Tower crane

Rotating crane with boom mounted on the upper part of the tower

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synonym Tower crane (Construction equipment) generally refers to tower cranes (rotary cranes with boom mounted on the upper part of the tower body)

This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Tower crane Tower crane , also known as Tower crane , originated in Western Europe. A revolving crane with a boom mounted on the top of a towering tower. Large working space, mainly used for vertical and horizontal transportation of materials and installation of building components in housing construction. It consists of metal structure, working mechanism and electrical system. Metal structure includes tower body, boom and base. The working mechanism has four parts: lifting, luffing, slewing and traveling. The electrical system includes Motor , controller, power distribution cabinet, connecting line, signal and lighting device, etc.

Chinese name: Tower crane
Foreign name: tower crane
Alias: Tower crane , tower crane

Place of origin: Western Europe
Purpose: Vertical and horizontal transportation of materials during construction
Classification: Upper slewing tower crane and lower slewing tower crane

catalog

brief introduction

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Tower crane is a rotating crane with a boom mounted on the top of a towering tower. It has a wide scope of work and is mainly used for the vertical transportation of materials and the installation of components in the construction of multi-storey and high-rise buildings. It consists of metal structure, working mechanism and electrical system. Metal structures include tower body, boom, base, attachment rod, etc. The working mechanism has four parts: lifting, luffing, slewing and traveling. The electrical system includes motor, controller, distribution frame, connecting line, signal and lighting device, etc.

Tower cranes are divided into two types: upper rotary crane and lower rotary crane:

1、 Upper rotating tower crane: the tower body does not rotate, and the boom, balance arm, etc. above the slewing ring make full rotation around the center line of the tower body through the slewing mechanism. According to the use requirements, it can be divided into running type, fixed type, attached type and internal climbing type. The traveling tower crane can run along the track, with a wide range of work and wide application, and is suitable for multi-storey building construction; If the crane base is fixed on the rail or the tower body is directly fixed on the foundation, it becomes a fixed tower crane, and its boom is longer; If a fixed tower crane is connected to a building with an attachment bar at a certain height on the tower body, it is an attached tower crane. It uses a tower body attachment device to make the upper rotating part of the crane rise with the rise of the building, which is used for high-rise building construction; The crane shall be installed in the elevator shaft or the connected holes Hydraulic cylinder The inner climbing tower crane is the one that enables the crane to climb up along the shaft according to the construction process. It saves part of the tower body, has a large service range, and does not occupy the construction site, but has certain requirements for the structure of the building.

2、 Lower rotary tower crane: the slewing ring is installed between the base and the turntable. Except for the traveling mechanism, other working mechanisms are arranged on the turntable to rotate together. In addition to track type, there are track type and tire type with track chassis and tire chassis as the walking device. It has low center of gravity, can be disassembled and transferred as a whole, lightweight and flexible, and is widely used. It is suitable for multi-storey building construction.

produce

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Tower crane (16 sheets)

It is recorded that the first patent for tower crane for construction was issued in 1900. In 1905, a crane with a fixed tower body and a boom appeared. In 1923, a prototype of a modern tower crane was made. In the same year, the first relatively complete modern tower crane appeared. In 1930, Germany began to mass produce tower cranes and used them for construction. In 1941, the German industrial standard DIN8770 on tower cranes was published. This standard stipulates that the lifting capacity of tower crane is expressed by the product (tm) of lifting load (t) and amplitude (m) together with the lifting torque.

The tower crane industry in China started in the 1950s Western European countries The tower crane industry in China is in a rapid development period due to the depression of the tower crane industry caused by the weakness of the construction industry.

However, driven by a series of favorable policies such as urbanization strategy, the tower crane market in China has been guaranteed to a certain extent, and the overall development of the industry is close to that of developed countries such as Europe and the United States. However, while tower crane technology tends to be more intelligent and green, and tower crane enterprise management tends to be international, the development of small and medium-sized tower crane enterprises in China is not optimistic.

Large companies like XCMG, Zoomlion and Sany have gone abroad to explore foreign markets, especially Zoomlion has become the world's largest tower crane enterprise. Without exception, these giant enterprises have very complete R&D, quality assurance system and operation management mechanism, and can participate in the competition for international market share. However, for small and medium-sized enterprises, there is no such opportunity. Due to their own technology and capital constraints, coupled with the intensification of the price war in the industry and the serious impact of arrears, the situation facing the entire industry is not clear.

characteristic

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From the perspective of technical development of tower crane, although new products have emerged in endlessly, and new products have improved in production efficiency, simple operation, easy maintenance and reliable operation, the technology of tower crane has not fundamentally changed. The research of tower crane is developing towards combination. The so-called combined type is to take the tower body structure as the core, divide the tower body into several parts according to the structural and functional characteristics, and then divide each part into several modules according to the requirements of serialization and generalization and the principle of modular system. According to the parameter requirements, select appropriate modules to form tower cranes with different technical performance characteristics to meet the specific needs of construction. The implementation of combined tower cranes will help speed up the progress of tower crane product development, save product development costs, and better serve customers.

classification

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Tower cranes are divided into upper slewing tower cranes and lower slewing tower cranes. Among them, the bearing capacity of the former is higher than that of the latter. In many construction sites, what we see is the tower crane with upward rotary jacking and joint elevation. According to whether it can move, it can be divided into walking type and fixed type. The fixed tower crane is fixed without rotation and installed on the whole concrete foundation, or on the strip or X-shaped concrete foundation. The walking type can be divided into four types: crawler type, automobile type, tire type and track type. The fixed type is generally used in the construction of houses. According to its luffing mode, it can be divided into horizontal boom trolley luffing and boom luffing; According to its installation form, it can be divided into three types: jack up type, integral quick disassembly type and assembly type. The most widely used are down slewing, fast disassembly and assembly, rail mounted tower cranes and self elevating tower cranes capable of one machine with four functions (rail mounted, fixed, attached and inner climbing).

national standard

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GB 5144-2006 Safety Regulations for Tower Cranes
GB 5226.2-2002 Safety of Machinery - Electrical Equipment of Machinery - Part 32: Technical Conditions for Hoisting Machinery
GB 5802-1986 Lifting Short Link Chains - Class T (8) Calibration Chains for Hoists and Other Hoisting Equipment
GB 5905-1986 Crane Test Specifications and Procedures
GB/T 5905-2011 Crane Test Specifications and Procedures
GB/T 5972-1986 Code of Practice for Inspection and Scrapping of Steel Wire Ropes for Hoisting Machinery
GB/T 5972-2006 Code of Practice for Inspection and Scrapping of Steel Wire Ropes for Cranes
GB/T 5972-2009 Crane Wire Rope Maintenance, Maintenance, Installation, Inspection and Scrapping
GB/T 5973-1986 Wedge Joints for Steel Wire Ropes
GB/T 5973-2006 Wedge Joints for Steel Wire Ropes
GB/T 5031-2008 Tower Crane

device management

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Equipment characteristics

The boom of tower crane is divided into horizontal type and pressure bar type. When the boom is horizontal, the truck operates along the horizontal boom for luffing, and the luffing motion is balanced. The boom is long, but the dead weight of the boom is large. When the boom is pressure bar type, the luffing mechanism pulls the boom to pitch and luffing, and the luffing movement is not as smooth as the horizontal type, but its dead weight is small.

