A weld cladding solution for finned walls

WHEN IT came to the weld cladding of the 12-meter-high finned walls used in waste incineration plants, SHI FW Energia FAKOP (FAKOP) chose a tower-high CMT cladding system operated with two elevator platforms from Fronius.

The large water-tube boilers used in commercial and industrial power generation use heating surfaces called finned walls made from tubes and flat iron. Due to the changing trends in fuels and the burning of increasingly difficult and aggressive fuels, it is necessary to develop additional anti-corrosion protection for the finned walls. Hardfacing is the most efficient way to protect the finned wall surfaces.

"To surface the finned tubes, we use a cladding tower from Fronius Welding Automation that is approximately 15 meters high," explained Arkadiusz Osuch, managing director of FAKOP. "It can accommodate two 12-meter-high and 1.6-meter-wide finned walls and is operated by two elevator platforms, each equipped with innovative CMT welding technology."
 
Iron in the weld metal diluted to less than 3%

Many challenges are associated with the process of overlay welding. The ratio of base material to applied alloy is crucial for the effectiveness of the corrosion protection. The aim is to keep the ratio as low as possible while ensuring good fusion between the base material and the protective layer. A lower base material content ratio means longer equipment service life. "The mixing ratio is now regularly below 3%," said Jaroslaw Olej, senior welding expert at Fronius.

Before the management of FAKOP decided to purchase a mechanical CMT welding system, the finned walls were surfaced using other techniques.

In order to satisfy the high quality demands of their customers, FAKOP's welding technology production engineers pay attention to every detail during the pretreatment of finned walls. Once the surface pretreatment is complete, the finned walls move on to overlay welding, which takes place in dust- and rust-free conditions.
 
The welding process is crucial

When opting for the Fronius welding tower, a key factor was the use of CMT technology. Its advantage lies in the digital process control, which independently detects short circuits and supports droplet detachment by retracting the welding wire. This creates a back-and-forth motion that keeps the arc phase short and reduces heat input. The result is a material transfer that enables spatter-free cladding results with a particularly smooth surface, soft seam overlaps, and a consistent layer thickness.

"Nowadays, we find the majority of our customers require the CMT process," said Olej, adding "You can safely say it's established itself as the standard, and those who know how to use it properly enjoy good opportunities in the market."
 
Ease of use is key

Welding is performed with horizontal oscillation from top to bottom in the vertical-down position (PG). Both elevator platforms are equipped with CMT welding technology and have intuitive HMI system controls with touchscreen, an ArcView camera and monitor, two CMT welding torches, and a joystick for fine adjustment.

Since welding torch temperature has a major influence on the dilution rate, all welding torches are water-cooled. To further ensure that the dilution limit of 3% is never exceeded, precise regulation by the plant’s cooling system is required.

One system optimisation worth mentioning is the new fine adjustment joystick for the welding torch position. Originally it was necessary to manually move the torch into position using a slide rail. This made fine adjustment almost impossible and always required extreme dexterity. With the ArcView camera and joystick, fine adjustment can now be carried out quickly, easily, and with millimeter precision.

For more information:

www.fronius.com

Tel:  +43 7242 241 0