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  1. Aug 2020
    1. 6.2.15. WIRE ROPE When power source and load are located at extreme distances from one another, or loads are very large, the use of wire rope is suggested. Design and use decisions pertaining to wire ropes rest with the user, but manufacturers generally will help users toward appropriate choices. The following material, based on the Committee of Wire Rope Producers, "Wire Rope User's Manual," current edition, may be used as an initial guide in selecting a rope.

      Wire rope is composed of (1) wires to form a strand, (2) strands wound helically around a core, and (3) a core. Classification of wire ropes is made by giving the number of strands, number of minor strands in a major strand (if any), and nominal number of wires per strand. For example 6 × 7 rope means 6 strands with a nominal 7 wires per strand (in this case no minor strands, hence no middle number). A nominal value simply represents a range. A nominal value of 7 can mean anywhere from 3 to 14, of which no more than 9 are outside wires. A full rope description will also include length, size (diameter), whether wire is preformed or not prior to winding, direction of lay (right or left, indicating the direction in which strands are laid around the core), grade of rope (which reflects wire strength), and core. The most widely used classifications are: 6 × 7, 6 × 19, 6 × 37, 6 × 61, 6 × 91, 6 × 127, 8 × 19, 18 × 7, 19 × 7. Some special constructions are: 3 × 7 (guardrail rope); 3 × 19 (slusher); 6 × 12 (running rope); 6 × 24 and 6 × 30 (hawsers); 6 × 42 and 6 × 6 × 7 (tiller rope); 6 × 3 × 19 (spring lay); 5 × 19 and 6 × 19 (marlin clad); 6 × 25B, 6 × 27H, and 6 × 30G (flattened strand). The diameter of a rope is the circle which just contains the rope. The right-regular lay (in which the wire is twisted in one direction to form the strands and the strands are twisted in the opposite direction to form the rope) is most common. Regular-lay ropes do not kink or untwist and handle easily. Lang-lay ropes (in which wires and strands are twisted in the same direction) are more resistant to abrasive wear and fatigue failure.

      Cross sections of some commonly used wire rope are shown in Fig. 6.2.123. Figure 6.2.124 shows rotation-resistant ropes, and Fig. 6.2.125 shows some special-purpose constructions.

      Figure 6.2.123 Cross sections of some commonly used wire rope construction. (Reproduced from "Wire Rope User's Manual, " AISI, by permission.) binary://mheaeworks/d03c7ddb475211da/158e7be668be00fdf011bdadd2ef3b2300f542e92687c6e02a998fc06e5a48d6/06x02_123.png Open in new tab Share Figure 6.2.124 Cross section of some rotation-resistant wire ropes. (Reproduced from "Wire Rope User's Manual, " AISI, by permission.) binary://mheaeworks/e19ef67be879c4d0/9ab225782b323010f79e566c12a458512274145d6877d8209774da72c34eda94/06x02_124.png Open in new tab Share Figure 6.2.125 Some special constructions. (Reproduced from "Wire Rope User's Manual, " AISI, by permission.) binary://mheaeworks/8627b14662f8a537/bb284940d47ada0df68e2027b63f42e8b5f813ef1a6eb57a1dc9e1bdcb726b5b/06x02_125.png Open in new tab Share The core provides support for the strands under normal bending and loading. Core materials include fibers (hard vegetable or synthetic) or steel (either a strand or an independent wire rope). Most common core designations are: fiber core (FC), independent wire-rope core (IWRC), and wire-strand core (WSC). Lubricated fiber cores can provide lubrication to the wire, but add no real strength and cannot be used in high temperature environments. Wire-strand or wire-rope cores add from 7 to 10 percent to strength, but under nonstationary usage tend to wear from interface friction with the outside strands. Great flexibility can be achieved when wire rope is used as strands. Such construction is very pliable and friction resistant. Some manufacturers will provide plastic coatings (nylon, Teflon, vinyl, etc.) upon request. Such coatings help provide resistance to abrasion, corrosion, and loss of lubricant. Crushing refers to rope damage caused by excessive pressures against drum or sheave, improper groove size, and multiple layers on drum or sheave. Consult wire rope manufacturers in doubtful situations.

