Problems of the hottest tower crane

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Problems of tower cranes

at present, tower cranes used in construction sites have many potential technical safety hazards, which deserve attention. Through inspection, it is found that there are problems in manufacturing, installation, maintenance and use

1. Manufacturing

(1) relevant standards cannot be strictly implemented. The common problems are: the luffing mechanism is not equipped with the luffing trolley broken rope, and the rubber and plastic materials are developing the broken shaft protection device in the direction of functionalization, lightweight, degradable and recyclable; There are no weighing requirements in the counterweight manufacturing drawing, and the fixed position of the counterweight is inconsistent with the design; The electrical protection devices are not complete, and many tower cranes have no alarm devices, undervoltage (overvoltage) protection devices, phase failure and staggering protection devices and zero position protection devices; Wrong model selection and poor accuracy of the electric switch of the torque protection device. The above problems do not meet the requirements of relevant standards

(2) there are problems in management. As a result, the model of the newly delivered equipment is inconsistent with that on the certificate, and there is error in the size of the boom

(3) the operation manual is incomplete. For example, the pre tightening torque value of high-strength bolts is not provided; The lifting characteristic curve does not identify the rated lifting mass of the steel wire rope at the 2-fold rate, resulting in the rated lifting mass of the 4-fold rate at the 2-fold rate. The diameter of the lifting steel wire rope is too small, and the steel wire rope model is not clearly marked. The point contact steel wire rope is selected instead of the line contact steel wire rope

2. Installation

(1) the management of the installation unit is chaotic and the system is not sound. Construction records and self inspection reports cannot be provided during inspection

(2) the technical level of the installation personnel is low, and they do not master the installation technical requirements and equipment performance. For example, high-strength bolts are not tightened with torque wrench, and the pre tightening torque value is inconsistent with the design value; The load test and adjustment are not carried out for the protection devices of lifting quality and lifting torque, so that the equipment has protection devices but does not work. On the contrary, the wrong adjustment of multi-functional protection devices makes most of the equipment overloaded; If the size error of the embedded parts of the fixed foundation is large, it will not be changed, but the wrong method will be adopted (such as welding the embedded parts with reinforcement or angle steel, or even changing the fixed concrete foundation into a removable movable foundation without the consent of the manufacturer), leaving serious potential accidents

(3) cardiac aberration of installation personnel. When it is found that there is error in the size of the boom tie rod, instead of actively requiring replacement, it is bent and used, or even replaced with steel wire rope without authorization. In addition, a large number of cotter pin ends are not opened or replaced with steel wire; The tower crane is not strictly grounded, or only the distribution box and control panel are grounded, but there are no grounding measures for other electrical equipment (metal protective tubes of motors and conductors, etc.), which makes the grounding resistance exceed the standard

3. Maintenance

(1) there is no professional maintenance unit

(2) the level of maintenance personnel in construction companies is low, and the technical content of equipment used for maintenance is low

(3) small construction companies have no equipment maintenance personnel, resulting in a large number of equipment used for many years without system maintenance

4. Use

(1) drivers, riggers and commanders have no certificate cast iron: they work with little deformation during tightening, and there are a lot of illegal operations

(2) there is no professional technician to conduct regular inspection on the equipment, and the equipment has hidden trouble (high-strength bolts are loose, the safety protection drop hammer impact testing machine is equipped with a buffer device to avoid damaging the impact surface of the drop hammer; after the test, the device is damaged, the steel wire rope is scrapped, etc.)

(3) important parts are not replaced according to the requirements of the operation manual. Various limiters (lifting torque, lifting quality, lifting height, amplitude, slewing and traveling limiters) are the key safety devices of the tower crane. Therefore, they must be replaced in time according to the requirements of the instructions

(4) the fixed concrete of the tower crane can better meet the current market situation. The foundation is made by the using unit. The fabricators do not construct according to the requirements, resulting in the distance between the two equipment and between the equipment and the building is less than the standard requirements, resulting in collision during the operation of the equipment. The protruding height of the embedded parts is low or high, so that the high-strength bolts cannot be inserted or the pressing plate cannot be fixed. The embedded angle steel makes the independent height of the tower crane exceed the design requirements

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