Selecting the right construction, angle and D/d ratio determines safe capacity – for example, a 5/8‑inch 6×19 EIPS wire‑rope sling is rated about 7.6 tonnes vertically, but only around 3.8 tonnes in a 60° choke.
2 min read – what you’ll gain
- ✓ Apply OSHA/ASME angle factors to calculate choker sling capacity accurately.
- ✓ Use a quick inspection checklist to spot kinks, broken wires and corrosion.
- ✓ Protect capacity by matching a ≥ 25:1 D/d ratio to your hook, sheave or load.
- ✓ Specify the right construction and core with iRopes OEM/ODM guidance.
Material and construction matter when determining choker sling capacity. Fibre rigging ropes can be made in polypropylene‑polyester, nylon‑polyester or polyester‑polyester blends and supplied as single‑braid or double‑braid. For steel wire‑rope slings, construction (e.g., 6×19, 6×37) and grade (such as EIPS) set the rating. Below, we explain the fundamentals, show the calculations, and help you choose the right size for every lift.
choker sling capacity
When you hear the term working load limit (WLL), think of the maximum weight a sling can safely carry. In a straight‑up lift the WLL printed on the tag is the vertical rating. Once you bend the rope into a choker, the effective capacity drops because the rope now bears both tension and a sideways component. That distinction between vertical and choker use is the cornerstone of every safe lifting plan.
“A choker’s capacity is never higher than its vertical rating; the angle simply dictates how much you must de‑rate it. Ignoring that reduction is a fast track to a dangerous overload.” – Mark J., Certified Rigger
OSHA and ASME have codified exactly how much you should de‑rate a choker. The rule of thumb is a simple percentage based on the angle between the legs:
- 120° – 0.75 of the vertical rating
- 90° – 0.65 of the vertical rating
- 60° – 0.50 of the vertical rating
Both the ASME B30.9 rigging standard and OSHA 1910.184 require a minimum 5 : 1 safety factor, meaning the rope’s ultimate strength must be at least five times the intended load. In practice you label the sling with the calculated choker sling capacity after applying the angle reduction and any D/d‑ratio adjustments. This conservative approach keeps the lift well within the engineered limits.
Now, you might be wondering: What is the capacity of a 5/8” wire rope choker? For a typical 5/8” 6×19 EIPS wire‑rope sling the vertical WLL is around 7.6 tonnes. Applying the 0.75 factor for a 120° choker gives roughly 5.7 tonnes (≈ 12,600 lb). Remember, that figure assumes a D/d ratio of at least 25:1; tighter wraps would shave capacity off the rating.
With the safety fundamentals nailed down, the next step is to explore how rope construction and diameter shape the underlying load capacity, guiding you toward the perfect custom solution.
steel choker rigging
Having nailed the basics of choker sling capacity, the next logical step is to look at the hardware that turns a rope into a reliable lifting tool. Steel choker rigging comes in a handful of proven configurations, each suited to a particular class of job – from rugged off‑road recovery to precise marine cargo handling.
Choker Types
A single‑part steel choker is a fixed loop that offers strong, predictable performance for general lifts such as crane‑to‑truck transfers. The sliding‑hook variant features a movable eye, ideal for gripping irregularly shaped loads or applications where the sling must be adjusted on‑the‑fly. Finally, a Flemish‑eye sling uses a Flemish splice secured with a ferrule and pairs with a thimble and shackle or hook, providing a robust connection point for heavy‑duty construction or offshore work.
Core and material choices influence durability and handling. For steel wire‑rope slings, select an independent wire‑rope core (IWRC) for higher temperature and crush resistance, or a fibre core for added flexibility. For fibre rigging rope, common blends include polypropylene‑polyester, nylon‑polyester and polyester‑polyester in single‑braid or double‑braid constructions; the blend you specify affects stretch, abrasion resistance and chemical/UV performance.
When you pull a steel choker off the rack, a quick visual inspection can be the difference between a safe lift and a costly accident. The industry‑standard answer to “How to inspect a steel choker?” breaks down into four straightforward steps:
- Look for broken wires or visible corrosion on the rope strands.
- Check the eye or hook for dents, cracks or a deformed shank.
- Verify the minimum D/d on the tag suits the actual hook, sheave or load diameter.
- Confirm the tag shows a current inspection date and the correct working load limit.
These points dovetail nicely with the safety‑first mindset championed earlier. Once the choker passes inspection, you can match its construction and material choice to the load profile, confident that the steel choker rigging will behave predictably under tension.
With inspection habits solidified, the guide will now shift focus to how rope construction and diameter shape the underlying load capacity, paving the way for a deeper dive into wire rope sling size and capacity.
wire rope sling size and capacity
Building on the inspection mindset, let’s explore how the rope’s construction and diameter dictate the numbers you see on a tag. When you know which strand pattern you’re holding and how big the rope is, you can instantly gauge whether it will meet the load you’re planning.
The most common patterns you’ll encounter are 6×19, 6×37 and 6×36 class. A 6×19 class rope has six strands with about 19 wires per strand; it favours abrasion resistance and high strength for general‑purpose rigging. A 6×37 class uses more, thinner wires, which improves flexibility and bending‑fatigue performance around smaller sheaves. The 6×36 class sits between these, offering a balanced strength–flexibility compromise for varied field conditions.
For detailed specifications, see our guide on steel wire rope specifications.
6×19
Six‑strand rope with ~19 wires per strand; offers a solid balance of abrasion resistance and strength, ideal for general‑purpose lifts.
6×37
More, thinner wires deliver greater flexibility and improved bending‑fatigue life, suited for tighter bends and dynamic loads.
3/8‑1 in
Vertical capacities typically range from 2.8 tonnes (3/8") up to 20 tonnes (1") for EIPS, IWRC slings; see the manufacturer’s chart for exact figures.
Choker factor
Multiply the published vertical rating by 0.75–0.80 for a typical choker; actual capacity depends on angle and the D/d ratio.
Because a choker’s effective rating is usually 75–80 % of the vertical rating, the diameter you select has a direct impact on how much you can actually lift when the rope is wrapped around a load. For example, a 5/8” 6×19 rope carries about 7.6 tonnes vertically; in a 120° choker that drops to roughly 5.7 tonnes. Tightening the wrap reduces the D/d ratio, and every step below the recommended 25:1 ratio can shave a meaningful percentage off the listed capacity.
Maintain a D/d ratio of at least 25:1; tighter wraps can reduce the stated capacity by up to 30 %.
With a clear picture of construction types, diameter choices and the 75–80 % choker rule, you can match the right rope to the job without guesswork. When a project calls for a non‑standard size or a special core, iRopes can tailor a wire‑rope sling that fits the exact wire rope sling size and capacity you need, backed by ISO 9001 quality assurance and comprehensive OEM/ODM support.
Ready for a custom rigging solution?
You've learned that the choker sling capacity drops with angle, that a 5:1 safety factor applies, and that proper inspection of steel choker rigging safeguards every lift. Understanding construction types such as 6×19 and 6×37, and the relationship between diameter and wire rope sling size and capacity, lets you pick the right rope quickly. For fibre rigging ropes, selecting the appropriate blend—polypropylene‑polyester, nylon‑polyester or polyester‑polyester—and choosing between single‑braid or double‑braid further tailors stretch and durability to your application.
For personalised guidance or a bespoke sling that meets your exact specifications, complete the form above. Our iRopes experts will design an ISO‑9001‑certified solution with protected IP, custom branding and on‑time delivery to your location worldwide.