      Wire-rope materials and their strengths are reflected as grades. These are: traction steel (TS), mild plow steel (MPS), plow steel (PS), improved plow steel (IPS), and extra improved plow (EIP). The plow steel strength curve forms the basis for calculating the strength of all steel rope wires. American manufacturers use color coding on their ropes to identify particular grades.

      The grades most commonly available and tabulated are IPS and EIP. Two specialized categories, where selection requires extraordinary attention, are elevator and rotation-resistant ropes.

      Elevator rope can be obtained in four principal grades: iron, traction steel, high-strength steel, and extra-high-strength steel.

      Bronze rope has limited use; iron rope is used mostly for older existing equipment.

      6.2.15.1. Selection of Wire Rope Appraisal of the following is the key to choosing the rope best suited to the job: resistance to breaking, resistance to bending fatigue, resistance to vibrational fatigue, resistance to abrasion, resistance to crushing, and reserve strength. Along with these must be an appropriate choice of safety factor, which in turn requires careful consideration of all loads, acceleration-deceleration, shocks, rope speed, rope attachments, sheave arrangements as well as their number and size, corrosive and/or abrasive environment, length of rope, etc. An approximate selection formula can be written as:

      DSL

      (NS) K b K sf where DSL (demanded static load) = known or dead load plus additional loads caused by sudden starts or stops, shocks, bearing friction, etc., tons; NS (nominal strength) = published test strengths, tons (see Table 6.2.65); Kb = a factor to account for the reduction in nominal strength due to bending when a rope passes over a curved surface such as a stationary sheave or pin (see Fig. 6.2.126); Ksf = safety factor. (For average operation use Ksf = 5. If there is danger to human life or other critical situations, use 8 ≤ Ksf ≤ 12. For instance, for elevators moving at 50 ft/min, Ksf = 8, while for those moving at 1,500 ft/min, Ksf = 12.)

      Table 6.2.65 Selected Values of Nominal Strengths of Wire Rope Classification

      Nominal diameter

      Fiber core

      IWRC

      Approximate mass

      Nominal strength IPS

      Approximate mass

      Nominal strength

      IPS

      EIP

      in

      mm

      lb/ft

      kg/m

      tons

      t

      lb/ft

      kg/m

      tons

      t

      tons

      t

      Source: "Wire Rope User's Manual," AISI, adapted by permission.

      6 × 7 Bright (uncoated)

      ¼

      6.4

      0.09

      0.14

      2.64

      2.4

      0.10

      0.15

      2.84

      2.58

      3 / 8

      9.5

      0.21

      0.31

      5.86

      5.32

      0.23

      0.34

      6.30

      5.72

      ½

      13

      0.38

      0.57

      10.3

      9.35

      0.42

      0.63

      11.1

      10.1

      16

      0.59

      0.88

      15.9

      14.4

      0.65

      0.97

      17.1

      15.5

      22

      1.15

      1.71

      30.7

      27.9

      1.27

      1.89

      33.0

      29.9

      1⅛

      29

      1.90

      2.83

      49.8

      45.2

      2.09

      3.11

      53.5

      48.5

      1 3 / 8

      35

      2.82

      4.23

      73.1

      66.3

      3.12

      4.64

      78.6

      71.3

      6 × 19 Bright (uncoated)

