rigging practices. To have a safe lifting operation, continue reading more about D/d Ratio, and the types of slings we carry at US Cargo Control to identify which is right for your lift.

What is D/d Ratio?

The term D/d ratio works as a simple mathematical equation where you’re learning the diameter or distance of the load you’re picking up. It is the ratio of the diameter (D) around the object which the sling might be bent, which could be a sheave or another object, then divided by the overall diameter (d) of the sling being used.

The Formula for D/d Ratio:

The diameter of the load divided by the diameter of the sling = D/d Ratio

Unirope's definition of D/d ratio
Photo Courtesy of Unirope

For example, you’re picking up an object that’s 12 inches in diameter and you use a 3/8″ chain to pick it up. This is 12″ divided by 3/8″ = 32, which 32 is the D/d Ratio. If the diameter is 10″ and the diameter of the rope is 1/2, the D/d Ratio is 20.

Why is D/d Ratio Important?

The D/d Ratio has a tremendous impact on sling capacity when using slings like wire rope, chain, polyester round slings, and nylon slings. It can determine the sling’s efficiency or capacity reduction, and allow you to make corrections before continuing the lift. If you see a tight bending of the sling, this means there’s a smaller than recommended D/d Ratio.

Using a smaller D/d Ratio that’s not recommended for your lift can aggravate the bending motion. This can result in fatigue, irregular wear, and increased deterioration. Once this occurs, you’d have to perform frequent inspections and go through costly wire rope replacements.

Each sling type has different strength efficiencies, which is why we included a table below that describes the efficiency of various sling constructions with standard D/d Ratios:

Mechanically spliced, single-part slings25 times rope diameter
Hand-Spliced, single-part slings15 times rope diameter
Braided multi-part slings of 6 parts25 times component rope diameter
Braided multi-part slings of 8 parts25 times component rope diameter
Helically laid multi-part slings25 times component rope diameter
Hand-tucked grommets and mechanically joined grommet5 times sling body diameter
Union Rope’s Rated Capacity, Design Factors, and D/d Ratios

What Will Sling Damage Look Like?

wire rope damage

When a sling is tightly bending around another object, there is a loss of sling capacity. As D/d Ratio decreases, this capacity loss becomes greater and the sling will become less efficient. There is a direct correlation between D/d Ratio and the efficiency of the sling (or rated capacity).

Not only is it important to understand the D/d Ratio of the lifting sling, but it’s also equally important that fittings and rigging hardware used in connection points are adequately strong and spatially correct. For instance, if smaller, alloy shackles are used, the webbing edges can get damaged and sling efficiency is lowered due to the bunching of the webbing.

When not used correctly, this could result in bunching, and being crammed into a space will reduce sling efficiency and capacity. Basically, putting too many slings in an undersized shackle or another fitting can result in lost strength.

To understand what slings or fittings should you use for your job, give our team a call at 800-404-7068, and we’ll be glad to assist you.

Different Type of Slings

Now that you have an idea of what D/d Ratio means, continue reading on what lifting slings you should use that’s worth the investment for your lifting situations.

nylon lifting slings

Nylon Slings

Known as synthetic web slings or nylon web slings, our nylon lifting straps perform well for lifting breakable, delicate objects. Its heavy-duty synthetic material has great stretch and flexibility that help the slings mold to the shape of the load. Not only that, the nylon lifting sling’s material is treated to improve abrasion resistance and reduce wear, even in the most rigorous lifting applications.

Chain Slings

If you’re depending on a sling that requires extra strength and durability, the chain sling is your best choice. The chain lifting sling is the strongest and most durable type of sling and is highly popular to use for heavy lifting operations. They will perform better than polyester round slings or nylon slings because they’re more durable, tolerant to hot temperatures, and cut-resistant.

chain lifting sling
Polyester round sling

Polyester Slings

Manufactured in the USA from a continuous loop of polyester yarn that creates exceptional strength, the round slings are versatile, pliable, convenient, and cost-effective. Because of their many benefits, you can use these in vertical, choker, or basket hitches, making them effective to lift a wide variety of cargo!

