Long Lines: Retirement & Inspections

Retirement

RETIRE THE ROPE FROM USE WHEN IT HAS REACHED ITS DISCARD POINT.

One of the most frequently asked questions is "When should I retire my rope?" The most obvious answer is before it breaks. But, without a thorough understanding of how to inspect it and knowing the load history, you are left making an educated guess.

Unfortunately, there are no definitive rules or industry guidelines to establish when a rope should be retired because there are so many variables that affect rope strength. Factors like load history, bending radius, abrasion, chemical exposure or some combination of those factors, make retirement decisions difficult.

Inspecting your rope should be a continuous process of observation before, during and after each use. In synthetic fibre rope the amount of strength loss due to abrasion and/or flexing is directly related to the amount of broken fibre in the rope's cross section. After each use, look and feel along every inch of the rope length inspecting for damage as listed below.

	Rope exhibits fibre-set from compression. A slight sheen is visible. This is not a permanent characteristic and can be eliminated by flexing the rope. This condition should not be confused with glazed or melted fibre (see below).

Rope displays two adjacent cut strands*. This rope should either be retired or the cut section should be removed and the remaining rope re-spliced. * Number of cut strands that indicates retirement depends on rope construction.

Knots

While it is true that a knot reduces rope strength, it is also true that a knot is a convenient way to accomplish rope attachment. The strength loss is a result of the tight bends that occur in the knot. With some knots, ropes can lose up to 50% of their strength. It is vital that the reduction in strength by the use of knots be taken into account when determining size and strength of a rope to be used in an application. To avoid knot strength reduction, it is recommended that a rope be spliced according to manufacturers instructions. Splice terminations are used in all our ropes to determine new and unused tensile strengths. Therefore, whenever possible, spliced terminations should be used to maximize the rope strength for new and used ropes.

Rope storage

Keep your ropes as clean and dry as possible and store them in a coil away from heat sources.

Shock loads

Shock loads are simply a sudden change in tension—from a state of relaxation or low load to one of high load. Any sudden load that exceeds the work load by more than 10% is considered a shock load. The further an object falls, the greater the impact. Synthetic fibers have a memory and retain the effects of being overloaded or shock loaded and can fail at a later time even though loaded within the work load range.

Abrasion

When the rope is first put into service the outer filaments of the rope will quickly fuzz up. This is the result of these filaments breaking and this 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 there is 25% or more wear from abrasion the rope should be retired from service. In other words, if 25% or more of the fibre is broken or worn away the rope should be removed from service. With three-strand ropes, 10% or more wear is accepted as the retirement point.

Look closely at both the inner and outer fibres. When either is worn the rope is obviously weakened. Open the strands and look for powdered fibre which is one sign of internal wear. Estimate the internal wear to estimate total fibre abrasion. If total fibre loss is 20%, then it is safe to assume that the rope has lost 20% of its strength as a result of abrasion.

Volume Reduction IMAGE 1:  Rope displaying original bulk. IMAGE 2:  Rope displaying 25%* strand volume reduction from abrasion—rope should be retired from service. IMAGE 3: Rope strands showing full volume. IMAGE 4:  Rope strands reduced by 25%* abrasion. * Amount of volume reduction that indicates retirement depends on rope construction.

Glossy or glazed areas

Glossy or glazed areas are signs of heat damage with more strength loss than the amount of melted fibre indicates. Fibres adjacent to the melted areas are probably damaged from excessive heat even though they appear normal. It is reasonable to assume that the melted fibre has damaged an equal amount of adjacent unmelted fibre.

Damage depicted caused by excessive heat which melted and fused the fibres. This area will be extremely stiff. Unlike fibre compression, melting damage cannot be mitigated by flexing the rope. Melted areas must be cut out and rope re-spliced or the rope must be retired.

Inconsistent diameter

Inspect for flat areas, bumps or lumps. This can indicate core or internal damage from overloading or shock loads and is usually sufficient reason to replace the rope.

Discolouration

With use, all ropes get dirty. Be on the lookout for areas of discolouration, which could be caused by chemical contamination. Determine the cause of the discolouration and replace the rope if it is brittle or stiff.

Inconsistency in texture/stiffness

Can indicate excessive dirt or grit embedded in the rope or shock load damage and is usually reason to replace the rope.

Temperature

When using rope, friction can be your best friend or worst enemy if it is not managed properly. By definition, friction creates heat, the greater the friction, the greater the heat buildup. Heat is an enemy to synthetic fiber and elevated temperatures can drastically reduce the strength and or cause rope melt-through.

* While the term "melting" does not apply to these fibres, they do undergo extreme degradation at these temperatures: Technora and Manila char; Zylon decomposes.

High temperatures can be achieved when surging rope on a capstan or drum end, checking ropes on bitts, and running over stuck or non-rolling sheaves or rollers. Each rope's construction and fibre 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 fibre 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 fibres can build up 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 circumstances let any rope come in contact with a steam line or any other hot surfaces.

The strength of a used rope can be determined by testing; however, the rope is destroyed in the process so the ability to determine the retirement point before it fails in service is essential. That ability is based on a combination of education in rope use and construction along with good judgment and experience.

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