Rotation-Resistant Ropes
 
Rotation-resistant ropes can frequently provide the best and most economical service in specific applications when you choose, handle and use them properly.

Contra-helically laid, rotation-resistant ropes are different from standard ropes because they're designed to reduce rope torque. Modes of failure and wear for rotation-resistant ropes can differ from those for standard rope constructions. The very nature of these ropes requires special handling, selection and usage not encountered with standard constructions. They are susceptible to kinking, crushing and unbalancing in the form of "core pops" and "birdcages." Use extreme care to avoid operational practices that can possibly lead to these conditions.

There are different types of rotation-resistant ropes, categorized by their resistance to rotation. Category 1 rotation-resistant rope has at least 15 outer strands, has three layers of strands (over a center) and has little or no tendency to rotate, or, if guided, transmits little or no torque. Category 2 rotation-resistant rope has 10 or more outer strands, has two or more layers of strands (over a center) and has significant resistance to rotation. Category 3 rotation-resistant has no more than 9 outer strands, has two layers of strands (over a center) and has limited resistance to rotation. For best performance, Category 2 and 3 rotation-resistant ropes should not be used with a swivel. Category 1 rotation-resistant rope may be used with a swivel.

Rotation-resistant ropes should be replaced when you see two randomly distributed crown wire breaks in six rope diameters -- or four randomly distributed crown wire breaks in 30 rope diameters. If any significant reduction in diameter is found in a short length of a rotation-resistant rope, the rope needs to be replaced.

Because rotation-resistant ropes are special, there are separate design, maintenance, inspection and removal criteria established for them by applicable industry regulations and standards.

We recommend that rotation-resistant ropes be used with a minimum design factor of 5.0.

Flex-X® 35

Tower crane and other long fall hoisting applications require superior rotation resistance and minimum torque—qualities you will find with the latest addition to our family of rotation resistant wire rope, Flex-X 35. It is a Category 1 rotation resistant rope.

Flex-X 35’s unique design minimizes load-induced torque and rotation of the rope. It is engineered to give you maximum strength per diameter while providing superior fatigue resistance. Flex-X 35 also assists you in maintaining proper load control in single-part hoisting or in multi-part hoisting where block rotation is a problem.

Flex-X 35 wire rope has one of the highest strength-to-diameter ratios on the market. ASME B30.5 Mobile and Locomotive Cranes require a design factor of 3.5 for 6-strand hoist ropes. The same standard requires a design factor of 5.0 for rotation resistant ropes. This means that using rotation resistant ropes frequently reduces the lifting capabilities of your crane due to the higher design factor.

Flex-X 35 eliminates this reduction. The Minimum Breaking Force (MBF) of Flex-X 35 is such that even with the 5.0 design factor, it has lifting capacities that equal or exceed 6-strand XIP ropes utilizing a 3.5 design factor. Other ropes of similar grade and construction do not provide this benefit.

The multi-strand design of Flex-X 35 combined with compacted strands and lang lay construction helps to maximize resistance to wear by greatly increasing wire and strand surface areas that contact sheaves and drums. Internally, the enhanced surfaces of the compacted strands help minimize strand-to-strand nicking between strand layers that occurs in other rotation resistant ropes. This feature results in greater resistance to fatigue.

The characteristics of Flex-X 35 enhance its performance in multiple-layer spooling as well. The lang lay design coupled with the special Flex-X features provides excellent resistance to abrasion that occurs at kickover areas in drum spooling. The rope construction combined with the compacted strand design of Flex-X 35 results in a rope cross-section of very high density. This feature provides increased resistance to crushing.

Flex-X 35 Flyer (right click to save)


 

 

Flex-x® 35 Minimum Breaking Force and Weights

Diameter
 (mm)

Approx.
 wt./ft.
 (lbs.)

Minimum Breaking Force
 (tons of 2000 lbs.)