      ¼

      6.4

      0.11

      0.16

      2.74

      2.49

      0.12

      0.17

      2.94

      2.67

      3.40

      3.08

      3 / 8

      9.5

      0.24

      0.35

      6.10

      5.53

      0.26

      0.39

      6.56

      5.95

      7.55

      6.85

      ½

      13

      0.42

      0.63

      10.7

      9.71

      0.46

      0.68

      11.5

      10.4

      13.3

      12.1

      16

      0.66

      0.98

      16.7

      15.1

      0.72

      1.07

      17.7

      16.2

      20.6

      18.7

      22

      1.29

      1.92

      32.2

      29.2

      1.42

      2.11

      34.6

      31.4

      39.8

      36.1

      1⅛

      29

      2.13

      3.17

      52.6

      47.7

      2.34

      3.48

      56.5

      51.3

      65.0

      59.0

      1 3 / 8

      35

      3.18

      4.73

      77.7

      70.5

      3.5

      5.21

      83.5

      75.7

      96.0

      87.1

      1⅝

      42

      4.44

      6.61

      107

      97.1

      4.88

      7.26

      115

      104

      132

      120

      1⅞

      48

      5.91

      8.8

      141

      128

      6.5

      9.67

      152

      138

      174

      158

      2⅛

      54

      7.59

      11.3

      179

      162

      8.35

      12.4

      192

      174

      221

      200

      2 3 / 8

      60

      9.48

      14.1

      222

      201

      10.4

      15.5

      239

      217

      274

      249

      2⅝

      67

      11.6

      17.3

      268

      243

      12.8

      19.0

      288

      261

      331

      300

      6 × 37 Bright (uncoated)

      ¼

      6.4

      0.11

      0.16

      2.74

      2.49

      0.12

      0.17

      2.94

      2.67

      3.4

      3.08

      3 / 8

      9.5

      0.24

      0.35

      6.10

      5.53

      0.26

      0.39

      6.56

      5.95

      7.55

      6.85

      ½

      13

      0.42

      0.63

      10.7

      9.71

      0.46

      0.68

      11.5

      10.4

      13.3

      12.1

      16

      0.66

      0.98

      16.7

      15.1

      0.72

      1.07

      17.9

      16.2

      20.6

      18.7

      22

      1.29

      1.92

      32.2

      29.2

      1.42

      2.11

      34.6

      31.4

      39.5

      36.1

      1⅛

      29

      2.13

      3.17

      52.6

      47.7

      2.34

      3.48

      56.5

      51.3

      65.0

      59.0

      1 3 / 8

      35

      3.18

      4.73

      77.7

      70.5

      3.50

      5.21

      83.5

      75.7

      96.0

      87.1

      1⅝

      42

      4.44

      6.61

      107

      97.1

      4.88

      7.26

      115

      104

      132

      120

      1⅞

      48

      5.91

      8.8

      141

      128

      6.5

      9.67

      152

      138

      174

      158

      2⅛

      54

      7.59

      11.3

      179

      162

      8.35

      12.4

      192

      174

      221

      200

      2 3 / 8

      60

      9.48

      14.1

      222

      201

      10.4

      15.5

      239

      217

      274

      249

      2⅞

      67

      11.6

      17.3

      268

      243

      12.8

      19.0

      288

      261

      331

      300

      3⅛

      74

      13.9

      20.7

      317

      287

      15.3

      22.8

      341

      309

      392

      356

      80

      16.4

      24.4

      371

      336

      18.0

      26.8

      399

      362

      458

      415

      Open in new tab Share Figure 6.2.126 Values of Kbend vs. D/d ratios (D = sheave diameter, d = rope diameter), based on standard test data for 6 × 9 and 6 × 17 class ropes. (Compiled from "Wire Rope User's Manual," AISI, by permission.) Interactive Graph Values of Kbend vs. D/d ratios (D = sheave diameter, d = rope diameter), based on standard test data for 6 × 9 and 6 × 17 class ropes. (Compiled from "Wire Rope User's Manual," AISI, by permission.) Click on the graph to launch interactivity or enter values below. D/d ratio Kb Open in new tab Share Having made a tentative selection of a rope based on the demanded static load, one considers next the wear life of the rope. A loaded rope bent over a sheave stretches elastically and so rubs against the sheave, causing wear of both members. Drum or sheave size is of paramount importance at this point.

      6.2.15.2. Sizing of Drums or Sheaves Diameters of drums or sheaves in wire rope applications are controlled by two main considerations: (1) the radial pressure between rope and groove and (2) degree of curvature imposed on the rope by the drum or sheave size.

      Radial pressures can be calculated from p = 2T/(Dd), where p = unit radial pressure, lb/in2; T = rope load, lb; D = tread diameter of drum or sheave, in; d = nominal diameter of rope, in. Table 6.2.66 lists suggested allowable radial bearing pressures of ropes on various sheave materials.