The lifting capacity of tower crane varies with the amplitude. The product of lifting capacity and amplitude is called load moment, which is the main technical parameter of this crane. Through the slewing mechanism and slewing bearing, the tower crane has a large lifting height and a large inertia mass for slewing and traveling, so it needs to have a good speed regulation performance. In particular, the lifting mechanism is required to be able to carry light load quickly, heavy load slowly, and install in place inching. In addition to resistance speed regulation, eddy current brake, frequency modulation, pole changing, silicon controlled rectifier and electromechanical combination are also commonly used for speed regulation.

data management

The construction enterprise or tower crane owner shall submit the tower crane's production license, product certificate, disassembly and assembly license, operation manual, electrical schematic diagram, hydraulic system diagram, driver's operation certificate, tower crane foundation drawing, geological survey data, tower crane disassembly and assembly plan, safety technology disclosure, and warranty of main parts (steel wire rope, high-strength connecting bolts, anchor bolts, and main electrical components, etc.) Report to the tower crane testing center. After passing the test by the tower crane testing center, obtain the safe use certificate and the handover record with the project manager department after installation. At the same time, strengthen the dynamic tracking management of the tower crane in daily use, make machine shift records, inspection records and maintenance records (including minor repair, medium repair, overhaul) and have them signed by the relevant responsible person, Materials and wearing parts replaced in the process of maintenance shall be provided with quality certificates or quality assurance certificates, and the above materials shall be timely sorted and filed, and one machine and one file account shall be established.

Disassembly management

The disassembly and assembly of tower crane is the accident prone stage. Safety accidents caused by improper disassembly and installation and unqualified installation quality account for a large proportion. Tower crane disassembly and assembly must be carried out by qualified disassembly and assembly unit, and installation and disassembly must be carried out within the scope of qualification. Disassembly and assembly personnel shall receive special professional training, have certain disassembly and assembly experience and work with certificates. At the same time, personnel of all types of work shall be complete, clear, perform their duties, and follow the unified command. In the process of commissioning, the technical level and sense of responsibility of professional electricians are very important. Electricians shall hold electrician certificates and lifting certificates. We have counted a large number of tower crane detection data, It is found that a disassembly unit in our city has installed 54 tower cranes in total, but 47 tower cranes failed the first inspection, and the qualification rate of the first inspection is only 13%. Most of them are due to the poor installation technology of the installation electricians, the disassembly unit is careless in management, and the safety awareness still needs to be further improved. Therefore, we have carried out special governance to strengthen business training for the unit, and achieved good results. In addition, the cost of disassembly and assembly in the disassembly and assembly market was not in accordance with the budget price, and even 400~500 yuan was used to install a tower crane, which also led to the decline of installation quality. Special disassembly and assembly plan shall be prepared for disassembly and assembly. The plan shall be reviewed and signed by the technical director of the installation unit, and special personnel shall be assigned to the warning area and warning line where the disassembly and assembly unit participates. Irrelevant personnel are prohibited from entering the site, and the operation shall be carried out in strict accordance with the disassembly and assembly procedures and instructions. Disassembly and assembly shall be stopped when the wind force exceeds level 4, and lifting operation shall be stopped when the wind force exceeds level 6. If it is really necessary to work at night under special circumstances, sufficient lighting shall be provided. If it is really necessary to work at night under special circumstances, sufficient consultation and consensus shall be reached with the truck crane driver on the procedures and precautions related to disassembly and assembly.

Tower crane foundation

Tower crane foundation is the foundation of tower crane. Practice has proved that many major safety accidents are caused by the problems of tower crane foundation, which is an important factor affecting the overall stability of tower crane. Some accidents are caused by careless installation when the concrete strength is insufficient in order to rush to work, some accidents are caused by insufficient ground endurance, some accidents are caused by excavation near the foundation, even landslide displacement, or uneven settlement due to ponding, etc., which will cause serious safety accidents. We must attach great importance to it without any ambiguity. The stability of the tower crane is its ability to resist overturning. The biggest accident of the tower crane is overturning and collapse. When building the tower crane foundation, it is necessary to ensure that the ground resistance meets the design requirements, and the strength of the reinforced concrete shall at least reach 80% of the design value. Special treatment measures shall be taken for tower crane foundation with basement works: some shall be driven under the foundation, and the reinforcement at the pile end shall be firmly welded with the foundation anchor bolt. The bottom surface of the concrete foundation shall be flat and compacted, and the bottom of the foundation shall not be made into a pot bottom. The size error of foundation bolts must be constructed in strict accordance with the requirements of the foundation drawing. The foundation bolts must be long enough to expose the ground. Each foundation bolt must be pre tightened with double nuts. Before installation, the foundation surface shall be treated to ensure that the levelness of the foundation does not exceed 1/1000. At the same time, the tower crane foundation shall not accumulate water, which will cause uneven settlement of the tower crane foundation. No pit or trench shall be excavated at will near the tower crane foundation.

safe distance

In the plane layout of tower cranes, it is necessary to draw a plan, especially in the real estate development community, where there are many residential buildings and tower cranes are like a forest. In addition, it is necessary to consider the safety distance of adjacent tower cranes, which should be no less than 2m in both horizontal and vertical directions. The tower body and boom of adjacent tower cranes should not interfere, and try to ensure that the tower crane can rotate freely when the wind is too strong. The safety distance between the rear arm of tower crane and adjacent buildings shall not be less than 50cm. The safety distance between tower crane and transmission line meets the requirements.

If the safety distance between the tower crane and the transmission line does not meet the specified requirements, the main tower shall be equipped with protective frame. In principle, the protective frame shall be erected without power supply. Metal materials shall not be used, but bamboo poles and other materials can be used. The distance between the bamboo pole and the power transmission line shall not be less than 1m, and it shall also have a certain stability strength to prevent it from being blown down by strong wind.

Safety devices

In order to ensure the normal and safe use of the tower crane, we must mandatorily require that the tower crane must be equipped with the specified safety devices during installation, mainly including: lifting torque limiter, lifting weight limiter, height limiter, amplitude limiter, rotary limiter, hook safety device, drum safety device, wind anemometer, wire rope groove breaking safety device, trolley rope breaking prevention device Trolley axle breaking prevention device, buffer, etc. These safety devices shall be intact, sensitive and reliable. If any damage is found during use, it shall be repaired and replaced in time, and it shall not be removed or adjusted arbitrarily.

stability

The ratio of tower crane height to bottom support size is large, and the tower body has high center of gravity, large torque, frequent starting and braking, and large impact force. In order to increase its stability, we need to analyze the main reasons for tower crane tipping as follows:

1、 Overload. Different types of cranes usually use the lifting torque as the main control. When the working range increases or the weight exceeds the corresponding rated load, the overturning torque of the weight exceeds its stable torque, which may cause the collapse of the tower crane.

2、 Inclined hoisting. When a heavy object is hoisted obliquely, its overturning moment will be increased, the horizontal component and vertical component will be generated at the hoisting point, and an additional overturning moment will be generated at the bottom bearing point of the tower crane, thus reducing the stability coefficient and causing the collapse of the tower crane.

3、 The foundation of the tower crane is uneven, the ground endurance is not enough, and the verticality error is too large, which will also increase the overturning moment of the tower crane and reduce the stability of the tower crane. Therefore, we should start from these key factors to strictly check and test to prevent major equipment and personal safety accidents.

Electrical safety

According to the requirements of the Standard for Safety Inspection of Building Construction (JGJ59-99), the special switch box of the tower crane should also meet the requirements of "one machine, one switch, one leakage box". The tripping rated action current of the leakage protector should not be more than 30mA, and the rated action time should not exceed 0.1s. The switchboard in the cab shall not be exposed. The electrical cabinet shall be in good condition, tightly closed, with complete door locks, the electrical components in the cabinet shall be in good condition, the lines shall be clear, the operation control mechanism shall be sensitive and reliable, and the performance of each limit switch shall be good. Professional electricians shall be regularly arranged for inspection and maintenance.

