Automated welding of pressure vessel nozzle connections increases the efficiency, reliability, and quality of the end-product.
The need for welding automation rises as several heavy fabrication industries are trying to combat the shortage of skilled welders. To minimize the effects of welder shortage, companies are required to automize certain processes in their manufacturing or even the entire production chain.
One of the industries that the shortage has hit is pressure vessel manufacturing. The process is demanding, and certain production phases, such as welding nozzle connections, require extremely good welding skills. By automating nozzle welding, the quality and reliability of the nozzle connection welding are raised significantly. This results in a highly improved efficiency of the manufacturing process.
When the goal is to modernize the entire pressure vessel production process, Pemamek provides a wide selection of solutions for each phase. In addition to the PEMA Nozzle welding station, PEMA Assembly and Welding stations, roller beds, positioners, and welding columns & booms meet the highest capacity demands of pressure vessel manufacturing.
The basics for efficient automation on PEMA Nozzle Welding Station
For automated and robotized welding to provide maximized benefits, it is required that other processes connected to welding work efficiently and are based on high-quality processes. As an example, it is crucial that weld preparations are at a certain level for automated welding to bring the desired results. The better the preparations are, the more productive welding automation is.
Holes for nozzle connections are recommended to be done with an automated process in order to maintain dimensional changes in the bevel as minimal as possible. Fitting and assembly of the nozzle to the hole needs to be done with care so that the end product will comply with the requirements. PEMA Nozzle welding station with adaptive welding and intelligent PEMA WeldControl 300 SCAN software is designed to overcome the changes in the weld groove caused in the groove preparation or assembly phase.
Usually, the nozzle connections are required to be full penetration welds. Manual welding is required for root pass so that high-quality root pass can be achieved. Robotized root pass welding would require very high accuracy in the preparation phase which in most cases is not technically or commercially feasible considering the whole production. After the root pass is manually welded, the robot welds fill and cap passes. Using robot welding for these phases is the most cost-effective solution as the most welding volume is in the fill and cap passes.
Adaptive nozzle welding equals high quality and reliability
Modern automation and robot welding technology is very adaptive to the variations in the welding groove. The robot adapts to the changes in the groove which enables correct filling and usage of optimized welding parameters. In other words, adaptive welding makes it possible for the robot to adjust its movements and control the welding equipment in a manner that will result in successful welding. And successful welding can be done to welds that are not exactly as they are designed in the drawings due to manufacturing or assembly tolerances.
The main components that are making adaptive welding possible in the PEMA Nozzle welding station are optical laser sensors and intelligent software. Optical laser sensor is used to measure the weld groove and provide data to the control software. Data of the scanned groove is processed and presented to the operator in the in-house developed and easy-to-use software. By implementing sensors and advanced control software welding robots can be raised to the next level of intelligence.
The scale that the welding speed and weaving parameters can be adjusted depends on factors, such as welded material and heat input limits. Before starting actual production, welding tests needs to be done to get validation of process for different materials, consumables and welding preparations. Continuous development is done at the PEMA Process Center where different welding processes for various applications are tested regularly. Additionally, the welding process support with the same welding equipment as in the nozzle welding station can be offered to our customers. Currently, Pemamek’s station is equipped with a single wire GMAW process, but other welding processes, used widely in the process industry, are under development and process test list.
Scanning of the weld groove enables adaptive welding. Same amount of weld passes even if the groove volume changes during welding.
After the root pass is manually welded, the robot welds fill and cap passes.
Intelligent programming and control system
The core philosophy of welding automation is that it transforms skilled welders into operators who manage the robotic welding station. One of the many responsibilities of the operator is to prepare the upcoming workpiece as the robot is still completing the previous work cycle. When the workpiece is brought inside the robot working area and operators are outside of the robot safety zone, programming of the laser scanning paths is started.
With PEMA WeldControl 300 OFFLINE software operator programs the scanning paths to the locations of the nozzle connections with just a few mouse clicks. After the robot has finished an automated scanning work cycle, the data of the scanned groove is presented in PEMA WeldControl 300 SCAN software.
The operator can utilize the library of the existing weld pass sequences for the scanned groove or create a new weld pass sequence, which can be saved in the library and applied in the future to similar connections. In the SCAN software, every single weld pass in the sequence is adapted to the scanned groove automatically by the software. The operator can do modifications for the parameters or the weld pass sequence if needed. Fine-tuning the parameters is the point where the special skills and knowledge of the welder are needed. While the robot is welding, programming can be done in either one of OFFLINE or SCAN software. This enables the robot to be utilized more in actual welding rather than path programming or for example online teaching.
Nozzle welding stations for shell diameters up to 3500 mm
Pemamek offers two standard-sized solutions for pressure vessels, which dimensions’ cover most of the current market needs. During summer 2020, PEMA Nozzle welding station for shell diameters under 2000 mm, is available for the audience at the Pemamek’s factory. The showcase enables visitors to see more accurately the technical features and advancements of the station. For customers with the heavier and larger diameter workpieces, Pemamek has developed also a bigger standard station that is for up to 3500 mm shell diameters.
About the author: Jyri Luhtio
Application Manager, Offshore and
After working seven years at Pemamek, Jyri has gained extensive expertise in designing optimized
welding and production solutions for the global offshore and process equipment manufacturing.