Synthetic Sling Selection: Round Slings and Web Slings

Synthetic slings are one of the most popular choices for industrial lifting - and for good reason. They are light, flexible, and gentle on loads that cannot afford surface damage. But not every synthetic sling is the right fit for every job. Choosing the wrong type, capacity, or material can lead to premature wear, failed inspections, and in the worst case, a dropped load.

This guide walks you through everything you need to know: what synthetic slings are made of, how to choose between web slings and round slings, what the color codes mean, the benefits that make synthetic slings stand out, and the safety and inspection rules that keep them in service longer.

What Is a Synthetic Sling?

A synthetic sling is a lifting assembly made from high-tenacity polyester or nylon fibers. Unlike chain slings or wire rope slings, synthetic slings are soft and pliable. They conform to the shape of the load, spread the lifting force across a wider contact area, and leave no marks on polished, painted, or coated surfaces.

Synthetic slings are the go-to choice in manufacturing plants, fabrication shops, and general industrial lifting wherever two things matter most - protecting the load and keeping things light and easy to handle.

They come in two main forms: flat web slings and round slings. Understanding the difference between the two is the first step to making the right selection. Browse Holloway Houston's full range of synthetic slings to see available configurations and capacities.

Web Slings vs Round Slings: What's the Difference?

Flat Web Slings

A flat web sling is exactly what the name suggests - a wide, flat strap woven from polyester or nylon fibers. The flat profile gives it a large contact surface, which is what makes it so effective at protecting sensitive loads. Instead of concentrating the lifting force on a narrow line, the sling spreads it across the full width of the strap.

Web slings are available in different ply ratings - single-ply, two-ply, three-ply, and four-ply. The higher the ply count, the greater the working load limit (WLL), while the sling stays the same width. This means you can get a much higher-capacity sling without needing a wider, more cumbersome strap.

Web slings work well for beams, plates, machinery components, and any load with a relatively flat or uniform contact surface.

Round Slings (Endless Round Slings)

A round sling is a continuous loop of load-bearing polyester fibers enclosed inside a woven polyester jacket. When the sling is placed under load, the individual fibers inside can shift and redistribute the tension between them. This gives round slings exceptional flexibility and makes them excellent at wrapping around irregular or cylindrical shapes.

Round slings are the preferred choice for spools, pipes, drums, and any delicate component where you need the sling to conform to the exact shape of the load without creating stress points.

Round Sling Color Codes (ASME B30.9)

Round slings are color-coded by WLL to the ASME B30.9 standard. This makes it easier to identify the right sling at a glance - but the color is a guide only. Always read the sling tag to confirm the actual rated capacity before use.

Important: Color coding gives you an approximate capacity. The sling tag is the definitive source for rated working load limits. Never use a sling with a missing or unreadable tag.

How to Choose the Right Synthetic Sling

Choosing the right sling comes down to matching the sling's properties to the requirements of your lift. Here are the key factors to work through:

1. Load weight and required WLL Start with the weight of the load. Factor in any sling angle if you are rigging in a basket or bridle configuration - as the angle from horizontal decreases, the tension in each sling leg increases significantly. Your sling WLL must exceed the calculated tension in each leg, not just the total load weight.

2. Load surface and shape If the load has a flat surface and you need to avoid surface marking, a web sling is usually the better choice. If the load is cylindrical, irregular, or delicate, a round sling will wrap the shape more naturally and distribute the load more evenly. See the full Holloway Houston synthetic slings range for available widths, lengths, and ply ratings.

3. Material: polyester vs nylon Polyester slings maintain their rated capacity when wet and are more resistant to most acids. Nylon slings are more elastic - which can be an advantage for shock-absorbing applications - but they lose up to 15% of their rated capacity when wet. Know your working environment before choosing.

4. Hitch type Your hitch configuration affects the effective WLL. A vertical hitch uses 100% of the sling's rated capacity. A choker hitch reduces this to approximately 75–80%. A basket hitch effectively doubles the rated capacity per leg. Always calculate your required WLL based on how you are going to rig the sling, not just the sling's listed rating.