      Table 6.2.66 Suggested Allowable Radial Bearing Pressures of Ropes on Various Sheave Materials Material

      Regular lay rope, lb/in2

      Lang lay rope, lb/in2

      Flattened strand lang lay, lb/in2

      Remarks

      6 × 7

      6 × 19

      6 × 37

      8 × 19

      6 × 7

      6 × 19

      6 × 37

      Source: "Wire Rope User's Manual," AISI, reproduced by permission.

      Wood

      150

      250

      300

      350

      165

      275

      330

      400

      On end grain of beech, hickory, gum.

      Cast iron

      300

      480

      585

      680

      350

      550

      660

      800

      Based on minimum Brinell hardness of 125.

      Carbon-steel casting

      550

      900

      1,075

      1,260

      600

      1,000

      1,180

      1,450

      30-40 carbon. Based on minimum Brinell hardness of 160.

      Chilled cast iron

      650

      1,100

      1,325

      1,550

      715

      1,210

      1,450

      1,780

      Not advised unless surface is uniform in hardness.

      Manganese steel

      1,470

      2,400

      3,000

      3,500

      1,650

      2,750

      3,300

      4,000

      Grooves must be ground and sheaves balanced for high-speed service.

      Open in new tab Share All wire ropes operating over drums or sheaves are subjected to cyclical stresses, causing shortened rope life because of fatigue. Fatigue resistance or relative service life is a function of the ratio D/d. Adverse effects also arise out of relative motion between strands during passage around the drum or sheave. Additional adverse effects can be traced to poor match between rope and groove size, and to lack of rope lubrication. Table 6.2.67 lists suggested and minimum sheave and drum ratios for various rope construction. Table 6.2.68 lists relative bending life factors; Figure 6.2.127 shows a plot of relative rope service life versus D/d. Table 6.2.69 lists minimum drum (sheave) groove dimensions. Periodic groove inspection is recommended, and worn or corrugated grooves should be re-machined or the drum replaced, depending on severity of damage.

      Table 6.2.67 Sheave and Drum Ratios Construction* †

      Suggested

      Minimum

      • WS—Warrington Seale; FWS—Filler Wire Seale; SFW—Seale Filler Wire; SWS—Seale Warrington Seale; S—Seale; FW—Filler Wire.

      † D = tread diameter of sheave; d = nominal diameter of rope. To find any tread diameter from this table, the diameter for the rope construction to be used is multiplied by its nominal diameter d. For example, the minimum sheave tread diameter for a ½-in 6 × 21 FW rope would be ½ in (nominal diameter) × 30 (minimum ratio), or 15 in.

      Note: These values are for reasonable service. Other values are permitted by various standards such as ANSI, API, PCSA, HMI, CMAA, etc. Similar values affect rope life.

      Source: "Wire Rope User's Manual," AISI, reproduced by permission.

      6 × 7

      72

      42

      19 × 7 or 18 × 7 Rotation-resistant

      51

      34

      6 × 19 S

      51

      34

      6 × 25 B flattened strand

      45

      30

      6 × 27 H flattened strand

      45

      30

      6 × 30 G flattened strand

      45

      30

      6 × 21 FW

      45

      30

      6 × 26 WS

      45

      30

      6 × 25 FW

      39

      26

      6 × 31 WS

      39

      26

      6 × 37 SFW

      39

      26

      6 × 36 WS

      35

      23

      6 × 43 FWS

      35

      23

      6 × 41 WS

      32

      21

      6 × 41 SFW

      32

      21

      6 × 49 SWS

      32

      21

      6 × 46 SFW

      28

      18

      6 × 46 WS

      28

      18

      8 × 19 S

      41

      27

      8 × 25 FW

      32

      21

      6 × 42 Tiller

      21

      14

      Open in new tab Download data Share Table 6.2.68 Relative Bending Life Factors Rope construction

      Factor

      Rope construction

      Factor

      Source: "Wire Rope User's Manual," AISI, reproduced by permission.

