Breaking Force Testing of Grade 8 Lifting Chain
SCIC·Shanghai Chigong Industrial Co., Ltd.·Lifting Chain Division
What the standard actually requires — and what SCIC verifies on every lot
Medium tolerance · Grade 8
The link is pulled until it breaks — never stopped at the minimum.
- Breaking force is a destructive result by definition: “maximum force which the chain withstands during the course of a static tensile test to destruction”.
- The force/extension diagram is recorded throughout, and total ultimate elongation is read at fracture — so the test cannot terminate at a target load.
- Pass requires the recorded peak ≥ Table 5 minimum and elongation ≥ 20 %. A failing sample is re-tested on two further samples.
A controlled force rate: 10 N/mm²/s, evenly applied.
- “The rate of loading shall be evenly applied (e.g. at a rate of 10 N/mm²/s).” The reference is stress on the nominal link section — not crosshead travel.
- No mm/min value exists in EN 818-1 or -2, by design: the mm/min equivalent depends on each machine’s stiffness and jaw seating, so it must be established by a calibration run.
- Practical cross-check: at 10 N/mm²/s the minimum breaking force is reached in ≈ 80 s for every size from 4 to 45 mm — much faster means the rate is too high.
Table 5 extract — forces and the equivalent machine setting
| d (mm) | WLL (t) | MPF (kN) | BF min (kN) | Load rate (kN/min) | Elong. A (min %) |
|---|---|---|---|---|---|
| 6 | 1.12 | 28.3 | 45.2 | 33.9 | 20 |
| 8 | 2 | 50.3 | 80.4 | 60.3 | 20 |
| 10 | 3.15 | 78.5 | 126 | 94.2 | 20 |
| 13 | 5.3 | 133 | 212 | 159 | 20 |
| 16 | 8 | 201 | 322 | 241 | 20 |
| 18 | 10 | 254 | 407 | 305 | 20 |
| 20 | 12.5 | 314 | 503 | 377 | 20 |
| 22 | 15 | 380 | 608 | 456 | 20 |
| 26 | 21.2 | 531 | 849 | 637 | 20 |
| 32 | 31.5 | 804 | 1290 | 965 | 20 |
| 36 | 40 | 1020 | 1630 | 1222 | 20 |
| 45 | 63 | 1590 | 2540 | 1909 | 20 |
Load rate = 10 N/mm²/s × nominal link area (2 × πd²/4), converted to kN/min for machine setting. Highlighted row: d13 — 212 kN minimum reached in ≈ 80 s at 159 kN/min.
SCIC quality control & assurance — applied to every lifting chain we supply
EN 818-1 Table 2 · EN 818-2 §6.2
1Steel & heat traceability
Cast and check analysis verified against EN 818-2 Table 4 — S ≤ 0.025 / 0.030 %, P ≤ 0.025 / 0.030 %. Heat number retained through to the finished lot.
2Heat treatment verified
Full hardening from above AC3, tempered ≥ 400 °C (≥ 1 h equivalent). Effectiveness confirmed by the re-heat test — samples re-heated 1 h at 400 °C must still pass BF and bend.
3100 % proof loading
Every metre proof-loaded to Table 5 MPF, then inspected link by link under proper lighting; faulty links cut out and replaced. Proof force re-applied after acid cleaning or plating.
4Destructive testing per lot
Samples drawn at random per 200 m lot and pulled to fracture at 10 N/mm²/s on a class-1 machine. Peak force and elongation recorded on the force/extension diagram and retained.
5Bend & dimensional checks
Single-link bend test to Table 5 minimum deflection, then examined for cracks and defects. Material diameter measured clear of the weld and away from flattening; pitch within tolerance.
6Marking & documentation
Grade “8” and manufacturer mark at every 20th link or 1 m. Inspection certificate to EN 10204 type 3.1 as standard, type 3.2 on request; records traceable to lot and heat.
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