Many stranded steel wire ropes are manufactured to standards compliant with the EN 12385 series. They include those used for general lifting applications within part 4 of this standard, EN 12385-4 “Steel wire ropes - Safety - Part 4: Stranded ropes for general lifting applications”. In this standard there are breaking strength tables for the different rope constructions and nominal diameters. The Minimum Breaking Force (MBF) for each rope diameter within these tables are specified in relationship to a rope grade, typically 1770, 1960, 2160. However, rope manufacturers also produce rope constructions offering increased breaking strength and performance which are used extensively, but their breaking strengths are not specifically given within these tables. The rope breaking strengths for those rope constructions, often referred to as high performance ropes, may be specified in the individual rope manufacturers catalogue. In these standards, rope grade (Rr) and wire tensile grade (R) are described:
Rope grade (Rr ): is a level of requirement of breaking force which is designated by a number (e.g. 1770, 1960, 2160) Extract: EN 12385-2 clause 3.10.11
Note: It does not imply that the actual tensile strength grades of the wires in the rope are necessarily of that grade.
Wire tensile grade (R): a level of requirement of tensile strength of a wire and its corresponding range. It is designated by the value according to the lower limit of tensile strength and is used when specifying wire and when determining the calculated minimum breaking force or calculated minimum aggregate breaking force, expressed in N/mm2. Extract: EN 12385-2 clause 3.1.10.
For those ropes where a rope grade is applicable, the tensile strength grades of the wires shall be subject to the limits given in the below. Extract: EN 12385-4 clause 5.2.1
| Wire tensile strength grades excluding centre and filler wires for given rope grades |
||
| Rope Grades | Wire tensile strength grades (N/mm²) |
|
| Min | Max | |
| 1770 | 1570 | 1960 |
| 1960 | 1770 | 2160 |
| 2160 | 1960 | 2160 |
| Permitted tensile strength variations |
||
| Nominal dimension wire diameter: d (mm) |
Permitted plus tolerance over the numerical value of tensile strength grade MPa (N/mm²) |
|
| 0.2 ≤ d < 0.5 | 390 | |
| 0.5 ≤ d < 1.0 | 350 | |
| 1.0 ≤ d < 1.5 | 320 | |
| 1.5 ≤ d < 2.0 | 290 | |
| 2.0 ≤ d < 3.5 | 260 | |
| 3.5 ≤ d < 8.0 | 250 | |
| Range of wire tensile strength guides |
||
| Rope Grade | Wire Tensile Strength Guide | |
| IPS (Improved Plow Steel) | Level 2 or 1570 to Level 4 or 1960 | |
| EIPS (Extra Improved Plow Steel) | Level 3 or 1770 to Level 5 or 2160 | |
| EEIPS (Extra Extra Improved Plow Steel) | Level 4 or 1960 to Level 6 or 2160 | |
| 1170 | 1570 or Level 2 to 1960 or Level 4 | |
| 1960 | 1770 or Level 3 to 2160 or Level 5 | |
| 2160 | 1960 or Level 4 to 2160 or Level 6 | |
A standard in frequent use in the oil and gas industries, is the American Petroleum Institute (API) specification 9A “Specification for steel wire ropes”, adopted the rationale
for rope grade specification from A1023. For those ropes where a rope grade is applicable, the tensile strength grade of the wires shall be subjected to the limits in the table below. Extract: API 9A table 1
| Range of wire tensile strength guides |
||
| Rope Grade | Wire Tensile Strength Guide | |
| IPS (Improved Plow Steel) | Level 2 or 1570 to Level 4 or 1960 | |
| EIPS (Extra Improved Plow Steel) | Level 3 or 1770 to Level 5 or 2160 | |
| EEIPS (Extra Extra Improved Plow Steel) | Level 4 or 1960 to Level 6 or 2160 | |
| 1170 | 1570 or Level 2 to 1960 or Level 4 | |
| 1960 | 1770 or Level 3 to 2160 or Level 5 | |
| 2160 | 1960 or Level 4 to 2160 or Level 6 | |
| Permitted tensile strength variations |
||
| Nominal dimension wire diameter: d (mm) |
Permitted plus tolerance over the numerical value of tensile strength grade MPa(N/mm²) |
|
| 0.2≤ d < 0.5 | 390 | |
| 0.5 ≤ d < 1.0 | 350 | |
| 1.0≤ d < 1.5 | 320 | |
| 1.5≤ d < 2.0 | 290 | |
| 2.0≤ d < 3.5 | 260 | |
| 3.5≤ d < 8.0 | 250 | |