WIRE ROPE SPECIALTY GUIDELINES
Inspection Guidelines for Specialty Rope
Plastic-infused Rope |
Compacted Rope |
|
Plastic-infused rope was developed to provide better fatigue, abrasion and crushing resistance derived from the cushioning and dampening effect of the plastic. However great the benefits, the plastic becomes at the very least an inconvenience when trying to inspect the wire rope. Because of the plastic coating, some operators choose to forego inspection and run the ropes to failure. Other operators may just visually inspect the plastic coating. Both practices are wrong and carry equally the potential for disaster.
|
Die drawn and swaged ropes fall into the compacted category. Compacting serves several purposes. By flattening the outer wires, metallic area increases allowing for a higher breaking strength as well as improved crushing and abrasion resistance. In addition, the compaction minimizes inter-strand nicking and thereby improves fatigue resistance. In the inspection of compacted rope designs, again it is imperative to follow the basic inspection guidelines and use both visual and actual measuring techniques to determine the remaining life of the rope. In fact, actual measuring techniques are very important when inspecting these ropes. While corrosion is relatively easy to visually determine, diameter reduction may not be due to the compacted rope’s appearance. Therefore the inspector must regularly measure for diameter reduction and closely examine the rope for lay lengthening. Measurements must be recorded and the rope monitored for sudden variations. By and large the most difficult retirement criteria to determine in compacted ropes is wire breaks. These breaks may not protrude from the rope due to the compaction and can be easily overlooked. Because of this, the inspector must slowly and carefully examine the rope, especially in those areas passing over drums and sheaves or in areas where problems existed in previous ropes. A wire break may appear as nothing more than a crack in the wire, and again can be easily overlooked. If the inspector notes a "flaw" in a wire, it should be carefully checked. The inspector should carry some type of magnifying device to determine if a flaw is actually a break. If a break has occurred, thoroughly check the area for additional breaks, both on the crown and in the valleys. Remember, valley breaks in round strand ropes are difficult to determine; compaction only increases the difficulty. The inspector must be slow and methodical in inspecting compacted ropes; a quick check will reveal nothing. Overall, perhaps the most important inspection technique is recognizing the limits of wire rope. While it’s true that compacted and plastic-infused ropes are more durable, neglect and abuse will still quickly end the rope’s life. There is no substitute for proper installation, handling and inspection techniques in combination with a preventative maintenance program. |