How to Inspect a Synthetic Sling and What Removes It From Service

Why this matters

A wire rope sling sheds broken wires for weeks before it lets go. A synthetic sling does not do that. Web and roundslings carry their load in fibres that are either intact or cut, and a sling can lose a large share of its strength through an injury that looks like scuffing. There is no gradual outward sign to trend, which means there is no version of this inspection where you weigh how much life is left. Either a removal condition is present or it is not.

That changes how the inspection is organised. Running it as a walk down the sling from eye to eye finds defects one at a time and tells you nothing about why they happened, so the shop replaces slings at a steady rate forever. Running it as a set of mechanism sweeps, where each sweep asks what kind of injury you are looking for, finds the same defects and also identifies the rig, the corner or the process that is producing them. The second version fixes the cause. This card is written that way.

Inspect with the sling off the load and hanging slack, never on a rigged sling under tension. Where a sling may carry chemical contamination, handle it with the glove type the substance's safety data sheet names rather than bare hands, do not shake or beat it out, and if that substance has an airborne route the area's respiratory protection programme under 29 CFR 1910.134 applies to the person doing the inspecting.

Who inspects, and when

Under 29 CFR 1910.184 for general industry, each sling and all its fastenings and attachments are inspected for damage or defects before use each day by a competent person the employer designates, with additional inspections during use where service conditions warrant. The construction counterpart is 29 CFR 1926.251, which carries the same daily duty for the work it covers. Establish which Part covers the job you are on; a field-service shop can be under either depending on the site.

On top of the daily duty, ASME B30.9, in the edition your authority having jurisdiction, contract or employer programme has adopted, calls for documented periodic inspection at intervals a qualified person sets based on how hard the slings are used. The daily inspection catches today's damage. The periodic record is the only thing that ever shows you a trend.

Sweep 1: identification

Look for a legible tag that belongs to this sling and carries its rated capacities, its material and its manufacturer.

Removes it: a missing tag, an illegible tag, or a tag whose details do not match the sling it is on. There is no rated capacity for a sling you cannot identify, and there is no experience-based substitute for the marking. This one is first because everything downstream is meaningless without it, and because it is the single most common finding on a rack that has been in service a few years.

What it implicates: tags go illegible from abrasion, ultraviolet and chemical exposure, so a rack full of unreadable tags is telling you about the storage and the environment before it tells you about the slings.

Sweep 2: cutting and abrasion

Run the whole surface, both faces of a web sling and the full circumference of a roundsling cover, including the eyes and the area around the label. On a roundsling, pay attention to whether the cover is only marked or actually opened.

Removes it: cuts, tears, snags, punctures or holes; broken or worn stitching in any load-bearing seam; and on a roundsling, any exposed core yarn through the cover. The cover is not structural, so a hole in it is not itself the strength loss, but it means the core has been reached and the core cannot be inspected once it is exposed.

Do not try to price the damage. A cut that removes a quarter of a web sling's width does not cost a quarter of its strength: the remaining fibres pick up the load unevenly and the cut is a stress raiser, so the loss is worse than proportional and there is no field method to measure it. That is why this criterion is pass or fail.

What it implicates: cuts come from edges and corners. A sling with a clean transverse cut has been over something sharp, and the fix is corner protection or a wear pad at that point rather than a new sling. Protection has to be inspected too, and it must not be the thing that hides the damage from the next inspection.

Sweep 3: heat

Look for glazing, hard or shiny patches, stiff areas that will not conform, melted or fused fibre ends, and weld spatter.

Removes it: melting or charring of any part of the sling. Any, not a percentage of the surface.

What it implicates: heat damage arrives from three routes that look similar and are fixed differently. A hot workpiece is a temperature question against the sling manufacturer's stated maximum operating temperature. Friction from a sling dragged under a load or allowed to slip through a bight is a rigging-method question. Weld spatter is a housekeeping question about where the sling was lying. Naming which one you are looking at is what stops it repeating.

Sweep 4: chemical

Look for discolouration, stiffening, a gritty or powdery feel, fibres that shed when rubbed, and any area that has changed texture relative to the rest of the sling.

Removes it: evidence of acid or caustic burns.

What it implicates: the family matters here more than anywhere else, because nylon and polyester are near mirror images on chemistry and a shop that stores both on one rack cannot tell which sling went into which bay. The materials card in this group carries that in full, including why chemical loss cannot be expressed as a percentage. What belongs in the inspection is the discipline: chemical evidence is a removal, made by the person who found it, not a finding set aside for a second opinion.

Sweep 5: ultraviolet and age

Look for fading, loss of pliability, a chalky surface, and fibre that fuzzes or breaks when flexed by hand.

Removes it: on its own, ultraviolet degradation is a judgement for the competent person rather than a listed criterion, so this sweep more often produces a routing than a removal. What it removes outright is anything that has crossed into the criteria above, and sun-degraded fibre reaches those quickly.

