Flooding Increases the Risk of Fire
In a bizarre twist, the recent floods actually increase the risk of fires on rural properties.
Hay bales and hay stacks affected by flood waters or heavy rain are likely to start heating up with the potential to spontaneously combust.
Heat is generated in wet hay when mould, yeast and bacteria begin to break down the hay.
Most farmers and hay contractors are very aware of how important the moisture content of the hay is when baling to avoid heating, but moisture added post baling can be just as dangerous.
Spontaneous combustion is a leading cause of haystack fires in Victoria and farmers with flood affected hay need to carefully look for signs of heating.”
Hay stacks and even individual hay bales still in paddocks become dangerous when heating approaches about 70 degrees Celsius. At this temperature they can increase to ignition point rapidly.
Hay stacks heat up inside, with the temperature on the outside often giving little indication of what is really happening deep within the hay.
A relatively easy way to determine the heat in a stack is to insert a crowbar into the stack as far as possible.
Remove the bar after a couple of hours and the temperature of the bar will give a good indication of how hot the stack might be - at least to the depth of the bar.
Temperature interpretation using a crowbar
|
Temperature (oC) |
Interpretation |
|---|---|
|
< 50 |
Can handle bar without discomfort Check temperature daily |
|
50 – 60 |
Can only handle bar for short time Check temperature twice daily Remove machinery from shed |
|
60 – 70 |
Can touch bar only briefly Check temperature every 2 - 4 hours Move hay to improve air flow |
|
> 70 |
Bar is too hot to hold Potential for fire. Call Fire Brigade immediately. Avoid walking on top of haystack |
Unfortunately, detecting heat in the middle of large stacks is not so easy.
To get an indicator of heat further into the stack Mr Mickan recommends using a pipe of 2.5 to three metres in length and about 20 millimetres in diameter. Flattened one end and drill two to three millimetre diameter holes about 75 millimetres above the flattened end.
Drive the flattened end into the stack and lower a small thermometer to the end of the probe using light wire as string may burn or break. Retrieve thermometer after about 15 minutes.
Farmers should seriously consider pulling stacks apart if at high temperatures and also suggests alerting the CFA prior to starting work as the bales could suddenly ignite when exposed to oxygen.
Make sure all equipment is removed from inside or nearby by locations if the stack is becoming seriously heated. He warned that haystacks become unstable as the flood affected lower bales start moulding badly, begin to heat up and lose their shape.
Don’t walk across the top of severely heated stacks as they could collapse inwards as a result of unseen charring in the middle.
If hay ignites watch for flying embers and the heat affect on nearby trees, fences, buildings and machinery.
Flooded bales in the paddock which have begun heating will already be starting to mould throughout most of the bale and will be worthless.
More information on how to monitor haystacks is available in DPI’s Haystack fires and What happens when hay heats publications.
DPI Forage Specialist Frank Mickan
