Rope Inspection
You must remove ropes from service when the discard point has been reached. One of the most frequently asked questions is, “When should I retire my rope?” The most obvious answer is, before it breaks. Without a thorough understanding of rope inspection and load history, you must make an educated guess. Unfortunately, there are no definite rules or industry guidelines to establish when a rope should be retired as a function of time because of many variables that affect rope strength. Factors like: load history, bending radius, abrasion, chemical exposure or combinations of these factors make retirement decisions difficult. Rope inspection should be a continuous process of observation before, during and after each use. In synthetic fiber ropes the amount of strength loss due to abrasion and/or flexing is directly related to the amount of broken fiber in the rope cross section. Before use, look and feel along every inch of the rope length, inspecting for the following damage:
Core & Cover Damage
The load bearing capacity of double braid ropes is divided equally between the inner core and the outer cover. During inspection if cut strands or significant abrasion damage is detected, the rope must be removed from service because the strength of the entire rope has been decreased.
Core dependent double braids such as AmSteel® II have 100% of the load bearing capacity carried by the core alone. The outer jacket can sustain damage without compromise to the load bearing core. Inspection of core dependent double braids can be misleading as it is difficult to see the core.
12 strand single braids such as AmSteel® and AmSteel® Blue have 12 strands and each strand carries 8.33% or 1/12th of the load. During inspection if cut strands or significant abrasion damage is detected, the rope must be removed from service and evaluated for possible repair. See pages 395-396 for visual inspection information.
Abrasion
When ropes are first put into service the outer rope filaments will quickly fuzz up. This is a result of filaments breaking and the roughened surface actually forms a protective cushion and shield for the fibers underneath. This condition should stabilize, not progress. If the surface roughness increases, excessive abrasion is taking place and strength is being lost. As a general rule for braided ropes, when 25% or more of the fiber is broken or worn away, the rope should be removed from service. For double braid ropes, 50% wear on the cover is the retirement point. With 3 strand ropes, 10% or more wear is the retirement point.
Look closely at both the inner and outer fibers. When either is worn the rope is obviously weakened. Open the strands and look for powdered fiber which is one sign of internal wear. Estimate the internal wear to determine total fiber abrasion. If total fiber loss is 20%, then it is reasonable to assume that the rope has lost 20% of its strength as a result of abrasion.
Glossy or Glazed Areas
Glossy or glazed areas are signs of heat damage with more strength loss than the amount of melted fiber indicates. Fibers adjacent to the melted areas are probably damaged from excessive heat even though they appear normal. It is reasonable to assume that the melted fiber area has an equal amount of unmelted fiber damage adjacent to the melted area.
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Inconsistent Diameter
Inspect for flat areas, bumps or lumps. These forms of damage indicate core or internal damage from overloading or shock loading and are usually sufficient reason to retire the rope from service. Remember the cost of rope replacement is dwarfed by death, injury or the destruction of property. “Dwarfed” is not intended to offend vertically challenged persons.
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Discoloration
With use, all ropes get dirty. Be aware of areas of discoloration which indicate chemical exposure. Determine the cause of the discoloration and replace the rope if it is brittle or stiff.
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Inconsistency in Texture / Stiffness
Inconsistency in texture and/or stiffness can indicate excessive dirt or grit embedded in the rope or shock load damage and is usually reason to replace the rope.
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Temperature
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When using rope, friction can be useful or harmful, if not managed properly. By definition, friction creates heat; the greater the friction, the greater the heat buildup. Heat is an enemy to synthetic fibers and elevated temperatures can drastically reduce strength and/or cause rope melt-through.
High temperatures are developed when surging ropes on a capstan or drum end, winching ropes on bitts and running ropes over stuck or non-rolling sheaves or rollers. Each rope construction and fiber type will yield a different coefficient of friction (reluctance to slip) in a new and used state. It is important to understand the operational demands and ensure the size, rope construction and fiber type be taken into account to minimize heat buildup.
