Lecture on Crane Operation Safety 16 (End)

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Safety of Crane Steel Cables (IV) – Fixing of Steel Cables. The ends of steel cables generally need to be connected to other components or fixed to other structures of the crane; fixing the end of the cable is an important aspect related to its safety. The fixing requirements for steel wire ropes must meet two conditions: first, the connection or fixing point must satisfy the corresponding strength and safety requirements; second, the method of connection or fixing must be appropriate for the intended use. There are various methods for securing steel cables, and the appropriate method is chosen based on different usage conditions and requirements. (1) Knotted connection: The knotted method involves bending the end of the rope into a loop; a heart-shaped ring is then placed inside this loop, so that the end of the rope (the shorter end) merges with the main part of the rope at the tip of the heart-shaped ring. A steel wire is used to secure the merged sections of the rope, and the end of the steel wire rope is fixed due to the friction between the two merged rope segments. The safety requirement is that the braid length should be more than 15 times the diameter of the steel wire rope, and should not be less than 300 millimeters ； The connection strength shall be not less than 75% of the breaking tension of the steel wire rope. (2) Clasp fixation: Due to its simplicity and reliability, as well as the fact that clamps can be removed and replaced, this method is widely used. When using cable clamps for fixation, attention should be paid to the number of clamps, the spacing between them, their orientation, and the strength of the area being secured. The strength at the fixed connection must not be less than 85% of the breaking tension of the wire rope. The number of cable clamps increases as the diameter of the steel wire rope increases. For example, if the diameter of the steel wire rope is 16 millimeters, 3 cable clamps are sufficient ； When the diameter of the steel wire rope is 45 millimeters, more than 6 rope clamps are required to meet the strength requirements at the fixing point. The rope clip plate should be on the longer side of the steel wire rope, while the U-shaped component should be at the shorter end; it must not be reversed or placed in the opposite order (see figure below). The spacing between rope clamps should not be less than 6 times the diameter of the steel wire rope. @Y01.gif (3) Wedge and wedge sleeve connection: One end of the wire rope is wrapped around the wedge, and the wedge’s locking action within the steel sleeve is used to secure the wire rope; the greater the force applied, the tighter the inclined surface of the wedge inside the sleeve presses on the wire rope. The strength at the fixation point is approximately 75% to 85% of the rope’s own strength. (4) Alloy sleeve casting method: The end of the wire rope passes through a conical sleeve, the wires are loosened, the wire at the head is bent into a small hook, and then molten metal is poured in to allow it to solidify. The strength of the fixing point is roughly the same as that of the wire rope itself. Use and maintenance of steel wire ropes: Use steel wire rope products that have passed inspection to ensure that their mechanical properties and specifications meet the design requirements. If necessary, stress calculations should be performed before use to ensure a sufficient safety factor. The maintenance of steel wire ropes should be determined based on the purpose of the heavy machinery, the working environment, and the type of steel wire rope. Before putting the wire rope on a lifting machine into use, it must be ensured that all devices related to the operation of the wire rope are installed and functioning properly. Appropriate protection should be provided for those parts that may come into friction with the wire rope mechanically. When drawing the steel wire rope from a reel or spool, it should be pulled in a clean area, and measures should be taken to prevent the rope from bending, kinking, or getting contaminated by debris, as well as to avoid damage or corrosion caused by external factors that could reduce its performance. During use, avoid subjecting the two steel cables to stress when they are crossed or overlapping; design the winding system properly to minimize the number of times the cables bend and to prevent reverse bending, thus avoiding knots, twisting, excessive bending, and abrasion. Wire ropes should be subject to enhanced inspection and proper recording, so that they can be replaced in a timely manner based on the relevant information. Under no circumstances should scrapped steel wire ropes be used. The newly replaced wire rope should generally be of the same type and specification as the one originally designed and installed. If different types of wire ropes are used, it is necessary to ensure that the new wire rope has performance no lower than that of the originally selected one, and that it fits well with the grooves on the drum and pulleys. Steel ropes should be cleaned regularly and coated with lubricant or grease, especially in those areas that are bent as they pass over pulleys. The type of lubricant applied should be suitable for the steel wire rope. To prevent damage to the spare steel wire rope, it should be stored in a clean, well-ventilated, and dry warehouse, and the markings indicating the technical parameters of the rope must be properly maintained.