INSPECTION OF WIRE ROPE

Wire Rope

Carefully conducted inspections are necessary to ascertain the condition of wire rope at various stages of its useful life. The object of wire rope inspection is to allow for removal of the rope from service before the rope’s condition, as a result of usage, could pose a hazard to continued normal operations. 

The individual making the inspection should be familiar with the product and the operation as his judgment is a most critical factor. Various safety codes, regulations, and publications give inspection requirements for specific applications. 

The following inspection procedure, taken from the ASME B-30 series, serves as a model of typical inspection requirements.

Frequent Inspection

All running ropes and slings in service should be visually inspected once each working day. A visual inspection consists of observation of all rope and end connections which can reasonably be expected to be in use during daily operations. These visual observations should be concerned with discovering gross damage such as listed below, which may be an immediate hazard: 

• Distortion of the rope such as kinking, crushing, unstranding, birdcaging, main strand displacement or core protrusion.
• General corrosion.
• Broken or cut strands.
• Number, distribution and type of visible broken wires.
• Lubrication.

Special care should be taken when inspecting portions subjected to rapid deterioration such as flange points, crossover points and repetitive pickup points on drums. 

Special care should also be taken when inspecting certain ropes such as: 

• Rotation-resistant ropes such as 19 x 7 and 8 x 19, because of their higher susceptibility to damage and increased deterioration when working on equipment with limited design parameters.
• Boom hoist ropes because of the difficulties of inspection and important nature of these ropes. 

When damage is discovered, the rope should either be removed from service or given an inspection as detailed in the section below.

Periodic Inspection 

The inspection frequency should be determined by a qualified person and should be based on such factors as: expected rope life as determined by experience on the particular installation or similar installations, severity of environment, percentage of capacity lifts, frequency rates of operation, and exposure to shock loads. Periodic inspections with a signed report should be performed by an appointed or authorized person. This inspection should cover the entire length of rope. The individual wires in the strands of the rope should be visible to this person during the inspection. Any deterioration resulting in appreciable loss of original strength, such as described below, should be noted and determination made as to whether further use of the rope would constitute a hazard:

• Distortion of the rope such as kinking, birdcaging, crushing, unstranding, main strand displacement, or core protrusion.
• Reduction of rope diameter below normal diameter due to loss of core support, internal or external corrosion, or wear of outside wires.
• Severely corroded or broken wires at end connections.
• Severely corroded, cracked, bent, worn, or improperly applied end connections.
• Lubrication. 

Special care should be taken when inspecting portions subjected to rapid deterioration such as the following: 

• Portions in contact with saddles, equalizer sheaves, or other sheaves where rope travel is limited.
• Portions of the rope at or near terminal ends where corroded or broken wires may protrude.

Rope Replacement 

No precise rules can be given for determination of the exact time for replacement of rope, since many variable factors are involved. Continued use in this respect depends largely upon good judgment by an appointed or authorized person in evaluating remaining strength in a used rope, after allowance for deterioration disclosed by inspection. Continued rope operation depends upon this remaining strength. 

Conditions such as the following should be sufficient reason for questioning continued use of the rope or increasing the frequency of inspection: 

In running ropes, six randomly distributed broken wires in one lay, or three broken wires in one strand in one lay. (The number of wire breaks beyond which concern should be shown varies with rope usage and construction. For general application 6 and 3 are satisfactory. Ropes used on overhead and gantry cranes, as defined in ASME B-30, 2-1983, can be inspected to 12 and 4. Rotation resistant ropes should be inspected to 4 in 30 rope diameters and 2 in 6 rope diameters.)

Wire rope removal criteria are based on the use of steel sheaves. If synthetic sheaves are used, consult the sheave or equipment manufacturer. 

• One outer wire broken at the contact point with the core of the rope which has worked its way out of the rope structure and protrudes or loops out from the rope structure.
• Wear of one-third the original diameter of outside individual wires.
• Kinking, crushing, birdcaging, or any other damage resulting in distortion of the rope structure.
• Evidence of any heat damage from any cause.
• Valley breaks.
• Reductions from nominal rope diameter of more than:

• In standing ropes, more than two broken wires in one lay in section beyond end connections or more than one broken wire at an end connection. 

Replacement rope shall have a strength rating at least as great as the original rope furnished by the equipment manufacturer or as originally specified. Any deviation from the original size, grade, or construction shall be specified by the equipment manufacturer, original design engineer, or a qualified person.

Ropes Not In Regular Use 

All rope which has been idle for a period of a month or more due to shutdown or storage of equipment on which it is installed should be given inspections as previously described before being placed in service. This inspection should be for all types of deterioration and should be performed by an appointed or authorized person.

Inspection Records 

Frequent Inspection – no records required. 

Periodic Inspection: In order to establish data as a basis for judging the proper time for replacement a signed report of rope condition at each periodic inspection should be kept on file. This report should include points of deterioration previously described. 

A long range inspection program should be established and include records of examination of ropes removed from service so a relationship can be established between visual observation and actual condition of the internal structure.

Galvanized Structural Wire Strand 

Carefully conducted inspections performed and recorded on a regular basis are necessary to ascertain the condition of structural strand at various stages of its useful life. The object of inspection is to allow for removal of the strand from service before its condition, as a result of usage, could pose a hazard to continued normal operations.

The individual making the inspection should be familiar with the operation, as his judgment is a most critical factor. Special care should be taken at end terminations or at dampener devices, as these are generally the most critical areas. 

Conditions such as corrosion, number, type and distribution of broken wires, and diameter reduction should be evaluated and compared with previous inspection results. 

The actual condition of the strand and inspection history together can then be used to decide if continued use of the product is advisable.

NOTE: Special methods and techniques may be used by wire rope engineers or qualified persons to determine the possible existence of internal corrosion or broken wires in structural strand or similar conditions which may exist out of sight in terminal connections.

EXAMPLE: Wire breaks may sometimes occur just inside the nose of the socket making visual inspection difficult. Judgments on wire integrity can be made by tapping or “sounding” the wire by a person experienced in this inspection technique. If you have doubt about the method to use for inspection, or the condition of the strand or fitting, contact your nearest CERTEX location.

For further information on wire rope inspection refer to the American Iron & Steel Institute’s Wire Rope Users Manual.