13

0.60

20.4

*16

0.90

30.6

18

1.2

38.5

*19

1.3

42.9

22

1.7

57.2

*25.4

2.2

75.8

26

2.3

79.3

28

2.7

91.6

*30

3.1

105

32

3.5

119

 

 

 

* Standard Inventory Items

Flex-X® 19

Flex-X 19 is made from 19 strands and is a category 2 rotation resistant rope. Six strands are laid around a core strand in one direction, then 12 Strands are laid around this first operation in the opposite direction. Because of its tightly compacted, smooth design, Flex-X 19 offers advantages:

  • More crush resistance than a standard 19x 7 rope while providing the same rotation resistance.
  • Higher strength-to-diameter due to compacted wires in the strands. With increased metallic area, it provides rope strengths equal to 6 strand XXIP IWRC ropes of the same diameter.
  • Resistance to bending fatigue due to the uniformity of the wires within each strand. The strand's outer surface is smooth, reducing contact pressures between the rope's strands and radial pressures as it operates over sheaves and drums.
  • Exceptional stability due to the higher density strands coupled with the smooth outer surface.
  • Improved handling, operating and spooling characteristics.
  • Reduced wear to sheaves and drums.

It's used in single-part or multi-part hoist lines wherever you encounter spooling problems, drum crushing, block twisting or have fast line speeds.

Flex-X 19 (right click to save)

19 x7 rope

A 19X7 is made from 19 strands and is a category 2 rotation resistant rope. It is used where resistant properties are essential for rope performance. Its rotation-resistant characteristic is achieved by laying six strands around a core strand in one direction, then laying 12 strands around the first operation in the opposite direction. Thus, when the rope is in tension, opposing rotational forces are created between the inner and outer layers.

While having similar rotation resistance to a Flex-X 19, a 19X7 has a lower strength, will crush easier and is not as fatigue or wear resistant.

8 x 25 Resistwist® rope

In a multi-part wire rope system where the blocks have a tendency to twist -- the 8 x 25 Resistwist rope has found successful application. It is a category 3 rotation resistant rope. The rotation-resistant characteristic is achieved by laying the eight outer strands around an independent wire rope core so these strands are in the opposite direction to the lay of the core. Thus, when the rope is in tension, opposing rotational forces are created between the core and the outer strands.

Though not as rotation-resistant, the 8 x 25 Resistwist is more stable than a 19 x 7 rope. It also has increased resistance to bending fatigue and crushing. This is achieved through the use of eight-strand construction with an independent wire rope core.

 

Flex-x® 19

19 x 7 XIP®

8 x 25 XIP®

Diameter
 (in.)

Approx.
 wt./ft.
 (lbs.)

Minimum Breaking Force
 (tons of 2000 lbs.)*

Approx.
 wt./ft.
 (lbs.)

Minimum Breaking Force
 (tons of 2000 lbs.)*

Approx.
 wt./ft.
 (lbs.)

Minimum Breaking Force
 (tons of 2000 lbs.)*

3/16

--

--

0.064

1.57

--

--

1/4

--

--

0.133

2.77

--

--

5/16

--

--

.0177

4.30

0.18

4.63

3/8

0.31

8.3

0.25

6.15

0.26

6.63

7-16

0.40

11.2

0.35

8.33

0.36

8.97

1/2

0.54

14.6

0.45

10.8

0.47

11.6

9/16

0.69

18.5

0.58

13.6

0.60

14.7

5/8

0.85

22.7

0.71

16.8

0.73

18.1

3/4

1.25

32.4

1.02

24.0

1.06

25.9

7/8

1.68

43.8

1.39

32.5

1.44

35.0

1

2.17

56.9

1.82

42.2

1.88

45.5

1 1/8

2.75

71.5

2.30

53.1

2.39

57.3

1 1/4

3.45

87.9

2.83

65.1

2.94

70.5

1 3/8

4.33

106

3.43

78.4

3.56

84.9

1 1/2

5.11

125

4.08

92.8

4.24

100

* These strengths apply only when a test is conducted with both ends fixed.  When in
use, the strengths of these ropes may be significantly reduced if one end is free to