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Introduction
In order for a wire rope to be used safely in any application it must be inspected regularly and in the proper manner. ASME standards such as B30.5 (Mobile
Cranes) and B30.2 (Overhead Cranes) are two safety standards that provide detailed inspection procedures and retirement criteria. Both standards specify
that all running roapes should be visually inspected daily. Bridon American believes that there is no more important aspect of operating a rope safely that
a proper rope inspection of all rope that will be used during crane operations on that day. The inspection must be more than just a quick look. A quick
look may not be sufficient to find evidence of damage or broken wires sufficient to require that the rope be taken out of service. The inspection must be
done carefully and in enough light so that broken wire and damage can be observed. It must also be remembered that a dirty or greasy rope is almost
impossible to inspect properly as dirt and grease may hide evidence of broken wires and damage. The individual making the inspection should be familiar
with the machine, the wire rope and the particular application.
There are a wide variety of wire rope constructions available to be used on cranes. It is important the the correct rope be used for each specific
application. Because wire rope wears in service the method by which the rope wears is an important factor in determining the most suitable rope. When there
is a question, consult with Bridon American about the rope construction most appropriate for the application.
The B30 standards provide information on both a frequent inspection to be done daily and a more detailed periodic inspection that is done on a weekly
basis.
Frequent Inspection
Basically a daily or frequent inspection will include all end connections and important wear areas of the rope. This is where the inspector should know
where and how the rope on the particular application wears out so that he can concentrate his daily inspection on the known wear areas.
Special care should be taken when inspecting portions of the rope subject to repetitive wear such as the following:
- Step up and cross over points on the drum.
- Repetitive pick up points.
- Areas of the rope operating through a reverse bend in the reeving system.
- Equalizer sheaves.
The inspection should be concerned with determining rope wear or damage which may require the rope to be replaced immediately. The inspection should be
looking for the following:
- Distortion such as kinking, crushing, unlying, birdcaging, strand distortion or core protrusion.
- Corrosion.
- Broken or cut strands.
- Number, type and distribution of broken wires.
- Lubrication condition.
Certain types of ropes and applications require special attention:
Rotation Resistant ropes, because of their unique construction, are susceptible to damage and increased deterioration when working under difficult
operating conditions.
Boom hoist ropes because of the difficulties of inspection and important nature of these ropes.
Periodic Inspection
The periodic inspections should be made on a weekly or monthly basis and covered with a detailed, signed report. The following factors should be considered
in determining how often a periodic inspection is completed:
- Typical length of rope service.
- Severity of application.
- Percentage of capacity lifts.
- Frequency of operation.
- Shock loading.
There are many duty cycle rope applications where the service life is less than a month or sometimes even a week so thorough daily inspections must be
done. The periodic inspection should include all the specifics as done in the frequent inspection with the addition of:
- Measuring rope diameter for loss of diameter below nominal rope diameter due to loss of core support.
- Internal or external corrosion.
- Wear of outside wires.
- More detailed inspection of end connections for broken wires and corrosion.
- Severely corroded, cracked, bent, worn or improperly applied end connections.
Rope Replacement
There are no precise rules to determine the exact time for the replacement of the rope since many variable factors are involved. Continued use is often
dependent on good judgement by an appointed or authorized person in evaluating the remaining strangth in a used rope, after allowance for deterioration
disclosed by inspection. Continued rope operation depends upon the remaining strength. Once a rope reaches any one of the specified removal criteria, it
may be allowed to operate to the end of the work shift, based on the judgement of a qualified person. The rope shall be replaced after the work shift, at
the end of the day, or at the latest time prior to the rope being used on the next work shift.
Conditions such as the following are sufficient reason to require the rope to be removed from service:
- For ropes operating on equipment covered by B30.5, in running ropes, 6 randomly distributed wire breakes per wire rope lay or 3 wire breakes per strand
per rope lay. A rope lay is the distance that it takes one outer strand to make one complete revolution around the rope. A 6 strand rope will typically
have a rope lay of 6.4 times the rope diameter (ie. a 1/2” 6X25 FW EIP IWRC RRL rope will have a rope lay of 3.2”).
- For ropes operating on equipment covered by B30.2, in running ropes is 12 randomly distributed wire breaks per rope lay or 4 wire breaks per strand per
rope lay.
- For all categories of Rotation Resistant ropes, the requirement criteria is 2 wire breaks in 6 rope diameters or 4 wire breaks in 30 rope diameters
(ie. 6 rope diameters in a 1” rope is 6”).
- One broken outer wire at the contact point with the core which has worked its way out of the rope structure and protrudes, loops out or is slightly
raised from the body of the rope.
- Wear of one third of the original diameter of the outside individual wires.
- Kinking, crushing, birdcaging or any other damage resulting in distortion of the rope structure.
- Evidence of heat damage from any cause.
- Reduction from nominal rope diameter of more than:
1/16” for ropes up to and including 5/16”
1/32” for ropes over 5/16” thru 1/2”
3/64” for ropes over 1/2” thru 3/4”
1/16” for ropes over 3/4” thru 11/8”
3/32” for ropes over 11/8”
- In standard ropes more than 2 broken wires in one lay away from the end connection or more than one broken wire at the end connection.
Broken wire removal criteria apply to rope used on steel sheaves and drums. If ropes are used on sheaves and drums of material other than steel, the
user should contact the sheave, drum or machine manufacturer for broken wire removal citeria.
Replacement rope must have a rated strength at least equal to the original rope supplied or recommended for the machine. Any change from the original
specification for the rope must be specified by the wire rope manufacturer, crane manufacturer or a qualified person.
All rope that has been idle for a month or more due to shutdown or shortage of a crane should be given a detailed inspection according to the
requirements of the periodic inspection provided by the B30 Standards.
WARNING: Any warranties, expressed or implied, concerning the use of this product apply only to the nominal strength of new, unused wire
rope. All equipment using this product must be properly used and maintained. Wire rope must be properly stored, handled, used and maintained. Most
importantly, wire rope must be regularly inspected during use. Damage, abuse or improper maintenance can cause rope failure. Consult the AISI Wire Rpoe
Users Manual, ASME or ASNI Standards, or Bridon American Corporation before usage. Wire rope removal criteria are based on the use of steel sheaves. If
synthetic sheaves are used, consult the sheave equipment manufacturer. WARNING!
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