Load Securement Guide
The essentials for choosing and using tie-downs and rigging: what the ratings mean, how many tie-downs a load needs, and when gear has to come out of service.
Contents: Working load limit · Aggregate WLL rule · How many tie-downs · Chain grade chart · Webbing chart · Inspection
What "working load limit" means
The working load limit (WLL) is the maximum load a tie-down, sling or fitting is rated to carry in normal service. It is always well below the break strength — the force at which the product fails in testing. The ratio between the two is the design (safety) factor: tie-down chain and hardware commonly use 4:1 and synthetic webbing tie-downs 3:1, while overhead lifting slings use the factors set by their ASME B30 standard.
Always plan with the WLL, never the break strength, and use the lowest-rated component in the assembly. A 6,600 lb chain with a 5,400 lb binder is a 5,400 lb tie-down.
The aggregate WLL rule
Under 49 CFR 393.106, the combined working load limit of all tie-downs securing an article must be at least half the weight of that article. When adding them up:
- A tie-down that runs directly from the vehicle to the article counts for half of its WLL.
- A tie-down that goes over, around or through the article and attaches to the vehicle on both ends counts for its full WLL.
Example: a 20,000 lb excavator needs an aggregate WLL of 10,000 lbs. Four 3/8" Grade 70 chains (6,600 lbs each) attached directly from the deck to the machine count 3,300 lbs each — 13,200 lbs total, which meets the rule.
How many tie-downs a load needs
Separately from the WLL total, 49 CFR 393.110 sets a minimum number of tie-downs for an article that isn't blocked against forward movement:
| Article | Minimum tie-downs |
|---|---|
| 5 ft or shorter and 1,100 lbs or lighter | 1 |
| 5 ft or shorter and over 1,100 lbs | 2 |
| Over 5 ft up to 10 ft (any weight) | 2 |
| Over 10 ft | 2, plus 1 for every additional 10 ft or part of 10 ft |
If the article is blocked by a headboard, bulkhead or other cargo, use at least one tie-down per 10 ft of length. Some cargo types — logs, metal coils, paper rolls, concrete pipe, intermodal containers, vehicles, heavy equipment and machinery and others — have their own, stricter rules in 393.116 through 393.136. Try the calculator ›
Chain grade chart — working load limit (lbs)
Default WLLs for tie-down chain by grade and size. Use the WLL marked on the chain or its tag when it differs.
| Grade | 1/4" | 5/16" | 3/8" | 7/16" | 1/2" | 5/8" |
|---|---|---|---|---|---|---|
| Grade 30 proof coil | 1,300 | 1,900 | 2,650 | 3,700 | 4,500 | 6,900 |
| Grade 43 high test | 2,600 | 3,900 | 5,400 | 7,200 | 9,200 | 13,000 |
| Grade 70 transport | 3,150 | 4,700 | 6,600 | 8,750 | 11,300 | 15,800 |
| Grade 80 alloy | 3,500 | 4,500 | 7,100 | — | 12,000 | 18,100 |
| Grade 100 alloy | 4,300 | 5,700 | 8,800 | — | 15,000 | 22,600 |
Grade 70 is the usual choice for flatbed and heavy haul tie-down. Only alloy chain (Grade 80 and up) that is specifically rated and tagged for it may be used for overhead lifting.
Synthetic webbing — default WLL (lbs)
| Webbing width | Default WLL |
|---|---|
| 1-3/4" | 1,750 |
| 2" | 2,000 |
| 3" | 3,000 |
| 4" | 4,000 |
These defaults apply to unmarked webbing. Most quality straps are tagged with a higher WLL — use the tag. A strap with a missing or unreadable tag should be removed from service.
Inspection & removal from service
Inspect every tie-down and fitting before each use. Take it out of service if you find:
- Webbing: cuts, tears, burns, melting, excessive abrasion, broken or worn stitching, knots, chemical damage, or a missing/illegible tag.
- Chain: stretched, bent, twisted or gouged links, cracks, heavy corrosion, heat discoloration, weld spatter, or links that don't move freely.
- Hooks & fittings: throat opening widened more than about 15%, a twisted or bent hook, cracks, or a missing or damaged latch where one is required.
- Binders & ratchets: bent handles, cracked bodies, worn or damaged threads and pawls, or any part that won't lock fully.
Protect straps and chain from sharp edges with corner protectors or sleeves, re-check tension after the first few miles and at every stop, and never repair load-bearing gear yourself.
This guide summarizes general industry practice and the federal cargo securement rules for convenience. It is not legal advice. Always follow the current regulations, the manufacturer's instructions and your company's procedures.