By Dean McDonald, founder, Crane Rope Solutions
How to read a wire rope designation
A wire rope designation lists six things in order: nominal diameter, construction, core, grade, finish, and lay type and direction. European and international ropes follow EN 12385-2 and ISO 17893. North American ropes use a similar order with different codes for grade and lay.
European example: 22 6x36WS-IWRC 1770 B sZ
| Part | Means |
|---|---|
| 22 | 22 mm nominal diameter |
| 6x36WS | 6 strands, 36 wires in each strand, Warrington-Seale strand type |
| IWRC | Independent wire rope core (a steel core) |
| 1770 | Rope grade 1770 N/mm² |
| B | Drawn galvanized, zinc coating class B |
| sZ | Right-hand regular (ordinary) lay |
North American example: 1-1/8 in 6x36 WS EIPS IWRC RRL
| Part | Means |
|---|---|
| 1-1/8 in | Nominal diameter (28.58 mm) |
| 6x36 WS | 6x36 class rope with Warrington-Seale strands |
| EIPS | Extra improved plow steel grade |
| IWRC | Independent wire rope core |
| RRL | Right regular lay |
If no finish is stated on a North American rope, it is usually bright (ungalvanized).
Construction: what “6x36”, “8xK26WS” and “35(W)xK7” mean
The first number is the number of outer strands. The second is the number of wires in each strand. Letters before or after the wire count describe the strand type.
- 6x36WS: 6 strands of 36 wires, Warrington-Seale.
- 8xK26WS: 8 compacted (K) strands of 26 wires, Warrington-Seale.
- 35(W)xK7: a rotation-resistant rope with 35 outer strands of 7 compacted wires. The (W) shows that the inner strand layers are laid in parallel (Warrington-type).
- 34(M)x7: the (M) shows that the inner part of the rope is cross-laid.
- 6x19 class and 6x36 class: North American groupings. A “6x19 class” rope can be 6x19S, 6x21F, 6x25F or 6x26WS. A “6x36 class” rope can be 6x31WS, 6x36WS or 6x41WS, among others. The class sets the strength table; the exact construction is on the certificate.
- Older German-style notation puts the wire count in brackets after the strand type: 6 x Fi(25) is 6x25F, 6 x WS(31) is 6x31WS and 8 x S(19) is 8x19S. You will still see this on older Liebherr and European crane rope specifications.
Strand types
| Code | Name | What it means | Wire layout (example) |
|---|---|---|---|
| (none) | Single lay | One layer of wires around a centre wire | 1-6 (7 wires) |
| S | Seale | Two layers with the same number of wires; the outer wires are larger | 1-9-9 (19 wires) |
| W | Warrington | The outer layer alternates large and small wires, with twice as many wires as the layer below | 1-6-6+6 (19 wires) |
| F, FW, Fi | Filler, filler wire | Small filler wires fill the gaps between two layers | 1-6-6F-12 (25 wires) |
| WS | Warrington-Seale | A Warrington layer under a Seale outer layer; common on 6x36 ropes | 1-7-7+7-14 (36 wires) |
| K | Compacted | The strand (or core, or whole rope) is compacted after stranding by drawing, rolling or swaging, which flattens the outer wires. More steel in the same diameter, a smoother surface and better crush resistance | 8xK26WS |
| M | Cross lay | The wire layers are laid at different angles, so they cross | 34(M)x7 |
| V, TS | Triangular strand | Strands with a triangular cross-section, mainly for mine hoisting | 6x25TS |
Core abbreviations
| Code | Means |
|---|---|
| FC | Fibre core |
| NFC | Natural fibre core |
| SFC | Synthetic fibre core |
| SPC | Solid polymer core |
| IWRC | Independent wire rope core: a small steel wire rope at the centre |
| IWRC(K) | Compacted IWRC |
| WSC | Wire strand core: a single steel strand at the centre |
| WC, SC | Steel core (general terms) |
| EPIWRC | IWRC covered (enclosed) with a polymer layer |
| PWRC | Parallel wire rope core (parallel-closed core) |
| PI | Plastic impregnated: plastic fills the spaces inside the rope (for example Bridon “PI” ropes) |
Plastic around or inside the core keeps the strands apart, holds lubricant in and dirt out, and helps the rope resist crushing on multi-layer drums. Each rope maker has its own brand name for it.
