Rain raises hay fire risk

FARMERS should carefully and regularly monitor haystacks affected by recent rains as there have been reports of heating hay in sheds and outside stacks.
Farmers who have had the bottom layer of their haystacks or rows of bales stored in paddocks inundated by recent floods could find the stacks may start heating, leading to mouldy hay and a real danger of spontaneous combustion.
Flooded round bales in the paddock which have begun heating will already be starting to mould throughout most of the bale and will be worthless.
Haystacks can become unstable as the lower bales start to deteriorate as they start heating severely and moulding badly.
As the heat and moisture rises, it affects bales further up the stack.
If the condensing moisture is not dried off by airflow throughout the stack, the higher bales also begin to heat.
This occurs more so in the large round bale stacks as they are not so densely baled nor so densely tacked. Heat generated at the bottom will escape up through the hay becoming draughts of hot gases or ‘flues’ rising to the top.
Large rectangular bales are much denser pressed and stacked with heat building up more than in the rounds.
It moves more slowly up the stack, making it more difficult to detect when monitoring the stack.
Stacks become dangerous when heating approaches about 70 degrees Celsius and can rapidly reach ignition point.
At this high temperature, seriously consider pulling stacks apart, although large rectangular bales in particular may suddenly ignite when exposed to oxygen.
The popular crowbar method of determining the heat in a stack is limited by the depth it could reach.
To get an indicator of heat further into the stack, use a pipe of 2.5 to 3 metres in length and about 20 millimetres in diameter.
Flatten 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. If hay ignites watch for flying embers and the heat affect on nearby trees, fences, buildings and machinery.