Wall attachment device

When the tower crane exceeds its independent height, a wall attachment device shall be erected to increase the stability of the tower crane. The wall attachment device shall be erected according to the requirements of the tower crane instructions. The wall attachment spacing and the free height above the wall attachment point cannot be arbitrarily overlong. The overlong wall attachment support shall be additionally designed and provided with a calculation sheet to check the strength and stability. The attachment frame shall be kept horizontal and firmly fixed on the same horizontal plane with the attachment rod, and firmly connected with the building. After attachment, the perpendicularity of the tower body below the attachment point shall not be greater than 2/1000, and the perpendicularity above the attachment point shall not be greater than 3/1000. The connection point with the building should be selected on the concrete column or concrete On the ring beam. Use embedded parts or wall bolts to effectively connect with the building structure. Some construction enterprises use expansion bolts instead of embedded parts, and cable wind ropes instead of attached supports, which are very dangerous.

Safe operation

The key of tower crane management is the management of drivers. The operators must be healthy, understand the mechanical structure and working principle, be familiar with the mechanical principle and maintenance rules, and work with certificates. The driver must maintain the crane according to the regulations, have a high sense of responsibility, carefully do cleaning, lubrication, fastening, adjustment, corrosion prevention and other work, do not work after drinking, do not work with disease or fatigue, operate in strict accordance with the tower crane machinery operating procedures and the "Ten Prohibitions, Ten Prohibitions" of the tower crane, do not operate in violation of regulations, rough operation, and have the right to refuse command in violation of regulations, Sufficient lighting shall be provided for night work. The key to safe use of tower crane at ordinary times lies in the technical level and sense of responsibility of operators, and the key to inspection and maintenance lies in mechanical and electrical maintenance workers. We should firmly establish the people-oriented ideology.

security check

Tower cranes shall be inspected before and after installation and during daily use. The welded joint of metal structure shall not crack, the metal structure shall not be plastic deformation, the quality of connecting bolts and pin shafts shall meet the requirements, and the connecting bolts shall be pre tightened regularly with personnel in the anti retreat and anti loosening measures, the wire rope shall be well lubricated and maintained, the number of broken wires shall not exceed the standard, and the strand shall not be broken plasticity Deformation, rope clamp joint meets the standard, gearbox and oil cylinder shall not leak oil, hydraulic system pressure is normal, brake The braking and limit insurance are sensitive and reliable, the transmission mechanism is well lubricated, the safety devices are complete and reliable, and the electrical control circuit is well insulated. In particular, it is necessary to urge tower crane drivers, maintenance electricians and mechanical maintenance workers to carry out frequent inspections, focusing on the inspection of steel wire ropes, hooks, transmission parts, limit safety devices and other vulnerable parts. If problems are found, it is necessary to deal with them immediately, so as to ensure that there is a fixed person, a fixed time, and a fixed measure, and strictly prevent mechanical operations with problems.

Exit mechanism

The state has made it clear that the obsolete models should be resolutely prohibited from use. The load use of tower cranes that have been in disrepair for a long time should be limited after identification and repair. There is no unified standard for the service life of tower cranes. There are different opinions and regulations in different places.

Some users excessively pursue profits and benefits, and do not pay attention to safety. The overloading of small horses and big cars is serious, which is one of the main causes of tower crane accidents. Some manufacturers, in order to meet the requirements of construction enterprises, expand sales, occupy the market, increase the independent height, lengthen the boom to increase the coverage of tower cranes, which will inevitably reduce the stability of tower cranes, reduce the rated lifting capacity, and increase unsafe factors. There are also some tower cranes that have been refitted privately and are privately engaged in assembly. These tower cranes have a long history, and they are cheap to buy second-hand ones, so they are unwilling to invest more money in maintenance. As a result, failures occur frequently. We should attach great importance to these. We should be realistic, make measures according to local conditions, and issue relevant supporting policies to solve this problem on the basis of widely soliciting opinions from all parties.

Conclusion

By strengthening the safety management of the tower crane in the above aspects, it can effectively prevent the occurrence of various accidents during the use of the tower crane, and play a preventive role. Practice has proved that as long as all construction enterprises, manufacturers, construction administrative departments and tower crane detection organizations can follow the above links and strengthen the special safety management of tower cranes, they can effectively control the occurrence of major tower crane safety accidents.

Inspection points

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1) Check the metal structure, especially the high-strength bolts. The connection surface shall be cleaned of dust, paint, traces and rust, and tightened according to the assembly technical requirements with torque wrench or special wrench.

2) Check the transmission system of each mechanism, including whether the bearing clearance of each working transmission mechanism is appropriate, whether the gear mesh is good, and whether the brake is sensitive.

3) Check the wire rope and pulley Whether the abrasion, anti falling device and rope end are fixed reliably.

4) Check whether the electrical components are in good condition, the closing degree of the contact points, and whether the connection is correct and reliable.

5) Check whether the traveling wheel is in good contact with the track and whether the rail clamping pliers are reliable. Whether the connecting bolts and clamping blocks are firm and reliable when installing attachment devices and internal climbing devices.

6) Whether the lightning protection grounding is safe and reliable.

7) Whether the drainage at the base is smooth.

8) Whether the safety devices are complete, sensitive and reliable.^[1]

Common tower crane

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The tower cranes commonly used in housing construction are introduced in the following aspects.

Metal structure

The metal structure of tower crane is composed of boom, tower body, turntable, pedestal, balance arm, underframe, tower tip, etc.

The structural type of the boom is trolley luffing horizontal boom, which is further divided into single lifting point, double lifting point and hammer head trolley luffing horizontal boom integrated with the boom and balance arm. Single lifting point is statically determinate structure, and double lifting points are statically indeterminate structure. The hammer head trolley luffing horizontal boom, installed on the top of the tower body, looks like a hammer head, and the tower body is like a hammer handle, without a tower tip, so it is also called the flat head type. The flat head type makes the structural form simpler, is more conducive to stress, reduces the dead weight, simplifies the structure and other advantages. The trolley luffing boom is mostly of equilateral triangle section.

Tower body structure, also known as tower, is the main body of tower crane structure. Nowadays, tower cranes all adopt square section, and the section size is widely used: 1.2m × 1.2m, 1.4m × 1.4m, 1.6m × 1.6m, 2.0m × 2.0m; The common dimensions of the standard section of the tower body are 2.5m and 3m. The connection mode adopted by the standard section of the tower body is the cover plate bolt connection and the stud bolt connection, followed by the socket pin shaft connection and the spigot pin shaft connection. The standard sections include the integral tower body standard section and the assembled tower body standard section. The latter has high processing precision and is difficult to manufacture, but the stacking area is small and the freight is small. Ladders must be set in the tower section to facilitate drivers and machinists to get up and down. The width of the ladder should not be less than 500mm, and the step spacing should not be more than 300mm. A retainer should be set every 500mm. When the height of the ladder exceeds 10m, the ladder shall be transferred in sections, and a rest platform shall be added at the transfer point.

The function of the tower tip is to bear the upper load from the jib pull rope and the balance arm pull rope, and transfer it to the tower body structure directly through the turret through the structural components of the slewing tower, turntable, pedestal, etc. The top of the jack up tower is of truncated cone column type, forward or backward inclined truncated cone column type, A-frame type and diagonal brace type.

