"Weighing Out" vs. "Cubing Out" in Liquid Bulk Transport
Every freight dispatcher must calculate whether a liquid consignment will fill the spatial volume of the container first (cube out) or exceed legal road and container payload weight limits first (weigh out):
Light Liquids: "Cube Out" (ρ < 1.0 kg/L)
When shipping ethanol (0.789 kg/L), diesel (0.832 kg/L), or acetone (0.784 kg/L) in a 24,000L ISO tank, filling to 95% capacity (22,800L) produces a payload of only ~18,900 kg—well below the container's 31,500 kg maximum payload limit. Check out diesel volume to mass calculations.
Heavy Liquids: "Weigh Out" (ρ > 1.3 kg/L)
When shipping liquid caustic soda (1.525 kg/L) or concentrated sulfuric acid (1.836 kg/L), a 24,000L tank reaches maximum legal road weight (31,500 kg payload) at only 17,150 Litres (71% volume), creating severe surge instability unless specialized baffles or smaller 17,500L heavy-acid tanks are used.
Standard Liquid Freight Packaging & Payload Limits
Capacity standards and tare specifications for intermodal chemical transport.
| Container Type | Volumetric Capacity | Max Gross Mass | Max Net Payload | Logistics Application |
|---|---|---|---|---|
| Standard 20ft ISO Tank (T11) | 24,000–26,000 L | 36,000 kg | 31,500 kg | Standard bulk liquid intermodal container |
| Standard 20ft ISO Tank (Heavy) | 14,000–17,500 L | 36,000 kg | 32,000 kg | Dedicated for high-density acids (H₂SO₄, HNO₃) |
| Standard 1,000L IBC Tote | 1,000 L | 1,500–2,000 kg | 1,850 kg | Rigid composite intermediate bulk container |
| Standard 208L (55 US gal) Drum | 208 L | 200–350 kg | 320 kg | UN 1A1 / 1A2 steel drum packaging |
| European Road Tanker (Tri-Axle) | 36,000–42,000 L | 44,000 kg (GVW) | 29,000 kg | Multi-compartment petroleum & chemical road tanker |
ADR / IMDG Ullage Regulation (The 80/95 Rule)
Liquid cargo in transit experiences dynamic inertial sloshing during vehicle braking and cornering. Dangerous Goods regulations (ADR Section 4.2.1.9.6 for European road transport and IMDG Code for international maritime transport) mandate:
Tanks without transverse baffles must not be transported between 20% and 80% capacity to prevent catastrophic dynamic fluid hammer and rollover.
Tanks must leave at least 5% vapor headspace to accommodate thermal expansion as cargo heats up during tropical transit without hydrostatic shell rupture.
Frequently Asked Questions
Transport, weighbridge, and customs mass-volume FAQs.