Wire Rope Slings

Known as steel cable or wire sling, these are more durable than synthetic slings and more cost-effective than chain slings. Wire rope slings are an excellent choice not only for lifting, but also for hoisting, towing, or anchoring loads. Its fabrication offers abrasion-resistance and heat-resistance, as they are made by weaving individual strands or wire around a core.

Wire rope sling

To understand what lifting slings you should use for any lifting operation, read 3 Factors to Consider When Choosing Lifting Slings.

Tackle the Toughest Lifting Jobs with High-Quality Rigging Hardware

We know the importance of quality when it comes to rigging supplies. We carry a variety of rigging hardware, as well as lifting beams and spreader bars that can lift heavy loads safely and efficiently.

Need a custom lifting sling? We can do that! We can customize a lifting sling to meet your specific needs.

Contact our sales team today at 866-444-9990. Our team of product experts is here to answer any questions about rigging hardware, lifting slings, and more.

What is Wire Rope, and How is it Different from Cable Rope?

Read what is wire rope, what are important specifications to look for, and how it’s different from cable rope.

Did you know wire ropes were used as far back as the 1830s for mining hoist applications? Nowadays, we can use steel ropes for many different applications such as lifting and hoisting in elevators and cranes, and for mechanical power transmission. US Cargo Control’s wire rope slings are an excellent choice for heavy-duty jobs as their fabrication offers excellent abrasion resistance and heat resistance for extreme conditions.

Although these slings are beneficial for the lifting and rigging industry, there are a few specifications to know before purchasing them. Continue reading what is wire rope, what are important specifications to look for, and how it’s different from cable rope.

What is Wire Rope?

Up close shot of wire rope sling on shackle
Photo Courtesy: Adobe Stock

These slings carry different properties that can determine their performance. Wire rope is constructed where a strand consists of two or more wires arranged and twisted in a specific arrangement. The individual strands are then laid in a helical pattern around the core of the rope. Once the wires are formed, they all come together to create greater strength and flexibility.

These slings work well for lifting, hoisting, towing, or anchoring loads. They’re manufactured in a variety of configurations, with 6×19 and 6×36 being the most common. When you see 6×19 or 6×36 from our website, these numbers represent the number of wires making up the strand and the number of strands wrapped around the core.

For example, a 6×19 indicates that there are 19 wires making up a strand, and 6 strands wrapping around the core. To learn more about our 6×19 wire ropes, look into our bestselling 1/2″ Galvanized Wire Rope EIPS IWRC, 1/2″ Stainless Steel Wire Rope IWRC T304, and 1/2″ Bright Wire Rope EIPS FC.

The configurations will offer different benefits for certain applications. In general, a smaller number of large outer wires offers better wear and corrosion resistance, while a larger number of small wires provides a better level of flexibility and fatigue resistance. Continue reading to learn which wire rope fits your job.

Terms that Define Construction and Properties of Wire Rope

Before immediately purchasing a wire sling, there are 7 properties that you should know about:

  1. Different Types of Wire Rope Slings
  2. Length
  3. Size
  4. Direction and Type of Lay
  5. Finish of Wires
  6. Grade of Rop
  7. Type of Core

1. Different Types of Wire Rope Slings

There are different versions of wire rope slings, ranging from single leg to 4 legs, as well as braided wire rope and domestic wire rope slings (manufactured in the U.S. with Crosby® hardware). When looking at the types of slings we offer at US Cargo Control, be sure to consider how much versatility and capability you need.

For example, a braided wire rope has increased flexibility and friction to grip loads over a regular wire rope. Adding an additional leg to the sling can add additional versatility and strength.

2. Length

the length of the wire rope sling

This is the total number of feet that are cut to size when wrapped around.

3. Size

the size and strand pattern of a wire rope

This is the measurement of the rope’s diameter and can be displayed in inches or millimeters. These sizes commonly display different strand patterns where the number of layers, wires per layer, and size of the wires per layer all affect the strand pattern. Wire rope can be constructed using one of the following patterns below or using two or more patterns.

