How to Properly Inspect and Maintain Lifting Slings

Why Sling Inspection Is Non-Negotiable

OSHA 29 CFR 1926.251 requires that all slings be inspected before each use by a competent person, and receive a thorough periodic inspection at intervals not exceeding 12 months. The reason is simple: sling failure during overhead lifting is one of the most dangerous scenarios in industrial workplaces. A 2-ton load falling from height generates forces equivalent to a car crash.

Inspection Frequency Requirements

Inspection Type	Frequency	Who Performs	Documentation
Pre-use visual	Before each use	Sling user (trained)	Not required but recommended
Frequent inspection	Daily to monthly (based on use)	Competent person	Recommended
Periodic (thorough)	Annually minimum	Qualified person	REQUIRED — written records
Post-incident	After any overload or impact event	Qualified person	REQUIRED

Web Sling Inspection Criteria (ASME B30.9)

Synthetic web slings are the most common type in general industry. Remove from service if ANY of the following are found:

Immediate Removal Criteria

• Acid or caustic burns: Any discoloration or stiffness from chemical exposure
• Melting or charring: Evidence of heat damage on any surface
• Holes, tears, or cuts: Any penetration of the webbing body
• Snags or punctures: Pulled or broken yarns that distort the weave pattern
• Broken or worn stitching: Especially in load-bearing seams at eyes or fittings
• Red core yarn visible: Many manufacturers weave red warning yarns into the core — if visible, the sling has been cut past the safe threshold
• Distortion of fittings: Bent, cracked, or deformed hardware (hooks, rings, links)
• Missing or illegible tag: The identification tag must show WLL, manufacturer, and sling type
• Knots: Never tie a knot in a web sling — it reduces capacity by 50%+
• Excessive abrasion: Wear-through of load-bearing yarns on any surface

Color Code System for Web Slings

ASME B30.9 establishes a color-based identification system for polyester web slings:

Color	Sling Width	Vertical WLL	Choker WLL	Basket WLL
Purple	1″	3,100 lbs	2,500 lbs	6,200 lbs
Green	2″	6,400 lbs	5,100 lbs	12,800 lbs
Yellow	3″	9,800 lbs	7,800 lbs	19,600 lbs
Tan	4″	12,600 lbs	10,100 lbs	25,200 lbs
Blue	5″	16,000 lbs	12,800 lbs	32,000 lbs
Orange	6″	19,000 lbs	15,200 lbs	38,000 lbs

Wire Rope Sling Inspection

Wire rope slings require a more nuanced inspection due to their complex construction:

Broken Wire Criteria

• Random distribution: Remove if 10 or more broken wires in one rope lay (one complete helical wrap of the strands around the core)
• Concentrated in one strand: Remove if 5 or more broken wires in one strand in one rope lay
• Valley breaks: Even one broken wire in the valley between strands is cause for removal — valley breaks indicate internal fatigue

Other Removal Criteria

• Severe corrosion (pitting or rust that prevents accurate wire inspection)
• Kinking, crushing, bird-caging, or core protrusion
• Diameter reduction of more than 5% from nominal
• Heat damage (discoloration from torch, arc strike, or friction)
• End fitting damage (cracked swage, damaged thimble, bent eye)

Chain Sling Inspection (Grade 80/100)

Removal Criteria per ASME B30.9

• Stretch: Remove if any link has stretched more than 5% from original measured length
• Wear: Remove if link cross-section is worn more than 10% of original diameter at any point
• Nicks and gouges: Sharp notches that could act as stress concentrators
• Cracks: Any visible cracks, regardless of size or location
• Bent or twisted links: Links that don’t hang straight
• Weld splatter or arc strikes: Any evidence of welding on the chain body
• Discoloration from heat: Blue, purple, or straw colors indicate the chain has been overheated and its heat treatment compromised

Storage Best Practices

• Web slings: Store indoors, away from UV light, chemicals, and sharp edges. Hang on dedicated sling racks — never pile on the floor
• Wire rope slings: Hang on racks or store on wooden pallets. Keep lubricated. Never store in puddles or damp areas
• Chain slings: Hang on hooks or racks. Lubricate with chain dressing. Inspect for rust before re-use after extended storage
• All slings: Keep ID tags visible and protected. Segregate removed/condemned slings immediately — cut or destroy them to prevent accidental re-use

Documentation Template

A proper periodic inspection record should include:

1. Sling identification number
2. Sling type, size, and rated capacity
3. Date of inspection
4. Name and qualification of inspector
5. Condition of each component (webbing/rope/chain, fittings, tags)
6. Disposition: returned to service, repaired, or removed from service
7. Date of next scheduled inspection

Common Inspection Mistakes

1. Skipping pre-use checks: “It was fine yesterday” isn’t an inspection. Damage can occur during any lift.
2. Ignoring tag damage: A sling with an illegible tag must be removed from service — there’s no way to verify its WLL.
3. Inspecting only the body: End fittings, stitching, and attachment points fail more often than the sling body.
4. Not documenting periodic inspections: OSHA can request records. No records = violation.
5. Re-using condemned slings: Once removed from service, slings must be physically destroyed or clearly marked “DO NOT USE.”

Common Mistakes to Avoid

Avoiding these common errors can prevent equipment failure, regulatory violations, and serious safety incidents in the field.

• Ignoring Sling Angle Reduction Factors: As the angle between sling legs decreases from vertical, load on each sling increases dramatically. At 60 degrees each sling bears 115% of its share, at 30 degrees it bears 200%. Never use slings at angles less than 30 degrees from horizontal without recalculating capacity.
• Cutting or Modifying Slings: Cutting a sling to length or removing identification tags voids the manufacturer’s rating and violates OSHA regulations. Custom lengths must be ordered from the manufacturer or a qualified sling fabricator with proper documentation.
• Storing Slings Improperly: Leaving slings on the ground, in direct sunlight, or near chemicals accelerates degradation. Polyester slings are vulnerable to alkalis while nylon slings are vulnerable to acids. Store all slings on racks in a clean, dry, covered area.
• Using a Sling Without Checking the Tag: Every lift requires verifying the WLL, hitch type rating, and inspection date from the identification tag. A sling’s capacity varies significantly by hitch configuration. A basket hitch typically doubles the capacity versus a vertical hitch.
• Shock Loading a Sling: Slings are rated for static or gradually applied loads. A sudden jolt can generate forces 2-3 times the static load, potentially exceeding the sling’s capacity and causing immediate failure.