Analysis of the current safety technical specifica

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Analysis on the safety technical specifications of China's current tower cranes

at the advanced material innovation exhibition held at the 109th annual meeting of the Association for science and technology in Changchun recently, I highlighted that most of the current technical specifications of China's current tower cranes were issued in the 1990s. Looking at the current situation, there is still a certain gap between various types of tower cranes produced in China and them, mainly in the problems of incomplete safety devices, lack of auxiliary mechanisms and so on. If there is a lack of drum rope falling prevention device; Some are lack of anti falling device for broken shaft of luffing trolley; Some lack anemometer; Some lack red obstruction lights. What's more, the three-phase five wire system of the electrical system has not been implemented yet

no rules, no circumference. Only when we are unified within the scope of standards and Specifications issued by the state, are familiar with the specifications and master the specifications, can we improve our manufacturing level and use level, and can we transform and update the old tower crane. If you don't implement the norms, there will be endless trouble, and even you will pay the price of your life. According to the notice on Further Strengthening the management of tower cranes to prevent major accidents issued by the Ministry of construction, it is not entirely estimated that since 1998, there have been 25 major accidents in which more than 3 people have died at one time in tower crane accidents, resulting in a total of 76 deaths and 18 serious injuries. According to the investigation and analysis of 1200 tower crane accidents by domestic authoritative departments, it is found that tower crane overturning and arm breaking accidents account for 70% of tower crane accidents, and the main reasons for these accidents are overload and illegal operation. Of course, the poor manufacturing quality of tower crane, incomplete safety devices or failure of function are also directly related. By being familiar with the specifications, we can not only ensure safe production, but also flexibly use the specifications. The following describes some regulations, specifications and standards of the tower crane, as well as personal understanding

distinction between non working state and working state of tower crane

the tower crane that has been installed and erected, does not lift the weight, all mechanisms stop moving, cut off the power supply, and take wind protection measures, which is called non working state. The tower crane operates under the control of the driver, including lifting operation, no-load operation or intermittent shutdown, which is called the working state of the tower crane

classification of tower crane inspection rules makes the working part of the sample subject to axial tension

(1) type inspection inspects the product samples according to the specified inspection methods to prove that the samples meet all the requirements of the specified standards or technical specifications. Generally, it is carried out by the manufacturer or national and local quality supervision institutions

(2) delivery inspection of products shall be carried out at the time of user acceptance. Including performance test, safety device inspection and continuous operation test

(3) routine inspection shall be carried out when the user is in normal use, including each transfer to the site. Work at the same place after installation, once a year, but the safety device is carried out once a half year. Routine inspection shall also be carried out after major faults are repaired. Routine inspection includes performance test and safety device inspection

tower crane performance test content (gb/t5031)

installation and disassembly test, insulation test, no-load test, load test (rated load, overload 25% static load, overload 10% dynamic load test), operation test

safety device of tower crane

lifting torque limiter, lifting weight limiter, trolley luffing rope breaking protection device and shaft breaking protection device, lifting height limiter, amplitude limiter, rotation limiter, travel limiter, rail clamp, anemometer, hook and drum rope breaking prevention device, etc

regulations on wind speed

according to Chinese standards, the wind speed at the maximum installation height for tower crane installation, disassembly, climbing or jacking operations is not greater than 13m/s, equivalent to grade 6 wind. The F0/23B tower crane introduced from France stipulates that the tower crane shall not be lifted when the wind speed exceeds 16.6m/s, which is equivalent to grade 7 wind (installation manual). The author believes that it is appropriate to implement China's standards

regulations on the verticality of the tower

(1) after the installation of the tower crane, under the no-load and no wind state, the lateral verticality of the axis line of the tower body to the supporting surface is 4/1000, and at the same time, the two directions forming 90 ° to each other should be measured. It should be noted that the boom and the measured tower body must be in the same plane during measurement, that is, when the boom is vertical, measure the verticality of the tower body in the lifting plane, and measure the lateral verticality of the tower body outside the lifting plane against the boom

(2) after the tower crane is attached, the deviation difference of the verticality of the tower body below the attachment point is no more than 2/1000, and it is still 4/1000 above the attachment point

(3) the internal climbing tower crane has contributed to the "cost reduction and efficiency increase" of the mine when measuring between the upper and lower support devices, and the verticality deviation of its tower body to the datum plane is not greater than 2.5/1000

(4) when the tower crane is lifting the rated load, the horizontal static displacement △ X of the boom root should not be greater than H/100, where h is the vertical distance from the connection between the tower body and the boom to the action plane that directly supports the whole tower body. For the attached tower crane, the vertical distance from the connection between the tower body and the boom to the highest attachment point. Δ X is calculated by the following formula:

