Danisco Austria manufactures preliminary products for sweeteners. For part of the process, 15 stainless steel pressure vessels that have been in use for more many years. The vessels run through many pressure cycles per day, which is a considerable number of load changes over the operating time. The containers have a diameter of 4.2 m and are between 3.8 and 5 m high.

Routine checks then also showed cracks at the transitions of the welded joints between the top cap and the jacket and between the jacket and the bottom cap. The fatigue of the welded joint was found to be the cause of the cracks.

Danisco Austria decided against the renewal of the system and began the renovation of all 15 pressure vessels over a period of almost 2 years. The welded joints in question were checked for damage. Detected cracks were ground out and welded on site.

In order to improve the fatigue life of the welded joints, the company HiFIT was entrusted with the post-weld-treatment of the weld seam. In close cooperation, the questions of the responsible parties were answered and a concept for the rehabilitation of the welded joints was developed. With the mobile HiFIT team the repaired weld seams were treated with the HiFIT process. The seams that were not repaired were also treated with HiFIT to prevent future cracks. At the request of the client, the shutdown of the production unit should be as short as possible. Again, the high processing speed of the HiFIT device helped to meet the requirements.

Since the life-prolonging effect of HiFIT has also been proven in numerous studies for welded joints that have already been damaged, all other welds, including those that have not been repaired, could also be treated with the HiFIT process [see REFRESH, Ummenhofer, Weich].