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Rotation-Resistant Wire Rope
18x7, 19x7, 32x7, 35x7 and 37x7 - what each construction does, and the breaking load every product publishes at 16 mm.
What makes a rope rotation-resistant
A wire rope twists under load. In a single-layer construction such as 6x19 or 6x36 the outer strands are all laid in the same direction, so tension in the rope produces a torque and a free end turns with it. A rotation-resistant rope carries an outer layer and an inner layer laid in opposite directions: the two torques cancel, and the rope resists kinking and spinning during lifting.
That construction is what the 18x7, 19x7, 32x7, 35x7 and 37x7 products share. The product pages name 17x7, 18x7 and 19x7 as the three commonly used specifications, and 32x7, 35x7 and 37x7 as the larger constructions supplied to further enhance flexibility and other performance characteristics. All are made to GB/T 20118-2006, in bright or galvanized finish, and several are also available compacted and with a coating.
Rotation resistance is not a single figure on a datasheet; it follows from the strand pattern. Two ropes with a similar breaking load can behave very differently on one fall, which is why the constructions are listed separately below rather than as one rotation-resistant category.
The range at a glance
Every product table in the range covers 16 mm, so that one diameter puts all eleven products on the same line. The figures below repeat each product table: the diameter range it covers, the weight at 16 mm, and the minimum breaking load at 16 mm with the grade it was published under.
| Construction | Diameters (mm) | Weight at 16 mm (kg/m) | Minimum breaking load at 16 mm |
|---|---|---|---|
| 18x7 | 6–22 | 1.04 | 132 kN (1570 MPa) |
| 19x7 | 5–26 | 1.03 | 149 kN (1770 MPa) 165 kN (1960 MPa) |
| 19x7 compacted | 12–30 | 1.13 | 163 kN (1770 MPa) 181 kN (1960 MPa) |
| 32x7 | 8–24 | 1.16 | 181 kN (1770 MPa) |
| 32x7 compacted | 8–22 | 1.25 | 198 kN (1770 MPa) 219 kN (1960 MPa) |
| 32x7 compacted, coated | 8–22 | 1.25 | 198 kN (1770 MPa) 219 kN (1960 MPa) |
| 35x7 | 12–30 | 1.16 | 181 kN (1960 MPa) |
| 35x7 compacted | 12–30 | 1.24 | 204 kN (1770 MPa) 226 kN (1960 MPa) |
| 35x7 compacted, coated | 12–30 | 1.24 | 204 kN (1770 MPa) 226 kN (1960 MPa) |
| 37x7 compacted | 14–32 | 1.25 | 203 kN (1770 MPa) 225 kN (1960 MPa) |
| 37x7 compacted, coated | 14–32 | 1.25 | 203 kN (1770 MPa) 225 kN (1960 MPa) |
Two figures in the breaking load column are the two grades the table publishes: 1770 MPa first, then 1960 MPa. A single figure with one grade is a table that publishes one grade. The other diameters, and the kilogram column each product table prints beside its kilonewton figure, are on the product page.
Standard, compacted and coated
Standard. The rope as stranded. 18x7, 19x7, 32x7 and 35x7 are supplied this way, bright or galvanized.
Compacted. After stranding the rope is compacted. The product pages describe what it buys - a higher breaking load and better wear characteristics at the same diameter - and their own tables show it: at 16 mm, 19x7 moves from 149 kN to 163 kN at 1770 MPa, 32x7 from 181 kN to 198 kN, and 35x7 from 181 kN to 204 kN at 1960 MPa. The 37x7 products listed here are compacted.
Coated. The 32x7, 35x7 and 37x7 compacted products also come with a coating. Their tables publish the same diameter rows and the same breaking loads as the uncoated compacted product, so the coating is a surface choice rather than a change in strength.
In every form the finish is bright or galvanized, and the surface treatments the product pages list - lubrication, plastic coating and compaction - are applied to your requirements for breaking load and wear.
