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SERVICES
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INSPECTIONOne 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 nor 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 fiber ropes the amount of strength loss due to abrasion and/or flexing is directly related to the amount of broken fiber 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.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 fiber 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 fibers. When either is worn the rope is obviously weakened. Open the strands and look for powdered fiber which is one sign of internal wear. Estimate the internal wear to estimate total fiber abrasion. If total fiber loss is20%, then it is safe to assume that the rope has lost 20% of its strength as a result of abrasion. Cut Strands Content Coming Soon. Melting Content Coming Soon. 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. High temperatures can be achieved when surging rope on a capstan, checking ropes on a cable, running over stuck or non-rolling sheaves or rollers. Each rope's construction and fiber type ill 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 fiber 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 fibers can buildup 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 an exhaust muffler or any other hot object. The strength of a used rope can be determined by testing but 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. Remember, you almost always get what you pay for in the form of performance and reliability. Volume Reduction Content Coming Soon. Compression Content Coming Soon. 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 Inconsistency in Texture and Stiffness Can indicate excessive dirt or grit embedded in the rope or shock load damage and is usually reason to replace the rope. Glossy or Glazed Areas Glossy or glazed areas are signs of heat damage with more strength loss than the amount of melted fiber indicates. fibers adjacent to the melted areas are probably damaged from excessive heat even though they appear normal. It is reasonable to assume that the melted fiber has damaged an equal amount of adjacent unmelted fiber. Discoloration With use, all ropes get dirty. Be on the lookout for areas of discoloration which could be caused by chemical contamination. Determine the cause of the discoloration and replace the rope if it is brittle or stiff. |
REPAIR AND RECERTIFICATIONCND Rope has a full repair facility. Winch lines, tow ropes, nets, ladders and tag lines can be inspected, repaired and if required, recertified. We also inspect, repair and recertify chain, wire and web slings. All products sent for repair are closely inspected to determine if downgrading is necessary.For more information regarding repairs and recertification please contact our sales department. |
ROPE CONSTRUCTIONEssentially, the characteristics of rope are a function of the fiber, or raw material, from which it is made, and the way those fibers are formed together, or its construction. Broadly speaking, there are two common methods of construction – twisting and braiding, and each result in rope with very different characteristics. It is important to select the correct rope construction for an application in order to optimize performance and safety.Twisted Ropes Twisted ropes are made by combining bundles of individual yarns by twisting them together to form 3 strands which are then themselves twisted together to form the rope. As the successive bundles of fiber are twisted together, the direction of the twisting is alternated such that the torque resulting from twisting in one direction is balanced against the torque resulting from twisting in the other direction, thereby counteracting the tendency of the three strands to unwind. These ropes are recognized by their spiral shape. Some larger ropes may be made up of more than three strands. Good construction design, and balanced twisting, will spread load evenly over all three strands. Twisted ropes are typically less expensive than braided ropes because the manufacturing process is faster. They are easily spliced. Despite the balancing of torque achieved by alternating the direction of twist, they do nevertheless retain some torque, and do have the tendency to hockle and rotate under load. Braided Ropes Braided ropes come in many variations and braiding patterns, but always consist of bundles of fiber which are formed into strands which are than interlaced or woven together by passing each strand over and under other strands. This structure creates a round rope as apposed to the spiral shape of twisted ropes. This makes them well suited for use with hardware such as pulleys, winches, and rope grabs. These ropes are inherently relatively torque free and non-rotating. Braiding is a slower process, so ropes made in this fashion tend to be more costly than twisted ropes. There are a number of variables, which the manufacturer can utilize to alter characteristics such as strength, elongation, flexibility, and durability. The following will describe the main characteristics of the common types of braided ropes. Solid Braid Ropes Solid braid ropes are sometimes referred to as “sash cord” because this pattern was used in sash windows. It is formed by braiding 12 or 18 strands in a reasonably complicated pattern with all the strands rotating in the same direction on the braider. The individual stitches are oriented in the same direction as the rope. The center may contain a filler core. These ropes maintain their round shape well and therefore work exceptionally well in pulleys and sheaves. They tend to have high elongation and are generally less strong than other forms of construction, and are difficult to splice. Diamond Braid Diamond braid or single braid or hollow braid is formed by having one half the strands rotating in one direction on the braiding machine while the other half rotate in the other direction. Braid is formed as the strands cross alternately over and under each other. This is quite a simple, but efficient, braiding pattern, although, the rope tends to flatten quite a bit. Sometimes a filler is put into the core of the rope to keep it rounder and firmer or to build it up to a desired size. This may however affect other characteristics of the rope and is more common on smaller sizes that have less critical applications. Double Braid Double braid is made by braiding a core rope, usually in a simple diamond braid as above, then braiding another rope over it so you can actually have a rope within a rope. The inner rope and outer rope are designed to share the load fairly evenly. These ropes are generally very flexible and strong and pleasant to handle. It is fairly easy to eye splice these ropes. Double braid ropes are very popular in boating and marine applications. Caution must be exercise, however, where double braid ropes are run over pulleys, through hardware or in any situation where the outer rope may slide along on the inner rope and bunch up. This condition, often called “milking” will cause dramatic loss of strength by causing the entire load to go onto the inner rope, because the sheath is bunched up and therefore not under the same tension as the inner rope. Kernmantle Ropes Kernmantle ropes are made by braiding a cover (mantle) over a core (kern). The core may be made of filaments of fibre lying essentially parallel inside the rope or, it may be twisted into little bundles much like miniature twisted ropes. In some cases it is made of small braided ropes. Kernmantle ropes are always designed, however, so that the inner core is taking most of the load (often all of the load) and the outer cover serves primarily to protect the inner core. If “milking” occurs on these ropes therefore, it does not affect strength very much because the rope is designed such that the inner core is the loadbearing member. These ropes are very strong and durable, and can be made to have very low elongation. By having the load bearing part of the rope inside the protective outer cover, it is well protected from abrasive action, dirt, and ultra violet rays, which are harmful to all ropes. All other forms of ropes have the load bearing fibres exposed, thereby resulting in more rapid deterioration. Kernmantle ropes cannot be spliced, although they can be terminated very efficiently with swaged fittings. Kernmantle ropes are often categorized as “static”, meaning having little stretch or “dynamic”, meaning they have more stretch. These terms are, of course, relative and vague since all ropes have some stretch. Kernmantle ropes have their origins in mountain climbing where the higher stretch versions are used to absorb energy if the climber falls. The low stretch versions are used in rappelling, rescue, and in most industrial safety applications where they are favoured because of their inherent toughness and the efficiency with which rope grabs work on them. They are generally more expensive than other ropes because they are normally made from only the finest fibres and with very stringent requirements for care in manufacturing because they are used so extensively in life critical applications. Most of the higher initial cost however is offset by their durability and because one can normally select a smaller kernmantle rope for any given application. Many other types and variations of ropes exist and many other factors should be considered in selecting the right rope for a specific application, and the user is urged to consider his requirements carefully. Fibre type, size, tensile strength, safety factors, elongation, weight, compatibility with hardware, and other factors must be considered. |