Sling Types, Inspection, and Removal-from-Service Criteria

Why Sling Inspection Matters

Every rigging lift begins with the sling — the component that physically holds the load. A failed sling can drop a load without warning, killing workers instantly. ASME B30.9, Slings, is the nationally recognized standard that governs sling construction, use, and inspection. Federal OSHA references ASME B30.9 as the authoritative guide for sling safety. Before any sling is used on a job site, a qualified rigger must inspect it visually. Knowing exactly what to look for — and having the courage to pull a sling out of service — is one of the most important skills in rigging.

Wire Rope Slings

Wire rope slings are extremely strong and resistant to abrasion, but they can degrade in ways that are not always obvious.

Broken wires are the primary concern. ASME B30.9 requires removal from service when a specified number of broken wires per rope lay length is reached. A lay length is the distance along the rope over which one strand makes a full spiral. Use a lay-length gauge and count every broken wire you can see as you rotate the rope slowly in good light.

Kinking occurs when a loop in the rope is pulled tight, permanently distorting the wire arrangement. A kinked sling must be removed — the deformation concentrates stress and cannot be corrected.

Corrosion — rust pitting or pitting between wires — weakens the rope from the inside. Surface discoloration alone may not disqualify a sling, but pitting, flaking scale, or broken wires associated with rust are removal criteria.

Core damage shows as unusual reduction in rope diameter (bird-caging), an unlaying of strands, or a soft, spongy feel under hand pressure. Any evidence of core failure means immediate removal.

Additional criteria include: severe heat damage (discolored, annealed wires), abrasion that flattens the outer wires noticeably, and end fittings that are cracked, deformed, or show evidence of slippage.

Alloy Chain Slings

Alloy chain slings are chosen for high-temperature environments and where abrasion would destroy other sling types. Inspection focuses on:

Stretch — elongation beyond the manufacturer's tolerance (commonly referenced as 3% elongation of a measured section). Carry a reference length or use the identification tag's stated link dimensions.

Nicks and gouges cut into link cross-section and reduce load capacity. Any nick or gouge deeper than the allowable threshold in ASME B30.9 is a removal criterion.

Bent or twisted links indicate shock loading or an improper previous use. They must not be straightened and reused; remove and replace.

Cracks anywhere in the link, weld, or master link are an immediate removal criterion.

Corrosion that causes pitting of the link surface is also a removal criterion.

Always check hooks, master links, coupling links, and mechanical attachments for deformation and proper function of safety latches.

Synthetic Web and Round Slings

Synthetic slings (nylon, polyester, or other engineered fibers) are popular because they do not damage finished surfaces and are light. However, they are vulnerable to hazards wire rope resists.

Cuts and abrasion — any cut that penetrates the outer jacket of a round sling, or any cut or abrasion that exposes load-bearing yarns in a web sling, is a removal criterion. Even a small cut can propagate to complete failure under load.

UV degradation — prolonged sun exposure embrittles synthetic fibers. Faded color, powdery or stiff texture, and surface cracking are signs. Slings stored or used outdoors for extended periods must be inspected especially carefully.

Heat damage — synthetic slings have low melting points. Glazed, melted, or discolored fibers indicate heat exposure. Remove immediately.

Chemical damage — acids and caustics can destroy nylon or polyester rapidly. Discoloration, stiffness, or deterioration of the fiber after known chemical exposure requires removal.

Missing or illegible tags — ASME B30.9 requires that every synthetic sling carry an identification tag showing capacity, reach, fiber type, and serial number. A sling without a legible tag must be removed from service regardless of apparent physical condition. You cannot verify its capacity.

Round slings have an outer sleeve protecting the load-bearing core. Inspect the sleeve for tears, holes, and seam separation. Damage to the sleeve does not automatically mean the core is cut, but you cannot inspect the core directly — any sleeve damage that exposes the core is a removal criterion.

The Inspection Process

1. Start with the tag. Confirm it is present, legible, and the capacity is appropriate for the planned lift.

2. Lay the sling out fully in good light on a clean surface.

3. Work from one end to the other, rotating wire rope slings so you inspect all sides.

4. Use your hands as well as your eyes — your fingers can feel kinks, broken wires, and changes in diameter that eyes alone miss.

5. Compare against removal criteria on your ASME B30.9 criteria card.

6. Make a clear pass or fail decision for every sling — there is no "probably OK."

Removal from Service

When a sling fails inspection, attach an out-of-service tag immediately, remove the sling from the rigging area, and report it to your supervisor. Never leave a defective sling accessible where someone might use it. Document the defect type and location on your condition report. In most cases, defective wire rope and chain slings are destroyed; synthetic slings are cut to prevent reuse.

Safety Reminders

• Never use a sling whose capacity is unknown.
• Inspection is required before each use, not just periodically.
• Damaged slings should never be repaired in the field by a non-qualified person.
• Wear leather gloves when handling wire rope — broken wires are sharp and can puncture skin.