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The hook plays the role of connecting the crane and heavy objects, and its maintenance must be paid attention to. For this reason, if the lifting height limiter or hook locking device of the hook fails or is damaged, it must not be used again; as for those who work without a certificate, the leadership should be held accountable.

Hooks can be divided into single hooks and double hooks according to their shapes; and according to their manufacturing processes, they can be divided into three types: sheet hooks and forged hooks and cast hooks. At present, the common hooks are forged single hooks. Cast hooks are not allowed to be used on cranes. Hooks are widely made of low carbon steel and carbon alloy steel to solve the problem of resistance and crack generation.

In order to ensure safety, the hook must be inspected. The main method of inspection is generally visual inspection, that is, careful observation with a magnifying glass. If necessary, coloring or flaw detection can be used. The wear amount of the dangerous section can be measured with a caliper or a caliper; the opening degree is tested by comparing the size measured by the caliper with the original size or the opening degree of the standard hook. Here is a simple and applicable method: when a new crane hook is first used, punch a small hole on both sides of the hook body opening, measure the distance between the two holes and record it. It is used to compare with the deformed size of the hook in the future to determine the change in opening degree. Torsional deformation can be measured visually or with the side of a steel ruler. If accuracy is required, a scribing ruler can be used on the platform to detect it. Items ⑤, ⑥, and ⑦ can all be inspected visually or with calipers.

From many years of maintenance and inspection work on truck cranes, the author found that the hooks of truck cranes wear very badly during operation (this kind of wear refers to the wear and tear caused by the truck crane during the transfer from the garage to the working site or between working sites in order to complete various loading and unloading tasks). Among them, the hooks of 5t, 7t, 8t, and 10t truck cranes are more seriously worn because when these tonnage truck cranes are in operation, the driver always locks the hook with a wire rope in front of the cab, and the two ends of the locking wire rope are hung in the two front traction hooks on the front bumper of the chassis of the crane.

Since the crane is moved and operated under poor road conditions at the work site, there will be more friction between the wire rope and the hook, causing the hook and the wire rope to wear each other. Since the two ends of the wire rope are hung on the traction hooks on both sides, the wire rope is like a harp string, and the vertical dangerous section of the hook is severely worn. When the road conditions are poor, such as when a truck crane in the electric power department is operating in the field, its hook is particularly severely worn, and sometimes it is necessary to replace the wire rope that locks the hook in a few months. This kind of wear of the hook is non-working wear. Three methods to reduce and prevent this kind of wear are as follows:

　(1) Install steel pipe on a single wire rope

Take a section of steel pipe 400mm long and 25.4mm in diameter, bend it into the shape shown in Figure 2, and put it on the steel wire rope. During the operation of the truck crane, since the wire rope and the surface of the hook are not in direct contact, the casing plays a role in protecting the crane.The function of the hook. The casing can also be made of other materials, such as thick rubber pipes, high-pressure hoses with steel mesh, etc.

　(2) Increase the number of locking hook wire ropes to 3

Take a steel wire rope about 4.2m long and fasten both ends with rope clamps. This changes the contact between the wire rope and the hook from one to three, increases the contact area between the wire rope and the hook, reduces friction and wear between them, solves the problem of one wire rope easily cutting into the surface of the hook, extends the life of the hook and rigging, and also extends the life of the wire rope locking the hook.

　(3) Use other materials instead of steel wire ropes

If the nylon rope or nylon lifting strap used on ocean ships is used instead of the steel wire rope, the effect is also very good. In addition, it is recommended that the length L of the locking hook wire rope used is 1.35-1.45m. We have learned from many tests that if the wire rope is too long, the hook will be hung high, which will affect the driver's field of vision; if the wire rope is too short, it will be inconvenient when hooking, and the hooker's waist and wrist will easily be sprained. Generally speaking, if the driver is tall, the larger value will be used, and if the driver is taller, the smaller value will be used. This makes the operation convenient and can take into account the driver's vision needs.

