A flexitank is a large single-use flexible bladder fitted inside an ordinary 20 ft dry container, turning a standard box into a one-way bulk liquid tank. Capacities typically run between about 16,000 and 24,000 litres, which for a refined vegetable oil corresponds to roughly 21 to 24 tonnes. It is the standard way to move a container-sized parcel of non-hazardous food liquid – vegetable oil, juice concentrate, wine, glycerine – without committing to a tank container.
Its advantages over an ISO tank are cost and the elimination of the previous-cargo question. The liner is new, food-grade and used once, so there is no cleaning certificate to review and no history to trace; the certificate of the liner material and its food-contact compliance replaces both. There is also no empty tank to reposition, which is what makes the economics work on one-way trade lanes.
What it demands in return is discipline on three points:
- Carrier approval. The shipping line must have approved the specific flexitank type for use in its containers. This is not a formality and lines do refuse.
- A fitted bulkhead. A liquid load surges, and the bulkhead at the door restrains it. Correct fill level matters for the same reason: a partly filled bladder is genuinely dangerous, not merely suboptimal.
- Documented loading and sealing. Photographs of the installation, the fill and the seals, with seal numbers recorded. On a bulk liquid the seal record is the first thing an insurer asks for when a shortage or contamination claim arises.
Its limitations are equally practical. A flexitank normally cannot be heated, so it does not suit fats that solidify or viscous cargoes. It is not designed for part discharge in the way a tank is. And a bladder failure is a total loss of the parcel rather than a partial one, which is why installation quality and the choice of supplier matter more than the price difference between two quotes.
For the comparison against ISO tanks, road tankers and drums, see the bulk commodity logistics guide.