determine the service life of the tower crane, how big is its real life
According to the GB5144 "Safety Regulations for Tower Cranes", the normal use of the main bearing structure of the tower crane should not exceed 1.25 × 10s working cycles. The rough estimate is about 8 to 10 years. According to the "Tower Suspension Design Code", the tower crane designed for this type of work cycle is of a lower grade and can only work under most medium loads and less maximum loads. In reality, most tower hoists on the market do not specify the design life of the product on the information provided to users such as instructions. How to determine the service life of the tower crane? What is the true life span of a tower crane?
The use of Tower hoist shows that in recent years, there have been more fatigue cracks in tower hoist steel structures using more than 10 years and less than 80 TM. At the same time, more and more fatigue cracks have been found in the steel structure of the tower crane that has been used for about 5 years. Some fatigue cracks were discovered in time, corresponding remedial measures were taken, and a few were not found, resulting in major accidents. Most of the cracks occur at the top and bottom of the tower and the bottom of the tower.
It can be seen that most of the tower cranes under the 80tm level, which are currently large in size, are no longer suitable for use for about 10 years, and small products(25tm, 31.5 TM, 40tm, 63tm, etc.) are in even worse condition. The status of towers above 100tm is better. Due to the widespread existence of severe overload, if fatigue cracks are used as a sign of expiration of life, it is estimated that 5 % of Tower cranes below the 80tm stage have early fatigue in about 5 years.
The industry standard "Technical Regulations for the Safety Assessment of Construction Lifting Machinery" implemented on August 1, 2010 has a landmark significance for the safety management of construction cranes. It changes this kind of equipment from "infinite life management" to "finite life management." The standard stipulates that the factory life of a tower crane below 63tm shall exceed 10 years, 63tm ~ 125tm tower shall be hung for more than 15 years, and 125tm tower shall be hung for more than 20 years. Construction lifts of the SC type for more than 8 years and SS type for more than 5 years must pass the assessment(qualified unit) before they can continue to be used or be downgraded. If the assessment is not satisfactory, it will be scrapped. In addition, the maximum effective period of 1 to 3 years after the evaluation of each type of tower crane and elevator was stipulated. In order to ensure that the evaluation is more operable, the standard determines the important parts and parts to be evaluated for tower lifts and lifts, evaluates the contents of the inspection, and checks the methods and instruments for measurement. As well as the basis for judging whether or not to pass, there are relatively clear provisions.
