A flexi-tank is a Thermoplastic bag of up to 24000 litre installed inside a 20ft box container. It is used to transport non-regulated (non hazardous) bulk liquids such as wines, lubricants and detergent. This method of transporting bulk liquids is an alternative to the tank container and might be of cost benefit where return loads are not viable and a degree of safety risk can be tolerated.
A flexitank is essentially a large plastic bag, fitted with a loading and discharge valve. Prior to loading, the flexi-tank bag is laid out into a box container.
The cargo is pumped into it through a valve and as the liquid fills the bag it expands to fill the container. Once loading is finished, the valve is shut off and the doors to the container are closed and secured.
The cost of the one trip flexi-tank varies. Reports of bags costing less than $500 and more than $1000 prevail but the cost depends upon the material, design, valve arrangements, whether or not a bulkhead is included, delivery costs etc. The majority of moves are arranged by logistics specialists who provide door to door full service including disposal of the contaminated bag.
Unlike the tank container, used repeatedly for many years, the flexi-tank is designed for one trip. The empty contaminated bag must be disposed in an approved waste facility. Certain materials can be incinerated and others might be suitable for shredding in preparation for re-cycling.
It has been reported that when fully laden the weight of the 24000 litre bag causes the side wall of the box container to distort outwards beyond ISO. The side wall is designed to withstand a certain pay-load for static cargo. The flexi-tank load is liquid and the laden bag effectively forms the shape of the box. Cargo surge during movement and transport of the box results in potentially excessive side and end wall loads and potential instability during trucking and lifting.
Currently containers are tested and approved by issue of a safety certificate (CSC). Flexi-tanks are tested independently of the container. It has been suggested that safety would be improved if manufacturers tested the integrated package of bag-in-the box and issued a safety approval certificate. At the present time there are no regulations to enforce such as test.