High on welding practices

December 29, 2009 8:23 am

For any crane manufacturer the boom of the crane is the single most complicated and finely brought out part of the entire machine. Almost all booms are bent in complex oviform shapes, many use a pinning system to reduce tip loadings. A huge amount of effort goes into reducing boom weight to keep the axle loadings below the magic sum of 12 tons per axle. All this can be ensured through high quality steel and most advanced welding practices.
 
For all major European crane manufacturers – Grove, Liebherr, Tadano-Faun and Terex Demag — advanced welding standards are of utmost importance to keep the boom weight reduced and also ensure that they are of strong variants to undertake heavy lifting applications. As per companies, steel fabrication and welding of high quality steel are their core competence in making the final product.
 
Prototypes and complex components are manufactured by companies themselves while they have developed manufacturing and welding technologies to ensure quality booms. The welding specifications are passed on to vendors manufacturing the booms. One of the prominent European crane boom manufacturers is Belgium-based Vlassenroot. Major European, Chinese and Russian crane manufacturers source booms from Vlassenroot.
 
Every Vlassenroot boom starts as plate steel shipped via Antwerp, Canada from SSAB in Sweden. The steel plates are then bent and welded together into boom sections. Inside the boom, longitudinal welds are made using metal active gas welding, outside the weld is made using submerged arc welding.
 
Where different widths of steel are needed to be joined together on the same boom (to save weight), cross welds are made manually. As the external weld is made, the metal will buckle and wave from the heat. Some of these changes in the shape of the boom are fixed by the metal springing back. However, to get the precise tolerances Vlassenroot aims for, the boom will need to be leveled before its final assembly.  
 
Apart from manufacturing booms, Vlassenroot also manufacturers boom heads and cups along side chassis for mobile cranes, thereby undertaking host of welding activities. It annually welds 12,000 boom components a year. The company plans to introduce robotic welding process for boom components. The new equipment will use twin-rotating tables, while the robotic welder works on one component, the staff is able to mount the next component on the second table.
 
When the first component is complete, the table switches positions, allowing the robot to work continuously. The company has sent two boom components, assembled with temporary welds to a potential European supplier. This will allow the supplier to design welding programme for robots.      
 
The importance of welding is also undertaken by crane manufacturers, those who make their own boom sections. As per Chinese tower crane manufacturer, Changlin, due importance is provided to welding practices for its tower cranes. The company claims to use advanced welding techniques of its tower cranes. Appropriate welding is of due importance for tower crane manufacturer as 80 per cent of the component of the tower cranes constitutes of steel, which has to be welded to the right order to prevent accidents.
 
Another prominent Chinese crane manufacturer, Fushun, also claims to lay due emphasis on quality welding practices adopting advanced techniques. According to the company, advanced welding practices provide its products with a competitive edge. At home, crane manufacturing major, Tractors India Ltd (TIL), which manufacturers mobile cranes under license from Grove, claims that its welding practices are much global in standard, undertaken through modern equipment from manufacturers based in Europe and USA. Based on the company’s strong engineering skills, which essentially involve welding, TIL is looking to supply critical crane components to export markets.