Detachment of pulp tower roof due to sudden pressure increase in Kuopio on 4 November 2024

EVENT
A paper machine at the fluting mill in Sorsasalo, Kuopio had operational problems on the morning of 4 November 2024, as a result of which production with the paper machine was stopped. This led to a decision to also interrupt pulp production. Interruptions in production and process shutdowns are normal mill operations. During the final phase of the interruption, a rapid and uncontrolled increase in pressure occurred in the pulp tower shortly before 12 noon. This caused the roof of the pulp tower to blow off. The torn roof fell onto the roof of the adjacent building and damaged it.

An emergency call was made from the mill at 12 noon. The initial situational information was a collapse of the intermediate ceiling of the production hall. This was later specified as being caused by the falling pulp tower roof. The mill’s fibre line control room began to investigate the event. One of the surveillance cameras in the mill area showed that the upper section of the pulp tower had blown off. The first rescue department units arrived at the scene of the accident at 12.11. A total of seven rescue services and five emergency medical services units arrived at the site. The identity of people in the mill area at any given time is known, which made it possible to determine that no one was trapped under the collapsed structures after the accident. The last rescue department units left the scene at 14:44. Clean up of the accident site at the mill began in the afternoon on 5 November 2024.

As it fell, the pulp tower roof damaged the roof of the adjacent production hall over an area of approximately 400 square metres. Those parts of the hall roof collapsed completely. The beams used to support the roof fell into the production hall and damaged the machinery there. Parts of the pulp tower flew a maximum distance of approximately 200 metres. At the time of the incident, several mill and subcontractor employees were working near the accident site. None of them were injured.

BACKGROUND INFORMATION
The fluting mill has operated in the same factory area since the 1960s. Over the years, the mill as a whole has undergone many changes and refurbishments that have affected production and processes. The fibre line was modernised approximately one year before the accident as part of a more extensive machinery and process renewal. The fibre line has been shut down several times during the year following introduction of the new machinery and processes. A similar surprising increase in pressure has not occurred during operation of the new fibre line.

OBSERVATIONS
In addition to the Safety Investigation Authority, Finland safety investigations in certain fields are carried out by the Finnish Safety and Chemicals Agency (Tukes). The fluting mill is subject to supervision b Tukes under the Chemical Safety Act (390/2005). Tukes appointed an investigation team to investigate the accident. The Safety Investigation Authority, Finland (SIAF) will not initiate a safety investigation into the incident. SIAF believes that the safety investigation carried out by Tukes will achieve a more effective safety benefit in the sector and better disseminate safety information to other operators in the sector and to similar institutions.

More information:
Chief Investigator Timo Naskali, tel. +358 2951 50740