Silo cleaning has a body count, and the incidents repeat with a grim similarity.
Material bridges over the outlet. Flow stops. Production is affected, so somebody goes in on a harness to poke at the blockage from above. The bridge collapses. A person standing on top of what looks like solid material drops into a void and is engulfed in seconds, and material behaves like a fluid once it starts moving, so self rescue is not realistic.
The common factor in almost every one of these events is simple: a person was inside the vessel.
Why silos bridge in the first place
Moisture is usually involved. Cement, fly ash, lime and flour all set up when they get damp, whether from a roof leak, condensation on a cold shell or product that went in wetter than it should have. Time does the rest. Material that sat static through a shutdown behaves very differently to material that keeps moving.
Vibration from neighbouring plant compacts it further. Then the outlet clears just enough to keep running for a while, which hollows out a rat hole through the middle and leaves a hardened ring around the walls. The silo looks like it is working right up until the moment it stops completely.
The methods that keep people out
Work through existing access points. Most silos already have inspection hatches, outlet doors or roof openings. Long reach tools and remote equipment can often reach the blockage from those, with the operator outside the vessel entirely.
Bring it down in stages. The instinct is to free the whole bridge at once. That is exactly what creates a sudden collapse. Controlled removal in smaller amounts, with monitoring between passes, keeps the material predictable.
Clean the walls, not just the outlet. Clearing the blockage and leaving the hardened ring means the same silo bridges again within weeks. If the wall build up is not addressed you are booking your next incident, just with a delay.
Treat entry as the last resort it is. Where entry genuinely cannot be avoided, it runs as a full confined space operation: permit, atmospheric testing before and continuously during, forced ventilation, harness and retrieval, a dedicated standby person and a rescue plan that has been rehearsed rather than filed. Anyone who treats that as paperwork should not be doing the work.
The questions to ask before anyone quotes
A contractor who quotes silo cleaning over the phone without asking these has told you something important about how they work.
- What is the material, and how long has it been static?
- Has it been wet, and is there a known roof or seal problem?
- What access points exist, and what is the structural condition around them?
- What is the atmosphere likely to be inside, and has it been tested?
- Is there a dust explosion risk, which changes everything for grain, flour and some organics?
- Does the structure contain asbestos or hazardous coatings, which is common on older vessels?
Production pressure is the real hazard
Every one of these incidents happens in a context where the plant wants the silo back. That pressure is understandable and it is also exactly what needs to be resisted, because the fastest sounding option and the safe option point in opposite directions.
The good news is that the gap is smaller than people assume. Planned properly, working from outside is usually competitive on time as well as being the method that does not put somebody under an unstable mass of material.
Talk to someone who has run these jobs
If you have one of these coming up, the earliest conversation is the cheapest one. Call 02 8015 6345 or read more about our silo, tank and vessel work.
Perfect Contracting acknowledges the Aboriginal and Torres Strait Islander people as Traditional Custodians of the country on which we live and work. We pay our respects to the Traditional Custodians and Elders past, present and future, and honour their connection to the land and ongoing contribution to society.