June 22 marked a milestone for us as we installed our most challenging project to date. The operation required a colossal 500-ton crane, standing 80 meters high, to position the tank within the plant.
The tank will store highly corrosive material, so during stainless steel tank manufacturing, we used superior materials and specialized welding techniques to ensure durability. The two-part tank system was built in partnership with IMH Kft. It’s now installed and ready for operation.
Why is duplex steel a challenge to work with?
The cellulose industry tank was made from 1.4462 duplex steel, that offers better corrosion resistance and nearly double the tensile strength of standard austenitic steel.
Although duplex steel is a weldable material, manufacturing the tank was still a major challenge. Its crystal structure consists of ferrite and austenite phases, which can change under heat. Therefore, during welding, the temperature must be maintained within a narrow range of 50-150°C. Strict technological regulations must be followed throughout the stainless steel tank manufacturing process.
With the support of welding engineers and test welds, we fine-tuned:
- current settings,
- welding speed, and
- gas flow.
However, the heat management of a 50 cm test piece is different from that of a 2600 mm diameter tank processed outdoors. Therefore, each step had to be handled with care, and all welds were thoroughly inspected.
Tank components waiting for assembly – visually indistinguishable from other duplex steels.
Delivery and crane lifting of the steel tank for the cellulose industry
The steel tank has impressive dimensions: a diameter of 2600 mm and a length of 25 meters. For easier transport, we manufactured 12-meter-long sections in our factory. We assembled the entire tank on-site. From there, it was lifted over the plant building and set upright inside.
A 9-axle, 500-ton mobile crane was needed for the lift, which took a day to assemble. The crane’s boom reached a height of about 80 meters to lift the 25-meter vertical tank. We recorded the entire process, documenting the manufacturing and welding of the tank components, as well as the crane lifting process, showcasing the impressive workflow.
Duplex steel tank manufactured with a special welding process
The tank manufacturing was a high-stakes task, as it needed to withstand both weather conditions and the corrosive nature of the stored material. Therefore, we approached the project with meticulous planning, which ultimately required 2,900 work hours.
Welding took center stage. The 8.2-meter circumference was welded ring by ring. A 90° elbow at the end was built from segmented parts, as bending isn’t feasible at this diameter.
Our team welded the tank components together using strict technological procedures
During the manufacturing of the duplex steel tank, we used tandem welding, with teams welding both the inside and outside simultaneously.
Due to the need to control heat load, welding progress had to be slow. Three pairs of teams worked on the project, making welds of 5-10 cm at a time. The material’s temperature was monitored with an infrared camera thermometer. Over time, a practice developed where welding would stop after approximately 100 mm, and then move to another section.
A ferritescope was used for quality control, though only on a sample basis, since it’s a partially destructive method. Traditional weld inspections cannot detect changes in the crystal structure, even if the weld appears good visually and under inspection.
Adhering to the proper welding method, machine settings, weld speed, and length was crucial to ensure high-quality.
The finished tank is ready for lifting
Reliable, high-quality execution of specialized steelworks
We successfully completed the manufacturing of the duplex steel tank, adding new skills to our portfolio. With strong project planning, skilled professionals, advanced technology, and a growing equipment base, we’re ready to take on more complex, custom tank manufacturing jobs.
If you need a custom-made tank from special grade materials, we’re here to help – with expertise, precision, and a focus on quality.