What it implicates: slings stored outdoors, on a truck deck, or hung on a fence get this and slings in a covered rack do not. It is a storage finding, and it is the cheapest one on this list to fix.

Sweep 6: load history

Look for permanent elongation, a roundsling that has gone noticeably slimmer over part of its length, distorted eyes, and knots.

Removes it: a knot in a sling, which is both a removal condition and a severe strength loss at the knot, and any distortion that indicates the sling has been overloaded or shock loaded. There is no field repair for any of it. Only the sling manufacturer or a qualified repair facility may repair a sling, per ASME B30.9 as adopted, and shortening a sling with a knot is not a repair or a technique.

What it implicates: this sweep is the one that points at people rather than at hardware. A knot means somebody had the wrong length and used the sling anyway.

Sweep 7: fittings and hardware

Check any end fittings, links and hooks that are part of the assembly.

Removes it: distortion, cracks, excessive pitting or corrosion, a hook that has opened or twisted, or a missing or inoperative latch where one is fitted.

What it implicates: a distorted fitting is an overload record that outlasts the event, and it usually means the sling itself has seen the same load.

Worked example: eight slings off one rig

A crew returned eight synthetic slings from a week on one rig. The bench inspection, done with every sling slack and gloved, produced three removals.

• Sling 1: roundsling cover opened on one face with core yarn visible. Sweep 2. Removed.
• Sling 2: tag worn to the point of being unreadable. Sweep 1. Removed.
• Sling 3: a hard, shiny, glazed patch across one face of a web sling. Sweep 3. Removed.

Three findings, three different sweeps, and the temptation is to log three sling replacements and reorder. Put them on a rate instead.

• Removals from this rig: 3 of 8 slings inspected, which is 37.5 percent of the slings on that rig.
• The shop's trailing rate, on the same unit and the same decision: say 4 removals out of 60 synthetic slings inspected in the prior quarter, which is 6.7 percent of slings inspected.
• Ratio: 37.5 / 6.7 = over five times the shop's own rate.

Both figures are removals per sling inspected, which is what makes them comparable; a count of removals against a count of jobs would not be. One caution on the comparator: if any of those four prior-quarter removals also came off this rig, the trailing rate is not clean, and taking them out makes the gap wider, not narrower.

A rig running at five times the shop rate is a rig with a defect, not a run of unlucky slings. So the sweeps get read as a set rather than as three tickets:

• Sweep 2's finding says an edge on that load is unprotected, and it says roughly where, because the cut is at a specific point along the sling.
• Sweep 3's finding says something on that rig is hot, or something is sliding under load and generating friction heat.
• Sweep 1's finding says the tags are being abraded, which is the same abrasion story as sweep 2 arriving on a different part.

The action that follows is not eight replacement slings. It is a directed re-inspection of the five surviving slings at the same locations on the same faces, corner protection fitted at the edge sweep 2 identified, a surface temperature taken on the workpiece against the sling manufacturer's stated maximum operating temperature before the next pick, and a note in the periodic inspection record so the next quarter's rate is measured against this one rather than against zero.

The failure mode if you skip the pattern read is specific and slow. Three slings get replaced, the rig keeps its unprotected edge and its heat source, and the next set of eight comes back with three more. The rate never moves, the cost is absorbed as consumables, and eventually one of the injured slings goes back on the rack because the day was busy and the cover only looked scuffed.

How to verify you got this right

Confirm every removal was made on a criterion and not on a feeling. Write which sweep and which condition triggered it. A removal logged as "looked bad" is unusable for a trend and unusable for an argument with whoever wants the sling back.

Confirm every removal was made physical. Cut the eyes or the body so the sling cannot be rigged, and take it out of the area. A tag hung on a rack is a note; a sling that cannot be rigged is a decision. This is the step that fails on a busy day and it is the one that puts a condemned sling back on a load.

Then check that each finding produced an implication as well as a decision. If your inspection sheet has three removals and no entry naming what caused them, you ran a walk-down rather than the sweeps, and you have bought a replacement rather than a fix.

Last, check the boring one. Count the slings you inspected against the slings that went out. A sling that never came back to the bench has not passed anything, and it is still on somebody's rig.

References

• 29 CFR 1910.184, slings, for general industry, including the daily inspection duty by a competent person and the removal-from-service criteria for synthetic web slings, and 29 CFR 1926.251, rigging equipment for material handling, for construction work.
• 29 CFR 1910.134, respiratory protection, where the exposure assessment for a contaminant on a sling calls for respiratory control.
• ASME B30.9, slings, in the edition your authority having jurisdiction, contract or employer programme has adopted, for documented periodic inspection intervals and for the rule that repairs are made only by the sling manufacturer or a qualified repair facility.
• The sling manufacturer's identification tag, maximum operating temperature and chemical compatibility statement for the specific product.
• See related: The Sling Materials and What Each One Cannot Tolerate; How a Wire Rope Sling Fails and What You See First.