Cause analysis and treatment method of steel wire rope cracking Posted by : admin / Posted on : Dec 25， 2020

1) Failure phenomenon The crane was newly put into use soon, about 2 months

Time, when the boom makes a luffing and hoisting action, between 40°～60°, that is, at the transition point between the second and third layers on the luffing winch drum, irregularities in the wire rope arrangement will occur, which will cause There are many times of "rope collapse" phenomenon of steel wire rope. The heavier the load of the crane, the more obvious the phenomenon of "rope collapse", which will be accompanied by sound and vibration. If the hoist continues to operate in this state, it will rapidly increase the wear of the wire rope, and there will be safety hazards for hoisting operations. Figure 4 shows the comparison between the normal working state of the wire rope on the winch and the winding state in the staggered "rope collapse" state.

Figure 4 Comparison of the normal work of the winch wire rope and the state of "rope collapsed" in the staggered arrangement

2) Reason analysis

①The reel does not match the newly installed steel wire rope, resulting in a gap smaller than the diameter of the steel wire rope (one round of the reel) on the reel after the first layer of steel wire rope is filled, which will cause irregular rope arrangement;

②After the smooth reel runs for a period of time, the first layer of steel wire rope will be deformed due to pressure for a long time, which will cause the guiding pattern of the wire rope to fail

③The deflection angle between the drum rope and the guide fixed pulley on the top of the A frame is too large;

④The direction of the rope outlet fixed by the pressure plate on the reel is not smooth, which will cause the second layer of rope to be arranged irregularly, or the last 1-2 laps of the second layer of rope will "break rope".

3) Treatment method The deflection angle of all Anti twist wire rope winding systems should not be greater than 4°, and the resistance to rotation of the wire rope should not be greater than 2°. You can reduce the length of the drum or increase the diameter of the drum, and increase the distance between the fixed pulley and the drum. Measures such as the distance to reduce the deflection angle. When the steel wire rope is wound in multiple layers on the winch drum, the skew angle of the steel wire rope at the drum flange should be greater than 0.5° to avoid the steel wire rope accumulation [1]. It is confirmed on site that the selection of the wire rope matches the winch drum, and the measured deflection angles are all within the design allowable range. By adding an arc-shaped guide strip that fits the diameter of the drum to the fixed rope outlet of the pressure plate, the length is 15 cm, the disorder of the rope arrangement and the problem of "rope collapse" are significantly improved. After using for a period of time, there are still slight irregularities in the rope arrangement. According to the site conditions, in conjunction with the rope outlet guide, a guide baffle with a length of 4 cm×6 cm on the outer side of the drum is added to make the wire rope " The problem of "corrupted rope" has been clearly resolved.

The guide strip is aimed at the S-shaped failure of the rope arranging caused by the defects of the pressure plate, the welding seam and the rope groove at the rope outlet of the drum, which causes the rope arranging to be staggered or "cracked" when the rope on the drum is arranged to the last lap of the second layer . At this time, by adding a guide bar at the initial rope exit of the reel, the order of the wire rope at the rope exit can be adjusted. The arc of the guide bar matches the diameter of the drum, and the maximum length is not recommended to exceed 1/4 of the circumference of the drum diameter. The cross-section of the guide bar is circular, and the maximum diameter does not exceed the diameter of the wire rope, and the diameter gradually shrinks.

Guide baffle The wire rope on the reel is staggered or the "rope collapsed" fault is more serious. When the problem cannot be completely solved by the guide bar, a guide baffle can be added to the inner wall of the reel according to the rope gap to solve the problem. The guide baffle can be divided into block and multi-piece circular ring. The inner arc surface diameter D matches the drum diameter, and the radial effective thickness H should be an integral multiple of the wire rope diameter. The guide baffle and the inner wall of the reel can be fixed by electric welding or fixed with holes.