Choosing Between a Tank Container and Drummed Packing
When a liquid chemical bound for Europe should travel in a tank container rather than drums, and the costs that each option keeps off the freight rate.
Representative scenario, not a specific client engagement. This page describes how a shipment of this kind is genuinely handled — the constraints, the approach, and where it commonly goes wrong. It does not name or describe a real Transeasy customer. Our two documented project moves are the Mexico container move and the India overweight cargo delivery.
The situation
A liquid chemical bound for Europe can travel in a UN portable tank container or in drums stuffed into a standard box, and the choice is often made by habit rather than by arithmetic. A twenty-foot tank shell holds somewhere in the region of 21,000 to 26,000 litres depending on the unit, while the same slot filled with 200-litre drums on pallets carries closer to 16,000 to 18,000 litres. On payload alone the tank looks like the obvious answer.
Payload is not the whole picture. A tank is a leased or owned asset that must be positioned empty to the filling point, cleaned to a certificate before the next product, and returned or repositioned after discharge, and the consignee needs a pump, a receiving tank and spill containment to take bulk liquid at all. Drums need none of that infrastructure, but they carry packaging cost on every single shipment, more handling, more potential leak points and a disposal obligation at the far end.
What made it difficult
- Under the IMDG Code a portable tank may only be used where the entry for the substance assigns a tank instruction, and the filling degree is bounded at both ends rather than simply kept below full.
- A tank needs a valid CSC safety approval plate, a current periodic inspection and a cleaning certificate identifying the previous product, so a nominally available unit is not always a usable one.
- Bulk discharge assumes the receiving site has pumping, storage and containment, and where it does not the drums are not the expensive option but the only one.
- Repositioning an empty tank is a real freight movement with a real cost, and on an imbalanced lane it can exceed the packaging saving entirely.
How it is approached
The comparison starts with the dangerous goods entry rather than the price list. The IMDG entry for the substance gives the portable tank instruction and any special provisions, and between them these fix the minimum shell thickness, the pressure rating, the relief arrangements and whether a bottom outlet is permitted. Where no tank instruction is assigned, the decision has already been made. Where one is, the filling degree rules apply, because a part-filled shell surges in transit and an over-filled one leaves expansion nowhere to go.
Compatibility then narrows the equipment further. Shell material and any lining have to suit the product, gaskets and valve seals are specified to it, and a tank that last carried an incompatible cargo needs documented cleaning rather than a rinse. For drums the equivalent question is UN specification: the packaging code must match the packing group assigned to the substance, the closure has to be applied by the method it was tested with, and steel or plastic is chosen on chemical resistance rather than on price.
Costing is then done per litre delivered rather than per container shipped. The tank case carries lease or ownership days, positioning of the empty, cleaning, inspection and the return leg; the drum case carries drums, pallets, wrap, stuffing labour, a lower payload per slot and the consignee's disposal cost. Clearance, inland movement and demurrage exposure are added to both. On most lanes a crossover volume appears, above which the tank is cheaper per litre and below which it is not.
Two factors that are not financial often settle the question. The first is discharge, since a consignee able to decant only by hand will hold a tank far beyond its free days, and detention on specialised equipment is not cheap. The second is risk concentration, because one tank puts a single containment barrier around the whole consignment while eighty drums fail one at a time. Where the product is high value or the receiving site is untested, drums first and a tank later is a defensible sequence.
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Takeaways
- The dangerous goods entry decides whether a tank container is permitted at all, before any cost comparison is worth making.
- A tank wins on payload per slot but brings positioning, cleaning, inspection and a return leg that drummed cargo does not.
- The receiving site's ability to take bulk liquid is usually the deciding factor rather than the freight rate.
- One tank concentrates the entire consignment behind a single containment barrier, whereas drummed cargo fails in units.
Frequently asked
A twenty-foot tank shell is typically in the region of 21,000 to 26,000 litres, against roughly 16,000 to 18,000 litres for 200-litre drums palletised into a standard twenty-foot box. The gap is real, but it is payload rather than saving: positioning, cleaning and the return leg sit outside the freight rate and have to be added before the two options are compared.
Yes, at both ends of the range. Portable tank provisions set a minimum filling degree, because a part-filled shell lets the liquid surge and destabilise the unit in transit, and they require an ullage allowance at the top so the cargo can expand with temperature without pressurising the shell. The figures that apply come from the tank instruction and special provisions for that particular entry.
A current CSC safety approval plate and periodic inspection record for the tank itself, plus a cleaning certificate identifying the product previously carried. The dangerous goods declaration also states the tank instruction applied. Drummed cargo instead needs UN specification markings on each packaging and a container packing certificate covering how the box was stuffed, secured and placarded before it left.