Wire Rope Examination and Discard: A Comprehensive Guide to Safety

Wire Rope Rejection - Introduction

DOCUMENT NO: ES-C-13-06 WIRE ROPE - EXAMINATION AND DISCARD

Wire Rope as a Machine

We need to think of a wire rope as a machine, by dictionary definition: "An assemblage of parts ... that transmit forces, motion, and energy one to another in some predetermined manner and to some desired end." A wire rope will generally deteriorate externally, which we can readily and easily evaluate with regard to damage and wear, but the majority of work and wear may be happen internally within the construction of the wire rope - this proves slightly more difficult to assess. A typical wire rope may contain hundreds of individual wires which are formed and fabricated to operate at close bearing tolerances one to another. When a wire rope bends, each of its many wires slides and adjusts in the bend to accommodate the difference in length between the inside and the outside bend. The sharper bend, the greater movement. This relative movement is the reason for the less prominent internal wear. Flexing the rope makes the strands slide against each other.

Wire Rope Components

Every wire rope has three basic components: . The wires which form the strands and collectively provide the rope strength; . The strands, which are helically around the core; and, . The core, which forms a foundation for the strands. Core may be Fibre Core (FC), Wire Strand Core (WSC) or the core of wire rope may be an Independent Wire Rope Core (IWRC), which in many cases is actually a rope in itself. In some rope constructions the IWRC rope provides between 10% and 50% (in non-rotating constructions) of the wire rope's strength. The greatest difference in wire ropes are found in the number of strands, the construction of strands, the size of the core, and the lay direction of the strand versus the core. The wires of wire rope are made of high-carbon steel. These carbon steel wires come in various grades. The term "Grade" is used to designate the strength of the wire rope. Wire ropes are usually made from 1770 N/mm2, 1960 N/mm2 or 2160 N/mm2 steel grades. One cannot determine the Tensile Grade of a wire rope by its feel or appearance. To properly evaluate a rope's tensile grade you must obtain the Grade from the rope test certificate or the certified supplier.

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Use and Care of Wire Rope

DOCUMENT NO: ES-C-13-06 WIRE ROPE - EXAMINATION AND DISCARD

Basic Information on Wire Rope Use

Some Basic Information about the use and care of wire rope. · Wire rope is a wearing component, it will fail if excessively worn, overloaded, misused, damaged, or improperly maintained. . In service, wire rope loses strength and work capability. Abuse and misuse increase the rate of loss. . The minimum breaking strength of wire rope applies only to a new, unused rope. . The minimum breaking strength should be considered the straight line pull with both rope ends fixed to prevent rotation, which will actually break a new, unused, rope. · The minimum breaking strength of a rope should never be used as its working load. . To determine the working load of a wire rope, the minimum or nominal breaking strength must be reduced by a design factor (formerly called a Safety Factor). The design factor will vary depending upon the type of application, installation and the work performed. . The equipment designer must determine the applicable design factor for rope use. For example, a Design Factor of "5" means that the Minimum- or Nominal Breaking Strength of the wire rope must be DIVIDED BY FIVE to determine the maximum load that can be applied to the rope system. Design Factors have been established by British Standards Institution, ISO, Industry bodies, ANSI, etc. and similar government International and industrial organizations. No wire rope should ever be installed or used without full knowledge and consideration of the design factor for the application. The application and fitment of a wire rope is specific to many individual factors including but not limited to the task, environment and duty cycle. Therefore when applying specific rejection criteria on a used wire rope, the Engineer Surveyor requires an understanding of the rope, its applications, limitations and the expectations for service lifecycle. Construction criteria on rope are outlined further in the source document - Wire Ropes - Construction and Manufacture Each termination / fitting attached to a wire rope has a specific efficiency rating which can reduce the working load of a rope assembly or rope system, and this must be given due consideration in determining the capacity of a wire rope system. Additional detail on wire rope terminations is contained in the source document - Wire Ropes - Terminations

Engineer Surveyor Action Point

Engineer Surveyor Action Point Wire rope is a consumable component, it is designed to provide longevity of service but it will ultimately wear. In the absence of certainty, seek further guidance, which may ultimately lead to the recommendation to replace the rope due to insufficient or inconclusive data. Specific manufacturers and or applications may require reduced or additional specific rejection criteria.

