When Jyväskylä Energy Group needed a new material for the power station’s chimney, the right type of stainless steel was found together with Outokumpu’s experts.
Stainless steel is often preferred because of its durability, strength and resistance to corrosion. In the long term, it pays for itself. Besides the long-lasting features of stainless steel, Outokumpu’s customers also benefit from the expertise of Outokumpu’s employees who help to identify the right material for every purpose.
In 2010, the city of Jyväskylä, in Central Finland, built a new power station with a 143 m tall chimney made of coated carbon steel. However, the circumstances were more aggressive than thought, and a widespread corrosion damage was identified in the chimney.
Jyväskylä Energy Group decided to choose Outokumpu as the new material supplier because of its well established reputation as one of the biggest stainless steel providers in the world, as well as the long-lasting and cost efficient features of stainless steel. Together with the customer, Outokumpu’s experts found the right type of stainless steel, Ultra 254 SMO, which is typically used in challenging environments.
Here are the phases of the cooperation for finding the right material:
1. Defining the requirements
The circumstances inside the flue gas duct and chimney are very unpredictable, given the combination of wet and dry conditions with relatively high temperatures. In addition, the presence of deposit forming particles can make the conditions very aggressive to stainless steel.
“We needed a material that could withstand the conditions in the flue gas duct and chimney, while also being cost-efficient. Stainless steel responded to these expectations well. The main reason for our choice was its high corrosion resistance,” says Aleksi Vuorenmaa, the project manager from Jyväskylä Energy Group.
The co-operation between the customer and Outokumpu was very open and constructive.
“Jyväskylä Energy Group had a very simple mission to find a suitable material for the challenging environment, and through our expertise we were able to name some considerable options”, says Pekka Heinonen, Sales Manager from Outokumpu.
2. Material testing
In order to find the optimal stainless steel, Outokumpu’s corrosion department in Avesta R&D Center, performed two period field tests, the first one lasting for two years and the second one six months, with a wide range of materials.
“When evaluating the samples, we were mostly paying attention to weight loss and visible corrosion, as signs of too aggressive conditions for the material. In this case, the conditions had clearly been very aggressive, as most steel grades showed some signs of corrosion,” says Björn Helmersson, a research engineer at the corrosion department at Avesta R&D center.
Outokumpu’s experts went through the results with the client. Two types of stainless steel performed the best, and Jyväskylä Energy Group chose the more cost-efficient one. Ultra 254 SMO is one of Outokumpu’s most corrosion resistant grades and performed significantly better in comparison to the lower-alloyed alternatives. Ultra 254 SMO is typically used in challenging environments where standard materials will heavily corrode.
3. Support for material use
Jyväskylä Energy Group felt important to receive support in using the material, as they had no prior experience of that type of stainless steel. Together with the subcontractor, the manufacturer of the chimney, Jyväskylä Energy Group received technical support from Outokumpu whenever needed.
“We have produced Ultra 254 SMO for decades and accumulated knowledge and experience with the use of this material over the years. Especially the welding of Ultra 254 SMO requires some special care, and I wanted the customer to pay attention to these aspects,” says Ravi Vishnu, Welding Metallurgy Specialist at Avesta Research Centre.