Mixed Cargoes in Multi-Compartment Tankers

Two batches of liquid raw material are heading in the same direction, but neither fills an entire tanker. Combining them on one trip seems convenient. Available capacity, however, does not establish whether the arrangement is acceptable: the products, equipment design and conditions at every delivery stage need separate checks.

When planning road tanker transport, a multi-compartment design can accommodate different products in isolated compartments, provided that the specific combination meets technical, regulatory and quality requirements. Approval applies to identified cargoes and an identified tanker, rather than to “any liquids” as a group.

Compartments and baffles serve different purposes

A cargo compartment is a separate space isolated by a liquid-tight partition. A baffle reduces liquid movement inside a tank but does not necessarily isolate one part from another. The number of manholes or internal plates therefore does not, by itself, establish that several products can be loaded.

The tanker documentation should identify the number and capacity of isolated compartments, together with shell, lining and seal materials. Pipework needs a separate review: compartments may have individual outlets while using a common manifold, pump or hose. Air and vapour lines should also be checked where relevant. Independent cargo spaces and fully independent equipment are different features.

A useful request to the carrier is a compartment and connection diagram for the actual vehicle. Photographs or a statement that “there are three compartments” are insufficient to approve a complex combination.

How to assess cargo compatibility on the same trip

For chemical transport, the product names on an order are not enough. The assessment needs the exact grade, composition or concentration, safety data sheet (SDS) and specification. Three distinct questions should be addressed:

• Chemical compatibility: could contact between the products cause a dangerous reaction, release gas or heat, or produce hazardous compounds?
• Quality preservation: would even trace contamination affect purity, colour, odour or the intended use of either product?
• Equipment compatibility: are the tank, fittings, seals and hoses suitable for each liquid?

If ADR applies, the assessment also covers cargo classification, approval of the particular tank and applicable dangerous goods transport conditions. Sharing a hazard class is not sufficient grounds for a combined trip.

ADR 4.3.2.3.6 specifically addresses substances liable to react dangerously when carried in adjacent compartments. Its exceptions involve defined requirements for the separating partition or an intervening empty space or compartment. Describing a vehicle as a multi-compartment tanker does not establish compliance; the documentation and applicable ADR provisions must support the decision.

Separate compartments do not remove contamination risks

Contamination can enter a product outside its compartment through residue in a shared pump, manifold, hose or discharge connection. Before approving the trip, trace each product’s route from the loading line to the receiving tank. Shared equipment requires a justified cleaning procedure or another suitable technical arrangement.

Previous cargo history is a separate check. This is covered in more detail in the article on compatibility between previous cargoes and the next load. An EFTCO Cleaning Document records cleaning operations performed; it does not, by itself, establish suitability for every subsequent product.

For food-grade vegetable oil transport, hygiene requirements also apply. In the EU, receptacles used for bulk liquid food transport must be reserved for foodstuffs. A partition does not automatically authorise carrying edible oil alongside an industrial chemical. Different food cargoes also require checks on contamination risks and cleanliness requirements.

Can adjacent compartments maintain different temperatures?

Several compartments do not necessarily provide several independent temperature zones. They may share a heating system, and heat transfers through metal structures. Insulation reduces heat exchange with the surroundings but does not make arbitrary temperature differences between products achievable.

When planning temperature-controlled cargo transport, compare the acceptable ranges during loading, transit and discharge. If one product needs heating that would be unsuitable for another, verify whether independent control is actually possible and how the adjacent compartment affects it. Without that confirmation, the combined trip should not be approved. Temperature also matters when calculating density and volume.

Calculate volume before allocating the load

Equal masses of different liquids occupy different volumes. For an initial calculation, divide mass by density at the relevant temperature. This illustrative example shows why compartment planning cannot rely on tonnes alone:

This is an arithmetic example, not an approved loading plan. A 10 m³ batch will not necessarily fit into a compartment with a nominal capacity of 10 m³: the permitted degree of filling, liquid expansion and applicable requirements must be considered. Partial-fill restrictions also depend on the design, product and regulatory rules.

Check axle loads and the permitted gross combination weight. The vehicle’s condition after each discharge matters too: an arrangement acceptable at departure may require different batch allocation to remain acceptable on the next route segment. An empty compartment may be part of the agreed plan rather than spare capacity available for another cargo.

Match each compartment to the discharge sequence

Agree the delivery order before loading. For every compartment, identify its product, the outlet used and the receiving tank it must reach. This is particularly important with several recipients or similar product names.

• Record the compartment number, product and batch, mass or volume, required temperature conditions and recipient in the loading plan.
• Agree the discharge sequence, connections, pumps and hoses, including how residues in shared lines will be managed.
• Before transfer, check the compartment, outlet identification, documents and receiving tank; record seals and control information required by the plan.

Prepare transport documents according to the actual consignments, recipients and cargo requirements. The number of compartments does not, by itself, determine the number of CMR consignment notes. Records must nevertheless provide an unambiguous link between each batch, its compartment and its delivery point.

When a multi-compartment tanker offers a practical advantage

A combined trip is worth considering when batch sizes suit the compartments, the products and equipment are compatible, and loading and delivery locations form an efficient route. This arrangement may allow several smaller batches to travel without a separate full vehicle for each one.

Assess savings across the whole trip. An extra factory stop, waiting for a delivery slot, special cleaning or filling restrictions can reduce the benefit. If line isolation, temperature conditions or acceptable load distribution after discharge cannot be confirmed, separate shipments should be costed.

What information is needed to assess a combined trip?

Provide a product list with grades and concentrations, SDS documents for chemical cargoes, the mass of each batch and density at a known temperature. Add loading and delivery addresses, time slots, the preferred delivery sequence and receiving conditions.

Specify requirements for cleanliness, previous cargoes, temperature, tank materials, pumps and connections. These details allow the actual vehicle to be assessed and the feasibility of carrying the products together to be established.

Send the batch details to Save Pro Solutions to develop a bulk liquid transport plan. The final choice of a multi-compartment tanker should rest on verified compatibility, equipment suitability and an agreed sequence of operations throughout the route.