All upper slewing tower cranes shall be equipped with counterweights, whose function is to support the counterweights, so as to form the balancing moment required in the design that is opposite to the direction of the lifting moment. In addition to the counterweight, a lifting mechanism is often installed at the tail. The reason why the lifting mechanism is placed at the tail end of the balance arm together with the counterweight is that, for one thing, it can play a part of the role of counterweight, and for another, it can increase the rope drum and tower tip Guide wheel The distance between is to facilitate the winding of steel wire rope and avoid rope disorder. The amount of counterweight is inversely proportional to the length of the balancing arm, and there is a certain proportional relationship between the length of the balancing arm and the length of the boom. The amount of counterweight is considerable. The light tower crane generally needs at least 3~4t, and the heavy one needs nearly 30t. The counterweight can be made of cast iron or reinforced concrete: the former has high processing cost but small windward area; The latter is not good for stability because of its large volume and windward face, but it is simple and economical, so it is generally used. The general practice is to divide the counterweight prefabrication into 2~3 specifications, with the same width and thickness, but the height is adjusted to match the boom with different lengths.

spare parts

Each tower crane uses many kinds of lifting parts, of which the largest number, strict technical requirements and complex specifications are steel wire ropes. According to different functions, the steel wire ropes used for tower crane include: hoisting steel wire rope, luffing steel wire rope, boom pulling rope, balance arm pulling rope, trolley pulling rope, etc. The characteristics of the wire rope are: the whole wire rope has high strength, the whole section is the same size, the strength is consistent, the self weight is light, it can withstand the vibration load, the elasticity is large, it can be wound into a reel, and it can be used at high speed Balanced motion There is no noise, and the outer skin will produce many burrs after wear, which is easy to find and timely dispose. The steel wire rope is usually twisted into strands by a strand of fine steel wire with a diameter of 0.3~0.4mm, and then twisted into ropes by strands. The tower crane uses interactive twisting, which is not easy to loosen and twist. In terms of strand section shape, High rise building construction The tower crane is most suitable for the use of multi strand untwisted steel wire rope, which is composed of two layers of rope strands in the same direction. The two layers of rope strands are twisted in the opposite direction. The principle of rotating torque balance is used for twisting, and the free end will not twist when the force is applied. The safety factor of tower crane lifting wire rope and luffing wire rope is generally 5~6, the safety factor of trolley traction rope and boom pulling rope is 3, and the safety factor of tower crane elevator lifting rope shall not be less than 10. The safety factor of the wire rope is an indispensable safety reserve factor, and the maximum allowable safety load of the wire rope must not be increased by virtue of this safety reserve surface without authorization. Due to the importance of steel wire ropes, it is necessary to strengthen the regular and comprehensive inspection of steel wire ropes, and store them in a warehouse with a closed dry surface, a wooden floor or an asphalt concrete floor to avoid corrosion. Do not damage the surface when loading and unloading, and store them upright when stacking. Systematic lubrication of wire rope can improve its service life.

Luffing trolley is an essential part of horizontal boom tower crane. The whole set of luffing trolley consists of frame structure, steel wire rope, pulley, traveling wheel, guide pulley, steel wire rope supporting pulley, steel wire rope anti slip roller, trolley traction rope Tensioner And rope breaking safety device. For extra long horizontal boom (with a length of more than 50m), a maintenance basket is hung on one side of the luffing trolley, which can carry maintenance personnel to each maintenance point for repair and maintenance. After the operation, the trolley drives back to the boom root to unhook the basket and the luffing trolley and fix them at the special support on the boom structure.

Other parts include pulley, slewing ring, hook and brake, etc.

Working organization

The working mechanisms of tower crane are as follows: lifting mechanism, luffing mechanism, trolley traction mechanism, slewing mechanism, jacking mechanism and crane traveling mechanism (traveling tower crane).

Electrical equipment

The main electrical equipment of tower crane includes:

·Cable drum - central collector ring;

·Motor;

·Electrical appliances used for motor operation, such as controller, master controller, contactor and relay.

Protective appliances, such as automatic fuses, overcurrent relays and limit switches.

·Control and switching appliances in main and auxiliary circuits, such as buttons, switches and instruments.

The auxiliary electrical equipment includes: lights, signal lights, bells, etc.

Hydraulic system

The main components in the tower crane hydraulic system are hydraulic pumps Hydraulic oil Cylinder, control element, oil pipe and pipe joint, oil tank and hydraulic oil filter, etc.

The hydraulic pump and hydraulic motor are the most complex parts in the hydraulic system. The hydraulic pump sucks the oil and sends it to the hydraulic cylinder or motor through the pipeline, so that the hydraulic cylinder or motor can operate normally. Hydraulic pump can be regarded as hydraulic pressure and heart, and is the energy source of hydraulic pressure. Most of the hydraulic pumps used in the hydraulic jacking system of tower cranes in China are CB-G gear pumps. CB is not the code of gear. Hagelung G is a fixed axial clearance, and the working pressure is 12. 5~16MPa。

The hydraulic cylinder is the actuating element of the hydraulic system. From the functional point of view, the hydraulic cylinder and the hydraulic motor are the same conversion device that converts the pressure energy of the working oil flow into the mechanical energy. The difference is that the hydraulic motor is used for rotary motion, while the hydraulic pressure is used for linear motion.

The whole process of a hydraulic jacking is:

·Move the counterweight so that the tower body is free from unbalanced torque. The boom is in place, facing the same direction as the imported track and locked. Lift a standard section of the tower body and place it on the ferry car;

·Jacking;

·The positioning pin is in place and locked, and the piston rod is lifted to form an introduction space in the frame;

·Introduction standard section;

·Lift the standard section and push out the ferry car;

·Put the standard section in place and install the connecting bolts;

·Slightly lift up and pull out the positioning lock to connect the transition joint and the connected tower body into a whole.

Safety devices

Safety device is indispensable for tower crane Key equipment One can be divided into: limit switch (limiter); Overload fuse (overload power-off device); Buffer stop device; Wire rope anti falling device; Anemometer; Emergency safety switch; Secure the audio signal.

The limit switch has the following functions: hook travel limit switch, slewing limit switch, trolley travel limit switch, crane travel limit switch.

Anti rollover

Overload operation is strictly prohibited; Do not pull the heavy objects obliquely; Do not brake suddenly; It is forbidden to operate hoisting operation in strong wind; After the work shift, the rail clamping device must be clamped to prevent the tower crane from sliding out of the track due to strong wind.

Jack up

When the jack up tower crane reaches its Free height In order to enhance its stability coefficient and maintain its lifting capacity, it must be attached to the building structure through anchorage when continuing to jack up and raise. The attachment level is related to the total height of the construction layer, the tower crane and tower body structure, and the free height of the tower body. Generally speaking, setting two anchoring inking can meet the needs. Attention shall be paid to the selection of attachment points on buildings: the distance between two attachment reinforcement points is appropriate; The fixing point shall be set at the T-shaped wall and the corner of the external wall; For frame structure, the attachment point should be arranged near the root of the column; It shall be arranged close to the floor slab to facilitate force transmission and installation.

In order to ensure the safe use of the tower crane and obtain a relatively long service life, it must be lubricated, troubleshooting, regular maintenance and parts overhaul.