  • Single Layer – a common example is a 7 wire strand. This has a single-wire center with six wires of the same diameter around it.
  • Filler Wire – this has two layers of uniform-size wire around a center with the inner layer having half the number of wires as the outer layer.
  • Seale – has two layers of wires around a center with the same number of wires in each layer. All wires in each layer are the same diameter.
  • Warrington – this construction has two layers of wires around a center with one diamter of wire in the inner layer, and two diameteres of wire alternating large and small in the outer layer.
  • Combination – when a strand is formed in a single operation using two or more of the above constructions, it’s referred as a “combined pattern.”

4. Direction and Type of Lay

The type of lay refers to the way the wires are laid to form a strand. They’re how the strands are laid around the core which can be regular lay, long lay, or alternate lay.

Regular Lay

The wires line up with the axis of the rope. This is where the wires are twisting in one direction, and the strands in the opposite direction create the rope. Regular lay is less likely to untwist and less likely to crush.

LAng Lay

This is the opposite of regular lay where the wires form an angle with the axis of the rope. The wires and strands spiral in the same direction and run at a diagonal to the centerline of the rope. Lang lay is more flexible and resistant to abrasion than regular lay wire ropes. The only con is this type of lay will be more likely to twist and crush than the regular lay.

Alternate Lay

Sometimes known as reverse lay, this type of lay consists of alternating regular lay and long lay strands. This unites the best features of both types, and it’s using relatively large outer wires to provide an increase of abrasion resistance.

5. Finish of Wires

steel wire rope sling in heavy industrial
Photo Courtesy: Adobe Stock

This refers to the protective coating that’s applied to the wire rope. There are three types of finishes which are galvanized (zinc-coated), stainless steel, and bright (unfinished steel).

Note that the galvanized material will provide extra corrosion resistance, and stainless steel is highly resistant to corrosion.

6. Grade of Rope

The grade of the rope means the grade of steel being used. The plow steel strength calculates the strengths of most steel wire ropes. Some classifications include Improved Plow Steel (IPS), Extra Improved Plow Steel (EIPS), Extra Extra Improved Plow Steel (EEIPS), Galvanized Improved Plowed Steel (GIPS), and Drawn Galvanized Imrpoved Plow Steel (DGEIP).

EIPS is 15% stronger than IPS, and EEIPS is 10% stronger than EIPS. Along with that, GIPS and DGEIP wires can add corrosion resistance to your application, but DGEIP wires have a higher break load than GIPS.

7. Type of Core

The type of core is what makes up the center of the wire rope. There are three types of core: Fiber Core (FC), Independent Wire Rope Core (IWRC), and Wire Strand Core (WSC).

A fiber core can be made of synthetic polypropylene fibers. The fiber cores offer greater elasticity than a steel core, but are more susceptible to crushing. This isn’t recommended for high heat environments.

A steel core can either be an independent wire rope or individual strand. The steel cores can provide adequate support, or in an operating environment where temperatures can exceed very high heat.

What’s the Difference between Wire Rope and Cable Rope?

A wire rope sling being used to lift a heavy load
Photo Courtesy: Adobe Stock

Wire and cable ropes are terms that are often interchangeable but do have one varying difference. Wire rope refers to the diameters that are larger than 3/8 inch. Sizes smaller than this are classified as cable rope or even cords. Regardless of the size difference, cable and wire rope are still classified as a “machine.” Even a group of strands laid around a core would still be called a cable or wire rope.

Tackle the Toughest Lifting Jobs with High-Quality Rigging Hardware

We know the importance of quality when it comes to lifting supplies. We carry a variety of rigging hardware, as well as lifting beams and spreader bars that are designed to lift heavy loads safely and efficiently. If you’re interested in other lifting slings, check the other types of slings we carry like nylon slings and chain slings.

Need a custom lifting sling? We can do that. We’ll work with you and customize a lifting sling to meet your specific needs.

Read more information about wire rope slings below!

How to Safely Apply Wire Rope Clips to Wire Rope Assemblies

How to Use Wire Rope Clips

What is Sling Protection, What are the Different Types of Slings, & How to Protect Them

Contact our sales team at US Cargo Control today at 866-444-9990. Our team of product experts is here to answer any questions about rigging hardware, lifting slings, and more.

