Water Well Journal
Issue link: https://read.dmtmag.com/i/629532
Crushed strands: This condition is a result of too many layers of rope wrapped around a drum. There should be no more than two layers of wire rope on the drum, espe- cially if the rope is a type with many small wires (such as 6 × 37). Crushing also occurs by cross winding, which is a result of poor winding procedures when the rope is wound in a pile in the middle of a drum. Corrosion: This problem is difficult to evaluate and is also much more serious than normal wear. Corrosion will often start inside the rope before it shows on the outside. A lack of lubrication is usually the cause. Wire pitting or severe rusting should be cause for immediate replacement. Kinks: Kinks are permanent distortions. After a wire rope is kinked, it is impossible to straighten the rope enough to return it to its original strength. If a rope cannot be un- kinked by hand, it should be removed from service. Electric arc: Wire rope that has been inadvertently (or purposely) used as a ground in welding or has been in contact with a live power line will have fused or annealed wires, and must be removed from service. Metal fatigue: This is usually caused by bending stress from repeated passes over sheaves, or from vibration such as crane pendants. Fatigue fractures can be external or internal. A larger sheave or drum size, or using a more flexible rope, may increase the rope life. Diameter reduction: Any noticeable reduction in diameter is a serious deterioration problem. A wire rope is measured across its diameter at its widest point. Diameter reduction could be caused by one fault or a combination of faults. Wire ropes should be replaced when the reduction in diameter is more than 5% from the nominal diameter. Wire rope stretch: Any new wire rope will stretch when the initial load is applied. After the initial stretch and a slight stretching over time during normal wear, the rope will begin to stretch at a quicker rate, which means it is approaching time for replacement. Bird caging: This is a torsional imbalance, which is a result of mistreatment such as pulling rope through tight sheaves, being wound on too small a drum, or sudden stops. Scrubbing: This is a wearing or displacement of wires resulting from rubbing against something. Protruding core: Any rope damage resulting in a spreading of the strands with the core bulging out means the rope should be replaced. A wire rope is lubricated during the manufacturing process. This provides the rope with protection for a reasonable time if stored under proper conditions. When the wire rope is in serv- ice, the initial lubrication will not be enough to last the life- time of the rope. Therefore, it is usually necessary to apply a lubricant to a wire rope under working conditions. A light mineral oil can be used for lubrication. Never use old crankcase oil. Fiber Rope Fiber ropes are preferred for some rigging applications because they are more pliant. However, they should be used only on light loads and must not be used on objects that have sharp edges capable of cutting the rope. Fiber ropes should also not be used where they will be exposed to high tempera- tures, severe abrasion, or acids. The choice of rope depends on its application. Manila is a natural fiber and has relatively high elasticity, strength, and resistance to wear and deterioration. Manila rope is generally the most common natural fiber rope used because of its qual- ity and relative strength. The principal synthetic fiber used for rope is nylon, which has a tensile strength nearly three times that of manila. The advantages of nylon rope are it is waterproof and has the abil- ity to stretch, absorb shocks, and resume its normal length. Nylon also has better resistance against abrasion, rot, decay, and fungus growth as compared to natural fibers. The strength and useful life of fiber rope is shortened con- siderably by improper care. To prolong the life and strength of the rope: • Make sure the rope is kept dry. Store in a cool, dry place to reduce the chances of mildew and rotting. • Coil rope on a spool or hang it from pegs in a way that will allow the circulation of air. • Avoid dragging rope through sand or dirt or pulling over sharp edges. Sand or grit between the fibers of the rope cuts the fibers and reduces its strength. • Slacken taut lines before they are exposed to rain or damp- ness because a wet rope shrinks and may break. • Thaw a frozen rope completely before using it; otherwise, the frozen fibers will break as they resist bending. • Avoid exposing rope to excessive heat and chemical fumes. Heat or boiling water decreases rope strength by 20%. The outside appearance of fiber rope is not a good indica- tion of its internal condition. The rope softens with use. Dampness, heavy strain, fraying and breaking of strands, and chafing on rough edges all weaken the rope considerably. Overloading a rope may cause it to break. For this reason, fiber ropes should be inspected at regular intervals to deter- mine their condition. Untwist the strands slightly to open the rope so the inside can be examined. Mildewed rope has a musty odor and the inner fibers of the strands have a dark, stained appearance. Broken strands or broken yarns ordinarily are easy to identify. Dirt and sawdust- like material inside the rope, caused by chafing, indicate dam- age. In rope having a central core, the core should not break Twitter @WaterWellJournl SAFETY continues on page 36 DACUM Codes To help meet your professional needs, this article covers skills and competencies found in DACUM charts for drillers and pump installers. DO refers to the drilling chart. The letter and number immediately following is the skill on the chart covered by the article. This article covers: DOB-3, DOD-1, DOD-6, DOE-1, DOK-10 More information on DACUM and the charts are available at www.NGWA.org. WWJ February 2016 35