256HC Mast Section How long is the service life of the tower crane
At present, most of the tower cranes in the market do not specify the design service life of the products on the data provided to users such as the manual. According to gb5144 safety regulations for tower crane, the normal use of main load-bearing structure of tower crane shall not exceed 1.25 × 10s working cycle, which is roughly estimated to be about 8-10 years. According to the code for design of tower crane, the tower crane of this kind of working cycle design belongs to the lighter level, and can only work under the condition that most of the medium load and less of the maximum load are used.
The use of tower crane shows that in recent years, the number of fatigue cracks in the steel structure of tower crane is more than 10 years, and there are serious corrosion and thinning of the wall thickness of the main material. At the same time, more and more tower crane steel structures which have been used for 5 years are found to have fatigue cracks. Some fatigue cracks have been found in time, and corresponding remedial measures have been taken, while a few have not been found, leading to major accidents. Most of the cracks are located at the top and bottom of the tower and the bottom of the tower body.
It can be seen that at present, most of the large-scale and wide-ranging tower cranes below 80tm are no longer suitable for use in about 10 years, and the condition of small products (25tm, 31.5tm, 40tm, 63tm, etc.) is worse, while the condition of tower cranes above 100tm is better. Due to the widespread occurrence of severe overloading, if the fatigue crack is taken as the sign of the end of service life, it is estimated that 5% of tower cranes below 80tm level have early fatigue in about 5 years.
The industry standard technical code for safety assessment of construction cranes implemented on August 1, 2010 is of milestone significance for safety management of construction cranes. It changes this kind of equipment from "infinite life management" to "limited life management".
Standard provisions:
(1) The factory life of tower crane below 63tm is more than 10 years.
(2) 63tm ~ 125tm tower crane for more than 15 years.
(3) More than 125tm tower crane for more than 20 years.
(4) The construction elevator with SC type more than 8 years and SS type more than 5 years can only be used continuously or degraded after passing the assessment (qualified unit). If it fails to pass the assessment, it will be scrapped.
(5) For each type of tower crane and lift, the longest period of validity after 1-3 years of evaluation is specified.
In order to ensure the operability of the evaluation, the standard has made clear provisions on the determination of important parts and parts to be evaluated for tower cranes and lifts, the contents of evaluation and detection, the methods and instruments for inspection and measurement, and the basis for judging whether they are qualified or not.
