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Investigation of the large fire at the Vaasa transformer plant completed – Tukes investigation team proposes several measures to improve the safety of companies

Publication date 5.10.2023 8.58 | Published in English on 1.11.2023 at 12.40
Press release

The report of the accident investigation team of the Finnish Safety and Chemicals Agency (Tukes) on the large fire at the Vaasa transformer plant has now been completed. The accident chain most likely originated from the missing grounding of the reactor that was being tested. The fire quickly developed into a major fire due to oil leak from the tank connected to the reactor. The fire continued to escalate as the test transformers in the factory premises became damaged, leading to further oil leaks. The large fire also caused financial damage. The accident did not cause any personal or environmental damage. The investigation team makes a number of recommendations to improve technical safety and the actions of companies to prevent similar accidents from reoccurring.

The strong fire was caused by oil catching fire in the test field 

Large electrical transformers and reactors are manufactured and tested at the plant. The investigation confirmed that the probable cause of the accident is related to inadequate grounding of the reactor to be tested.

The facility solutions of the test hall require the tested device to be moved and the groundings disconnected and reconnected as the testing progresses. In the event of an accident, one grounding of the reactor under testing was disconnected, and when the voltage was increased, the metal wire-reinforced oil hose attached to the reactor heated up and caught fire.

Despite the first aid firefighting actions, the fire escalated rapidly because more oil was leaking from the tank. The fire escalated into a major fire in stages, when several test transformers in the premises became damaged and started leaking oil that also caught fire.

After the roof collapsed, the rescue department managed to contain and control the fire.  

The investigation team also found room for improvement in the organisation’s operations 

The investigation team identified a number of safety hazards behind the accident, such as the need to move the device to be tested and the lack of procedures to ensure grounding after these transfers. The investigation team also assessed the company’s maintenance procedures and the implementation of corrective actions.

In 2020, Rescue Services had estimated that the company’s operations would require a Tukes chemical safety permit, and had again instructed the company to apply for a Tukes permit in 2022. The amount of hazardous chemicals handled and stored in the company varied, but, based on the investigation, the company should have had a Tukes chemical safety permit. The investigation team presented several observations and recommendations related to process safety (industrial processing and storage of hazardous chemicals), which are normally addressed in the Tukes chemical safety permit and the related periodic inspections. The company’s chemical safety permit procedure was initiated in Tukes after the accident, in July 2023.

The plant’s electrical equipment has been serviced and the statutory periodic inspections have been carried out. A Supervisor of Operational Works had been appointed for the electrical equipment and the persons participating in the testing were electrical professionals. From the point of view of electrical safety, the investigation team considers the measures that had been taken to be sufficient.

The investigation team proposes several measures to improve safety of industrial companies 

In its report, the investigation team makes a number of recommendations to prevent similar accidents and improve safety. These recommendations are related to technical safety and the actions of companies and authorities. Tukes emphasises that the recommendations apply to a wide range of industrial sectors.

For example, the following recommendations are given to improve technical safety:

  • The test facility for transformers and reactors is designed and built so that moving the object and disconnecting groundings during the test phase is not necessary. In addition, the company must have a technical system or procedure for detecting missing groundings before voltage is switched on.
  • Shut-off valves are secured and, if necessary, installed in the pipelines of hazardous chemicals. These need to be easily accessible even in the event of an accident.
  • Changes in production facilities and access routes are also assessed from the perspective of emergencies and accidents, and it is ensured that the shutdown and restriction measures of all equipment can be carried out promptly and without hindrance when necessary.  

Recommendations for developing the management and operations of companies include: 

  • The company regularly assesses the amount of hazardous chemicals handled and stored at the site and, if necessary, applies for a Tukes permit when the scope of operations changes.
  • Safety-critical equipment and installations are identified and included in the preventive maintenance programme. The adequacy of maintenance operations is monitored.
  • Safety-critical work stages are identified and work processes are supported by check-lists and/or cross-checks.
  • A person familiar with the site is appointed as the responsible party, who must meet the Rescue Services when they arrive at the accident site. The responsible person must be able to leave behind their other duties and be available to the Rescue Services throughout the situation.

The investigation team’s report discusses the course of the accident at the Vaasa transformer plant, as well as the investigation team’s recommendations for preventing similar accidents in more detail.

Tukes Accident Investigation Report: Fire at Hitachi Energy Finland Oy’s transformer plant in Vaasa on 29 March 2023 

Slide show about the accident investigation: Fire at a transformer plant in Vaasa (pdf)

More information: 
Kirsi Levä, Director, tel. +358 29 5052 162
email: [email protected]


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