Materials used in rope construction

Synthetic fibers - Nylon is the predominant fiber for rescue rope and webbing.

Synthetic fibers are recommended for rescue rope for the following reasons:

• they run continuously throughout the length of the rope.
• they have greater resistance to rotting.
• they don't absorb water readily as natural fibers.
• they melt or burn at a higher temperature.
• their strength is greater.
• they have a higher resistance to shock loads.

Attributes of synthetic fiber:

• Predominant material for life safety ropes due to its superior characteristics and cost effectiveness.
• It is more elastic than its closest cousin "polyester".

Drawbacks to synthetic fiber:

• Loading over a sharp edge can cause then to fail.
• Prolonged exposure to sunlight (ultraviolet rays) can damage the rope.
• Contact with acids or alkalis can damage the rope fibers.
• It loses 15% of its strength when wet. Though it will regain that strength when dried.
• It has a melting point of 480 degrees.

Manufactures or distributors reference nylon rope as nylon-6-6 or nylon-6.6. These numbers refer to the chemical formula of the polymer itself. You may also see Dupont-707, etc.

Polyester is another fiber that is used by the fire and rescue community for rescue rope.

Attributes of polyester fiber:

• Doesn't absorb water.
• Has a much higher resistance to ultraviolet light.
• Better resistance to abrasive wear.
• Better resistance to acids.

Drawbacks to polyester fiber:

• 10% less strength than nylon
• Has 1/2 the shock absorbing capacity of nylon.
• Can be damaged by contact with alkali.

Combination ropes make with nylon kerns and polyester mantels are called "Vectran HS".

Attributes of Vectran fiber:

• High strength
• Low moisture absorption.
• Doesn't creep.
• Retains its properties over a broad temperature range.
• Extraordinary chemical resistance.
• It is easily knotted.

Drawbacks of Vectran fiber:

• Cost 15 times as much as raw polyester.
• Polyolefins: monofilament or multifilament fibers.

Attributes of polyolefin fiber:

• Floats on water. Resists degradation by many chemicals.

Drawbacks to polyolefin fiber:

• Low tensile strength.
• Rapid deterioration from exposure to sun light.
• Knots poorly.
• Has 60% of the energy absorption of nylon.
• Melts at 200 degrees.
• Poor resistance to abrasion.

This material is popular for water rescue situations where rescuers are supported by a primary flotation device rather than the rope. The bottom line is that this material shouldn't be used for life dependent activities.

Aramid family of fibers (Kevlar)

Attributes of Kevlar type fiber:

• High strength to weight ratio Good stretch resistance
• Excellent tension - tension fatigue life
• It is usable over a wide temperature range
• Electrically non conductive
• Doesn't creep
• Outstanding environmental and chemical resistance
• Pound for pound, 5 times as strong as steel

Drawbacks of Kevlar fibers:

• Poor resistance to abrasive surfaces.
• Poor shock absorbing qualities.
• Bending it into a small radii (such as tying and untying a knot) will damage the rope.

Rope Construction

A life safety rope must be of block creel construction. This means that the fibers run continuously through out the rope.

Kernmantle rope is recommended for rope rescue work. There are two types of kernmantle rope: Static & Dynamic

Static Kernmantle was developed for "Spelunkers" who needed a rope with a high resistance to abrasion, and low stretch and low spin. The fire and rescue community use static kernmantle most of the time. The life safety rope that most use is of 1/2" diameter construction and has a breaking strength of 9000 lbs. with a working to breaking safety factor of 15.

Dynamic kernmantle is used for mountain climbing because of its higher ability to stretch. It also has a lower resistance to abrasion than static kernmantle. It is used in situations where shock loading might occur.

Because many situations performed in fire and rescue require low stretch rope, static kernmantle is the primary rope used. However, dynamic rope should be used in situations where fire and rescue personnel might fall or need to be belayed.

Static ropes are typically manufactured in one color and have a contrasting color as a tracer. Dynamic ropes come in three to four colors.

Purchasing Rope

• Check material used in the core and sheath.
• Check weight per 100 feet. (a heavier production indicates greater strength or higher abrasion resistance.
• Sheath thickness can affect abrasion resistance. Some ropes are designed to take more abuse however the trade off is a stiffer rope. Some ropes are coated in an effort to increase their abrasion resistance.
• What color rope? Many are white with a color tracer. Colored ropes are less expensive.
• What length? Most American rope companies sell rope by the foot. For rescue work 200 ft. is quickly becoming a standard length.

Accessory Cordage

Used for prusiks, chock slings, and tie downs. Cordage under 8mm nylon static kernmantle not rated for self supporting life applications.

Webbing

Two types: tubular and flat.

Tubular is recommended for fire and rescue service with a minimum width of 1-inch.

Testing

NFPA 1983 lists the minimum breaking strength for one and two person ropes (4500 and 9000 lbs. respectively). The three sigma process located in the 1995 revision of the 1983 Standard spells out how to determine minimum breaking strengths. It is determined by subtracting three standard deviations from the mean of five test samples.

Manufacturers will also test their ropes over an abrading surface to see how many repetitions it will take to break. The UIAA standard test dynamic ropes for overall strengths and the number of falls it can handle.
 

Anytime fall factors approach 0.25% you need to work with dynamic rope. A fall test is conducted using a 176 lb. weight which is dropped while the rope is pulled over a 30 degree edge (simulating a carabiner on a climber). To receive a UIAA certification the rope must withstand at least five drops without breaking.

Rope Management:

All ropes, webbing, harnesses, hardware, and other items should be bagged and stored in a way that provides quick access and easy deployment.

They should be stored in a clean, cool, dry area.

The rope is "stuffed" into a rope bag rather than coiled. Tie a figure eight stopper on the first end of the rope out of the bag. If you drop the rope bag yell "rope" and wait a few seconds to clear the area. It is better to only use as much of the rope as needed.

Rope Care:

• Never step on a rope; it grinds abrasive dirt into the sheath which could potentially damage the fibers.
• Protect the rope from sharp edges or abrasive surfaces.
• Protect the rope from heat, flame, and chemicals.
• Protect the rope from unnecessary shock loading. If the rope is shock loaded; inspect the rope or better yet discard from life safety use.
• Protect the rope from contacting other fabrics (such as nylon against nylon). Friction between ropes and other fabrics can cause the rope to melt, burn, or fail.
• Wash, dry, and inspect the ropes after each use.

Washing Ropes

Wash rope in a solution of mild soap and cool water. Rinse several times to removal all soap residue. Never use bleach or a stiff scrub brush on a rope as it damages the fiber and sheath.

Drying Rope

Air dry in a shaded area. Ultra-violet rays can damage rope.

Inspecting Rope

• Slowly run ropes, webbing and accessory cord through your hands to inspect it.
• Feel the fabric inch by inch being alert for discoloration, depressions, core slippage, abrasions, flat spots, and hard spots.
• One way to confirm fiber breakage and retraction is to stretch out the rope and tension it with the equivalent of a one person load.

Common visual indications are:

• sheath worn through the core.
• core fibers popping out of the sheath. Discoloration.
• Shiny markings.

Log all rope use in your rope log.

Remember to use edge protection every time you use ropes. It is also recommended that if you use rope for a rescue, you should inspect and or replace the rope.

Howard Hoff
DART Technical Rescue Team