One element of synthetics that will take some getting used to is “What is normal wear and tear?” and “What does it look like?”. Where steel cable holds its look other than flat spots and dirt, synthetic fibre takes on a worn look as it is used. Many people ask us if this is normal and how do they know when the rope has been comprimised.
The photo on the right shows a rope that has gone through sheaves multiple times. As the rope is used it is normal for the color to fade slightly as well for the rope to become a little “hairy”. This does not comprimise the strength of the rope. What needs to be visible are partly severed strands, completely severed strands or visible damage to the rope.
Many tow operator’s are working with synthetic tow lines for the first time are are not used to its properties, this is all part of the learning curve. As operators become more familiar with the rope they will be able to identify what is normal wear and what is a flaw in the line.
For further details on when to retire synthetic lines you can refer to the Cordage Institutes PDF on “Fiber Rope Inspection and Retirement Criteria“.
Any rope or steel cable will fail if it is worn out.
Always inspect your rope.
Never use the nominal, tensile or break strength listed for a rope or steel cable as the working load limit.*
*A safe “Working Load Limit” or WLL is determined by dividing the nominal strength of a rope by an appropriate design factor. For example: A factor of 10 to 1 would mean a rope with a minimum break strength of 30,000lbs would have a WLL of 3,000lbs.