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    Yale Cordage: Index of Engineering

    Yale Cordage: Index of Engineering

    INDEX OF ENGINEERING

    Selecting a Rope: Always consult the manufacturer before using rope when personal safety or possible damage to property is involved. Make sure the rope is adequate for the job. Do not use rope that is too small or the wrong type.


    * See specific product pages for information
    ** We recommend you consider all ropes as conductive when in use.

    YALE COATINGS

    Yale Maxijacket is a spliceable urethane coating, which is applied after the rope is braided. Maxijacket firms the rope, increases snag resistance, improves abrasion resistance and helps keep contaminants from entering the rope. Unlimited lengths may be processed at the mill through automatic coaters, which apply and control the polymer penetration, curing the coating at precisely controlled temperatures. Maxijacket maintains rope splicing characteristics and is available in a range of colors. The colors are useful to track time in service, to color code for load rating, for phase identification or to make the rope more visible. Maxijacket coating is also available in clear or white.

    INDEX OF ENGINEERING (cont..)

    USAGE

    Handling: Never stand in line with a rope under tension.
    If a rope fails it can recoil with lethal force. Synthetic rope has higher recoil tendencies than natural fiber rope. Reverse rope ends regularly, which permits even wearing and ensures a longer, useful life. When using tackle or slings, apply a steady, even pull, to get full rope strength.

     

    Overloading and Use of Work Load Limits

    Because of the wide range of uses for rope, exposure to factors affecting rope behavior and the degree of risk to life and property involved, it is impossible to make blanket recommendations about Work Load Limits. However, to provide guidelines, Work Load Limits are calculated for rope in good condition with appropriate splices, in non-critical applications and under normal service conditions.


    A higher Work Load Limit may be selected only with expert knowledge of conditions and professional estimate of risk; if the rope has not been subjected to dynamic loading or other excessive use; if the rope has been inspected and found to be in good condition and is to be used in the recommended manner; and if the application does not involve elevated dynamic loading (see explanation below) such as sudden drops, snubs, or pickups. For all such applications and for applications involving more serious exposure conditions or for recommendations on special applications, consult the manufacturer. Many uses of rope involve serious risk of injury to persons or damage to valuable property. Workers should never be under a suspended load. An equally dangerous situation occurs if persons are in line with a rope under tension; should the rope fail, it may recoil with lethal force. Persons should be warned against the serious danger of standing in line with any rope under tension.


    In all cases where such risks are present, or there is any question about the loads involved or the conditions of use, the Work Load Limit should be substantially reduced and the rope properly inspected.
    Minimum Break Strength is based upon test data of new, unused rope and is a value not greater than two standard deviations below the mean.


    Dynamic Loading Voids Work Load Limits

    Normal Work Load Limits are not applicable when rope is subject to significant dynamic loading. Instantaneous changes in load up or down, in excess of 10% of the line’s rated Work Load Limit constitutes hazardous shock load and would void normal Work Load Limits. Whenever a load is picked up, stopped or swung, there is an increased force due to such dynamic loading. The more rapidly action occurs, the greater the increase will be. In extreme cases, the force put on the rope may be two, three or even more times the normal Work Load involved and may result in the rope breaking. Examples could be picking up a tow on the slack line or using a rope to stop a falling object. Therefore, in all such applications: towing lines, lifelines, safety lines, climbing ropes, etc. Work Load Limits as given DO NOT APPLY.

     

    COMPUTING ENERGY ABSORPTION REQUIREMENTS

    Users should be aware that dynamic forces are greater on a low-elongation, high modulus, aramid rope and less on a higher elongation nylon rope. Dynamic forces are greater on a shorter rope than on a longer one. Work Load limits contain provision for very modest dynamic loading. This means, however, that when the Work Load Limit has been used to select a rope, the load must be handled slowly and smoothly to minimize effect and avoid exceeding provision for them.

     

    Example: A load of 3,500 Lbs. is being lowered using 5/8 in. diameter, Double Esterlon, which has a maximum recommended Work Load Limit of 3,060 Lbs. With 15 feet of line in tension, the line accidentally slips, dropping the load one foot before arresting the fall.
    Questions: How much energy did the rope have to absorb? What was the maximum load on the rope? Has the rope been overloaded or damaged?
    Data:
    Work done (Ft. Lbs.) – (Weight)(Length of Fall) = 3,500 Ft. Lbs.



