B 1/1996 YThe steel tank downfall in Valkeakoski, 27 March 1996
A massive steel tank of 6000 cubic metres, having the total height of about 35 metres, suddenly fell over at the end of the test filling. The tank was being filled with water to test its water tightness. A little earlier before the tank actually tipped over it was noticed that the tank was tilting. The time between the first observation of tilting and the actual capsizing was around 12 minutes.
One electrician, who was just finishing his daily work nearby destroyed building, died in the accident.
A part of the factory's machine repairshop, the automation and electricity workshop, the forklift truck repairshop, restrooms and other facilities for the employees, the canteen as well as the site huts on the roof, were crushed by the falling tank. In addition to this, the walls of the nearby buildings and site huts, cars, a truck and a lorry in the yard were crushed by a water volume of 5000 cubic metres that flooded from the tank.
On a cable bridge leading to the roof of the repairshop there was an industrial piping through which electricity, district heating, steam water etc. were drawn. This piping partially fell down and was damaged. It then caused further damages in three other factories and in the district heating net of the city.
The Accident Investigation Board found in its preliminary investigations that personal injuries and other damages would have been more extensive. This would have happened if the accident had occurred in the daytime or the tank had tippet over in the opposite direction where dangerous material, e.g. fluid oxygen, was being stored. For this reason an independent investigation group was nominated to investigate the accident as a disaster situation and to give recommendations to prevent similar accidents.
The following causes of this disaster are based on the conclusions of the investigation group.
Mistakes in the design process
The tank itself was made of steel and it was made correct enough, although, its design and dimensions were drawn up by only a simple hand calculation method.
Shortages in driving of the foundation piles
After driving of all the foundation piles, no feedback, not even in form of driving record, was given to the planning engineer once the construction of the piles had been completed.
Testing of the tank
Supervision of the project
The municipal building inspection official did not participate in the supervision, which was entrusted to a person who worked at the same time in the project team as a site leader of the building project. This is a common method to supervise large industrial projects in Finland.
The whole building project was divided into several contracts and subcontracts to ensure specialised knowledge and quality, and also to control of the total costs. In fact this is a common, modern, acceptable and very efficient way to control large building projects.
Traditionally it is not the duty of the safety group to discern possible mistakes in the planning process and to consider the consequences which may follow. In fact, in this case it was nobody's duty, because the engineers relied on right doing of everyone too much.
To prevent similar accidents the investigation group has made some recommendations for actions. The actions are focused on as following