Well worth a read, it may save your life.
General Information –
All load numbers given are when the product is new in the factory. The same load numbers do not apply to that bit of chain (whatever) you’ve had for 20 years, they could be very very different and not in a good way.
Shock loads will kill many products here, if not weaken them sometimes by a lot.
Look after most items on this site and they will perform, retain strength and last longer.
Rope Specific Information –
Use rope properly: do not abuse or shock load it. Observe recommended usage factors for bending and work loads. Keep ropes clean and eliminate abrasion whenever possible.
Working Loads
Working loads are for rope in good condition with appropriate splices, in noncritical applications and under normal service conditions. Working loads are based on a percentage of the approximate breaking strength of new and unused rope of current manufacture. For the three-strand, eight strand, twelve-strand and double braid rope products depicted in this manual, when used under normal conditions, the working load percentage is 20% (10% if climbing on it) of published strengths. Normal working loads do not cover dynamic conditions such as shock loads or sustained loads, nor do they cover where life, limb or valuable property are involved. In these cases a lower working load must be used. A higher working load may be selected only with expert knowledge of conditions and professional estimates of risk, if the rope has been inspected and found to be in good condition, and if the rope has not been subject to dynamic loading (such as sudden drops, snubs or pickups), excessive use, elevated temperatures, or extended periods under load.
Normal Working Loads
Normal working loads are not applicable when rope has been subject to dynamic loading. Whenever a load is picked up, stopped, moved or swung there is an increased force due to dynamic loading. The more rapidly or suddenly such actions occur, 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 load involved. Examples could be ropes used as a tow line, picking up a load on a slack line, or using rope to stop a falling object. Dynamic effects are greater on a low elongation rope such as polyester than on a high elongation rope such as nylon, and greater on a short rope than on a long one. Therefore, in all such applications normal working loads as given do not apply.
Dynamic loading
For dynamic loading applications involving severe exposure conditions, or for recommendations on special applications, consult the manufacturer.
Danger to Personnel
Persons should be warned against the serious danger of standing in line with a rope under tension. Should the rope part, it may recoil with considerable force and speed. In all cases where any such risks are present, or where there is any question about the load involved or the condition of use, the working load should be substantially reduced and the rope properly inspected before every use.
Splicing & Knots
Splices should be used instead of knots whenever possible because knots can decrease rope strength up to 50%. When splices are used, always use the manufacturer’s recommended splicing procedures. When knots are used, be sure to take into consideration the knot’s corresponding reduction to the rope strength and adjust your working load accordingly.
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 be guaranteed to accurately and precisely determine the actual residual strength. When the fibers show wear in any given area, the rope should be re-spliced, downgraded, or replaced. Check the line regularly for frayed strands and broken yarns. Pulled strands should be re-threaded into the rope if possible. A pulled strand can snag on a foreign object during rope operation. Both outer and inner rope fibers contribute to the strength of the rope. When either is worn, the rope is naturally weakened. Open the strands of the rope and look for powdered fiber, which is one sign of internal wear. A heavily used rope will often become compacted or hard which indicates reduced strength. The rope should be discarded if this condition exists.
Avoid all Abrasive Conditions
All rope will be severely damaged if subjected to rough surfaces or sharp edges. Chocks, bitts, 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.
Avoid Chemical Exposure
Rope is subject to damage by chemicals. Consult the manufacturer for specific chemical exposure, such as solvents, acids, and alkalis. Consult the manufacturer for recommendations when a rope will be used where chemical exposure (either fumes or actual contact) can occur.
Avoid Overheating
Heat can seriously affect the strength of synthetic ropes. The temperatures at which 50% strength loss can occur are: Polypropylene 250° F, Nylon 350° F, Polyester 350° F. When using rope where the temperature exceeds these levels (or if it is too hot to hold), consult the manufacturer for recommendations as to the size and type of rope for the proposed continuous heat exposure conditions. When using ropes on a capstan or winch, care should be exercised to avoid surging while the capstan or winch head is rotating. The friction from the slippage causes localized overheating which can melt or fuse synthetic fibers, resulting in severe loss of tensile strength.
Storage
All rope should be stored in a clean, dry area, out of direct sunlight, and away from extreme heat. It should be kept off the floor on racks to provide ventilation underneath. Never store on a concrete or dirt floor, and under no circumstances should cordage and acid or alkalis be kept in the same vicinity. Some synthetic rope (in particular polypropylene and polyethylene) may be severely weakened by prolonged exposure to ultraviolet (UV) rays unless specifically stabilized and/or pigmented to increase UV resistance. UV degradation is indicated by discoloration and the presence of splinters and slivers on the surface of the rope.
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.
Chain and Components Specific –
Chain and associated components can be subject to wear, twisting, misuse, overloading, intentional alteration, and corrosion. These and other usage variables may cause a reduction in working load limits. It is, therefore, important to regularly inspect all products to determine their safety prior to continuing their use.
Low and high carbon steel welded and weldless chain and accessories to be used in tension or pull applications are not to be used for lifting or hoisting purposes or when failure is likely to cause damage to property or persons. Jerking, shock loading or acceleration in the rate of application of a load multiplies the stress on the chain very rapidly and should be avoided. Actual applications should determine the size and grade of chain to be used.
Working Load Limits
This is the maximum load in pounds which should ever be applied to chain, even when the chain is new and when the load is uniformly applied in direct tension to a straight untwisted length of chain. The term “working load limit” contains no implication of what load the chain will withstand if any of the above factors are changed.
Proof Test
This is the load which the chain has withstood, in the condition and at the time it left the factory. Under this test, the load has been applied in direct tension to a straight length of chain with a uniform rate of speed on a standard chain testing machine. The sole purpose of this test is to discover defects in the material or manufacture. Every metre of our Maggi Group, CR, MFI, Sefafini and Gunnebo chains are proof tested. We have serious reservations as to if any or all Asian made chain is proof tested and if it is, to what degree, use with extreme caution. Where attachments, such as hooks or rings, are desired for use with chain in sustaining loads, care should be taken to select the attachments of the type and size compatible with the chain with which the attachments are intended to be used.
MOST OF THE CHAIN PRODUCTS SHOWN ON THIS WEB SITE ARE NOT TO BE USED FOR OVERHEAD LIFTING OR HOISTING APPLICATIONS BUT SOME ARE. MAKE SURE YOU USE THE RIGHT CHAIN FOR THE APPLICATION YOU HAVE OR IT MAY JUST KILL YOU OR YOURS. IF IN DOUBT CLICK HERE TO ASK US.
