A Grain Silo With a Hot Spot and a Delivery Due
You manage a 500-tonne flat-bottom silo of wheat on a mixed farm. It was harvested in December at about 12.5% moisture and has been in store since. In late summer you notice a warm patch on the silo wall about 2 m up, condensation on the inside of the roof hatch, and a faint musty smell when you open the hatch. A buyer's truck is due in three days to take 80 tonnes. The aeration fan works but the power to the silo is shared with the shearing shed and the shed is booked for shearing on the same days.
1. Diagnose what is likely happening and decide what to do before the truck arrives.
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Diagnose: a warm patch, roof condensation and a musty smell together point to a moisture migration and heating problem - likely a hot spot from grain respiring, with moisture moving to the cooler surface. At 12.5% it went in dry, but temperature gradients in a large silo can move moisture over months, and a warm patch is a warning, not a small issue.
Actions before the truck:
- Probe and sample. Take samples from the warm area and from a few depths, check moisture and smell, and look for insects or mould. Do not load out 80 tonnes blind.
- Run the aeration fan as soon as possible - cool the grain to slow the heating. This is the priority use of the shared power; negotiate with the shearing shed or run the fan at night when the shed is idle.
- Do not blend the suspect grain into the delivery. Mixing a hot spot through a load can turn a small problem into a rejected truck and a residue or quality claim.
- Call the buyer before the truck leaves if the sample shows quality issues, and discuss options: delay, deliver clean grain only, or price adjustment.
Judgement point: the exam wants you to connect the symptoms to a cause, act early to cool the grain, and protect the delivery from contamination rather than hiding the problem.
2. The shearing contractor needs the power and the buyer wants the full 80 tonnes. How do you prioritise and communicate your decision?
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Prioritise by consequence. A hot spot that is not cooled can ruin a 500-tonne silo - far more value than one shearing day or one delayed truck. So aeration comes first. But that does not mean the shearing shed loses power for days; it means you negotiate a schedule.
Plan:
- Run the aeration fan at night and in the early morning when the shed is not shearing, and again after the shed finishes. Grain cooling does not need to be continuous if the fan is run in the coolest hours.
- Tell the shearing contractor the reason and the new power windows, so they can plan around them.
- Tell the buyer honestly what you found and what you are doing. Offer to load the clean grain first and hold the suspect section pending sampling. A buyer who is told early can work with you; a buyer who finds out at the weighbridge will not.
Record: temperatures, moisture readings, fan run times, samples taken and what was sent. If a dispute arises, those records show you acted promptly.
Judgement point: competing demands (contractor, buyer, grain quality) must be ranked by the size of the loss each one risks, and the decision must be communicated before the other parties discover it themselves.