Overview of foreign development

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The tower crane was really developed after the Second World War. After the war, countries are faced with the arduous task of rebuilding their homes. A large number of tower cranes with good performance are urgently needed for the huge construction work. Since tower crane showed its skill in construction and gradually became an important branch of construction machinery, it has a history of more than 50 years, during which it has experienced a complicated development stage. At the end of the 1970s, due to various reasons, the foreign tower crane manufacturing industry fell into a low ebb. Many small and medium-sized factories were shut down or changed production, and only a few large factories were able to maintain. It did not show a gradual recovery until the end of the 1980s. 1994 was the year of recovery, and Germany was the country with the best recovery momentum. According to relevant data, in the 1970s, when the tower crane manufacturing industry was at its peak, West Germany had 48500 tower cranes of all kinds, and the total number decreased to 1/3 in the 1980s. In recent years, the East and West Germany merged, the infrastructure scale expanded, and the output of tower cranes increased. There are nearly 40000 tower cranes, half of which are less than 5 years old.

At present, the most popular regions in the world tower crane market are Eastern Europe and Asia Pacific (especially Southeast Asia). The famous manufacturers active in the tower crane market are; Liebherr, Peiner and Wolff in Germany, Potain and BPR in France, Potain Simma in Italy Comedil 、 Nauva 、 EDILMAC ， Comansa in Spain, Betrox in Finland, KR φ LL in Denmark, Favco in Australia. In order to occupy more shares in the international tower crane market, these large factories all pay attention to summing up experience, carefully analyze market dynamics, and make great efforts to update and develop products. [3] In terms of new product development, foreign tower cranes generally have the following characteristics:

(1) More manufacturers pay attention to developing economical urban tower cranes and expand them into series.

(2) Among the new products of foreign tower cranes, some new light and medium-sized folding fast installation tower cranes are quite eye-catching.

(3) According to the relevant regulations of some national urban construction authorities, in order to prevent the tower crane boom from running in a narrow space, and to avoid the boom from colliding with each other and touching adjacent buildings, the boom type self elevating tower crane must be used for construction in urban high-rise building intensive areas.

⑷ After a long period of development, the crawler type horizontal boom tower crane is officially launched as a new product.

⑸ Frequency conversion speed regulation system has been popularized and applied in new tower crane products abroad.

(6) High technology has been applied to tower cranes.

(7) The plane design and space treatment of the cab are very important for both up and down slewing tower cranes.

China's development

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Crane

In the early 1950s, the tower crane in China started from imitation, and in 1954, the East German architect I tower crane was imitated; In the 1960s, we designed and manufactured 25tm, 40tm and 60tm models by ourselves, most of which are boom type; In the 1970s, with the increase of high-rise buildings, new requirements were put forward for construction machinery, so 160tm attached tower cranes, 45tm internal climbing tower cranes, 120tm jack up tower cranes and other tower cranes came out one after another; Since the 1980s, China's tower crane industry has developed rapidly, especially in recent years, the sales volume of tower cranes has continued to rise. In 2001, the industry statistics sales volume was 9738 sets, and in 2002, it became the first country in the world where the annual output of tower cranes exceeded 10000 sets. In 2004, due to the role of macro-control and Crane industry As a result of structural adjustment, the production and sales of tower cranes fell back. In 2005 and 2006, driven by the rapid economic growth, the production and sales of tower cranes in China resumed rapid growth. In 2006, the sales volume exceeded 20000 sets.

The production and application of tower cranes in China has a history of more than 40 years, and has gone through a process from mapping imitation to self design and manufacturing.

In the 1950s, China introduced Former Soviet Union And tower cranes in some Eastern European countries, and copy them. In 1954, it copied the prototype designed by Democratic Germany Fushun The first TQ2-6 tower crane in China was successfully trial produced. Later, the 15t and 25t tower cranes were developed following the prototype of the former Soviet Union. During this period, the number of tower cranes produced and used in China was small.

In the 1960s, due to the development of high-rise and super high-rise buildings, internal climbing tower cranes and external attached tower cranes were widely used, and more advanced technologies were used in working mechanisms, such as DC motor speed regulation, silicon controlled speed regulation, eddy current brakes, and hydraulic couplings were installed in slewing and running mechanisms. During this period, China began to design and manufacture tower cranes by itself. In 1961, Hongqi-11 tower crane was first successfully trial produced in Beijing, which is also the first tower crane designed by China itself. Subsequently, China designed and manufactured TQ-6 tower cranes by itself. By 1965, there were more than 10 manufacturers nationwide, producing more than 360 tower cranes. These tower cranes are of the lower rotating arm type and can be transported as a whole, which can meet the needs of civil construction below six floors.

In the 1970s, tower cranes served a wider range of customers. The range, lifting capacity and lifting height of tower crane have been significantly improved. In order to meet the requirements of all aspects of the market, tower cranes are also developing in the direction of multi use. China's tower cranes have entered a new stage of technology improvement and variety increase. In 1972, China's first downward rotating light wheeled rail crane came out: Beijing Hotel During the construction, China also designed and manufactured QT-10 self elevating tower crane, whose lifting torque is 1600kN · m. During this period, ZT 100, ZT 120, ZT 280 and other trolley luffing self elevating tower cranes, QT-20 trolley luffing internal climbing tower cranes, QTL 16, TQ 40, TQ 45, TD 25, QTG 40, QTG 60 self erecting quick loading tower cranes with lower slewing booms, etc. were developed successively, with an annual output of more than 900, marking a new stage for China's tower crane industry.

In the 1980s, there were many new products of tower cranes in China, mainly including self elevating tower cranes such as QTZ 100 and QZT 120, and down slewing fast loading tower cranes such as QT 60, QTK 60 and QT 25HK. The performance of these products is close to the level of foreign countries in the 1970s, and the maximum annual output during this period reached 1400 sets. At the same time, with the reform and opening up and International technical exchange In order to meet the needs of construction, Zengduo has also introduced some tower cranes from abroad, including Federal Germany Liebherr, Potain in France and Edilmac in Italy. Because these tower cranes have good manufacturing quality and advanced technical performance, they have greatly promoted the progress of design and manufacturing technology of tower cranes in China.

Since the 1990s, China's tower crane industry has entered a new boom period with the increase of construction tasks nationwide. The annual output has soared year after year, and some products have been exported abroad. The total number of tower cranes in China has also increased from dozens in the 1950s to about 60000 in 2000. At present, there are more than 300 manufacturers nationwide, and 241 have obtained production licenses; The annual output is about 9000 sets: there are more than 10 enterprises with an output value of more than 100 million yuan and profits and taxes of more than 10 million yuan. Since 1992, the annual export volume of tower cranes has been greater than the import volume, and the annual export amount has been greater than the import amount. So far, the annual trade surplus has reached more than 8 million dollars. On the premise of basically meeting the needs of national economic development, the following can be exported to earn foreign exchange. Up to now, China has become a big tower crane country in terms of production scale, application scope and total amount of tower cranes. However, due to China's accession to the WTO, the current situation of tower crane production in China is not optimistic, and there are the following problems:

Unreasonable product structure, similar varieties and slightly different models

Technical regulations have restricted product development. Since the product model classification standard formulated by China in the 1980s has strictly stipulated the main parameters such as lifting speed, slewing speed, luffing speed, walking speed, jacking speed, lifting weight, lifting torque and other geometric dimensions such as leg span and tail turning radius of the lower slewing tower crane, This severely limits the technical progress of tower cranes. The instability of the user base also restricts technological progress. In China, a large number of small and medium-sized construction enterprises are not well funded and lack long-term planning. They use second-hand products that have been eliminated by large enterprises and old tower cranes that have been out of service for a long time. Therefore, the fast erection tower crane widely used in developed countries, which is convenient in transportation, rapid in erection and safe in use, has been neglected in China. meanwhile, Enterprise innovation capability The shortage also affects the development of products. Many new enterprises have weak research and development capabilities. Most of the products are jointly developed with colleges, universities and scientific research institutions. The same product can be produced by several or even dozens of companies, without forming their own characteristics.