Δ x=[1/(1-Fn/Fe)]* Δ M

where: long FN - all the vertical forces above the connection between the tower body and the boom under the rated lifting load

fe - Euler critical load

Δ M - horizontal displacement of the connection between the tower and the boom caused by the bending moment M of the rated lifting load on the center line of the tower

in order to simplify the calculation, some units also use H/100 for the attached tower crane, and H is defined as the vertical distance from the connection between the tower body and the jib to the highest attachment device. Obviously, the calculated value is too large

driver's cab

the driver's cab shall be equipped with signal indication of main power on/off status, overload torque and overload weight alarm or signal indication. The cooling and heating fan used in the cab shall be of iron shell protection type and fixed installation, and the shell shall be grounded. The power supply shall be set separately for the air conditioner. When the tower crane is working, the noise in the cab shall not exceed 80dB (a). The cab cannot be hung on the boom, and its position should not be directly below the boom. It can be attached to the turret. 8 for the safety indicator and anemometer, the tower crane whose top is higher than 30m shall be equipped with red obstacle indicator at its highest point and arm end, and its power supply shall not be affected by shutdown. For the tower crane with the hinge point at the root of the boom more than 50m, an anemometer should be set at the top, and when the wind speed exceeds the specified value, it should be able to alarm

as for the first provision, some regions have done well, and the technical supervision organization that has not been installed will not accept it. For the second regulation, almost all tower cranes have not been installed. Only when individual users take the initiative to put forward when ordering, the manufacturer will install them. 9 provisions for trolley luffing tower crane

under no-load state, the offset of any roller and track support point of the lifting trolley from the plane composed of other roller and track support points shall not exceed 1/1000 of the nominal value of the wheelbase

for cranes with a maximum luffing speed of more than 40m/min, when the trolley runs outward, when the lifting torque reaches 80% of the rated value, it should automatically switch to low-speed operation. When the amplitude limit switch acts, the minimum distance between its end and the buffer device shall be 200mm when the trolley stops

lifting height limiter

the lifting movement shall be stopped immediately when the top of the hook device of the boom luffing tower crane is deleted from the lower end of the boom. The minimum distance from the top of the hook device of the trolley luffing tower crane to the lower end of the trolley frame is 1000mm for the steel wire rope of the upper rotary tower crane at 2 times and 700mm at 4 times; The second rate of the next rotary tower crane is 800mm, and the fourth rate is 400mm. At this time, it should be able to stop lifting immediately

provisions of lifting torque and lifting limiter

when the lifting torque exceeds the specified value of its corresponding amplitude and is less than 110% of the specified value, stop the action of luffing in the lifting direction and outward direction

when the lifting weight exceeds the maximum excess weight and is less than 110% of the maximum lifting weight, stop the operation in the lifting direction, but allow the mechanism to move in the downward direction

regulations on drums and pulleys

(1) one of the following conditions shall be scrapped:

cracks and flange damage; The wear of the drum wall thickness reaches 10% of the thickness; The wear of pulley groove wall thickness reaches 20% of the thickness; The wear of pulley groove bottom exceeds 20% of the corresponding wire rope diameter

(2) the pulley shall be equipped with a steel wire rope anti sloughing device, and the gap between the anti sloughing device and the outermost edge of the pulley shall not exceed 20% of the diameter of the steel wire rope

regulations on the use of hooks

(1) repair welding of hooks is prohibited

(2) those with one of the following conditions should be scrapped:

observe the surface with a 20x magnifying glass to see if there are cracks and breaks; There is permanent deformation of dangerous sections such as coupler tail and threaded part and coupler reinforcement; The wear of the cross-section at the hanging rope exceeds 10% of the original height; The wear of spindle exceeds 5% of its diameter; The opening is 15% more than the original size

regulations on using high-strength bolts

when using high-strength bolts for connection, a torque wrench or a special wrench must be used and tightened according to the assembly technical requirements. The crane must be equipped with this wrench when leaving the factory

regulations on the retainer of the vertical ladder of the tower crane

the vertical ladder of the tower crane should be equipped with a retainer, and any point of the retainer should be able to withstand 1000N concentrated load. When the ladder is set inside the crane structure and the distance between the outside of the ladder and the structure is less than 1.2m, the retainer may not be set

regulations on repair after member deformation

when the tower crane structural parts are transported or transferred to the construction site, it is inevitable to collide and deform, resulting in rod bending or assembly difficulties. At this time, local flame correction is generally allowed. However, if the deformation of the main chord of the main structural member is too large, the manufacturer must be contacted for proper treatment

regulations on scrapping of structural parts

when the corrosion depth of the main structural parts of tower crane reaches 10% of the original thickness, they should be widely used for scrapping of buildings, thermal insulation, packaging, freezing and daily necessities. Of course, it can also be determined by calculation, that is, the stress of the main structural members increases due to corrosion. When it exceeds 15% of the original calculated stress, it should be scrapped

regulations on steel wire rope of outgoing tower crane

the manufacturer prints the tower crane above 60tm, and when the lifting height is below 70m, the steel wire rope is generally equipped at a four fold rate; If the height is more than 70m, it should be used at twice the rate, otherwise the length is not enough. You can also ask the manufacturer for special orders

regulations of hydraulic system

the hydraulic system shall be equipped with a device to prevent overload and hydraulic shock. The adjustment pressure of the overflow valve shall not be greater than 110% of the rated working pressure of the system

in order to prevent the hydraulic cylinder from overspeed falling and falling of the load part due to the influence of load and the rupture of oil pipe, reliable balance valve and hydraulic lock should be set in the hydraulic system. The hydraulic lock and balance valve should be connected to the hydraulic cylinder

regulations on the electrical system of the tower crane

the power supply of the tower crane should be set with a main circuit switch, which can easily cut off the power supply of the whole machine

the electrical system adopts three-phase five wire system. There shall be reliable protection devices, including short-circuit and overcurrent protection, undervoltage, overvoltage and loss of voltage protection, zero position protection, power phase staggering and phase failure protection. The grounding resistance of tower crane shall not be greater than 40, and the repeated grounding resistance shall not be greater than 10 Ω. The insulation resistance of the circuit to the ground shall not be less than 0.5m Ω

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