What Is a Silo Tanker?
A silo tanker (dry bulk trailer) is a closed-tank semi-trailer designed to carry dry bulk goods such as flour, cement, lime, plastic granules and animal feed without sacks or packaging. The product is loaded through manholes on top of the tank and discharged pneumatically: a compressor delivers pressurised air that fluidises the cargo over aeration pads and pushes it through discharge pipework, allowing silo-to-silo transfer.
Silo tankers are built from aluminium or steel. In food-grade applications, interior surface quality and cleanability are essential. Tank volume, axle count and discharge equipment vary by product and by national regulations.
V-Type Silo Tankers
In a V-type silo, the bottom of the tank ends in one or several V-shaped cones. The steep cone angles let the cargo flow towards the discharge outlet under gravity, assisted by air.
- Well suited to poorly flowing, clump-prone powders such as flour, starch or milk powder.
- More cones mean fewer dead zones inside the tank and less residual product.
- A frequent choice for food-grade work, where complete discharge and easy cleaning matter most.
W-Type Silo Tankers
In a W-type silo, two rows of cones side by side form a "W" cross-section at the bottom. This geometry spreads the tank volume across a lower body.
- The centre of gravity sits lower, which helps stability when driving loaded.
- More volume can be achieved at the same overall height.
- Common for dense mineral powders such as cement, lime and fly ash.
Vacuum (Pressure-Vacuum) Silo Tankers
A vacuum silo tanker does not only discharge under pressure; its equipment can also create a vacuum and suck the product into the tank, so the trailer can load itself.
- Advantageous when collecting product where no silo or loading station exists — ship holds, open heaps, rail wagons.
- Suits two-way logistics scenarios because it can both suck and blow.
- The equipment (blower/compressor, filter group) is more complex than on a standard silo, so maintenance demands rise accordingly.
Which Type for Which Product?
- Flour and food powders: complete discharge and hygiene come first, so V-type designs with food-grade interiors dominate.
- Cement, lime and mineral powders: their high density favours the low centre of gravity of W-type tanks, though V-types are also used.
- Plastic granules and pellets: they flow freely, so either geometry works; the critical issue is cleanliness and preventing colour or material cross-contamination.
- Sites without loading infrastructure: vacuum types come into play.
Exact volumes, pressures and axle figures depend on the model, the manufacturer and national regulations. The choice should always weigh the product's density, flow behaviour and hygiene class together.
Barlas Trailer manufactures and repairs V-type, W-type and vacuum silo tankers for a wide range of dry bulk products.