Manufacturing technology does not adapt to large-scale industry

In the past 20 years, although the level of tower crane manufacturing industry in China has improved, it is still backward compared with the advanced manufacturing technology of some other industries, and there is also a big gap compared with our similar backbone construction machinery enterprises. Many manufacturers have low production efficiency, high environmental pollution, and it is difficult to ensure the welding quality and finished product appearance quality. Only a few enterprises have treated the substrate before coating. The management mode and production mode of most enterprises are still the traditional multi-level progressive static unchanged mode, some are small and complete or large and complete, the degree of specialization, process equipment and management level are low, it is difficult to adapt to the fierce competition of multi variety batch production and commodity economy, and it is difficult to form their own national scale industry.

Because the industry statistics only counted the sales volume of twenty or thirty manufacturing enterprises, the sales volume of the whole industry must far exceed the statistics. There is no doubt that China has become a major producer of civil tower cranes in the world and one of the main demand markets for tower cranes in the world. According to preliminary statistics, at present, there are more than 400 tower crane manufacturers with production licenses in China, while there were less than 100 in the 1980s.

Safety regulations

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1、 Pre operation inspection

1. 1 On duty, shift handover procedures must be carried out, and the filling and recording of mechanical resume and shift handover records must be checked.

1.2 Before operation, loosen the rail clamp and fix it according to the specified method. Clear the obstacles on the traveling track, check that the travel limit stops at both ends of the crossing track are not less than 2~3m away from the end, and check the straightness, gradient and height difference of the two tracks, which should comply with the relevant safety technical regulations of the tower crane. The subgrade should not have subsidence, slope sliding, cracks, and other phenomena.

1.3 After track installation, the following requirements must be met:

(1) The height difference between the two tracks is not more than 1/1000.

(2) The longitudinal and transverse slopes are not more than 1/1000.

(3) The error between the gauge and the nominal value is not more than 1/1000, and the absolute value is not more than 6mm.

(4) Rail joint The gap is between 2~4mm, the height difference between the two rail tops at the joint is not more than 2mm, and the two rail joints must be staggered by 1.5m.

1. 4 Check the fastening of each main bolt, and the weld and main steel shall be free of cracks, open welds, etc.

1. 5 Check whether the oil level of mechanical transmission gear box, hydraulic oil tank, etc. meets the standard.

1. 6 Check whether the brake wheel and brake band (shoe) are free of damage and brake is sensitive; The hook, pulley, snap ring and wire rope shall meet the standards; The safety devices (torque limiter, weight limiter, travel, height variation limit, hook safety, etc.) are sensitive and reliable.

1.7 The operating system and electrical system shall be in good contact without looseness, exposed wires, etc.

1.8 For tower cranes with elevators, it must be verified that all safety devices are safe and reliable.

1. 9 Before power transmission of distribution box, the linkage controller shall be at zero position. After switching on, check that there is no leakage in the metal structure before starting the machine.

1.10 All electrical systems must have good grounding or neutral protection. A group of grounding shall be made every 20m and shall not be connected to the building. The grounding resistance shall not be greater than 4 Ω.

1.11 All parts of the crane shall be free of obstacles within 1m during operation.

1. 12 The tower crane shall be operated without load or tested before operation, and can be put into production only after confirmation.

2、 Safe operation

2.1 The driver must operate according to the lifting performance of the tower crane he drives. Lifting objects must comply with 30.1.7 of this procedure.

2.2 In case of fault, failure or inaccuracy of various safety protection devices on the machine during operation, the machine must be stopped immediately for repair. It is strictly prohibited to operate with faults and carry out maintenance during operation.

2.3 The driver must operate in strict accordance with the command signal, semaphore and gesture under the command of the person wearing the command signal armband. Sound signal shall be sent before operation, and blind operation is not allowed if the command signal cannot be identified clearly. Have the right to refuse to execute the command error or take preventive or corresponding emergency measures.

2.4 When the lifting weight, lifting height, luffing and other safety devices display or approach the critical alarm value, the driver must pay close attention to them, and forced operation is strictly prohibited.

2.5 During operation, the driver shall not chat, smoke, read books, newspapers or do other things irrelevant to the operation. Do not leave the operation post without permission.

2.6 When the hook Pulley block Low speed lifting shall be applied when the lifting is close to the boom.

2.7 It is forbidden to drop the weight freely. When the lifting object drops close to the positioning point, it must be positioned slowly. When the heavy object is in place, the brake can be used to slow it down.

2.8 When using the non direct impact height limiter, the height limiter shall be adjusted to: the distance between the hook pulley block and the corresponding lowest part shall not be less than 1m, and the direct impact height limiter shall not be less than 1.5m.

2. 9 It is strictly prohibited to directly hang heavy objects with hooks.

2.10 When operating the controller, it is necessary to start from zero, push it to the first gear, and then step up the gear, stopping for 1~2s at each gear until reaching the highest gear. When it is necessary to change the direction of the transmission device in motion, pull the controller to the zero position first, and then reverse the operation after the transmission stops. It is strictly prohibited to directly change the running direction. Tower cranes with operation time limit on the slow positioning gear must be used according to the specified time, and the slow positioning gear shall not be used without restriction.

2.11 When translating the lifting object during operation, the object shall be at least 100mm higher than the obstacle it crosses.

1.12 When the crane moves close to the rail limit, it shall slow down and stop in advance.

1. 13 When lifting heavy objects, it is not allowed to lift unstable heavy objects, and it is strictly prohibited to attach heavy objects to the lifted objects. When lifting scattered materials or special-shaped components, they must be firmly bound with steel wire ropes. The heavy objects should be lifted about 50cm from the ground and stopped, and the braking, material binding and lifting slings should be confirmed. After confirmation, the lifting can be commanded.

1.14 When the crane works at night, there must be enough lighting.

1.15 When the crane is stopped, resting or in the middle of power failure, the heavy objects shall be unloaded and shall not be suspended in the air.

1. 16 Irrelevant personnel are not allowed to enter the operation room, and it is forbidden to place inflammable materials and objects that hinder operation.

1. 17 The crane is strictly prohibited to transport or lift personnel. When lifting or lowering heavy objects, it is strictly forbidden to stand under them.

1.18 The boom and lifting objects of the crane must be connected with the high and low pressure Overhead transmission line The safety distance shall comply with the provisions in Table 30.1.6 of this procedure.

1. 19 When two lift cranes are operating on the same track or two parallel or mutually perpendicular tracks, the safety distance between any part of the two cranes shall be kept, and the minimum distance shall not be less than 5m.

1.20 Suspend the hoisting operation in the following cases:

(1) In case of severe weather, such as heavy rain, heavy snow, heavy fog, and strong wind above level 6 (including level 6) on the construction surface, the safety of construction is affected.

(2) The crane has electric leakage.

(3) The wire rope is severely worn and reaches the scrapping standard (see the scrapping standard of wire rope).

(4) The safety protection device fails or the display is inaccurate.

2.21 The driver must go up and down the escalator. It is strictly prohibited to carry tools and articles when going up and down the escalator.

2.22 It is forbidden to throw any object or defecate from the tower crane.

2.23 Measures against electric shock and fire shall be taken when heating in tower crane operation room in winter.

2.24 All tower cranes with elevators must comply with the provisions in the elevator operating instructions, and overload and violation of operating procedures are strictly prohibited.

