Chain Sling Inspection Under ASME B30.9: Links, Hooks, and Stretch

By Jo MartinJul 22, 2026Updated Sep 12, 20269 min read

Chain sling inspection is link by link, or it is not an inspection. Chain slings are the rigging that survives what destroys everything else — heat, sharp edges, abrasion, chemicals — and that durability is exactly why they get inspected least. A sling that shrugs off the conditions that visibly wreck webbing accumulates its damage invisibly, one link at a time, in a form that only measurement reveals.

The other reason chain gets inspected badly is that doing it properly is tedious. ASME B30.9 expects a link-by-link examination, and a twenty-foot leg has a lot of links. Programs that shortcut it look at the ends, glance along the middle, and miss the one link that matters.

Grade is the first thing to set up

Only alloy chain is acceptable for overhead lifting. Grade 80 and Grade 100 are the common alloy grades; Grade 120 exists for specific applications. Grade 30, 43, and 70 chain — proof coil, high test, and transport chain — are not lifting chain, regardless of how strong they feel or how they are marked for towing.

Transport chain in a lifting application is a finding we still encounter, usually on a truck where a binder chain was pressed into service. The visual difference is not reliable. The marking is. Alloy lifting chain carries grade identification, and the sling assembly carries a tag with the manufacturer, grade, size, reach, and rated capacity. Missing or illegible identification removes the sling from service on its own — the same rule that governs synthetic slings and hardware.

The measurements that decide it

Stretch is the criterion that requires a baseline, and it is the one most often unmeasurable in practice because the original reach was never recorded. Record it at first inspection, stamp or tag the assembly, and the check becomes a tape measure rather than a guess.

Stretch tells you the sling was overloaded

Alloy chain elongates before it fails, which is a designed-in warning. A sling that has stretched has been loaded beyond its rating, and the stretch is permanent evidence of it.

The subtlety is that elongation concentrates. A single link that took the abuse can be visibly longer and narrower than its neighbors while the overall reach barely changes, particularly on a long leg. That is why link-by-link matters: comparing each link against its neighbors catches localized stretch that an overall measurement averages away.

Hold the chain vertically under light tension and look along it. Links that have stretched appear elongated and their inside width narrows — the shape change is visible once you know to look for it, and it is more sensitive than a tape measure across twenty feet.

Where the damage actually concentrates

• At the master link and coupling links. The transition points carry the most complex loading and wear fastest.
• At the hook and its attachment. Wear at the saddle, and at the link riding in the hook.
• Wherever the chain bears on the load. Choker points, corners, and any place the chain has been bent around something.
• Link-to-link bearing surfaces. The inside of each link where it contacts the next — the surface that carries the load and the one you have to measure.
• Anywhere heat has been applied. Weld spatter from an adjacent operation is enough. Alloy chain’s strength comes from heat treatment, and local heating destroys it invisibly.

Heat is the failure mode people underestimate

Chain’s resistance to heat is relative, not absolute. Alloy chain loses strength progressively above roughly 400°F, and the loss is permanent even after cooling. Manufacturers publish derating tables by temperature, and above their stated maximum the sling is out of service permanently rather than until it cools.

The common exposures are not obvious: chain used near welding, chain lifting hot castings or forgings, chain stored where a torch operation showers it, and chain that has been in a fire. Weld spatter on a chain leg is both physical damage and evidence of thermal exposure, and it is a removal condition on both counts. In foundry and heavy manufacturing environments, thermal history is the dominant removal cause and it leaves less visible evidence than mechanical damage.

Never repair chain in the field

Chain slings may only be repaired by the manufacturer or a qualified person equivalent to the manufacturer, and repaired slings must be proof tested before return to service. Field repair is not permitted, and the specific practices to prohibit outright are:

Do not weld a link. Do not replace a link with a bolt, a connecting link not rated for lifting, or a shackle inserted into the chain. Do not shorten a chain with a knot — and yes, this happens. Do not heat and bend a link back into shape. Each of these either alters heat treatment or introduces a component with no matched rating into a load path.

Shortening is a legitimate need with a legitimate solution: grab hooks and shortening clutches designed for the chain grade and size, used per the manufacturer’s instruction. Improvising it is where the failures come from.

Chain sling inspection intervals and who performs them

Two levels apply, as with all rigging. Before each use, the user or a designated person inspects the sling — a condition check, not a documented event. Periodically, a documented inspection by a designated person at intervals determined by service severity, frequency of use, and environment, not exceeding one year under B30.9 for normal service.

Severe service shortens that substantially. Chain working daily in a foundry, around chemicals, or in continuous high-cycle use should be on a materially shorter cycle than shop chain used occasionally. This is the same logic that changes the inspection clock for cranes, and it applies with more force to rigging because rigging has no instrumentation to warn anyone.