What is Sling Protection, What are the Different Types of Slings, & How to Protect Them

Sling protection products can protect slings, the load, and even the load’s surroundings. Read to learn how to improve the durability of your slings and create safety and cost saving solutions in the workplace.

Are you constantly having to buy new lifting slings, or finding that your slings keep getting damaged? Are you noticing that improper use of the load or load damage is often caused by the sling itself? These issues are related to one of the most common lifting problems – lack of proper sling protection.

Luckily, we have a few tips on how to improve the endurance and longevity of your slings. In this blog, we’ll explain what is sling protection, when slings require protection, and the best sling protection products.

What is Sling Protection?

Use Corner Guards to Protect Lifting Slings

Sling protection is a common term in the lifting and rigging industry. Just like adding a screen protector to your phone, there are sling protection products that can protect your slings from sharp corners and edges.

We need to ensure the lifting sling is not cut or abraded during the lift, and the load is secured. We’re able to achieve that through products that support the durability of the lifting slings.

When researching sling protection products, it’s important to understand that some products are good for preventing abrasions while others are good for resistance to cutting. It’s also critical to know that the most common sling protection materials are polyester or nylon webbing, Kevlar, rubber, leather, and wood. While learning about your slings or the slings you wish to get, make sure to know what application you are using the sling for as well as the physical properties of the load and sling protection products.

We’re emphasizing the importance of sling protection producs because it’s typically less expensive to replace sling protection products multiple times than to replace the lifting sling.

When do Slings Require Protection?

Rigging wire rope and shackle

All types of lifting slings like nylon, polyester, wire rope, and chain must be protected from edges, corners, and protrusions. You can use products like corner guards, sleeves, reinforced eyes, and wear pads to help your slings. We also carry a line of Straightpoint Load Monitoring Loadcells to precisely measure and safely monitor the tension of loads involving wire rope, guy wire, synthetic rope, shackles, and more.

While all types of lifting slings require protection from sharp corners and edges, it’s common to use sling protection products to a synthetic sling like round slings and web slings. This is because the nylon and polyester fibers of a synthetic sling are more susceptible to cuts, tears, and abrasion than stronger sling materials like wire rope or chain. In fact, the cutting of synthetic slings during use is the number one cause of sling accidents.

The sling can make contact with the load or hardware:

  • Around any lift points like load edges, hoist rings, and eye bolts
  • Around the crane hook, shackle, and master link.
  • On load edges that could be above the hookup points

What Happens When I Don’t Protect My Slings?

How to Protect your lifting slings from sharp edges

There are several ways slings could be destroyed if you don’t use sling protection products. Without the usage of sling protection products, there is potential for:

  • Injury or loss of life
  • Higher turnover of slings, especially synthetic ones
  • Major damage to the sling, load, and around the load’s surroundings if the sling is cut, and the load is dropped
  • Damage caused to the load itself from lack of protection, especially when using wire rope and chain slings which can exert crushing forces on a load

As explained above, when you’re not using the proper sling protection, it can result in a dropped load or scratching and damaging it. This can be dangerous as this could result in injury, dismemberment, or loss of life.

In addition to that, if you’re not protecting your slings, you’re creating a higher turnover in slings and this will result in higher equipment costs. To learn more about what lifting slings you should use for the right job, read 3 Factors to Consider When Choosing Lifting Slings.

How Do Sharp Edges or Corners Damage Slings?

What is sling protection, how to protect any lifting sling

Edges can damage different types of slings in several different ways.

If you’re using chain slings, the edges can cause nicks and gouges, crushed links, and bent or twisted links. When using wire rope, the corners could damage broken wires, kinks, or doglegs. Lastly, nylon and polyester slings can be cut or abraded easily.

If your sling isn’t protected and it gets damaged, it’s more expensive to replace the sling than the sling protection product. It is much more cost-effective to replace the sling protection rather than replacing the sling itself.

Nylon and polyester slings can be easily confusing as they have a few similarities. To understand which web sling you should get, read Polyester Slings vs Nylon Slings: Which Web Sling Type is Better?