2. When operating with more than 25 cranes, avoid overlapping operations of two or more tower cranes within the turning radius. In special cases, when overlapping operations are required, the vertical safety distance of the boom and the safety distance between each other when lifting materials must be guaranteed and reliable Safety technical measures The construction can be carried out only after being approved by the competent technical leader.

2. 26 The jib crane can lift, rotate and travel at the same time after the load is lifted off the ground, but the luffing can only be carried out separately, and the luffing with load is strictly prohibited. The crane with load luffing allowed shall not luffing when it is at or near full load.

2.27 If the hoisting winch is not installed on the rotating part of the crane, it shall not rotate continuously in one direction during the hoisting operation.

2.28 For cranes equipped with mechanical torque limiter, after multiple amplitude changes, the tonnage indicator of the overload limiter must be adjusted according to the turning radius and the rated load of the radius.

2.29 The curved rail subgrade must meet the requirements. When the crane turns, sand should be sprinkled on the outer rail surface, and grease should be coated on the inner rail surface and both wings. The counterweight box should be turned to the direction of the turning outer wheel. It is strictly prohibited to carry out hoisting operations or turn the hoisted load on the curve.

3、 Check after shutdown

3.1 After the tower crane stops operation, it is necessary to select a suitable position between the barrier free and the rail when the tower crane rotates and the boom stops along the wind, and lock all rail clamps.

3.2 For tower cranes with normally closed slewing mechanism or braking device, after stopping operation, the driver must remove the handle and release the brake, so that the crane can rotate in the downwind direction under strong wind.

3.3 The hook shall be lifted to the position with the minimum distance not more than 5m from the lifting wall. It is strictly prohibited to hang heavy objects on the hook. When reliable measures are not taken, no method shall be used to limit the boom to rotate with the wind.

Driver requirements

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(1) The driver must be specially trained and can operate independently only after being assessed and certified by relevant departments.

(2) The driver shall have an annual physical examination, and can not operate after drinking or with physical maladjustment.

(3) Implement the system of specially assigned person and special plane, strictly implement the shift handover system, and non drivers are not allowed to operate.

The driver shall be familiar with the mechanical principles, maintenance rules, safety operation procedures and command signals and strictly follow them.

(4) Newly installed and repaired tower cranes must be commissioned according to regulations, and can be used only after being confirmed as qualified by relevant departments.

2、 Driver's requirements before operation

(1) Check whether the subgrade meets the requirements of the instructions, whether there is no obstacle on the track, whether the retaining body on the track is firm, and whether the travel switch is reliable.

Check whether the track slope, the height difference between the two tracks and the track meet the requirements.

(2) Whether the oil quantity of reducer in each transmission part is sufficient, and whether the bolts of each part are fastened. Loosen the rail clamp for test run, and check whether the transmission part has abnormal noise and the tightness of the brake shoe.

(3) After the main switch is closed, use a test pencil to check the controller shell and confirm that it is safe before starting the machine.

(4) Check the wire rope for wear.

(5) Before the work starts, a comprehensive inspection shall be carried out to check the reliability of each controller, transmission device and brake, and the operation can be carried out only after all parts are confirmed to be completely normal.

3、 Requirements for driver operation

(1) The lifting capacity specified by the crane must be strictly mastered, and the lifted object must be understood in detail. Overload operation is not allowed.

(2) The driver shall closely cooperate with the signal commander, and the operation can be started only after the signal is clear. Before the action of each mechanism, the bell shall be pressed, and the operation shall be stopped if the signal is unclear.

(3) No person is allowed to ride or use the crane to lift.

(4) The controller shall be operated step by step from the zero position, and it is strictly prohibited to operate beyond the gear.

(5) No matter which part changes during operation, first turn the controller back to zero position, and then start reverse operation after the transmission stops. Reverse operation is prohibited.

(6) When the lifting object rises, the distance between the hook head and the end of the boom shall not be less than 1m.

(7) Tower cranes shall generally be equipped with two drivers, one operating in the cab and the other monitoring on the ground.

(8) When the crane is running, it is forbidden to drive to the place within 2m from the end.

(9) After each luffing of the tower crane boom, the tonnage of the overload limit device must be adjusted in time according to the working radius and weight of the load.

(10) When the crane lifts a heavy object, the jib shall not be luffing operated, it must be unloaded, and luffing cannot be carried out simultaneously with any of the other three actions (operation, rotation, lifting).

(11) When tower cranes are operating, it is forbidden to pull weights or lift buried objects.

(12) The horizontal distance between the edge of the hoisted object and the outermost serviceman of the high-voltage line shall not be less than 2m.

(13) When two tower cranes operate on the same track, the horizontal distance between the lifting hook ropes of the two cranes shall not be less than 5m.

The tower body shall not work on the curve with small curvature or walk with lifting objects.

(14) No one is allowed to go up and down the escalator during work, and maintenance work is strictly prohibited during work.

(15) The crane shall not be suspended in the air during work, rest or off duty.

(16) In case of severe weather such as strong wind above level 6 and heavy rain during operation, the lifting operation shall be stopped, the boom shall be lowered to a safe position, and the rail clamp shall be fastened.

(17) During night shift operation, sufficient lighting must be provided, and the commander and driver shall use obvious semaphore signals.

4、 Requirements for drivers after operation

(1) After the work is completed, the crane shall be driven to the middle of the track and parked, the rail clamp shall be clamped, the hook shall be lifted to 2~3m away from the boom end, and the boom shall be parallel to the track direction.

(2) Pull all controllers to zero after operation, and cut off the main power switch.

(3) Close and lock the cab doors and windows before leaving.

(4) In case of stormy weather, reinforcement measures shall be taken for tower crane.

Accident emergency

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(1) The tower crane foundation sinks and inclines: ① Stop the operation immediately and lock the slewing mechanism to limit its rotation. ② The ground anchor shall be set according to the situation to control the tilt of the tower crane.

(2) Tower crane balance arm, boom folding: ① tower crane cannot do any action. ② According to the rescue plan, the tower crane structure shall be strengthened by means of welding or other means according to the situation, or the tower crane structure shall be connected with other objects by means of connection to prevent the tower crane from tipping over and accidents during the removal process. ③ 2-3 cranes of appropriate tonnage are used, one for locking the boom and the other for locking the balance arm. One of them acts as a balancing moment when dismantling the boom to prevent tipping due to sudden changes in force. ④ According to the order specified in the rescue plan, take down the deformed connecting pieces in the boom or balance arm connecting pieces, cut them with gas welding, and take down the boom with a crane; ⑤ The tower crane shall be removed according to the normal tower removal procedure, and the deformed structure shall be cut by steam welding.

(3) Tower crane overturning: ① adopt welding and connection methods to increase the balance torque without damaging the unstable stress and control the development of dangerous situations. ② Appropriate tonnage cranes shall be selected to remove the tower crane according to the rescue plan, and deformed parts shall be cut or adjusted by gas welding.

(4) Dangerous situation of anchoring system: ① The tower type balancing arm shall be corresponding to the building, and the arm turning process shall be stable and locked. ② Anchor the tower crane System reinforcement 。③ If it is necessary to replace the anchoring system components, first lower the tower crane to the specified height, and then replace the components.

(5) Deformation, fracture and open welding of tower body structure: ① Corresponding tower type balancing arm to the deformed part, and the process of rotating arm should be stable and locked. ② According to the situation, the tower crane structure shall be strengthened by means of welding, etc. ③ Drop the tower and replace the damaged structure.

parameter

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The main technical parameters of tower crane include maximum lifting capacity, end lifting (lifting torque), maximum/minimum amplitude, maximum lifting height, structural type, luffing mode, tower body section size, etc.