The link-by-link inspection, practically

Doing it properly is a procedure rather than a look:

1. Clean the sling. Chain covered in grease, paint, or process residue cannot be inspected. This step is skipped constantly and invalidates everything after it.
2. Hang it free from the master link so each leg is straight and under its own weight.
3. Verify the tag — manufacturer, grade, size, reach, capacity, and that it matches the assembly in front of you.
4. Measure overall reach and compare against the recorded original.
5. Work link by link from the master link down each leg, rotating each link to see all surfaces, feeling for nicks, and comparing shape against neighbors.
6. Measure at wear points with a caliper wherever a link looks thinned, against the manufacturer’s minimum thickness for that chain size.
7. Inspect the fittings — master link, coupling links, hooks and latches — to their own criteria.
8. Record the identifier, the measurements taken, and the disposition.

Records, and the identifier problem

Chain slings need the same register any rigging inventory needs: a unique identifier that survives the environment, capacity and reach recorded, in-service date, and documented periodic inspections referencing the identifier rather than a description.

The tag is the weak point. Tags get torn off, painted over, or worn illegible, and a sling without identification cannot stay in service regardless of its physical condition. Durable stamped identification on the master link, backed by the register, survives what tags do not. A structured inspection sheet keeps the criteria consistent and the records comparable between inspectors and between years.

Where chain is the right choice, and where it is not

Chain is chosen for durability, and the selection logic explains the inspection emphasis. It handles sharp edges that would cut webbing, tolerates temperatures that would destroy synthetics, resists abrasion in gritty environments, and can be shortened with rated hardware for adjustable rigging. Those advantages put chain in the harshest applications on most sites.

The trade-offs are weight, the risk of load damage from a hard sling against a finished surface, and the fact that chain gives less visual warning than webbing does. A cut on a nylon sling is obvious to anyone. A stretched link is not. That asymmetry is the argument for the documented periodic inspection rather than relying on the pre-use check.

Where the same crew runs chain, wire rope, and synthetics out of one locker, the criteria have to branch by material. Wire rope slings follow broken-wire counts that differ from the running rope on the crane, and below-the-hook devices fall under B30.20 entirely. An inspection routine that applies one visual standard across a mixed inventory will pass gear it should not.

Building the program around the register

Chain inspection is the clearest case for inventory control, because the criteria depend on baselines that only a register preserves. Original reach, chain size, grade, and in-service date are all facts that exist once and are then lost unless someone writes them down.

The workable minimum is the same as for any rigging: durable identification stamped on the master link, a register connecting the identifier to grade, size, reach, and capacity, and documented inspections referencing that identifier. Colour-coded periodic tags make overdue assemblies visible without opening the file, which matters when the locker is shared between crews.

Where an inventory has accumulated over years with no register — the normal condition — a baseline rigging inspection sets up what exists and what its measurements are. That first pass is the expensive one. Every inspection afterward is a comparison, which is both faster and considerably more useful.

Common questions

What grade of chain can be used for overhead lifting?
Alloy chain only — Grade 80, 100, or 120 as applicable. Grade 30, 43, and 70 chain is not lifting chain and must not be used overhead regardless of its apparent strength.

How much stretch condemns a chain sling?
Any measurable elongation beyond the manufacturer’s allowance. Stretch is evidence of overload, and localized stretch in a single link condemns the sling even when overall reach looks acceptable.

Can a damaged link be replaced?
Only by the manufacturer or an equivalent qualified person, with proof testing afterward. Field replacement using connecting links or hardware is not a repair.

How often must chain slings be inspected?
Before each use by the user, and a documented periodic inspection at intervals based on service, not exceeding one year in normal service. Severe service requires shorter intervals.

Does chain need to be proof tested?
New slings are proof tested by the manufacturer. Proof testing is required again after repair, and is appropriate where an assembly’s history is uncertain.

Can chain slings be used at high temperature?
Within the manufacturer’s derating table, with reduced capacity. Above the stated maximum the sling is permanently removed from service — the strength loss does not reverse on cooling.

What is the most common chain sling finding?
Missing or illegible identification, followed by wear at the link bearing points and damage at the hooks. All three are found on first inspections at rates that surprise owners — consistent with the pattern in first-visit findings generally.

Link by link is the only method that works

Chain rewards inspection more than any other rigging, because its failures are gradual, measurable, and entirely detectable before they matter. It also punishes shortcuts, because the one link that has stretched looks identical to the others from three feet away.

If your chain slings have no recorded reach, no register, and no documented periodic inspections — which is the normal starting point — a baseline rigging inspection sets up the measurements, removes what has to go, and leaves you a record the next inspection can actually compare against.

Reviewed by Patrick Salazar, NCCCO-Certified Crane Inspector — every article on this site is checked against current OSHA and ASME B30 requirements before it publishes.