The powder / silo ISO tank discharges dry-bulk cargo via pneumatic conveying rather than gravity flow. Cylindrical or tub-shaped pressure vessel at a 2 bar working pressure rating. Aluminium 5083 is the preferred shell material for lower tare; carbon steel is the cost alternative. Capacity 17,500 to 25,000 L typical. The cargo population is dry-bulk industrial materials: cement, fly-ash, plastic pellets, flour, sugar, animal feed, fertiliser. Operators with deep dry-bulk-fleet expertise (Bertschi, Hoyer, Den Hartogh, Suttons silo division, VTG Tanktainer) move millions of tonnes per year of these cargoes through ISO 22-series silo equipment.
What powder / silo is built for
Cement, fly-ash, lime, bentonite, limestone powder, soda ash, calcium carbonate, gypsum, alumina, carbon black, kaolin, talc. Plastic pellets and granules (PE, PP, PVC, PET, ABS, polymer compounds). Food-grade dry-bulk: flour, sugar, milk powder, animal feed, starch, soybean meal, salt. Specialty: caustic soda flakes and pearls in specialised builds, fertiliser. The plastics fleet alone runs into thousands of tanks because polyolefin manufacturers ship pellets in containerised pneumatic equipment between production sites and converter plants worldwide.
Construction and materials
Cylindrical or tub-shaped pressure-vessel shell, aluminium 5083 (preferred for lower tare, around 4,200 kg) or carbon steel (around 5,000 kg, lower build cost). 8 mm reference shell typical. 2 bar pressure rating. 60-degree conical bottom for gravity-assisted fluidisation. Pneumatic discharge system: an air compressor (own or onsite at the discharge depot) at 2 bar pressurises the tank, fluidises the product through aeration pads in the conical bottom, and conveys the cargo through a 4-inch hose to the receiving silo. Top manlids 500 mm diameter for inspection and small-batch loading; main loading via top-mounted gravity drop or pneumatic top-fill.
Some food-grade builds add rotary valves on the outlet for batch dispensing and allergen-segregation controls. The ECTA (European Chemical Transport Association), Cefic (European Chemical Industry Council), and EFTCO (European Federation of Tank Cleaning Organisations) maintain a Best-Practice Guidelines for Cleaning of Dry-Bulk Polymer Transport Tanks document (current Issue 5, November 2024) covering “zero-pellet-loss” handling and cross-contamination prevention.
When powder / silo is the right choice
Powder / silo is the right tank for any dry-bulk cargo above the 15 to 20-tonne ISO-tank threshold where pneumatic discharge is the receiving-side handling preference. The plastic-pellet trade is the largest user of this fleet: polyolefin pellets ship from Saudi Arabia, the US Gulf, and Iran to Asian and European converter markets in dedicated polymer-pellet ISO silo tanks. Cement and fly-ash ship from cement plants to construction sites in regional silo fleets.
When powder / silo is the wrong choice
Powder / silo is the wrong tank for any liquid cargo. The pressure rating, the conical bottom, and the pneumatic-discharge geometry are all liquid-incompatible. Powder / silo is also the wrong choice for granular cargoes that don’t flow under pneumatic conveying (oversize granules, sticky / clumping materials); these need bulk-bag handling or a different equipment class.
How a powder / silo booking is verified
Pre-loading inspection covers the standard plate stack (CSC, TIR, PED) plus the pneumatic-discharge system functional test (compressor connection, air-pad operability, hose integrity). Cleaning verification follows ECTA / Cefic / EFTCO Best-Practice Guidelines: pellet-count residual check, dedicated-fleet history showing no chemical-cargo cross-contamination, food-grade cleaning ECD where applicable.