Tackle the Toughest Lifting Jobs with High-Quality Rigging Hardware

We know the importance of quality when it comes to lifting supplies. We carry a variety of rigging hardware, as well as lifting beams and spreader bars that are designed to lift heavy loads safely and efficiently. 

Need a custom lifting sling? We can do that. We’ll customize a lifting sling to meet your specific needs.

Curious about Straightpoint products and how they work? Read more information about them below!

Do You Know How Much That Weighs? Straightpoint Load Cells Do

Compression Type Load Cells: Wireless vs. Wired

How to Select a Load Cell

Contact our sales team at US Cargo Control today at 866-444-9990. Our team of product experts is here to answer any questions about rigging hardware, lifting slings, and more.

Grade 120 Chain and Components at US Cargo Control

We’ve added a wide selection of the strongest and toughest chain grade components to our inventory.

A full line of Grade 120 chain and chain sling components are now available through US Cargo Control.

Grade 120 is a high-strength, ultra-premium quality alloy steel with the highest working load limits in the industry. Now it’s easier than ever to get the G120 products you need to tackle the toughest overhead lifting and transportation jobs.

We’ve added a wide selection of the strongest and toughest chain grade components to our stock. And with a large inventory of bulk g120 chain, fittings, chain and binder kits, and more, you can count on US Cargo Control for all of your Grade 120 transport and rigging and lifting needs!

4 Benefits of Grade 120 Components

Length of blue grade 120 chain showcasing the square-link design.

1. It’s the Strongest Chain in the Industry

Grade 120 chain and components are 50% stronger than Grade 80 and 20% stronger than Grade 100 products. That added strength means you can select a smaller chain size for the job that’s lighter in weight and easier to handle – all without sacrificing working load limits.

2. It’s Extremely Durable

G120 chain features a revolutionary square link design that offers superior fatigue and bending resistance, making it an excellent choice for a wide variety of lifting applications. The patented square profile also offers increased contact between the surfaces on the links, resulting in a better grip than a traditional round link-style chain. A blue powder-coated finish adds corrosion protection.

3. It’s Easy to Identify

All Grade 120 Chain and Components feature a light-blue powder coating for quick and easy identification. You will also find either “120” or “12” markings on the chain and components as additional identification as Grade 120 alloy.

4. It’s Made by Pewag

Our Grade 120 chain and components are made by Pewag, an industry leader in quality chain products. With a history dating back over 500 years, Pewag is an established and trusted manufacturer in the transportation and lifting industries.

Grade 120 Chain Slings

Chain slings manufactured with grade 120 chains offer the highest strength available on the market. They are excellent for heavy-duty lifting applications.

There are two main types of lifting slings: standard and adjustable. Both options allow the user to customize the sling to suit their specific lifting application. Choose from several options including the number of legs, length of the chain, and type of end fitting.

Blue Grade 120 standard chain sling with a sling hook and oblong link at opposing ends of the length of chain.

Standard Chain Sling

Features a fixed-length of Grade 120 Chain and available in a variety of length and end fitting combinations

Blue adjustable single-leg chain sling with a sling hook and oblong link at opposing ends of the length of chain.

Adjustable Chain Sling

Can be designed with the same leg configurations as standard slings, but an additional fitting allows the user to adjust the length of the chain.

Grade 120 Fittings

We stock a wide selection of G120 end fittings. Like all Grade 120 components, end-fittings all feature the distinctive blue powder-coat finish for superior corrosion protection and easy identification. Some of the most common options include:

Blue Grade 120 oblong master link ring.

Oblong Master Links are used at the top of chain slings.

Blue Grade 120 grab hook.

Eye Grab Hooks are designed for optimal interaction between chain and hook, making them excellent for a variety of lifting applications.

Blue Grade 120 self-locking hook.

Self-Locking Hooks feature a larger opening than typical eye sling hooks and automatically close and lock under load.

Blue Grade 120 sling hook with silver galvanized safety latch.

A Sling Hook has a forged and galvanized safety latch for a secure connection in a variety of lifting applications.

