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Safety technology of lifting and hoisting steel wire rope

Safety technology of lifting and hoisting steel wire rope
1. the type of wire rope
Wire ropes are classified according to the number of strands of the rope and the number of outer steel wires, and are divided into 14 groups and 16 categories (refer to GB/T8918-2006 "Important Use Wire Rope"). Each type of steel wire can be divided into four types according to the different twisting methods: RHLL, RHOL, LHLL, LHOL. According to the surface treatment of the steel wire, it can be divided into two types: smooth surface and galvanized; according to the rope core, it can be divided into two types: fiber core and steel wire core.
2. Specifications and parameters of wire rope
In general lifting operations, steel wire ropes of 6×7, 6×19, 6×37, 35W×7 and other specifications are commonly used in GB/T8918-2006 "Wire Ropes for Important Purposes".
When the end of the wire rope is braided and fixed, according to the requirements of JGJ196-2010 "Safety Technical Specifications for Installation, Use and Disassembly of Tower Cranes in Construction", the length of the braided part shall not be less than 20 times the diameter of the wire rope, and shall not be less than 300mm. The connecting rope strands should be tightened, the protruding part should be smooth and flat, and an appropriate length should be reserved at the end of the plug connection, which should be fastened with metal wires. Regulations" LD48 requirements. If it is plugged by other methods, it should be ensured that the plug connection strength is not less than 75% of the minimum breaking force of the rope.
When using rope clips, the minimum number of wire rope sling rope clips should meet the following requirements:

Rope clip specifications (nominal diameter of wire rope)

Dr(mm)

Minimum number of wire rope clamps (group)

≦18

3

18～26

4

26～36

5

36～44

6

44～60

7


The wire rope sling must be made of the whole wire rope without joints in the middle. Ring slings should only have one joint allowed. When two or more points are used for hoisting, the number of slings should be consistent with the number of hoisting points, and the materials, structural dimensions, fixed connection at the end of the cable eye, end fittings and other properties of each sling should be the same. Wire ropes are strictly prohibited to use knots to tie hanging objects. When the bending radius of the sling is less than twice the nominal diameter of the wire rope, the shackle should be used to connect the sling to the lifting point.
3. Scrap standard of wire rope
The scrapping of wire ropes shall comply with the provisions of the current national standard "Crane wire rope maintenance, maintenance, installation, inspection and scrapping" GB/T5972-2009. The damage of the steel wire rope is caused by the comprehensive accumulation of various factors. It must be carefully checked before use to make a correct judgment. The safety level of the wire rope is determined by the following items:
(1) The nature and quantity of broken wires
The broken wires of the 6-strand steel wire rope mainly occur on the surface, and the total number of broken wires on the surface of the steel wire rope exceeds ("Crane Wire Rope Maintenance, Maintenance, Installation, Inspection and Scrap" Table 1 Control standard for the number of broken wires of round-strand wire ropes working on steel pulleys) The specified value shall be discarded. When lifting molten or red hot metals, acid solutions, explosives, flammables and toxic items, the number of broken wires on the watch should be reduced by half.
(2) Local aggregation of broken wires
If the broken wires are close together to form a local cluster, the wire rope should be scrapped. If the broken wires are gathered within the length range of less than 6d (d is the diameter of the wire rope) or concentrated in any one strand, even if the number of broken wires is smaller than the value listed in Table 1, the wire rope should be scrapped.
(3) The increase rate of broken wires
The increase rate of broken wires refers to the occurrence of broken wires after the wire rope has been used for a period of time. As the number of broken wires gradually increases, the time interval becomes shorter and shorter. In this case, in order to determine the increase rate of broken wires, it should be carefully checked and recorded, and the "rules" should be found out to determine the scrap date of the wire rope.
(4) Broken strands
When the whole strand breaks, it should be scrapped immediately.
(5) Reduced rope diameter due to damage to the rope core
When the fiber core of the wire rope is damaged or the steel core (or the inner strands in the multi-layer structure) is broken and the rope diameter is significantly reduced, the wire rope should be scrapped.
(6) Reduced elasticity
The reduction of the elasticity of the steel wire rope is difficult to detect. Generally, the reduction of elasticity is accompanied by the following phenomena:
①The diameter of the wire rope is reduced;
② Wire rope lay length elongation;
③ The gap between the wires and between the strands is reduced;
④ The wire rope is obviously not easy to bend and the diameter is reduced much faster than that caused by the wear of the wire. The reduction of the elasticity of the wire rope leads to sudden breakage under the action of dynamic load. If the elasticity is found to be reduced, the wire rope should be scrapped immediately.
(7) External and internal wear
Internal wear of wire ropes is caused by friction between the strands and the wires in the rope. The external wear of the wire rope is caused by the contact friction with the pulley and the drum rope groove under the action of pressure. Insufficient lubrication and uncleanliness will aggravate wear. When the outer steel wire wears up to 40% of its diameter, the steel wire rope should be scrapped. When the wire rope diameter is reduced by 7% or more from the nominal diameter, it should also be scrapped if no broken wire is found.
(8) External and internal corrosion
Due to corrosion, deep pits appear on the surface of the wire rope, and there is slack between the wires, which should be scrapped.
(9) Deformation
The deformation of the wire rope is divided from the appearance, mainly in the following categories:
①Wave deformation. When wavy deformation occurs, if the length of the wire rope is not greater than 25d, if it is more than 4/3d, the wire rope should be scrapped. Among them: d---nominal diameter of steel wire rope;
d1---The diameter of the envelope after deformation of the wire rope.
② cage distortion. Cage-distorted wire ropes should be discarded immediately.
③Extrusion of rope strands. Wire ropes extruded from the strands should be discarded immediately.
④ Steel wire extrusion. Wire ropes with serious wire extrusion should be scrapped.
⑤ The rope diameter increases locally. Wire ropes with locally increased rope diameters should be scrapped.
⑥ kink. Severely kinked wire ropes should be discarded immediately.
⑦The rope diameter is locally reduced. Wire ropes with locally severely reduced rope diameters should be scrapped.
⑧ Parts are squashed. The wire rope caused by the mechanical accident is partially crushed, and the wire rope should be scrapped in serious cases.
⑨ Bend. Wire ropes that are bent should be scrapped.
⑩Damage due to heat or arc. The steel wire rope should be scrapped when it has undergone special thermal action and has a recognizable color on its surface.
4. Precautions when using wire rope
(1) Before the wire rope enters the site, the project material personnel and the electromechanical administrator shall jointly check the wire rope. The acceptance standard shall refer to "Crane Wire Rope Maintenance, Maintenance, Installation, Inspection and Scrap" GB/T5972-2009 and JGJ196-2010 "Construction Construction" The requirements for the braided length of steel wire ropes in the Safety Technical Specifications for Installation, Use and Disassembly of Tower Cranes.
(2) The project janitor (or crew leader) shall be responsible for safety education, technical disclosure and training assessment for hoisting commanders and slingers to ensure that they are proficient in the maintenance, use and scrapping standards of wire ropes and the safe operation procedures for hoisting operations , with the corresponding professional skills.
(3) The project department should make a regular wire rope rack, indicating the size and rated load of each wire rope.
(4) The project material team is responsible for establishing wire rope files. The inspected wire ropes are marked with color rings. When replacing the wire ropes, the system of handing over the old ropes and getting the new ones shall be implemented, and the old ropes shall be handled uniformly by the project.
(5) The hoisting commander must inspect the slings and rigging before instructing the hoisting and construction. The inspection standards refer to JGJ196-2010 "Safety Technical Specifications for Installation, Use and Disassembly of Tower Cranes in Construction" and "Lifting Machinery Spreaders" It can be put into use only after meeting the requirements of the "Safety Regulations for Rigging".
(6) The hoisting commander should correctly select the hoisting tool and hoisting method according to the hoisting object, select the binding point, the binding should be firm, and the sharp corners should be padded with soft objects.
(7) Production managers at all levels of the project, large equipment crew leaders and tower crane captains should conduct special inspections on spreaders and riggings every week. Tower crane drivers and tower crane commanders should inspect the wire ropes before shifts to detect damage in time. In the case of deformation, the wire rope should be scrapped immediately if it meets the scrapping standard of the wire rope.
(8) When the steel wire rope is used as a sling, its safety factor shall not be less than 6 times.

