Welding of tanks and vessels is mostly performed using dedicated welding machines when the components are circular and articulated robots when they are not circular (D-shape and other geometries).
Typical applications in this area use seam tracking for welding water heater tanks and truck fuel tanks. These two applications use single pass welding which is adequate for low pressure vessels (however, the process requires high accuracy to get required sealing of the tank). On the other end of the spectrum, high pressure vessels having wall thicknesses of up to 200 mm require more complex features for multi-pass welding of deep narrow gap joints.
Tank welding
A manufacturer of gas and electric water heaters uses the GMAW process to weld the longitudinal joint in the shell and the circumferential around end caps.
The existing process involved a special welding machine with one torch that was manipulated over the joint to be welded. To achieve sound welds, the torch must be maintained by the operator at the proper position in the joint. Laser vision has made possible welding at faster travel speeds (sometimes in conjunction with tandem arc) to be achieved with a dramatically lower leak rate.
Fuel tanks for trucks
The square shape of these tanks makes it difficult to use dedicated or Cartesian systems to weld them; therefore articulated robots are being used.
Laser vision seam tracking systems are applied for two types of welds; first to weld stiffeners inside the tanks and second, to weld the caps of the tanks. The first installation uses a standard GMAW process. The more recent installations are using tandem twin wire GMAW technology allowing welding speeds of up to 4 meters on these complex shapes.
Narrow gap welding
In order to minimize the welding cycle time and distortions on plates of up to 250 mm in thickness, manufacturers are adopting the method of narrow gap welding. The difficulties with these types of parts is to get access to the joint due to the tooling and providing accurate positioning of each welding pass inside the narrow space which is available.
Multi-pass Submerged Arc Welding is used and special torches are used to fit this special application. SERVO-ROBOT has developed a special tracking system which can view the complete joint including a sensor head that has the same narrow width as the welding torch.
Steel storage tank
Large tanks made from stainless or aluminum are used to store liquids for overland hauling. To maintain the proper liquid temperature, water jackets must be used. SERVO-ROBOT seam finders are used to precisely locate pre-formed holes on the circumference to allow the pre-programmed robot path to be corrected and to measure the gap so as to optimize the weld parameters.
