Wire Rope Breaking Strength

Wire Rope Breaking Strength

Minimum breaking loads, safe working load and the reference data behind the tables.

Minimum Breaking Load

The minimum breaking load (MBL) is the load at which a rope fails in a tensile test, published per construction, diameter and wire grade in the standard tables. It is a laboratory figure - a ceiling for comparison, never a working load.

Wire grade sets the band the MBL falls in. Our carbon steel ropes come in 1770 and 1960 MPa grades - the same diameter in 1960 carries more load than 1770. Stainless ropes and some constructions run the 1570 MPa band. All of our wire rope is made to GB/T 20118-2006.

From MBL to Safe Working Load

The safe working load (SWL) divides the breaking load by a safety factor: SWL = MBL ÷ safety factor.

Many lifting applications use a factor of 5, though the factor that applies to your job depends on the standard and jurisdiction governing it - always confirm against the regulation in force before lifting.

Worked example: a 6x19 IWRC rope at 20 mm in 1770 grade has an MBL of 252 kN. Divided by 5, that is about 50.4 kN, or roughly 5.1 tonnes.

Two practical notes. Terminations reduce rope capacity - a splice or fitting is rated by its own efficiency, not the rope's. And in service, wear, broken wires and corrosion reduce strength over time, so inspection and retirement follow the applicable standard rather than the original table.

Reference Breaking Strengths

Construction Diameter Grade (MPa) MBL (kN)
1x19 10 mm 1770 / 1960 92.9 / 103
7x19 10 mm 1570 55.6 (5669 kg)
6x7 10 mm 1770 58.8
6x36 IWRC 10 mm 1770 / 1960 63 / 69.8
6x36 IWRC 40 mm 1770 / 1960 1008 / 1116
6x19 filler IWRC 20 mm 1770 / 1960 252 / 279
6x19 filler IWRC 48 mm 1770 / 1960 1452 / 1608
19x7 compacted 20 mm 1770 / 1960 255 / 283
32x7 20 mm 1770 282
35x7 20 mm 1960 282
18x7 20 mm 1570 206
Stainless 1x19 10 mm 1570 95.8
Stainless 6x36 IWRC 20 mm 1570 224
Stainless 7x7 10 mm 1570 59.3

A cross-section of the range, taken from the published product tables; each product page lists every diameter it is made in. Where two grades are shown, the figure before the slash is 1770 and after is 1960.

Using the Tables

  • Match all three: construction, diameter and grade - the same size in a different construction carries a different load.
  • Then divide by your safety factor to reach the working load for the application.
  • Account for terminations: fittings and splices are rated by their own efficiency.
  • Inspect in service: wear, broken wires and corrosion reduce capacity; follow the applicable retirement standard.

Need the full table for a construction? See the construction guide for how the patterns behave and the core types guide for FC and IWRC differences,

browse the wire rope range, or send the construction, diameter and grade you need to admin@greenlogy.cn and we will return the exact figures.

Frequently Asked Questions

What is the breaking strength of wire rope?

The minimum breaking load (MBL) is the load at which the rope fails in a tensile test, published per construction, diameter and wire grade in the standard tables. It is a laboratory figure, not a working load.

How do I calculate the safe working load?

SWL = MBL ÷ safety factor. Many lifting applications use a factor of 5, so a 6x19 IWRC rope at 20 mm and 1770 grade (MBL 252 kN) works out at about 50.4 kN, or roughly 5.1 tonnes. The factor that applies to your job depends on the governing standard.

What is the difference between 1770 and 1960 grade wire rope?

They are wire tensile grades in MPa. A 1960-grade rope of the same construction and diameter has a higher published breaking strength than a 1770-grade one - for example 6x19 IWRC at 20 mm is 252 kN at 1770 against 279 kN at 1960.

Does diameter alone determine breaking strength?

No. Construction, core and wire grade all matter: a 20 mm 18x7 rope is rated 206 kN at 1570 grade, while a 20 mm 6x19 IWRC reaches 252 kN and up. Always read the table for the exact product.

Where can I find the breaking strength table for your ropes?

Each product page lists the published breaking strength across its diameter range, and this page shows a cross-section of the range. Tell us the construction and diameter and we will send the exact figures.