Never let ropes under tension rub together or move relative to one another. Enough heat to melt the fibers can buildup and cause the rope to fail as quickly as if it had been cut with a knife.
Always be aware of areas of heat buildup and take steps to minimize it. Under no circumstance let any rope come in contact with a steam line or other hot surfaces.
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Critical and Melting Temperatures
(Expressed in degrees Fahrenheit)
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*Material
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Critical
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Melting
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*Nylon
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325
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425-490
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*Polyester
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350
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480
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*Polypropylene
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250
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330
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*Dyneema®
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150
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300
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*Vectran®
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300
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625
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*Technora®
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520
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930
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*Zylon® (PBO)
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750
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1200
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*Manila
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180
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300
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*While the term “melting” does not apply to these fibers, they do undergo extreme degradation at these temperatures. Technora® and Manila char.
Zylon® decomposes.
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Single Braid Rope Inspection
Any rope that has been in use for any period of time will show wear and tear. Some characteristics of a used rope will not reduce strength, while others will. If during inspection you detect any of the following conditions, before deciding to repair or remove the rope from service you must consider the following: rope length, length of service life, type of work done , location of damage and the extent of the damage. In general, it is recommended that: the rope is considered for repair if the damage is in localized areas or the rope be removed from service if the damage is over extended areas. As ropes are used they will undergo normal changes such as constructional elongation and splice setting. Compression and pulled strands are conditions that do not reduce rope strength and can be corrected.
Volume Reduction
*Amount of volume reduction that indicates retirement depends on rope construction. Refer to check list below.
Cut Strands
Rope displays two adjacent cut strands.* Rope should either be retired or the cut section removed and after inspection, the remaining rope re-spliced.
*Number of cut strands that indicate rope retirement depends on
rope construction. See check list below.
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Compression
Rope exhibits fiber-set from compression. A slight sheen is visible. This is not a permanent condition and can be eliminated by flexing the rope. This condition should not be confused with glazed or melted fiber. (See Melting).
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Pulled Strand
Caused by snagging on equipment or surfaces. Not a permanent condition that can be corrected by working the pulled strand back in to the rope, if it is not cut or damaged.
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Melting or Glazing
Damage depicted is caused by excessive heat which melted and fused the fibers. This area will be extremely stiff. Unlike fiber compression, melting damage cannot be mitigated by flexing the rope. Melted areas must be cut out and the rope re-spliced or retired.
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Inconsistent Diameter
Flat areas or lumps and bumps that may result from shock loading or broken internal strands.
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Discoloration
Fused, Brittle, Stiff Fibers which indicate chemical exposure and contamination.
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Rope Inspection Check List
Double Braid & Core-Dependent Rope Inspection
There are two types of Double Braid ropes. Consider the following: Double Braid has the cover integrated with the core and Core-Dependent Double Braid has a cover only for abrasion protection and the core bears the entire weight of the load.
If the cover is damaged on a Double Braid, the strength of the rope has been compromised. If the cover of Core-Dependent Double Braid has been damaged, the strength of the rope may not be compromised and close inspection of the line will be necessary to make the determination.
Retire the Rope when it's Time, Before it's too Late
Regular inspection will help determine when the rope will need to be retired.
Internal abrasion can be determined by pulling one strand away from the others and looking for powdered or broken filaments. (Figures 1 and 2).
To determine the extent of outer fiber damage from abrasion, a single yarn in all abraded areas should be examined. The diameter of the abraded yarn should then be compared to a portion of the same yarn or an adjacent yarn of the same type that has been protected by strand cross over and is free from abrasion damage. (Figure 3).
Residual Strength Testing
The strength of a used rope can be determined by testing. Samson offers our customers residual strength testing of their ropes, which is critical in determining retirement criteria. Periodic testing of samples taken from ropes currently in service ensures that retirement criteria reflect the actual conditions of use.
The ability to determine the retirement point before failure in service without strength testing is essential and is based on a combination of education in rope use and construction along with good judgment and experience. Remember, if you have any doubt about the condition of a rope; do not use it, until you consult with a qualified person.
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