    Assuming Double Esterlon has a working energy absorption capacity of 291 ft. Lbs. per pound of rope and a weight of 13.7 Lbs. per 100 ft., or .137 Lbs./ft.
    Rated Maximum Working Energy Absorption Capacity of:
    16 ft. of 5/8” Double Esterlon =
    (16 ft.)(.137 Lbs./Ft.)(291 Ft. Lbs./Lbs.) = 638 Ft. Lbs.
    In this example:
    2.19 Lbs. of rope (16 ft. x .137 Lbs./ft.) in use must absorb:
    3,500 Ft. Lbs. or 3,500 ÷ 2.19 Lbs. =1,596 Ft. Lbs./Lbs. of rope.

     

    In this example the maximum working energy absorption capacity has been exceeded by nearly six (6) times. The effect is to drive the maximum load the rope encounters until it arrests the load or breaks.
    Ultimate energy absorption of 5/8” x 16 Ft. Double Esterlon = (16 Ft.)(.137Lbs./Ft.)(7,711 Ft. Lbs./Lb.)=16,902 Lbs.


    Any dynamic load beyond this would break the line. There is a linear relationship between the weight of the rope in tension versus rope energy absorption capability. In the above example, some degree of the rope integrity has been compromised and prudent safety practices would dictate for discarding the line.
    A short film on this subject may be viewed at
    www.yalecordage.com/videos

     

    Computing Weight in Seawater:

    Sling Inspection & Storage

    ABRASION

    Avoid all abrasive conditions for rope. All rope will be damaged severely if subjected to rough or damaging surfaces or edges. Chocks, bits, winches, drums and other surfaces must be kept in good condition and free of burrs and rust. Pulleys must be free to rotate and should be of proper size to avoid excessive wear. Clamps and similar devices will damage and weaken the rope and should be used with extreme caution. Do not drag rope over the ground. Dirt and grit picked up by rope can work into the strands cutting the inside fibers. Cut fibers reduce rope strength.


    CHEMICALS

    Avoid exposing rope to chemicals. Rope is subject to damage by chemicals. Consult the manufacturer for recommendations when a rope will be used where chemical exposure (either fumes or actual contact) can occur.


    TEMPERATURE

    Temperature has an effect on tensile strength. The Tensile Strength Charts apply to ropes tested at normal room temperature (70°F). Ropes have lower tensile strength at higher temperatures; tensile strength loss is 30% or greater at the boiling point of water (212°F) and tensile strength continues lowering down to zero strength as temperature increases. Continued exposure at elevated temperatures can melt and part synthetic ropes or cause permanent damage.

    DIELECTRIC STRENGTH

    Dielectric strengths are shown on page 403 as a guideline to assist you in comparing different fibers and constructions. We recommend that you consider all ropes, regardless of their initial, new rated dielectric strength as conductive when in use. A short video is available for viewing at www.yalecordage.com


    SPLICING

    Join rope by splicing. Use Yale’s recommended splices for maximum efficiency. The strengths shown are for spliced assemblies. Other terminations can be used, but the actual strength loss for particular ropes and constructions should be determined and never assumed.


    KNOTS

    Knots and abrupt bends significantly decrease rope strength, lowering Work Load Limits.


    STORAGE AND CARE

    All rope should be stored clean, dry, out of direct sunlight and away from extreme heat. Some synthetic rope (particularly polypropylene, polyethylene, and aramid) may be weakened severely by prolonged exposure to ultraviolet (UV) rays unless specifically stabilized and/or pigmented to increase their UV resistance. UV degradation is indicated by discoloration and the presence of splinters and slivers on the surface of the rope.

    INSPECTION

    Avoid using rope that shows signs of aging and wear. If in doubt, destroy the used rope. No type of visual inspection can accurately determine actual residual strength. When fibers show wear in any given area, the rope should be re-spliced to eliminate the damaged area, downgraded or replaced.


    Check the line regularly for frayed strands and broken yarns. Pulled strands should be rethreaded into the rope if possible. A pulled strand can snag during a rope usage.
    Both the outer and inner rope fibers contribute to the strength of rope. When either is worn, the rope is compacted or hard, rope strength is reduced. The dielectric strength of rope in this condition also is reduced.

     
    Energy Absorption

    The colorized graphs represent the ability of ropes to absorb energy. Values are expressed in foot-pounds per pound of rope in tension. Green represents rope Work Load Limits.

    Work Load Limits are based on static or moderately dynamic lifting/pulling operations. Instantaneous changes in load, up or down, in excess of 10% of line’s Work Load Limit constitutes hazardous shock loading and would void normal Work Load Limit recommendations. See the engineering information found on page 404 and consult Yale Cordage for guidelines regarding Work Load Limits and safe use of rope. Knots and abrupt bends significantly reduce rope strength and lower Work Load Limits.