      6 × 7

      0.61

      6 × 36 WS

      1.16

      19 × 7 or 18 × 7

      0.67

      6 × 43 FWS

      1.16

      Rotation-resistant

      0.81

      6 × 41 WS

      1.30

      6 × 19 S

      0.90

      6 × 41 SFW

      1.30

      6 × 25 B flattened strand

      0.90

      6 × 49 SWS

      1.30

      6 × 27 H flattened strand

      0.90

      6 × 43 FW (2 op)

      1.41

      6 × 30 G flattened strand

      0.89

      6 × 46 SFW

      1.41

      6 × 21 FW

      0.89

      6 × 46 WS

      1.41

      6 × 26 WS

      1.00

      8 × 19 S

      1.00

      6 × 25 FW

      1.00

      8 × 25 FW

      1.25

      6 × 31 WS

      1.00

      6 × 42 Tiller

      2.00

      6 × 37 SFW

      Open in new tab Download data Share Figure 6.2.127 Service life curves for various D/d ratios. Note that this curve takes into account only bending and tensile stresses. (Reproduced from "Wire Rope User's Manual, " AISI, by permission.) Interactive Graph Service life curves for various D/d ratios. Note that this curve takes into account only bending and tensile stresses. (Reproduced from "Wire Rope User's Manual, " AISI, by permission.) Click on the graph to launch interactivity or enter values below. D/d ratio Relative rope service life Open in new tab Share Table 6.2.69 Minimum Sheave- and Drum-Groove Dimensions* Nominal rope diameter

      Groove radius

      New

      Worn

      in

      nm

      in

      mm

      in

      mm

      • Values given are applicable to grooves in sheaves and drums; they are not generally suitable for pitch design since this may involve other factors. Further, the dimensions do not apply to traction-

      type elevators; in this circumstance, drum- and sheave-groove tolerances should conform to the elevator manufacturer's specifications. Modern drum design embraces extensive considerations beyond the scope of this publication. It should also be noted that dram grooves are now produced with a number of oversize dimensions and pitches applicable to certain service requirements.

      Source: "Wire Rope User's Manual," AISI, reproduced by permission.

