Chunhua Group shares with you the development history of the crane and the current use and maintenance of the crane during the break-in period
It was not until the 15th century that Italy invented the jib crane to solve this problem. This crane has a tilting cantilever, and a pulley is installed on the top of the boom, which can be raised and lowered. But until the 18th century, all kinds of lifting machinery used by humans were still powered by human or animal power, and their lifting capacity, range of use and work efficiency were very limited.
After the improvement and invention of the steam engine by British Watt in the middle and late 18th century, it provided power for lifting machinery. In 1805, Granny Engineer Lenny built the first steam cranes for the London Dock. In 1846, Armstrong of England changed a steam crane in Newcastle Dockyard to a hydraulic crane.
In the early 20th century, tower cranes were used in Europe.
The crane mainly includes a lifting mechanism, a running mechanism, a luffing mechanism, a slewing mechanism and a metal structure. The lifting mechanism is the basic working mechanism of the crane. Most of them are composed of a suspension system and a winch. There are also lifting and lowering weights through a hydraulic system. The running mechanism is used to move heavy objects vertically or adjust the working position of the crane, and generally consists of a motor, a reducer, a brake and wheels. The luffing mechanism is only equipped on the boom type crane. The amplitude decreases when the boom is raised, and the amplitude increases when it is lowered. It is divided into two types: balanced and unbalanced. The slewing mechanism is used to rotate the boom, and is composed of a driving device and a slewing support device. The metal structure is the skeleton of the crane. The main load-bearing components such as bridges, booms, and masts can be box-shaped structures or truss structures, or web structures. Some types of steel can be used as supporting beams.
In October 2011, the overall downturn in the construction machinery industry in China remained unchanged. Among them, excavator sales fell 29.92% year-on-year; bulldozer sales fell 21.34% year-on-year.
In 2011, due to the impact of national macro-controls, the credit tightening policy slowed the progress of some construction projects and delayed the start of some projects. At the same time, consumers were affected by the credit tightening policy and the reduction in purchase costs caused demand for construction machinery reduce. Although the current construction machinery market is facing severe challenges, China's economic growth momentum is still strong. In the future, China's construction machinery industry is still in a period of rapid development, especially the prospect of the crawler crane industry. The "Industrial Structure Adjustment Guidance Catalogue (2011 Edition)" issued by the National Development and Reform Commission clearly states that crawler cranes of 400 tons and above have been selected as "encouraging" products as emerging industries, and the prospect of crawler cranes is promising.
In the first three quarters of 2011, China's heavy truck industry sold a total of 712,200 vehicles. The development of the heavy truck market is entering a downward phase:
The first is the increasingly stringent industry policies. The state has promulgated a lot of laws and regulations on safety, environmental protection, energy saving, etc. At the same time, it has a stricter trend in the implementation. The enactment and enforcement of these regulations will increase the technical requirements of products in the heavy truck industry and increase the cost of products.
Second, market competition is becoming increasingly fierce. China's truck market has already faced a globalized competitive landscape. Although the domestic market share of domestic brands in the heavy-duty truck industry currently accounts for a large proportion, this does not mean that the future structure will always be maintained, factors such as improved product technology and reduced local manufacturing costs, etc. In the future, the competitive environment of the heavy truck industry will change.
With the continuous development of the crane industry, more and more enterprises have joined the crane industry. Gao Man pointed out that the risks of construction machinery include technical risks, supply and demand risks, and economic fluctuation risks. At present, the core technology of some products of construction machinery is mainly reflected in the overall design and technical integration. If the company fails to research and develop new technologies, new processes and new products in time to meet market requirements, the product may face the risk of being eliminated.
Due to the fierce competition in China's construction machinery industry, especially the international construction machinery giants have entered the Chinese market. Compared with foreign competitors, Chinese enterprises still have a large gap in terms of product types, research and development strength, technological level, capital scale and brand influence. In addition, the fluctuation of the world economy may also bring certain uncontrollable risks to the industry.
The current use and maintenance of cranes during the break-in period.
The use and maintenance of the crane during the running-in period:
1. Fast wear speed
Due to factors such as processing, assembly and adjustment of new machine parts, the friction surface is rough, the contact area of the mating surface is small, and the pressure condition of the surface is uneven. During the operation of the machine, the concave and convex parts on the surface of the part are fitted and rubbed against each other, and the metal chips that have fallen off are used as abrasives to continue to participate in friction, which further accelerates the wear of the mating surface of the part. Therefore, during the running-in period, it is easy to cause the wear of parts (especially the mating surface), and the wear speed is fast. At this time, if the work is overloaded, it may cause damage to components and cause early failure.
2. Poor lubrication
Because the fitting clearance of newly assembled components is small, and due to assembly and other reasons, it is difficult to ensure the uniformity of the fitting clearance, and the lubricant (grease) is not easy to form a uniform oil film on the friction surface to prevent wear. As a result, the lubricating efficiency is reduced, causing early abnormal wear of the parts. In severe cases, it can cause scratches or occlusions of the friction surface of the precision fitting, resulting in failure.
3. Looseness occurs
Newly assembled components have deviations in geometry and fit dimensions. At the beginning of use, they are easily affected by alternating loads such as shocks and vibrations, as well as heat and deformation, and excessive wear. The originally tightened parts become loose.
4. Leakage occurs
Due to the looseness of the parts, the vibration and the heat of the machine, there will be leakage at the sealing surface and pipe joints of the machine; some casting and processing defects are difficult to find during assembly and debugging, but due to vibration during the operation Impact, this defect is exposed, manifested as oil (water) leakage (seepage). Therefore, leakage occurs easily during the running-in period.
5.Many operating errors
Due to insufficient understanding of the structure and performance of the machine (especially for new operators), it is easy to cause failures due to operating errors, and even cause mechanical accidents.