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Wire Rope Types

DOCUMENT NO: ES-C-13-06 WIRE ROPE - EXAMINATION AND DISCARD

Principal Wire Rope Types

There are typically two principal types of wire rope - Single layer wire rope - the strength of the rope is in the visible (outer) strands. Multi-layer wire rope - The strength or the rope distributed throughout the rope (inner and outer) strands. Within these two rope types there are of course numerous variations of construction. The two most widespread applications of wire rope we encounter, is in the lifts and cranage sectors. A rope used in these two aspects of our work have completely differing functions and complexities, but the principal component, the wire rope has the same characteristics, the same issues and similar failure modes.

Lift Suspension Ropes

Lift suspension ropes Typically within the lift sector the majority of suspension ropes require replacement due to fatigue. There are exceptions due to incorrect alignment, mechanical damage and installation damage, etc., but the vast majority of excessively worn lift ropes have just simply reached the end of their serviceable life. Within the controlled environment of a lift shaft, this is a very reliable and predictable failure mode. With appropriate regular maintenance, a set of lift suspension ropes will provide many years of predictable trouble free service.

Crane Ropes

Crane ropes A load rope fitted to a crane experiences a very different life. Exposed to the elements, susceptible to external factors and damage, combined with the possibility of overload and or shock load, a crane rope has a tougher working life. The failure modes for crane ropes are less predictable due to the unpredictable nature of the environment and usage requirements of the equipment, it is fitted to. In saying that equipment designers have taken these factors into account and a crane wire rope is ultimately the only component fit for the job. Historically, wire rope evolved from wrought iron chains, which had a record of mechanical failure. While flaws in chain links or solid steel bars can lead to catastrophic failure, flaws in the wires making up a steel wire rope are less critical as the other wires easily take up the remaining load. While friction between the individual wires and strands causes wear over the life of the rope, it also helps to compensate for minor failures in the short run. Consequently - what would happen if during continued service more and more of the wires break? Surely if all of the wires fail the rope would fail? Actually no, although it sounds incredible, a wire rope may still be serviceable even if every one of its wires is broken at some point along their length (as long as it is not localised in one area.) Each wire break merely represents a localised reduction of the ropes breaking strength. A few millimetres away from the location of the break the broken wire will again bear its full share of the load.

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Contents

1. Wire Rope Rejection - Introduction 3
2. Use and Care of Wire Rope 4
3. Wire rope types 5
4. Standards and guidance 6
5. Wire Rope Inspection Standards / Guidance 6
6. Wire rope - definitions - examination points 7
7. Components of Wire Rope 7
8. Strand and Rope Lay / Pattern 8
9. Wire Rope Construction 10
10. Compacted wire rope 11
11. Single layer stranded ropes 12
12. Multi-layer wire rope - Including Rotation Resistant Wire Rope 13
13. Rotation resistant wire rope 13
14. RCN - Rope Category Number 16
15. Wire rope diameter 17
16. Measuring worn wire rope diameter 17
17. Wire rope rejection criteria - General 18
18. Wire rope rejection criteria - lift suspension ropes 19
19. Lift suspension ropes - Broken wires 20
20. Diameter reduction - 20
21. Wire rope rejection criteria - Cranage - Crown wire breaks 21
22. LeBus Spooling 22
23. Localised Grouping 23
24. Visible Broken Wires - Single Layer wire rope (steel sheaves) 23
25. Visible Broken Wires - Multi-layer wire rope (steel sheaves) 24
26. Valley Breaks (see also section 13.7) 24
27. Single-layer Wire Rope - Broken Wire Rejection Criteria 25
28. Diameter Reduction 25
29. Multi-Layer Wire Rope - Broken Wire Rejection Criteria 25
30. Decrease / Increase in Rope Diameter 26
31. Wire rope rejection criteria - other factors 27
32. Non-metallic Sheaves .27
33. Severity Ratings 28
34. Magnetic Rope Testing (MRT) - Loss of metallic area (LMA) 28
35. Fracture of strands 29
36. Corrosion - three distinctive factors 29
37. External 29
38. Corrosion - Internal 29
39. Rouging (Fretting Corrosion) 30
40. Deformation and Damage 32
41. Valley Wire Breaks - (Crane wire rope) 36
42. Termination broken wires 38
43. Knots 39
44. Thermal Damage 39
45. Rope Dressing 39
46. Galvanising (Zinc Coating). .39
47. High Stranding 39
48. Wear 40
49. Fleet Angle (see also - ES-C-14-05 -- section 6) 40
50. Sheave and Drum Diameters 41
51. Reverse bending 41
52. Excessive twist 41
53. Overall cost 41
54. Martensite Formation 42
55. Inspection Procedure 43

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DOCUMENT NO: ES-C-13-06 WIRE ROPE - EXAMINATION AND DISCARD

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