Wire Rope Sling Inspection Guide

Wire rope slings that fail during a lift can drop loads weighing thousands of pounds, causing fatal struck-by injuries and massive property damage. OSHA requires wire rope slings to be inspected before each use (29 CFR 1910.184 for general industry, 29 CFR 1926.251 for construction) and removed from service when they show specific signs of damage or deterioration. ASME B30.9 provides the detailed inspection criteria and rejection standards that safety professionals and riggers use to make remove-from-service decisions.

This guide walks through every inspection point, explains the rejection criteria that trigger mandatory removal from service and provides a practical framework for building a sling inspection program that keeps your lifts safe and your facility compliant.

Types of Wire Rope Sling Inspections

OSHA and ASME B30.9 define two distinct levels of sling inspection. Both are required and each serves a different purpose.

Initial Inspection

Before a new or repaired sling is placed into service, it must be inspected to verify it meets the manufacturer's specifications, has legible identification markings and shows no damage from shipping or storage. Check that the sling tag displays the rated capacity, sling type, size, length and manufacturer identification.

Frequent Inspection (Before Each Use)

Every wire rope sling must be visually inspected by a designated person before each use or at the start of each shift if the sling remains rigged. This inspection is a visual check that looks for obvious damage, distortion or deterioration. It does not need to be documented (though documentation is considered best practice), but it must be performed consistently.

Periodic Inspection

Periodic inspections are more thorough, documented examinations performed at regular intervals based on the frequency and severity of sling use. ASME B30.9 recommends intervals ranging from monthly to annually depending on service conditions. Periodic inspections require written records that include the sling identification, inspection date, findings, inspector name and disposition (returned to service, repaired or removed).

Wire Rope Sling Rejection Criteria

The following conditions require immediate removal from service. These are the specific wire rope rejection criteria defined by OSHA and ASME B30.9. A sling that meets any one of these criteria must be taken out of service immediately - it does not need to fail multiple criteria to be rejected.

Broken Wires

Broken wires are the most common reason for sling rejection. The specific limits depend on the sling configuration:

• Single-part slings - Ten randomly distributed broken wires in one rope lay, or five broken wires in one strand in one rope lay
• Cable-laid and braided slings - Twenty broken wires per lay length
• Any type - Broken wires at end fittings (splices, swaged fittings, ferrules or thimbles) require immediate rejection regardless of the count

A "rope lay" is the distance along the rope in which one strand makes one complete helical wrap around the core. Measuring this distance correctly is essential for accurate broken wire counts. If you cannot confidently identify one rope lay, reject the sling and consult a qualified rigger.

Diameter Reduction

Wire rope slings lose diameter as they wear. OSHA requires removal from service when the rope diameter is reduced below its nominal diameter by the following amounts:

• Ropes up to 3/4 inch nominal diameter - Reject if diameter reduction exceeds 1/64 inch
• Ropes 7/8 to 1-1/8 inch - Reject if diameter reduction exceeds 1/32 inch
• Ropes 1-1/4 to 1-1/2 inch - Reject if diameter reduction exceeds 3/64 inch

Measure diameter at the widest point (crown to crown of two opposite strands) at several locations along the sling. Use a wire rope caliper or a micrometer designed for rope measurement - standard calipers can give inaccurate readings on round strand rope.

Kinking

A kink is a permanent deformation caused by pulling a loop tight or bending the rope over a sharp edge. Kinks create stress concentration points where the rope is dramatically weakened. Any visible kink is grounds for immediate rejection - there is no "acceptable" kink. Kinks cannot be straightened out to restore the rope's strength.

Corrosion and Pitting

Surface corrosion reduces the cross-sectional area of the wires, lowering the sling's capacity. Internal corrosion (between wires and strands) is even more dangerous because it is not visible from the outside. Reject slings that show:

• General surface rust with visible metal loss
• Pitting (small holes in the wire surface)
• Stiffness or reduced flexibility that suggests internal corrosion
• Rust-colored dust weeping from between strands when the rope is bent

Heat Damage

Exposure to temperatures above 400 degrees Fahrenheit (204 degrees Celsius) can reduce the tensile strength of carbon steel wire rope. OSHA requires that slings exposed to temperatures exceeding this threshold be removed from service unless the manufacturer confirms suitability for high-temperature use. Evidence of heat damage includes discoloration (blue, brown or black tinting) and loss of lubrication.

