A silo tanker (silobas) is a closed, pressure-resistant tank trailer used to carry dry bulk powders and granules such as cement, lime, flour, sugar and plastic granulate without packaging. The cargo is filled through hatches on top; for discharge, a compressor blows air into the tank and the product is conveyed pneumatically through a hose into the consignee's silo. For food and chemical cargo, consignees usually require a tank cleaning certificate.
How does a silo tanker work?
A silo tanker is a tank made of aluminium or steel, either horizontal or divided into conical compartments. There are filling hatches at the top and a discharge outlet at the bottom or rear. With powders, aeration surfaces on the tank floor fluidise the product. With granules, some models raise the tank hydraulically (tipping silo tanker) so that the product flows to the rear. The air needed for discharge comes from a compressor mounted on the tractor unit or connected to the vehicle.
- Preparation: The tank must be cleaned of the previous cargo and dry; the cleaning certificate travels with the vehicle.
- Filling: The product flows from the factory silo through the top hatches into the tank, and the vehicle is weighed.
- Sealing: Hatches and valves are sealed; the seal numbers are entered in the shipping documents.
- Connection: On arrival, the discharge hose is connected to the consignee's silo pipe.
- Pressurisation: The compressor blows air into the tank; the product is conveyed through the hose into the silo.
- Check: It is checked that the tank has been completely emptied; residues could contaminate the next load.
Which cargo is carried?
| Cargo group | Examples | Point to watch |
|---|---|---|
| Construction materials | Cement, lime, fly ash, gypsum | Moisture causes lumping; heavy cargo reaches the weight limit before the volume is full |
| Food | Flour, sugar, starch, corn grits | Tank dedicated to food and a food-grade cleaning certificate |
| Plastics and chemicals | PE and PP granulate, PVC powder | Cleaning that prevents mixing of colours and grades |
| Dangerous powders and granules | Certain chemicals covered by ADR | ADR-approved tank and vehicle and a certified driver |
The upper weight limit is set by the Turkish Highway Traffic Regulation: for combinations with five or more axles, the maximum gross weight is 40 tonnes. The net payload depends on the tare weight of the tractor and the tank. With dense products such as cement, the weight limit is reached before the tank volume is full; with light products such as plastic granulate, volume is the deciding factor.
Why is a cleaning certificate required?
Because the same tank carries different products, the consignee wants to be sure that no residue from the previous load has mixed with its own product. The common proof in Europe is the ECD (EFTCO Cleaning Document) of EFTCO, the federation of tank cleaning organisations. The federation represents 630 cleaning stations in 26 European countries. Each ECD carries a unique number and documents that the cleaning was carried out in line with the customer's request and with legal, safety and environmental rules. Cleaning is performed according to the last product carried in the tank. For food-grade cleaning, EFTCO runs a separate food assessment; the 2026 version has been available since 1 October 2026 and becomes mandatory on 1 January 2027.
For food cargo, many consignees require a dedicated food tank and a list of previous loads. Switching a tank that has carried chemicals to food service is generally prohibited in consignee contracts.
Relationship with ADR
Cement, flour and plastic granulate are not dangerous goods. However, some powdered and granular chemicals fall under ADR. For these loads, the tank and vehicle must be ADR-approved, the driver must hold an ADR certificate and the vehicle must be marked. The rules are explained in the entries what is ADR and ADR certificate of approval for vehicles. The difference from tankers used for liquid chemicals is covered in the entry on chemical transport, and the intermodal option in the entry on the ISO tank container.
Common mistakes
- Not asking the consignee in advance about the silo connection type, pipe length and discharge time.
- Asking for the cleaning certificate only at the time of loading; without the document, the vehicle can be turned away.
- Filling with open hatches in humid weather.
- Using the same tank for food and chemical loads in succession without documentation.
How does Voltim Global support you?
For jobs requiring a silo tanker, Voltim Global sources the vehicle from its partner carrier network; loads covered by ADR are planned with partners that hold the relevant certificates. Details are on the dangerous goods (ADR) page.