Synthetic slings don't give the warnings wire rope does. There are no broken wires to count, and damage to the load-bearing core can be hidden under a cover that looks fine. That's why inspecting round slings and web slings takes a specific checklist. Here it is, along with how often to inspect, the removal criteria, and how Slingmax's Check-Fast® system takes the guesswork out.
Quick answer: inspect every synthetic sling before use on each shift, plus a documented periodic inspection at least once a year (more often in severe service). Remove it from service if the tag is missing or unreadable, if there are cuts, holes, tears, snags, melting, charring, chemical burns, knots, broken stitching, exposed core yarns or red warning yarns, or if fittings are damaged. When in doubt, take it out.
How often to inspect synthetic slings
| Inspection | Who | When |
|---|---|---|
| Initial | Designated person | Before a new or repaired sling goes into service |
| Frequent | Competent person or the user | Before use on each shift, and during use as conditions warrant |
| Periodic | Designated or qualified person | At least annually; monthly to quarterly for severe service. Keep a written record |
OSHA 1910.184 and 1926.251 set the shift-by-shift requirement. ASME B30.9 sets the periodic inspection and removal criteria.
Synthetic sling inspection checklist
| Check | Remove from service if… |
|---|---|
| Tag | Missing or unreadable |
| Cover or webbing | Holes, tears, cuts or snags |
| Round sling core | Core yarns visible through the cover |
| Web sling warning yarns | Red (or other) warning yarns showing |
| Heat | Melting, charring, glazed or stiff areas |
| Chemicals | Acid or caustic burns, discoloration, brittle fibers |
| Stitching | Broken or worn stitching in load-bearing splices |
| Knots | Any knot in the sling |
| Abrasion | Excessive wear, fuzzing or thinning |
| Fittings | Pitted, corroded, cracked, bent, twisted or broken |
| Anything else | Any condition that makes you doubt the sling's strength |
How to inspect, step by step
- Read the tag first. No tag, no lift. Confirm the rated capacity covers the hitch you plan to use.
- Lay the sling out flat in good light, on a clean surface.
- Go hand over hand along the full length of both sides, feeling for lumps, soft spots, stiff areas and changes in thickness, and looking at every inch.
- Check the eyes and splices on web slings, where stitching carries the load.
- Check fittings for cracks, distortion, corrosion and sharp edges that could cut the sling.
- Check the Check-Fast® tag on slings that have one (see below).
- Tag out anything that fails with "Do Not Use" and pull it from the rack immediately.
Round slings vs web slings: what to look for
- Round slings: the load is carried by the core yarns inside the cover. The cover protects them but isn't load-bearing. Any core yarn showing through the cover means removal. A torn or burst cover may mean core damage underneath.
- Web slings: the webbing itself carries the load. Many have red warning yarns woven inside; when they show, the sling is worn out. Pay extra attention to the eyes and the stitched splices.
Heat and chemical limits
| Sling material | Max temperature | Chemical notes |
|---|---|---|
| Nylon | About 194°F | Damaged by acids |
| Polyester | About 194°F (Slingmax polyester and Covermax® covers: 180°F) | Damaged by alkalis |
| Slingmax K-Spec® core | 180°F | Check with the manufacturer |
| Slingmax Sparkeater® (aramid) | 300°F | Check with the manufacturer |
Cold down to -40°F doesn't affect strength. For anything outside these limits, ask the manufacturer before you lift.
How Check-Fast® works
The Check-Fast® Inspection System on Slingmax roundslings gives a GO/NO-GO answer about the core, replacing a subjective hand-over-hand judgment. An External Warning Indicator (EWI) is connected to the internal core yarns and shows on the outside of the sling. If the core is damaged by severe overload, fiber-on-fiber abrasion or fatigue, the EWI is designed to disappear before the sling fails.
- EWI visible and intact: the core check passes. Finish the rest of the inspection.
- EWI missing or retracted: the sling fails. Remove it from service.
The EWI is sacrificial and not part of the load path, so it reports damage without weakening the sling. Check-Fast is available on Slingmax polyester and K-Spec® roundslings, including Twin-Path®, Single-Path® and Sparkeater®.
What to do with a failed sling
- Tag it "Do Not Use" and remove it from the work area right away.
- Slingmax roundslings with cover damage can go back to the manufacturer for a repair evaluation; Twin-Path® slings are repairable.
- Standard round and web slings that fail are destroyed, cut up so they can't be used again.
- Record the removal in your inspection log.
Keep slings out of trouble
Most synthetic sling damage comes from edges, heat and dragging. Use a sleeve or pad on every edge (see our sling protection guide), keep slings off the ground, store them dry and out of sunlight, and follow the rigging inspection checklist for the rest of your gear.
Synthetic Sling Inspection FAQs
How often do synthetic slings need to be inspected?
Before use on each shift by a competent person, plus a documented periodic inspection at least once a year, more often for severe service.
What does it mean when red yarns show on a web sling?
The red warning yarns mean the webbing has worn through to the point of removal. Take the sling out of service.
Can a cut round sling be repaired?
Standard round slings are destroyed. Slingmax roundslings can be sent to the manufacturer for a repair evaluation, and Twin-Path® slings are repairable.
What is the Check-Fast EWI?
The External Warning Indicator on Slingmax roundslings. If it's missing or retracted, the core may be damaged and the sling must come out of service.
Can I use a synthetic sling with a knot in it?
No. A knot is a removal criterion. It weakens the sling significantly.