End Fitting Damage

Inspect all end fittings for:

• Cracks, deformation or excessive wear on hooks, shackles and links
• Swaged fittings with visible movement between the fitting and the rope
• Splices that are unlaying or have tuck legs pulling out
• Thimbles that are distorted, cracked or missing
• Ferrules (Flemish eye terminations) that are crushed, cracked or slipping

Other Rejection Criteria

• Crushing or flattening - Localized sections where the rope is deformed from its round cross-section
• Bird-caging - Outer strands forced outward from the rope axis, creating a bulge that resembles a bird cage
• Core protrusion - The core (fiber or independent wire rope core) pushing out between the strands
• Missing or illegible identification tag - A sling without a readable identification tag showing its rated capacity must be removed from service until the tag is replaced and the sling is re-evaluated
• Evidence of unauthorized repair - Wire rope slings must only be repaired by the manufacturer or a qualified sling fabricator; field repairs are prohibited

How to Perform a Wire Rope Sling Inspection

Follow this step-by-step process for a thorough frequent or periodic inspection. For detailed rigging safety context, see our rigging and lifting safety guide.

Step 1: Clean the Sling

Remove dirt, grease and debris so you can see the rope surface clearly. A wire brush and solvent-dampened rag work for most conditions. Do not use abrasive cleaning methods that could damage the wires.

Step 2: Inspect End to End

Start at one end fitting and work your way to the other, rotating the sling as you go to inspect the full circumference. Work systematically so you do not skip sections. Run the sling slowly through your gloved hands (wearing leather gloves), feeling for broken wires, flat spots and distortion that may not be immediately visible.

Step 3: Check End Fittings

Inspect each end fitting carefully. Look for cracks, deformation, wear and proper engagement. Open the hook latch to verify it functions and springs closed. Check that swaged fittings are secure and that thimbles are seated properly in the eye.

Step 4: Measure Diameter

Take diameter measurements at the widest point at multiple locations along the sling length. Compare to the nominal diameter listed on the sling identification tag. Record measurements for periodic inspections.

Step 5: Check the Identification Tag

Verify the tag is present, legible and securely attached. The tag must show the rated capacity, sling type, size and manufacturer. If the tag is missing or unreadable, remove the sling from service.

Step 6: Document Findings

For periodic inspections, record your findings on an inspection form or in your digital inspection system. Include sling identification number, inspection date, specific findings (positive and negative), inspector name and the disposition decision.

Building a Sling Inspection Program

An effective sling inspection program includes the following components:

• Sling inventory - Maintain a complete list of all wire rope slings with unique identification numbers, specifications, purchase dates and inspection history
• Designated inspectors - Identify and train qualified persons to perform frequent and periodic inspections
• Inspection schedule - Establish periodic inspection intervals based on service conditions, with more frequent inspections for slings in heavy or severe-duty service
• Documentation system - Maintain inspection records for each sling, tracking its condition over time and providing a clear audit trail
• Removal and replacement process - Define a clear procedure for removing rejected slings from the worksite (cut and destroy to prevent reuse) and ordering replacements
• Training program - Ensure all riggers and equipment operators who perform frequent inspections understand the rejection criteria and know how to escalate concerns

Common Sling Inspection Mistakes

Avoid these errors that undermine even well-intentioned inspection programs:

• Cursory glance instead of inspection - A real inspection takes time; rushing through it misses broken wires, early corrosion and heat damage
• Ignoring internal condition - External appearance can be acceptable while internal wires are corroded and broken; flex the rope in both directions to open strands and check for internal deterioration
• Accepting "borderline" conditions - If you have to debate whether a condition meets the rejection criteria, remove the sling from service; slings are far cheaper than the consequences of failure
• No tracking of sling condition over time - A sling that passes today but shows a trend of increasing broken wires or decreasing diameter should be flagged for more frequent inspection or preemptive replacement

Keep Your Rigging Operations Safe

Wire rope sling inspection is a non-negotiable part of safe rigging practice. Every lift depends on the integrity of the sling and that integrity depends on thorough, consistent inspection by trained personnel. Make Safety Easy provides the inspection forms, scheduling tools and documentation management you need to run a sling inspection program that is both thorough and efficient. Request a demo to see our inspection platform in action, or review pricing to find the plan that fits your team.