Fully welded ball valves
These fully welded by two circumferential welds ball valves are normally used in oil and gas transport systems.
Narrow gap welding profile.
Nominal size: DN 300-1400 mm
Weld profile depth range: 25-120 mm
Maximum weight: 30000 kg
Maximum diameter of welds: 2300 mm
Since there are polymers inside a cooling system is required.
Customer’s technical requirements.
Parallel and independent welding of two welds
Compensation of deformation and abnormalities of the gap
Forced cooling and temperature control in the welding area.
Automatic feeding and recycling of flux.
According to our customer’s requirements, we built two systems in order to cover a vast range of sizes. Both systems are identical, based on the two-armed robot FANUC R-710iC and single-axis positioner.
Robot's arm positions the welding torches while the positioner rotates the part.
The positioning and cooling.
The valve covers are installed on the valve to make sure the cooling system is leak proof.
After the valve has been placed on the bearings, the gap search process is started so that the robotic system can automatically start welding the root pass and all the subsequent passes with the help of the laser positioning system.
Once the root pass has been weld, the cooling system starts working and monitoring the temperature of the work pieces to avoid overheating the polymeric seals.
Owing to this and many other implemented automation solutions, the efficiency, quality and flexibility of the process has been increased.
The welding head.
A special welding head has been developed by us for this task. It has the right and left-hand version. Compact and easy to maintain. It has everything you need: a sensor for collision detection, wire sensor, flux sensor, push-inlet valve for flux feed rate control , protection against welding wire stick, wire straightener, laser scanner system to monitor the gap. The thickness of the welding gun is just 10 mm. We also developed a flux recirculation system, which allows to significantly reduce the load on the robot and ensure movement flexibility.
The tracking system.
VistaWeld is a tracking system that searches, finds and tracks weld joints and weld seams using optical triangulation. It provides a reliable non-contact method for controlling the position of welding torches. The system is connected to the robot’s controller via Ethernet.
Vista Weld was successfully integrated with the robot controller by a common protocol, wich let the robot have access to the parameters and states of the laser system without having to require the user to change them manually on Vista weld’s panel.
The high computing power of the robot controller enables you to control all the devices of the system, including the laser tracking systems, welding machines, flux recycling system, cooling system, and the temperature monitoring system near the heat-affected zone.
Following our philosophy of ergonomics and simplicity, we made a simple and easy to use interface on the robot’s Teach Pendant, which made the system easy to use yet fully controllable. The advantages of this approach are evident, the operator can take the Teach Pendant to his work place next to the piece being welded and can reach every single parameter in the system, he has the information of the state of the whole robotic system including welding current and voltage and can control any parameter including welding speed and robot’s position.
The welding process.
The welding process comprises gap filling layer by layer. Each layer has three passes. The robot has the ability to tilt the torch when approaching the walls of the gap. This allows to increase penetration and reduce the likelihood of defects. While filling the gap expands but for the robot that is not a problem because it can increase the cross sectional area of the welding pool. To ensure uniformity of heat input at the weld zone throughout the depth of the gap, robot increases the welding speed as the value of heat input increases. If for whatsoever reason two gaps are not equally filled, the robot can also change the cross sectional area of the welding pool to align the filling of two gaps. You can also carry out separate welds .
Advantages of this system:
- The management of all elements and modules is performed from one controller and by means of one remote control.
- The welding process is carried out fully automatically , the influence of the human factor is excluded.
- The cooling system protects the internal components of the valve, and reduces the heat input at the weld region to improve the mechanical properties of the weld.