(3) Lifting characteristics of tower crane

① The boom is installed on the upper part of the tower body, so the effective lifting height and working range are relatively large, which is the common feature of different types of tower cranes.

② High hoisting efficiency and stable operation.

③ The use period of tower crane in a construction site is generally longer. After a project is completed, it needs to be removed, transferred and moved, and then installed in a new fence construction site. It is more troublesome than general construction machinery, and the requirements are also strict.

④ Tower cranes are mostly operated in the open air on the construction site, and the conditions are different from indoor ones, so the machinery must be lubricated, cleaned and maintained.

5.1.2 Tower type Crane Installation method

(1) Rotating installation

This method is to use the lifting winch and boom of the tower crane itself to install by self rotating lifting (when lifting the tower body, the boom is used as the installation mast).

① The installation parts of the tower crane are set on the track with the help of the truck crane, and then the tower body and boom are assembled and connected with the traveling frame (gantry).^[2]

② Set the ground anchor and rigging, and lift the boom to the installation position.

③ Tension the boom to raise the steel rope, make the tower rotate at a certain angle, and install the counterweight cantilever on the upper part of the tower.

④ Continue to tension the jib to raise the steel rope to make the tower vertical and fix it on the traveling frame (gantry) (during the process of tower erection, the tower body needs to be pulled firmly with the rope).

⑤ Install ballast on traveling frame (gantry) and counterweight.

⑥ Remove the boom and lift it to the vertical position.

⑦ Lift the boom to the working position and install the lifting wire rope.

(2) Safe formal installation method

Assemble the underframe (or portal frame) with a motorized crane, place the ballast, and then install the tower body (including the jacket and transition joint for the self elevating tower crane), balance arm, boom, etc.

(3) Tower body heightening of self elevating tower crane

This article only introduces the jacking process of the attached self elevating tower crane. The head lift of the attached self elevating tower crane is carried out in several processes as shown in Figure 5-2 by using the function of the hydraulic system.

① Preparations before jacking. Determine the lifting height, lift the standard section onto the ferry trolley 8, remove the connecting bolts between the original tower body and the jacket, check and adjust the position of the hydraulic cylinder, roller, etc., connect the power supply of the hydraulic pump motor, and prepare for lifting.

② Jacking jacket and upper tower top structure. Start the oil pump to make the high pressure oil enter the upper part of the hydraulic cylinder. The oil circuit at the lower part of the hydraulic cylinder is connected to the oil circuit of the oil return tank. The jacket and upper structure are jacked up and raised to the height of more than one standard section (generally 3.3m). Lock the jacket with a locating pin. At this time, all the weight above the jacket is transferred to the tower body through the locating pin.

③ The standard section is introduced into the tower body. First retract the piston rod of the hydraulic jack to form the introduction space, and then drive the ferry car 8 with standard section 7 into the introduction space.

④ Install the tower body and connect the standard section. Use the hydraulic jack to slightly lift the standard section, exit the ferry trolley, press the standard section down with the piston rod and place it on the lower tower body smoothly, and connect them with bolts.

⑤ Pull out the locating pin 6, lower the jacking jacket 1, connect the transition joint with the new standard section and the tower body as a whole, and then carry out the new lifting work.

To connect several standard sections at a time, repeat the jacking process ①~⑤.

With device

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Tower crane must have load lifting limiter , torque limiter, height limiter, travel limiter, amplitude limiter, etc.

(1) Lifting capacity limiter: also known as overload limiter, it is a safety device that can prevent the crane from overload operation. When the lifting capacity exceeds the rated lifting capacity, it can automatically cut off the power supply of the lifting mechanism to stop or give an alarm. There are two types of lifting limiter: mechanical and electronic.

(2) Moment limiter: for luffing crane, only a certain amount of lifting is allowed. If it is overweight, there is a danger of tipping. Torque limiter is a kind of protection device developed according to this feature. In a certain range, if the lifting object exceeds its corresponding weight, the circuit will be cut off, making the lifting impossible and ensuring the stability of the crane. There are three types of torque limiter: mechanical, electronic and composite.

(3) Height limiter: also known as hook height limiter. It is usually installed at the head of the boom. When the hook slides to the limit position, the lever is lifted. Press the lower limit switch, cut off the circuit and stop. When closing again, the hook can only drop.

(4) Travel limiter: a safety device to prevent the crane from crashing or to limit the travel within a certain range. It is generally installed on the inner side of the driving trolley, mainly to install a travel switch that can pull the handle. In addition, a fixed limit position baffle is installed at the end of the track (at the position limited for operation). When the tower crane moves to this position, the limit baffle will touch the handle of the travel switch, cut off the power supply for controlling travel, and then the tower crane can only run in the opposite direction when it is switched on.

(5) Amplitude limiter: also known as luffing limit or amplitude indicator, an amplitude indicator is hung on the boom of general boom cranes. It consists of a fixed circular indicator board, with a vertical movable pointer installed in the center of the board. When luffing, the pointer indicates the rated lifting capacity at various ranges. When the boom moves to the upper and lower limit positions, press the lower limit switch respectively, cut off the main control circuit, and the luffing motor stops to limit the position.

Maintenance

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In order to ensure safe and economical use of the tower crane and extend its service life, the maintenance, repair and lubrication of the tower crane must be done well.

Tower crane maintenance

1. Keep the whole machine clean and clean it in time.

2. Check the oil quantity of each reducer and add oil in time.

3. Pay attention to check whether the steel wire rope at each part is loose, broken, worn, etc. If it exceeds the relevant regulations, it must be replaced in time.

4. Check the efficiency and clearance of the brake to ensure reliable sensitivity.

5. Check the sensitivity and reliability of each safety device.

6. Check all bolt connections, especially the connection bolts of the standard section of the tower body. After each period of use, they must be tightened again.

7. Check whether the pressing plate and clip of each wire rope end are loose and fasten them in time.

The scrapping of wire ropes, drums, pulleys, hooks, etc. shall strictly comply with the provisions of GB5144 and GB5972. 8. Check whether there are cracks on the rods, web members and welds of all metal components. Pay special attention to the places and parts where the paint flakes off, especially the most dangerous ones where the paint strips at an angle of 45 °. The causes must be quickly identified and handled in a timely manner.

9. The connecting bolts and nuts at all parts of the tower body (including the connection between the foundation section and the underframe), and the pin shaft with the connection diameter greater than Φ 20 at all parts are special purpose parts. Under no circumstances can they be substituted. When installing the tower body, each bolt must be tightened with two nuts.

10. The performance grade of bolts in the standard section is 10.9, and the performance grade of nuts is 10 (double nut locking). The top surface of the bolt head and the top surface of the nut head must be marked with the performance grade, or they are not allowed to be used.

11. Derusting and painting shall be carried out for the whole machine and metal mechanism after each project is used.

12. Check whether the automatic multiplying device of the lifting appliance and the anti dropping device of the hook are safe and reliable.

13. Observe whether the electrical contacts are oxidized or burned, and repair or replace them in case of poor contact.

14. All limit switches and buttons shall not be out of order, and parts shall be replaced in time if they are rusted or damaged.

15. Each electrical switch must be well insulated from the switch board, and its insulation resistance should not be less than 0.5M Ω.

16. Check whether the fastening bolts of the electrical components are loose, and whether the cables and other wires are broken. If any, remove it in time.