Forensics

Medium Density Board Factory Fires

Forensic Services Newsletter

The occurrence in 2007 of fires at presses at three different medium density fibreboard (MDF) factories in Malaysia has highlighted the risks the insurance industry faces in this industry. Nevertheless, the situation is improving in the long term. This newsletter explains why.

File Photo 1 - The side of an MDF press, unaffected by fire. There are so many hoses, ducts, motors, electrical wiring and instrumentation around a typical press that it is difficult to see how they operate.

MDF presses are largely made of steel. The highest potential contributors to fuel load are the thermal and hydraulic oils, which are sealed in plates and piping and are effectively not available to burn, at least in the early stages of a fire. At any one time there is not enough product passing through the machine to cause its destruction if it were to burn. Why then are there disastrous fires of sufficient destruction to cause these presses, worth tens of thousands of US$, to be scrapped?

The answer lies in the fibres that are continually being emitted from the machines as product passes through. Although most fibres are produced at the infeed and exit ends, they accumulate all over the press and a fire is able to quickly spread from end to end, sometimes over the top where the exhaust ducts predominate, also via the pit under the press.

File Photo 2 - A press after a serious fire, with everything stripped except the frames and platens. The paint has been largely burnt away from the frames.

The fibres by themselves do not explain why there can be such destruction, since they are light and do not contribute much fuel load. A press is continuously exuding oil from moving parts, particularly the roller chains that encompass the platens. In industry it is common to use sawdust to soak up spills of oil. MDF presses do this naturally, and over time the surfaces in and surrounding the machine become covered with layers of oil-soaked wood fibres. It is the burning of such accumulated material that can severely damage a press, and if thermal/hydraulic oil is released, cause total destruction.

When we started investigating fires at MDF presses 10 years ago, we observed that the approach to housekeeping was comparable to other industries, whereby when the presses stopped for maintenance the accumulated material was removed. The first change we have noted is with this cleaning philosophy. Progressive companies now recognize that MDF presses need to be continually cleaned, and at one press we visited recently there were two workers on each shift devoted to cleaning, round the clock. This emphasis on housekeeping is the first change that has lessened the likelihood of a press being destroyed by fire.

File Photo 3 - A spark/fire detector located in the pit under an MDF press.

The second change is the deployment of water mist spray fire protection systems. Articles about this technology in fire magazines read like an answer in search of a problem. It has been suggested they be used in aircraft and computer rooms. However if there is one application to which they are well suited it is MDF presses. To begin with, the non-life threatening mist can be activated the instant that a fire, or even a spark, is detected [1]. This compares with CO2 extinguishment systems where there must be a warning period (during which the fire can continue to grow) to allow workers to withdraw to safety. Then the fine mist is drawn into the press by the existing ventilation, where the small particles of water cool the fire, wet fibres and displace oxygen (by steam formation). Mist spray nozzles typically emit 10-20% of the water from a conventional spray nozzle, so that water reserves will last a long time. Workers can attack particular areas with hand held extinguishers while the mist spray system is in operation.

[1] For example, mist spray systems can be accidentally triggered by camera flashes.

There are a number of companies that specialize in the fitting of mist spray systems to MDF presses. All the fires we have attended where the MDF press was destroyed, were without such mist spray systems. At all of the fires we have been to where the MDF press had a mist spray system installed by a recognized specialist, there was limited damage and the press was able to restart within days.

File Photo 4 - A water mist spray outlet with multiple nozzles. The fibres accumulate over time.

The three fires mentioned that occurred in Malaysia this year well illustrate the points we are making. The first was at a press with a mist spray system and production restarted after 10 days. The second was at a press where a mist spray system was being installed, but not yet commissioned. For the third press, a mist spray system was to be installed in 2008. The last two presses will be out of commission for months and the fact that the presses were not destroyed is likely attributable to rigorous housekeeping regimes along the lines described above.

The advantages of water mist spray systems in this area of industry are so apparent that one can foresee insurers refusing to cover presses that are not protected in this way.

If you have a query you may contact us in any of the following ways.

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Regards,


Barry Dillon

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