The hook plays the role of connecting the crane and heavy objects, and its maintenance must be paid attention to. For this reason, if the lifting height limiter or hook locking device of the hook fails or is damaged, it must not be used again; as for those who work without a certificate, the leadership should be held accountable.

Hooks can be divided into single hooks and double hooks according to their shapes; and according to their manufacturing processes, they can be divided into three types: sheet hooks and forged hooks and cast hooks. At present, the common hooks are forged single hooks. Cast hooks are not allowed to be used on cranes. Hooks are widely made of low carbon steel and carbon alloy steel to solve the problem of resistance and crack generation.

In order to ensure safety, the hook must be inspected. The main method of inspection is generally visual inspection, that is, careful observation with a magnifying glass. If necessary, coloring or flaw detection can be used. The wear amount of the dangerous section can be measured with a caliper or a caliper; the opening degree is tested by comparing the size measured by the caliper with the original size or the opening degree of the standard hook. Here is a simple and applicable method: when a new crane hook is first used, punch a small hole on both sides of the hook body opening, measure the distance between the two holes and record it. It is used to compare with the deformed size of the hook in the future to determine the change in opening degree. Torsional deformation can be measured visually or with the side of a steel ruler. If accuracy is required, a scribing ruler can be used on the platform to detect it. Items ⑤, ⑥, and ⑦ can all be inspected visually or with calipers.

From many years of maintenance and inspection work on truck cranes, the author found that the hooks of truck cranes wear very badly during operation (this kind of wear refers to the wear and tear caused by the truck crane during the transfer from the garage to the working site or between working sites in order to complete various loading and unloading tasks). Among them, the hooks of 5t, 7t, 8t, and 10t truck cranes are more seriously worn because when these tonnage truck cranes are in operation, the driver always locks the hook with a wire rope in front of the cab, and the two ends of the locking wire rope are hung in the two front traction hooks on the front bumper of the chassis of the crane.

Since the crane is moved and operated under poor road conditions at the work site, there will be more friction between the wire rope and the hook, causing the hook and the wire rope to wear each other. Since the two ends of the wire rope are hung on the traction hooks on both sides, the wire rope is like a harp string, and the vertical dangerous section of the hook is severely worn. When the road conditions are poor, such as when a truck crane in the electric power department is operating in the field, its hook is particularly severely worn, and sometimes it is necessary to replace the wire rope that locks the hook in a few months. This kind of wear of the hook is non-working wear. Three methods to reduce and prevent this kind of wear are as follows:

　(1) Install steel pipe on a single wire rope

Take a section of steel pipe 400mm long and 25.4mm in diameter, bend it into the shape shown in Figure 2, and put it on the steel wire rope. During the operation of the truck crane, since the wire rope and the surface of the hook are not in direct contact, the casing plays a role in protecting the crane.The function of the hook. The casing can also be made of other materials, such as thick rubber pipes, high-pressure hoses with steel mesh, etc.

　(2) Increase the number of locking hook wire ropes to 3

Take a steel wire rope about 4.2m long and fasten both ends with rope clamps. This changes the contact between the wire rope and the hook from one to three, increases the contact area between the wire rope and the hook, reduces friction and wear between them, solves the problem of one wire rope easily cutting into the surface of the hook, extends the life of the hook and rigging, and also extends the life of the wire rope locking the hook.

　(3) Use other materials instead of steel wire ropes

If the nylon rope or nylon lifting strap used on ocean ships is used instead of the steel wire rope, the effect is also very good. In addition, it is recommended that the length L of the locking hook wire rope used is 1.35-1.45m. We have learned from many tests that if the wire rope is too long, the hook will be hung high, which will affect the driver's field of vision; if the wire rope is too short, it will be inconvenient when hooking, and the hooker's waist and wrist will easily be sprained. Generally speaking, if the driver is tall, the larger value will be used, and if the driver is taller, the smaller value will be used. This makes the operation convenient and can take into account the driver's vision needs.