To ensure repeatability for the welding process, a defined weld bevel preparation is attached to the pipe ends. In addition, the U-seam preparation, which is applied compared to the classic V-joint shape, significantly reduces the seam volume in order to reduce both the total heat input into the material and to minimise the overall effort. The weld bevel is tested and determined by our specialists in a process-optimized manner, and attached to the pipes in the field by means of a pipe beveling machine . The pipe beveling machines are usually lifted with a standard hydraulic excavator and driven by the on-board hydraulics.

A self-propelled internal line up clamp (ILUC) is used in the tube, which is either pneumatically or electro-hydraulically driven to move from seam to seam. At the end of the tube, the device clamps by means of individual punch feet distributed over the circumference, and pushes any out-of-roundness out of the tube. Then the pipe to be welded is placed bluntly on the pipe string and clamped with a second clamping circuit. For mechanized root welding, the J- Preparation are driven together to a technical zero gap.

The welding process is guided by a CNC-controlled orbital machine clamped on the tube . For this purpose, two automatic welding machines are placed on a guide belt on the pipe and weld the first layer (root layer). The precisely parameterized MAG welding process (STT) ensures a defined melting of the pipe material, and creates a seam root inside the pipe which is testable and durable. The rooting process with an input of approx. 5mm weld metal connects the pipes permanently and so stably that the inner clamping device can then be released and the pipe can finally be put down.

After the root welding has been completed, the pipe string is placed on wooden stocks or similar. The internal line up clamp is loosened and moved forward, and a new pipe can be attached and then welded. The total cycle time depends on the pipe diameter and is, for example, approx. 10 minutes for a 40inch pipe.

Filling process: Optional 136 FCAW Uphill (PH) Flux Cored Wire or 135 GMAP- Pulse downhill (PJ) Solid Wire The process is individually tailored to the requirements. The welding process is shielded by a welding cabin, which protects against weather influences such as wind, rain, sun and cold. All the necessary equipment and tools are ergonomically positioned in the cab and support our welders in carrying out the welding process. The welding cabins are moved from seam to seam over the construction site using our modern and self-developed paywelders. Everything required is mounted on the welding bead, including electricity and gas supply. The number of welding stations determines the number of welds that can be completed in a working day.

The whole process also includes a thorough cleaning of the pipe surface and cap layer, as well as a visual inspection and approval by our foremen immediately after the welding. This ensures that a weld seam is handed over to our customer or the commissioned testing company free of external irregularities. They then continue to check the seam for internal irregularities using non-destructive testing methods such as radiography or ultrasonic testing. Automated test methods such as TOFD, phased array or combinations on so-called AUT systems are common use.