Which construction for which duty
18x7 is the small end of the family, from 6 mm to 22 mm. Its product page puts it on davit cranes and crane wire ropes that require low rotation, and lists marine crane rope and marine/seawater duty among its applications.
19x7 is the offshore and deck crane construction. The page lists offshore crane wire rope, deck crane wire rope, pillar crane wire rope, lifting slings and main hoist wire rope; standard it runs from 5 mm to 26 mm, compacted from 12 mm to 30 mm.
32x7, 35x7 and 37x7 carry more strands and publish a higher breaking load at the same diameter: at 16 mm compacted, 32x7 is 198 kN, 35x7 is 204 kN and 37x7 is 203 kN at 1770 MPa, against 181 kN for standard 32x7 and 149 kN for standard 19x7. They also run larger - 32x7 to 24 mm standard, 35x7 to 30 mm, 37x7 to 32 mm - and the product pages describe the larger constructions as the route to greater flexibility as well as load.
The construction guide explains what the strand counts mean and how a rope is laid; the core types guide covers fiber core against IWRC, and the galvanized wire rope guide covers the finish.
Minimum breaking load is not a working load
Every figure above is a minimum breaking load (MBL): the load the rope is required to withstand without breaking. It is never a working load. Working load is the MBL divided by a factor set by the application and the standard that governs it - lifting gear is treated differently from a static guy - and the breaking strength guide works through how that factor is chosen and what the arithmetic looks like at 5:1, 6:1 and 8:1.
If the diameter and the factor are already fixed, take the MBL from the rotation-resistant product table rather than from a standard 6x19 or 6x36 row: the constructions are different and so are their published figures.
Frequently Asked Questions
What is a rotation-resistant wire rope?
A wire rope with an outer and an inner layer of strands laid in opposite directions, so the torques cancel and the rope resists kinking and spinning in lifting service. Our range covers the 17x7, 18x7 and 19x7 family and the larger 32x7, 35x7 and 37x7 constructions, to GB/T 20118-2006, bright or galvanized.
What is the difference between 18x7, 19x7 and 32x7?
18x7 runs from 6 mm to 22 mm and its product page names davit cranes and low-rotation crane ropes. 19x7 runs from 5 mm to 26 mm standard and is listed for offshore, deck and pillar cranes, lifting slings and main hoist rope. 32x7, 35x7 and 37x7 carry more strands, publish a higher breaking load at the same diameter, and run to 24 mm, 30 mm and 32 mm respectively.
What does compaction change?
At 16 mm the published minimum breaking load moves from 149 kN to 163 kN for 19x7 at 1770 MPa, from 181 kN to 198 kN for 32x7 and from 181 kN to 204 kN for 35x7 at 1960 MPa. The product pages also cite better wear characteristics.
Which diameters are available?
From 5 mm to 32 mm across the range: 18x7 from 6 mm to 22 mm, 19x7 from 5 mm to 26 mm standard and 12 mm to 30 mm compacted, 32x7 from 8 mm to 24 mm standard and 8 mm to 22 mm compacted, 35x7 from 12 mm to 30 mm, and 37x7 compacted from 14 mm to 32 mm.
What standard are they made to?
GB/T 20118-2006. Every product in the range is supplied bright or galvanized, and the 32x7, 35x7 and 37x7 compacted products are also made with a coating.
What is the difference between bright and galvanized?
Bright is the wire as drawn; galvanized carries a zinc coating for corrosion protection. Every product in the range is supplied in either finish, and the galvanized wire rope guide covers how the coating is applied and when to choose it.
What to put on the enquiry
Construction, diameter, grade where the table publishes two, finish, coating if wanted, length, end fittings and the duty. The how-to-order guide covers the rest of the process - quotation, trade terms, inspection and shipping - and the wire rope range lists everything we stock.
More on wire rope
Construction guide · Core types: FC vs IWRC · Breaking strength and working load · Galvanized wire rope · Stainless steel wire rope · All guides