Lay type and direction
The capital letter is the direction of the rope (strands around the core). The lower-case letter is the direction of the wires in each strand. Same letters means Lang’s lay; different letters means regular (ordinary) lay.
| ISO / EN code | North American code | Means |
|---|---|---|
| sZ | RRL, RHRL, RHOL | Right-hand regular (ordinary) lay |
| zS | LRL, LHRL, LHOL | Left-hand regular (ordinary) lay |
| zZ | RLL, RHLL | Right-hand Lang’s lay |
| sS | LLL, LHLL | Left-hand Lang’s lay |
| aZ | ARHL | Right-hand alternate lay (regular and Lang’s lay strands alternate) |
| aS | ALHL | Left-hand alternate lay |
| Z / S | - | Right / left lay of a spiral (single-strand) rope |
“Long lay” on a quote or certificate almost always means Lang’s lay.
Grade
Rope grade is the tensile strength level used to calculate the rope’s minimum breaking force, in N/mm² (MPa).
| ISO / EN grade | Closest North American grade |
|---|---|
| 1570 | - |
| 1770 | IPS: improved plow steel (approximately) |
| 1960 | EIPS, EIP or XIP: extra improved plow steel |
| 2160 | EEIPS, EEIP or XXIP: extra extra improved plow steel |
| 2360, 2560 | Higher grades made by a few rope makers |
North American grades are matched to strength tables, not to a single wire tensile grade, so treat the pairs above as a guide. Bridon-Bekaert, for example, lists its crane ropes as “EIP / 1960” and “EEIP / 2160”. A rope sold as one grade can also contain wires of other grades.
Finish
| Code | Means |
|---|---|
| U, BRT, Ung | Bright (ungalvanized, greased) |
| B | Drawn galvanized, zinc coating class B |
| A | Zinc coating class A (heavier coating) |
| Zn/Al, B(Zn/Al) | Zinc-aluminium alloy coating, more corrosion resistant than zinc alone (for example Teufelberger-Redaelli Zn95Al5) |
| GALV | Galvanized (class not stated; ask which) |
Rotation resistance
| Term | Means |
|---|---|
| RR | Rotation resistant |
| LR | Low rotation |
| NR | Non-rotating (an older term; no rope is completely non-rotating) |
| Category 1, 2, 3 | ASME B30.5 rotation-resistant categories by number of outer strands and layers (see how to order a replacement crane rope) |
| Type I, II, III | The same categories in US OSHA 1926.1414 |
| RCN | Rope category number, used in ISO 4309 to look up discard criteria |
Breaking force and strength
| Code | Means |
|---|---|
| MBF / MBL | Minimum breaking force (load): the value the rope must meet or exceed in a break test. The figure to compare when you order |
| CBF / CMBF | Calculated (minimum) breaking force: worked out from the metallic area and grade of each wire |
| ABF / ABL | Actual (measured) breaking force from a break test |
| Agg BF | Aggregate breaking force: the sum of the breaking forces of all the individual wires |
| WLL / SWL | Working load limit / safe working load |
| DF | Design factor: MBF divided by the maximum line pull |
Example from a rope maker’s test of a 28 mm hoist rope (metallic area 435 mm², grade 1960): aggregate breaking force 948 kN, calculated breaking force 853 kN (1.96 x 435), actual breaking force 798 kN, minimum breaking force 726 kN. The MBF is always the lowest number, and it is the one that counts.
Other terms on rope certificates and specifications
| Term | Means |
|---|---|
| d | Nominal rope diameter |
| D, D/d | Sheave or drum diameter, and its ratio to the rope diameter |
| Tolerance (+2% / +4%) | How far above nominal the actual diameter may be |
| PF, PRF / NPF | Preformed / non-preformed |
| Lay length | The distance along the rope for one strand to go once around |
| EN 10204 3.1 / 3.2 | Inspection certificate from the rope maker (3.1), or with a third-party sign-off (3.2) |
| MTR | Mill test report (mill certificate) |
German terms on Liebherr and other European rope specifications
| German | English |
|---|---|
| Gleichschlag | Lang’s lay |
| Kreuzschlag | Regular (ordinary) lay |
| rechtsgängig / linksgängig | Right-hand / left-hand |
| blank | Bright |
| verzinkt | Galvanized |
| Mindestbruchkraft | Minimum breaking force |
| Nenndurchmesser | Nominal diameter |
| Spitze | Tapered (pointed) end, for pulling the rope in |
| Anschweißöse | Weld-on eye (pull eye) |
| Vollkausche | Solid thimble (DIN 3091) |
| Bohrungs-Ø | Bore (pin hole) diameter |