How Many Drums of IPA Fit in a 20 ft and 40 ft Container? Net Weight and Gross Weight Limits

2-Propanol (isopropanol, IPA, CAS 67-63-0) is consigned as UN 1219, Class 3, Packing Group II, with a flash point of 12 °C by ISO 3679 closed-cup and a boiling point of 82.5 °C at 101.3 kPa. The drum count question for 20 ft and 40 ft ISO general-purpose containers is not a simple floor-area division. It is governed by the outside diameter of the UN-certified tight-head drum, the filled volume at the reference temperature, the tare mass of steel or HDPE packaging, the payload rating of the container, and the ullage constraints applicable to flammable liquids. A common 200 L tight-head drum has a nominal capacity of 208 L, an outside diameter of 571.5 mm, a height of 880 mm, and a steel body mass of 16–19 kg; the same drum in HDPE 1H1 construction has a tare mass of 8.5–10 kg. At 20 °C, the density of IPA is 0.785 g/cm³ by ASTM D4052, giving a net mass of 157.0 kg per 200 L fill.

How Many 200 L Tight-Head Drums Fit in a 20 ft General-Purpose Container Without Exceeding Payload?

A representative 20 ft ISO 1CC container has internal length 5,898 mm, width 2,352 mm, height 2,393 mm, and payload of 28,250 kg against a maximum gross mass of 30,480 kg under ISO 668:2020. A UN 1A1 tight-head steel drum with outside diameter 571.5 mm and height 880 mm allows four drums side-by-side across the container width: 4 × 571.5 mm = 2,286 mm, leaving 66 mm of cross-width clearance. Ten rows lengthwise consume 5,715 mm, leaving 183 mm at the doors. Two-high stacking consumes 1,760 mm of interior height, leaving 633 mm under the roof. The resulting loose-load count is therefore 4 × 10 × 2 = 80 drums.

If drums are palletized on 1,140 mm × 1,140 mm four-way wooden pallets, two pallets fit across and five fit lengthwise per layer. A single layer carries 10 pallets and 40 drums. A double-stacked palletized load carries 20 pallets and 80 drums. With steel drum tare of 17.5 kg, the gross mass per palletized four-drum module is 723 kg. For 80 drums on 20 pallets, net IPA mass is 12,560 kg; steel drum gross mass is 13,960 kg; and gross mass including pallets is 14,460 kg. That is approximately 51% of the 20 ft container payload. No gross weight reduction is required for the 20 ft configuration unless the container has an unusually low payload rating below approximately 14,500 kg.

Against a 28,250 kg payload, the allowable gross mass per pallet position in a 20 ft double-stacked arrangement is 1,412.5 kg when 20 pallet positions are used. The steel four-drum module at 723 kg leaves a margin of 689.5 kg per position. The 20 ft drum count is therefore geometry-limited rather than weight-limited.

Gross Weight at the 40 ft Palletized Double-Stack Threshold Is Strongly Pallet-Mass Dependent

A representative 40 ft ISO 1AA container has internal length 12,032 mm, width 2,352 mm, height 2,393 mm, and payload of 28,750 kg against a maximum gross mass of 32,500 kg. Loose steel drums can be arranged 4 across, 21 rows lengthwise, and 2 high, giving 168 drum positions. Net IPA mass at 157.0 kg per drum is 26,376 kg. Steel gross mass at 174.5 kg per drum is 29,316 kg, which exceeds the 28,750 kg payload by 566 kg. The weight-limited count for loose steel drums is therefore 164 drums, yielding net mass of 25,748 kg and gross mass of 28,618 kg. If HDPE 1H1 drums are used, the same 168 positions can be filled because gross mass is 27,972 kg at 166.5 kg per drum.

Palletized double-stack loading uses 2 pallets across and 10 pallets lengthwise per layer; two layers produce 40 pallets and 160 drums. The net IPA mass is 25,120 kg. Steel-drum gross mass of 27,920 kg plus 40 × 25 kg of pallet mass equals 28,920 kg, exceeding the 28,750 kg payload by 170 kg. At a lower pallet mass of 20 kg, the total becomes 28,720 kg, nominally compliant but leaving only 30 kg of margin. At a steel tare of 19 kg and a 25 kg pallet, the total reaches 29,240 kg. The same geometry with HDPE 1H1 drums yields 27,640 kg including pallets, leaving 1,110 kg of margin. Published data for specific combinations of pallet moisture content and drum gauge therefore determines whether 160 steel drums can be loaded without violating the payload plate.

When the Density Reference Temperature Moves from 20 °C to 25 °C, Net Weight Shifts by 0.8 kg per Drum

The density of IPA at 15 °C is approximately 0.789 g/cm³; at 20 °C it is 0.785 g/cm³; at 25 °C it is 0.781 g/cm³. For a 200 L fill, the corresponding net weights are 157.8 kg, 157.0 kg, and 156.2 kg. Across a 160-drum 40 ft load, the difference between 20 °C and 25 °C is 128 kg, which is below typical container payload rounding but can be material when steel drums and pallets place the load at the 28,750 kg payload boundary.

The 200 L fill is not the brimful capacity of a 55 US gal drum, which is 208.2 L; the fill ratio is therefore 96.1%. The coefficient of cubical expansion of IPA is approximately 1.1 × 10^-3 K^-1, and the fill temperature determines the ullage needed to prevent hydraulic pressure failure in closed steel or HDPE drums. Published datasheets for IPA specify a maximum fill ratio of 95–98% for drum shipments depending on the packaging approval, so the 200 L fill remains within the operational envelope for standard tight-head drums.

UN 1219 Packaging, Closure, and Segregation Requirements for Isopropanol Drum Loads

Because UN 1219 is a Class 3 Packing Group II flammable liquid, the drum must bear the appropriate UN specification marking. A common steel drum marking is UN 1A1/X/1.4/250; the corresponding HDPE marking is UN 1H1/Y/1.4/100 or equivalent. The 1.4 indicates a maximum liquid specific gravity of 1.4 for test purposes; the final numeral reports the hydrostatic test pressure in kPa. IPA with specific gravity 0.785 is below the packaging test density. Closure systems must be capable of retaining liquid under the pressure differentials of ocean transport. Under the IMDG Code, Class 3 flammable liquids are segregated from Class 1, Class 2.1, Class 5.1, and incompatible Class 8 acids unless specifically permitted. The container must display Class 3 placards, and the transport document must list UN 1219, Isopropanol, Class 3, PG II, flash point 12 °C.

On truck chassis, road axle and bridge formulas may impose a lower operational limit than the container payload plate. A 40 ft container with 28,750 kg of cargo can exceed the legal gross vehicle weight of a standard tri-axle chassis in some jurisdictions if the tractor/chassis tare is high. Shippers therefore compare the payload plate, the transport chassis tare, and the route-specific axle limits before approving a 160-drum steel palletized load. Moisture absorption in wooden pallets can add 2–5 kg per pallet, consuming 80–200 kg across 40 pallets. This effect is significant only at the 40 ft steel-drum threshold. Either reducing drum count to 156 drums on 39 pallets or shifting to HDPE 1H1 drums restores compliance when payload margins are negative without altering the net IPA mass per drum.