The key points of safety inspection of tower crane: fixing the end of steel wire rope

At present, the combination of wedge sleeve and rope clamp is mainly used to fix the rope end of lifting wire rope and boom head of tower crane. The rope end fixing method of luffing wire rope and luffing trolley mainly adopts rope clamp. Let's introduce them respectively.

Fixing method of combination of wedge sleeve and rope clamp

The key points of safety inspection of tower crane: fixing the end of steel wire rope

Wedge sleeve

At present, domestic and foreign tower crane manufacturers adopt different methods to fix the combination of wedge sleeve and rope clamp. When foreign tower crane manufacturers connect the wedge sleeve with the steel wire rope, the rope clamp must not connect the steel wire rope at the stressed end and the fixed end together, as shown in Figure a. When the wedge sleeve of the wedge is connected with the steel wire rope by domestic tower crane manufacturers, the rope clamp connects the steel wire rope at the stressed end and the fixed end.

Next, discuss the advantages and disadvantages of these two combined fixing methods of wedge sleeve and rope clamp at home and abroad.

The advantage of foreign methods is that they can well protect the steel wire rope and reduce the damage of the steel wire rope, which will not lead to the inclination of the wedge sleeve after the steel wire rope is loaded, and the steel wire rope at the outlet of the wedge sleeve will not be damaged by additional bending pressure. The operation method is that the wire rope tail at the fixed end should be pulled out of the wedge sleeve at least several wire rope diameters, and the wire rope tail at the outlet of the wedge sleeve must be fixed with a wire rope clamp immediately. However, with this method, if the end connection is suddenly unloaded, it will lead to the possibility of loosening the wedge and even falling out of the wedge sleeve.

The advantage of domestic method is that the wedge is reliably connected with the wedge sleeve, and the wedge will not fall out of the wedge sleeve. However, it will lead to the inclination of the wedge sleeve of the loaded wedge of the steel wire rope, and the steel wire rope at the outlet of the wedge sleeve will be damaged by additional bending pressure. Due to the frequent bending of the steel wire rope around the built-in wedge, the structure of the steel wire rope will often open outside the curve, so that the rope core of the steel wire rope can be seen. Under normal circumstances, this will not be dangerous, but it will cause some damage to the structure of the steel wire rope. In the process of hoisting wire rope threading and winding, the installer will hammer repeatedly in order to push the wire rope and wedge into the wedge sleeve. In this process, the steel wire on the surface of the wire rope may be damaged.

The key points of safety inspection of tower crane: fixing the end of steel wire rope

Fixing of rope clamp

According to gb5976-86 standard, the number of rope clamps is generally not less than 3-5. The spacing of rope clamps should be 6-7 times the diameter of steel wire rope. The number of clamps depends on the diameter of steel wire rope. At least 3 clamps are set for ≤ 19mm, 4 clamps are set for 19-32mm and 7 clamps are set for 32-38mm.

The steel wire rope clamp shall be used together. The U-ring part shall be clamped on one side of the rope head, and the pressing plate shall be placed on one side of the main rope.

Pay attention to the following points when using the wire rope clamp:

a) The size of the clip shall be suitable for the thickness of the steel wire rope. The net distance inside the U-ring shall be 1-3mm larger than the diameter of the steel wire rope. If the net distance is too large, it is not easy to clamp the rope, which is prone to accidents.

b) When installing the rope clamp, be sure to tighten the bolt until the rope is flattened by 1 / 3-1 / 4 diameter. After the rope is stressed, tighten the rope clamp bolt again to ensure that the joint is firm and reliable.

c) The rope clamps shall be arranged in a straight line, and the U-shaped part shall be in contact with the rope head, not with the main rope. If the U-shaped part is in contact with the main rope, the wire is easy to break when the main rope is flattened.

d) In order to check whether the joint is reliable and find whether the steel wire rope slides, install another rope clamp about 500mm behind the last rope clamp, and let out a "safety bend" at the rope head, as shown in Figure B. In this way, when the steel wire rope of the joint slides, the safety bend is straightened first, and measures should be taken immediately.

Fixing method of wire rope end

In addition to the above two rope end fixing methods, some auxiliary steel wire ropes of tower crane will also adopt other rope end fixing methods, mainly including the following methods:

The key points of safety inspection of tower crane: fixing the end of steel wire rope

1) Braiding method: after the end of the steel wire rope is bypassed by the heart-shaped collar, the rope head is broken and inserted into the working rope strand respectively, and then tied tightly with a thin steel wire rope. The binding length L = (20-25) d, and D is the diameter of the steel wire rope. At the same time, it shall not be less than 300 mm.

2) Wedge casing method: fixed with special steel wire rope wedge block.

3) Lead filling method: dismantle the end of the steel wire rope, thread it into the conical quilt cover, bend it into a hook shape, and then fill lead for consolidation.

4) The end of the steel wire rope is divided into six strands by the aluminum alloy indenter method. The reserved ends of each strand are staggered, and the length of the reserved ends does not exceed the length of the aluminum sleeve. The rope core is cut off, bent 180 degrees and then inserted into the main cable. Then insert the casing, press it into an oval shape on the steam hammer, and then press it with a die.