Tackle The Toughest Lifting Jobs With Grade 120

We recommend heavy-duty Grade 120 Chain for the toughest jobs. Whether you are in the trucking and transportation or lifting and rigging industries, the high-strength and superior quality of G120 alloy steel can stand up to even the most demanding applications.

If you’re looking for more information on chain slings, check out our main chain slings page on our website or our lifting slings category on our blog.


Are you ready to get your hands on some Grade 120 products? Contact our sales team today at 800-404-7068. Our team of product experts is here to answer any questions about rigging chain, lifting slings, and more.


We also do custom orders! Need a custom lifting sling? We can do that! Because we assemble all of our Grade 120 chain slings in-house, we can customize a lifting sling to meet your specific needs.

From Houston to Orlando, Why Are the USCC Team Traveling Everywhere?

Wondering where the USCC team is going? Read to find out!

It is tradeshow season, and our dedicated USCC team members have been traveling to several states during the past two months! The reason why we attend tradeshows every year is because we care about making connections and cultivating strong relationships. Check out some of the shows we attended recently.

Also, leave a comment below if you have attended a tradeshow this year and if you saw us and our booths!

College HUNKS Annual Reunion

CHHJ trade show

One of the industries that US Cargo Control serves in is Moving Equipment, so since we have partnered with College HUNKS as a vendor for the past six years, we sought the opportunity to go to the reunion and support one of our partners! Some of our team members attended the show in Orlando, FL, and had a blast at this event. Along with that, we gave people the opportunity to enter the chance to win custom CHHJ Nike shoes! How sweet is that?

This was a great event to talk with new and existing franchisee owners to build relationships.  This event is instrumental in visiting with many franchisee owners in one location

Carla Weeks, sales

If you would like to learn more about our moving supplies, check out our high-quality professional moving equipment that will do the job whether it is big or small.

Specialized Carriers and Rigging Association (SC&RA) Symposium

trade show booth at SCRA
Our salespeople Adam S. and Alex L. getting ready for this event

Another event we attended this year is the Specialized Carriers and Rigging Association (SC&RA) Symposium, and what a show it was! The meeting featured over 40 companies, and brought together oversize/overweight transportation professionals and permitting officials to discuss permitting harmonization and safety concerns.

Three of our salespeople Tim, Adam, and Alex enjoyed every bit of it. If you saw them in Charlotte, NC, you might have participated in a putting challenge.

USCC tradeshow display
Tim S., Adam S., and Alex L. hosting the Ping Putter Challenge

To win the putting challenge, whoever makes the hole-in-one will have a chance to win a Ping Putter. We did have a winner, and it was Ben Mayer from Great Lakes Heavy Haul! Check out the snazzy picture below:

winner of the putting challenge at the trade show booth

The Maintenance Council (TMC) Annual Meeting & Transportation Technology Exhibition

TMC Trade show

In Atlanta, GA, we attended the TMC annual meeting which covers the most innovative educational sessions covering all aspects of vehicle maintenance and design. At US Cargo Control, staying on top of industry practices is important to us, and this is a great event that covers industry practices for trucking and transportation.

What Else Happened?

touring iuoe cranes and machinery
Our salespeople Alex L. and Adam D. at IUOE’s training facility

Recently, two of our salespeople had the amazing opportunity to tour International Union of Operating Engineers‘ training facility. At this tour, they had the chance to see the large cranes and machinery that our products are used on up close. While we have product experts who are so knowledgeable in every product we carry here at US Cargo Control, we will always seize the change to learn more about these machines up close.

The people that operate these machines are very smart and very well trained.   Products like lifting slings, shackles, spreader bars and lifting beams, are a critically important part of every lift, and it was inspiring to me to see these cranes up close.

Alex Ledger, Sales
international union of operating engineers training facility

Where is the Next Tradeshow?

This week, our team members are going to Nashville, TN to attend the LKQ Vendor Fair. Catch us there, and maybe try to find us at a hot chicken restaurant!

Want to learn more about USCC? Check our 4 Great Reasons to Do Business with the US Cargo Control Team

If you have any questions about the products we carry, give our team a call at 866-444-9990.