Sawmills are often associated with a high risk of fire, given that a high fire load – timber – is produced and stored in them. The fire safety systems in Koskisen’s new sawmill go beyond the requirements, although the hope is, of course, that they will never be needed.
Like any other building, a sawmill building must meet the stipulations of both the Building Act and the Rescue Act. Fire safety planning must take into account construction materials, fire-extinguishing systems, emergency exits and fire protection. Sitowise Group Oyj has been responsible for fire safety planning at Koskisen’s sawmill.
“The new sawmill is a concrete building, and while the exterior walls are made of wood elements, there is concrete underneath them. Inside the sawmill, the intermediate walls of the production areas are made of sheet metal and wool elements, and all the spaces with high ceilings and separate spaces are fire-compartmented. Since only 4 or 5 people normally work in the sawmill during a shift, there was no need to plan extra emergency exits. Besides the normal access routes, there are also emergency exits leading to the roof, from where it is possible to climb down ladders to safety in the event of a fire. Every emergency exit door is equipped with a push-button fire alarm,” explains Tauno Tonteri, Koskisen’s fire chief since 2017.
Tonteri, who has worked at Koskisen since the 1990s, says that once the fire safety plans were completed, a discussion with the insurance company began.
“The insurance company gave the green light, as the sawmill’s fire safety systems exceed the minimum legal requirements. For example, instead of fire hydrants, we have a separate fire-extinguishing water system in our yard area,” he says.
Fire-extinguishing water on site
Located on the lot of the sawmill is southern Finland’s second-largest water-pumping station, whose task is to ensure the supply of water to the fire sprinklers and fire-extinguishing water system in case of a fire.
“The volume of the sprinkler water reservoir is over a million litres, and each of its three diesel pumps can pump 6,000 litres of water per minute at 9.5 bar. The fire water reservoir has roughly 600,000 litres of water and two pumps, which are as powerful as the pumps in the sprinkler pumping station,” says Tonteri.
Both the sawmill’s and the dimension-sorting plant’s ceilings are equipped with sprinklers, and an automatic extinguishing system can also be found on the platforms of the maintenance levels and auxiliary spaces. There are a total of 1,540 sprinklers in the sawmill and its related spaces. Automation is also used in the sawdust extraction pipes.
“ATEX spaces are potentially explosive spaces, in which a flammable substance – in this case sawdust – can, in combination with normal air pressure, cause an explosive atmosphere. For that reason, the sawdust extraction pipes are equipped with a spark extinguishing system whereby a spark will automatically trigger a dense water mist that prevents an explosion,” explains Tonteri.
Some spaces also have multi-criteria fire detectors, which measure temperature, changes in temperature, and smoke. All electrical rooms and exterior transformers, as well as timber storages, are equipped with these detectors.
“The starting point for planning is compartmentation. If that is not possible, the spaces are equipped with sprinklers. If sprinklers are not possible, fire detectors are used,” says Tonteri.
Although the prevention, detection and extinguishing of fires is highly automated, human input is still needed. All employees have completed Occupational Safety Card training, in addition to which, maintenance personnel have also completed Hot Work Card training. If necessary, AS1 first-hand extinguishing training is organised, and the exercises are also part of the sawmill’s routines. The exercises go over, among other things, the use of fire blankets, foam extinguishers and fire hydrants.
“Our approach is to first try to extinguish the fire on our own, and if that doesn’t work, we press the fire alarm button. We must not put ourselves or others in danger, of course. Not everyone will be able to leave the area immediately, however, because there must be people around to guide the fire brigade. In many cases, the forklift drivers are responsible for guiding traffic,” says Tonteri.
The equipment is maintained and tested every month, serviced every year, and inspected for operation by authorities every few years. The most important measure of all, however, is fire prevention. Tonteri says maintaining cleanliness is a priority in that respect to ensure that flammable substances do not accumulate in places where they do not belong. Production spaces should also be free from sawdust or fine dust, which at Koskisen is collected and transported by conveyors and pipes for use in heat production. Fires can also start outside the sawmill, which is why machinery must be parked at least 30 metres from a potentially burning structure.
“People are well-informed, and they understand the risks. We don’t see deliberate acts of negligence or recklessness here,” stresses Tonteri.
Sometimes maintenance work that entails a risk of fire does take place in the sawmill. Koskisen has its own hot work plan that again begins with cleaning.
“Before any work is started, the issuer of the hot work permit specifies, among other things, what is to be cleaned, what fire extinguishing equipment is to be provided and whether something needs to be covered. In spaces that may contain dust, a foam layer is applied before the hot work begins. Hot work is always performed by two people, and at Koskisen, the post-work fire watch is two hours instead of the usual one hour,” explains Tonteri.
If a fire were to ignite somewhere in the sawmill, however, flames are not the only threat: burning wood quickly generates considerable smoke. Smoke extraction has been a focus of the new sawmill, and mechanical fans efficiently blow smoke through the smoke exhaust vents.
Koskisen no longer has its own mill fire brigade and is instead served by the contractual fire brigade Järvelän VPK. Tonteri says the fire brigade carries out drills in the mill areas ten times a year and describes the co-operation as excellent. The fire brigade’s main “area of attack” is the inside yard of the mill. Tonteri considers the area difficult to navigate and, particularly to outsiders, confusing. Despite the drills and a visit from Päijät-Häme Rescue Services to familiarise themselves with the area, more signs are needed in order to ensure the fire extinguishing equipment gets to the optimal stations as quickly as possible.
“We believe we have done our best and taken all factors into consideration to ensure fire safety. My greatest wish, however, is that this is all unnecessary and these systems and equipment will never be needed,” Tonteri sums up.