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The type, structure, raw material and production process of wire rope depend on its application. General steel wire ropes use carbon steel wires with a diameter of 0.1 to 6.0 mm and a circular section. When twisting sealed and semi-sealed wire ropes, Z-shaped and other special-shaped wires are used. The types of wire ropes are divided according to their purposes: there are wire ropes for suspension bridges and mine wire ropes, aerial cableway use wire ropes, traction wire ropes for transmission devices, wire ropes for elevators, wire ropes for bundling and dragging goods, etc. The variety of wire ropes is increasing, and the structure is increasingly complex. In addition to various coated steel wires, stainless steel wires and bimetallic steel wires are also used. In order to ensure the safety and reliability of the use of steel wire ropes, the steel wire ropes are required to have sufficient strength, good flexibility, compactness of twisting, compression resistance, wear resistance, corrosion resistance and fatigue resistance, among which strength is the most important.
The selection of wire ropes should meet the following requirements:
① Generally, the left and right intertwined wire rope is used so that it will not twist and loosen when lifting the goods, and it must have a quality certificate.
②The steel wire rope with asbestos core should be used for lifting and transporting hot or molten metal wire rope.
③The hoisting and luffing mechanism shall not use braided and jointing in length steel wire ropes. When other wire ropes need to be jointed, it must be ensured that the connection strength of the joint is not less than 90% of the breaking force of the wire rope, and it must not pass through the pulley into the drum.
When the wire rope meets one of the following conditions, it should be scrapped:
① The number of broken wires of the wire rope in one twist pitch exceeds 10% of the total number of wires.
②The wear amount of the outer steel wire exceeds 40% of the original diameter. When it is insufficient, it can be scrapped according to the number of broken wires after dismantling.
③ The number of broken wires of wire ropes for lifting hot metal or dangerous goods reaches half of the scrapped broken wires for general lifting equipment wire ropes, including the reduction of surface corrosion of steel wires.
④ The diameter of the wire rope is reduced by 7%.
⑤ The whole strand of the wire rope is broken or the fiber core is exposed, the partial outer steel wire is stretched out in a cage-like or hard knot state.
When replacing an old wire rope, the qualified original design model, diameter, nominal tensile strength and wire rope must be used. If only the same diameter is satisfied and other requirements are lower than the original specifications, the service life of the wire rope will inevitably be affected.
It is forbidden to use wire ropes without qualified certificates. If the diameter of the wire rope does not conform to the original design, it must first ensure that the total breaking force is equal to the original design, and then the difference of the diameter should not exceed: 1mm when the original diameter is less than 20mm and 1.5mm when the original diameter is over 20mm. Too much thick than its original will cause the wire rope to rub against each other when it is wound on the drum and increase the wear and tear.
When replacing or winding the wire rope, please be careful not to let the wire rope knot. Practice has proved that the knotted wire rope is most likely to wear and break during use. It is forbidden to connect two steel wire ropes in the hoisting mechanism.