5. Environmental conditions Synthetic slings are not suitable for every environment. High heat, sharp edges, chemical exposure, and prolonged UV light all degrade synthetic fiber over time. Match your sling material and protective features to the conditions the sling will actually face. For a detailed breakdown of chemical hazards and temperature limits, see our Synthetic Sling Safety, Inspection & Care guide.

Benefits of Synthetic Slings

Synthetic slings offer several advantages that make them a strong choice across a wide range of lifting applications:

Lightweight: Synthetic slings are dramatically lighter than chain or wire rope slings of equivalent capacity. This reduces the physical effort of rigging and makes handling easier on every lift, particularly for repetitive tasks.

Load protection: The soft, wide bearing surface of a synthetic sling minimises surface marking on polished, coated, or otherwise sensitive components. For precision-machined parts, painted equipment, or finished goods, synthetic slings reduce or eliminate the risk of cosmetic damage.

Flexibility: Synthetic slings wrap and conform to the shape of the load. This distributes the lifting force more evenly and reduces the risk of stress concentration at a single contact point.

Non-sparking and non-conductive: Synthetic slings do not generate sparks and do not conduct electricity. This makes them a safe choice in environments near electrical equipment, or where spark generation is a risk.

Synthetic Sling Safety: 6 Rules Every Rigger Follows

Safety starts before the lift begins. Every use of a synthetic sling should follow these six rules:

1. Always confirm the WLL from the sling tag before use. A sling with a missing or illegible tag must be removed from service immediately. The tag is the only source of confirmed rated capacity.

2. Protect slings from sharp edges. A sharp corner or edge concentrates the full tension of the sling on a single contact line. Even a load well within the WLL can cut through a synthetic sling if edge protection is not in place. Install corner protectors, wear pads, or softeners at every sharp contact point before lifting.

3. Do not use near heat sources. Polyester slings begin to lose capacity above 180°F (82°C). Nylon slings are also affected. Keep synthetic slings away from furnaces, welding operations, and hot surfaces.

4. Keep away from acids, alkalis, and solvents. Chemical degradation of synthetic fibers is often invisible from the outside - the damage happens inside the jacket where you cannot see it. If a sling has had any contact with chemicals, remove it from service unless you can confirm no damage occurred. Full chemical hazard guidance is covered in our Synthetic Sling Safety & Inspection guide.

5. Never drag a sling across the ground or a surface. Dragging cuts through the outer jacket and the load-bearing fibers underneath. Always carry or lay slings down carefully - never pull them out from under a load.

6. Store correctly between uses. Hang slings on a clean, dry storage rack away from UV light, heat, moisture, and chemical exposure. Ultraviolet light degrades polyester and nylon fibers over time even when the sling is not in use. A proper storage environment extends sling service life significantly.

Synthetic Sling Inspection: What to Look For

Both OSHA 29 CFR 1910.184 and ASME B30.9 require inspection before every use. A qualified person must inspect each sling and remove it from service immediately if any of the following are found:

• Acid or caustic burns - any discoloration, brittleness, or change in the texture of the jacket material

• Heat damage - melted, glazed, or fused fibers visible on the jacket

• Cuts, holes, or tears - any break in the cover material that exposes the internal load-bearing fibers

• Excessive abrasion - worn areas of the jacket where the underlying fibers are becoming visible

• Broken or worn stitching - particularly at the load-bearing eye splices where the sling connects to the rigging

• Distorted fittings - elongated eyes, bent rings, or any deformation of metal end hardware

• Knots or kinks - a knotted or kinked sling body has disrupted fiber geometry and must be removed from service

• Embedded contaminants - grit, debris, or particles inside the jacket that cannot be removed

• Missing or illegible tag - without a readable tag, rated capacity cannot be confirmed and the sling cannot be used

For the complete pre-use inspection checklist, chemical hazard reference table, removal criteria, and storage requirements, see the full guide: Synthetic Sling Safety, Inspection, Care & Best Practices

Ready to Find the Right Sling?

Browse Holloway Houston's full range of synthetic slings - web slings, round slings, and endless configurations across a wide range of capacities and widths. All slings are proof tested and certified to ASME B30.9 before shipment.

Need help selecting the right sling for your application? Call 713-675-3900 or Request a quote at Holloway Houstonlifting.com to speak with an Holloway Houston rigging specialist.