      ¼

      6.4

      0.135

      3.43

      .129

      3.28

      5 / 16

      8.0

      0.167

      4.24

      .160

      4.06

      3 / 8

      9.5

      0.201

      5.11

      .190

      4.83

      7 / 16

      11

      0.234

      5.94

      .220

      5.59

      ½

      13

      0.271

      6.88

      .256

      6.50

      9 / 16

      14.5

      0.303

      7.70

      .288

      7.32

      5 / 8

      16

      0.334

      8.48

      .320

      8.13

      3 / 4

      19

      0.401

      10.19

      .380

      9.65

      7 / 8

      22

      0.468

      11.89

      .440

      11.18

      1

      26

      0.543

      13.79

      .513

      13.03

      1⅛

      29

      0.605

      15.37

      .577

      14.66

      32

      0.669

      16.99

      .639

      16.23

      1 3 / 8

      35

      0.736

      18.69

      .699

      17.75

      38

      0.803

      20.40

      .759

      19.28

      1⅝

      42

      0.876

      22.25

      .833

      21.16

      45

      0.939

      23.85

      .897

      22.78

      1⅞

      48

      1.003

      25.48

      .959

      24.36

      2

      52

      1.085

      27.56

      1.025

      26.04

      2⅛

      54

      1.137

      28.88

      1.079

      27.41

      58

      1.210

      30.73

      1.153

      29.29

      2 3 / 8

      60

      1.271

      32.28

      1.199

      30.45

      64

      1.338

      33.99

      1.279

      32.49

      2⅝

      67

      1.404

      35.66

      1.339

      34.01

      71

      1.481

      37.62

      1.409

      35.79

      2⅞

      74

      1.544

      39.22

      1.473

      37.41

      3

      77

      1.607

      40.82

      1.538

      39.07

      3⅛

      80

      1.664

      42.27

      1.598

      40.59

      83

      1.731

      43.97

      1.658

      42.11

      3 3 / 8

      87

      1.807

      45.90

      1.730

      43.94

      90

      1.869

      47.47

      1.794

      45.57

      96

      1.997

      50.72

      1.918

      48.72

      4

      103

      2.139

      54.33

      2.050

      52.07

      109

      2.264

      57.51

      2.178

      55.32

      115

      2.396

      60.86

      2.298

      58.37

      122

      2.534

      64.36

      2.434

      61.82

      5

      128

      2.663

      67.64

      2.557

      64.95

      135

      2.804

      71.22

      2.691

      68.35

      141

      2.929

      74.40

      2.817

      71.55

      148

      3.074

      78.08

      2.947

      74.85

      6

      154

      3.198

      81.23

      3.075

      78.11

      Open in new tab Share Seizing and Cutting Wire Rope Before a wire rope is cut, seizings (bindings) must be applied on either side of the cut to prevent rope distortion and flattening or loosened strands. Normally, for preformed ropes, one seizing on each side of the cut is sufficient, but for ropes that are not preformed a minimum of two seizings on each side is recommended, and these should be spaced six rope diameters apart (see Fig. 6.2.128). Seizings should be made of soft or annealed wire or strand, and the width of the seizing should never be less than the diameter of the rope being seized. Table 6.2.70 lists suggested seizing wire diameters.

      Figure 6.2.128 Seizings. (Reproduced from "Wire Rope User's Manual, " AISI, by permission.) binary://mheaeworks/b5689cae67236644/dabbb5c8ab916a67588e9e15144fa3607cde3a92171221b8c915b2690ccc4448/06x02_128.png Open in new tab Share Table 6.2.70 Seizing* Rope diameter

      Suggested seizing wire diameter†

      in

      mm

      in

      mm

      • Length of the seizing should not be less than the rope diameter.

      † The diameter of seizing wire for elevator ropes is usually somewhat smaller than that shown in this table. Consult the wire rope manufacturer for specific size recommendations. Soft annealed seizing strand may also be used.

      Source: "Wire Rope User's Manual," AISI, reproduced by permission.

      ⅛- 5 / 16

      3.5-8.0

      0.032

      0.813

      3 /

      8

      9 / 16

      9.4-14.5

      0.048

      1.21

      ⅝- 15 / 16

      16.0-24.0

      0.063

      1.60

      1-1 5 / 16

      26.0-33.0

      0.080

      2.03

      1 3 / 8 -1 11 / 16

      35.0-43.0

      0.104

      2.64

      1¾ and larger

      45.0 and larger

      0.124

      3.15

      Open in new tab Share Wire Rope Fittings or Terminations End terminations allow forces to be transferred from rope to machine, or load to rope, etc. Figure 6.2.129 illustrates the most commonly used end fittings or terminations. Not all terminations will develop full strength. In fact, if all of the rope elements are not held securely, the individual strands will sustain unequal loads causing unequal wear among them, thus shortening the effective rope service life. Socketing allows an end fitting which reduces the chances of unequal strand loading.

      Figure 6.2.129 End fittings, or terminations, showing the six most commonly used. (Reproduced from "Wire Rope User's Manual, " AISI, by permission.) binary://mheaeworks/93cbb5f808260c54/0b81d52ad105f0752c71c8e820d154a2b2caedd00b267e91c7d74013bc0b3bbc/06x02_129.png Open in new tab Share Wire rope manufacturers have developed a recommended procedure for socketing. A tight wire serving band is placed where the socket base will be, and the wires are unlaid, straightened, and "broomed" out. Fiber core is cut close to the serving band and removed, wires are cleaned with a solvent such as SC-methyl chloroform, and brushed to remove dirt and grease. If additional cleaning is done with muriatic acid this must be followed by a neutralizing rinse (if possible, ultrasonic cleaning is preferred). The wires are dipped in flux, the socket is positioned, zinc (spelter) is poured and allowed to set, the serving band is removed, and the rope lubricated.

      A somewhat similar procedure is used in thermoset resin socketing.

      Socketed terminations generally are able to develop 100 percent of nominal strength.