(9) It is strictly forbidden to use the new wire rope directly under high-speed and heavy-load conditions, but run it for a period of time under low-speed and medium-load conditions to adapt the new rope to the state of use, and then gradually increase the speed of the wire rope and increase the lifting load, that is, New wire ropes must go through an initial break-in stage.
(10) It is strictly forbidden to skip the wire rope, otherwise the wire rope will have extrusion deformation, kink, broken wire and broken strand, which will seriously shorten the service life of the wire rope.
(11) It is strictly forbidden for the wire rope to rub against other objects when running at high speed.
(12) It is strictly forbidden to wind the wire rope in a random manner. When the wire rope is wound on the drum, it should be arranged as neatly as possible. If it is scattered and wound, the wire rope will also be damaged due to mutual extrusion during operation, resulting in early wire breakage, which directly affects the service life of the wire rope.
(13) It is strictly forbidden to overload the wire rope.
(14) It is strictly forbidden for the wire rope to be subjected to severe shock and vibration. During the use of the wire rope, if the running speed changes rapidly and frequently, it will cause shock load. Although each impact is only loaded instantaneously, it contains great harm. When the impact load exceeds the allowable working stress of the wire rope, the rope breakage will occur.
(15) The steel wire rope should be kept free of water as much as possible during use, and should not pass through stagnant water and wet sand. Wire ropes should be used as dry as possible. Galvanized steel wire rope is recommended for rust-prone conditions.
(16) After the wire rope is used, use a wire brush to remove the rust and dirt on it. Apply anti-rust oil to the wire rope in use at least once a month for the entire length of the rope, and store it in a clean place according to the specifications.
(17) Wire ropes stored in the open air should be raised below and covered with a rain cloth cover.

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