New approach solves a tricky welding problem

#2/2009
Text: Risto Pakarinen

For many years, Warkaus Works had been looking for a better alternative for preheating during the welding process. A specialist team from Germany came up with a solution for the Finnish company.

Warkaus Works Oy is a Finnish engineering company that manufactures soda-recovery boilers and pressure-bearing components for power boilers used in industrial applications.

“We manufacture furnace-wall elements for power stations,” says Teijo Tuppurainen, welding expert at Warkaus Works. “The problem is that the material has to be preheated before it can be welded, and the available solutions are both expensive and complicated to use.””

For many years Warkaus Works has developed its own welding processes in collaboration with AGA. Now it wanted to develop them a step further.

“For example, it was not possible for us to operate multiple welding heads simultaneously,” says Tuppurainen. “I’d been looking for a solution to this problem for many years.”

Their long-term cooperation with AGA led to new openings.

“Warkaus Works received an order in which preheating was a must for the welding process,” says Jyrki Honkanen, head of sales for AGA's welding and laser applications. “A difficult type of material was required, and no suitable preheating burners were available.”

AGA directed enquiries to Linde in Germany, where there is a department that specialises in solutions for this type of burner.

The specialist group from Linde went to Finland and assessed the situation at Warkaus Works. They identified the problem and set about constructing a test burner.

“I ordered a few burners for testing, to see whether they could withstand the temperatures that would be encountered,” says Tuppurainen. "Once we saw that they worked, we ordered burners to fill all our needs.”

The project took six months to complete, and in January 2009 Warkaus Works switched to the new burners.

Teijo Tuppurainen is happy. “We had previously tried electrical and liquefied gas methods as alternative solutions, but in this solution we now use oxygen and compressed air,” he says. “This means that we can use several welding heads simultaneously, as the method does not generate excess heat. The technology has also proven to be durable, requiring no spare parts.”

Warkaus Works’ client is also happy with the solution, which uses acetylene instead of liquefied gas, which is otherwise customary.

“Preheating liquefied gas is a risky business, as it generates moisture at low temperatures, something that the client wants to avoid,” explains Tuppurainen.

“Using acetylene avoids this risk,” he adds. “If higher temperatures are needed, then these can be attained by using liquefied gas, but this is not suitable at
the temperatures used here.”