Epichlorohydrin (ECH, CAS 106-89-8) is transported as UN 2023, a Class 3 flammable liquid with a Class 6.1 toxic subsidiary and packing group II. The loading calculation for Epichlorohydrin containers and ISO tanks determines net weight from the calibrated volume, regulatory filling degree at 15 °C, and the density of the actual production batch. ECH has a density of approximately 1.180 g/cm³ at 20 °C, a closed-cup flash point of 31 °C, a boiling range of 115–116 °C, and a vapour pressure near 1.7 kPa at 20 °C. These figures are used at terminals only after the tank or packaging is verified clean, dry, and compatible, because ECH is an epoxide that can hydrolyse in the presence of free water and can polymerise under acidic or alkaline contamination.

What Limits the Loaded Mass in a Closed Tank?

The permissible loaded mass is not set by the maximum gross mass of the container alone. For a closed tank, thermal expansion of the liquid governs the maximum filling degree. The net weight is expressed as m_net = V_tank × F / 100 × ρ_ref, where V_tank is the calibrated capacity, F is the filling degree at 15 °C, and ρ_ref is the batch density at the reference temperature. Under ADR 4.3.2.2.2 and the corresponding IMDG Code tank requirements, UN 2023 in an ISO tank is restricted to a 95% maximum filling degree at 15 °C. The 95% value is the stricter toxic-liquid limit applied because of the Class 6.1 subsidiary. A terminal that treats ECH only as a Class 3 liquid and fills to 97% at 15 °C leaves insufficient ullage for a hot-climate transit temperature rise.

For drums and single-pack IBCs, the packaging-based limit is less severe because the closure is not a pressure vessel and the container is not expected to sustain liquid-phase hydraulic pressure. ADR 4.1.1.4 and IMDG 4.1.1.4 permit a maximum filling degree of 98% at 15 °C for UN 2023 in metal drums and rigid IBCs. However, the practical terminal rule often reduces drum ullage only after the closure is fully seated and the package is checked for leakage, because ECH vapour can degrade elastomer gaskets not specified for epoxide service. The 98% filling degree is a certification maximum, not a routine target for short-sea or tropical lanes.

The values in the table are method values only. Actual shipment mass must be calculated from the batch density stated on the certificate of analysis at the same reference temperature as the volumetric fill, normally 15 °C for transport documentation. If density is measured at 20 °C by ASTM D4052, the loading master should correct both volume and density to a common reference temperature before the final net weight is printed on the bill of lading. The common error of multiplying a 15 °C volume by a 20 °C density creates a small but avoidable bias in the loaded mass.

Steel Drum, Composite IBC, and ISO Tank Fill Coefficients

For a UN 1A1 steel drum of 208 L nominal capacity, the maximum filled volume at 15 °C is 203.8 L. Using a density of 1.180 kg/L gives a reference net mass of 240.5 kg. A 1,000 L IBC filled to 98% contains 980 L and a reference net mass of 1,156 kg. These package masses are small enough that the filling degree can be controlled by gravimetric checkweighing rather than by volumetric level measurement. In automated filling lines, the fill mass is trimmed by a Coriolis flowmeter or by a weighbridge, and the closure is applied only after the vapour space is verified. For ISO tanks, the 25,000 L nominal capacity tank loaded to 95% at 15 °C contains 23,750 L. With a reference density of 1.180 kg/L, the demonstration net mass is 28,025 kg. The actual certified capacity of the tank may differ from the nominal value; therefore the calculation must use the capacity stamped on the tank certificate and the latest periodic inspection report.

Because ECH is a Class 3 liquid with a flash point below 60 °C, all filling operations are performed in electrically classified areas. The use of bottom loading with a vapour return line reduces free-fall static generation and keeps the displaced vapour out of the breathing zone. The loading arm or hose should be purged with nitrogen before and after transfer, and the tank vapour space must be padded with nitrogen to reduce oxygen concentration below the limiting oxygen concentration. Published data for the limiting oxygen concentration of ECH in nitrogen is limited; terminals generally use conservative inerting setpoints and verify the oxygen level before starting the transfer pump.

When the Loading Temperature Deviates from 15 °C

The regulatory filling degree is fixed at 15 °C, but many terminal tanks hold ECH at a higher or lower temperature. The permissible loaded volume at the actual filling temperature is adjusted by the coefficient of cubical expansion. For an engineering ullage calculation using α = 0.0010 K⁻¹, the fill volume at temperature t is obtained from V_fill(t) = V_tank × F / 100 / (1 + α × (15 − t)). At a loading temperature of 30 °C, a 25,000 L ISO tank can be filled to 24,112 L and will return to approximately 23,750 L if the liquid cools to 15 °C. At 10 °C, the same tank would be filled to a smaller volume because the liquid is denser and occupies less space for the same regulatory ullage.

The filling master must not use a single density correction for all cargoes. ECH density decreases as temperature rises, so the net mass at 30 °C is not the same as at 15 °C. The terminal should use a Coriolis meter with online temperature compensation or draw a sample at the loading temperature and measure density by ASTM D4052. If the volume is corrected to 15 °C but the density is not corrected from 20 °C, the resulting mass is not a true net weight. This distinction is critical in ISO tank shipments because the tank is a closed pressure vessel, and an overfilled tank can develop liquid-full conditions if the pressure-relief valve setpoint is reached during transit.

The maximum filling degree is also linked to tank pressure. UN 2023 is assigned to tank code L4BH under ADR, where the tank is designed for a minimum test pressure of 4 bar. The tank is equipped with pressure-relief devices and should be checked for correct set pressure and tightness before loading. The presence of a 4 bar design pressure does not permit filling above the 95% limit at 15 °C; it only provides a margin for vapour pressure increase and thermal expansion. Overfill protection systems, level sensors, and independent high-level alarms must be tested before the tank is connected. If the overfill protection is not functional, the transfer should be stopped.

ECH vapour is heavier than air and can accumulate in low areas. During container filling, the displaced vapour is returned to a closed scrubber or vapour recovery unit. Open venting is not acceptable for ECH because the lower explosion limit is approximately 3.8 vol% and the upper explosion limit is approximately 21 vol%. The vapour space must remain inerted even when the tank is nominally empty, since a residual film of ECH can generate a flammable mixture during cleaning or inspection. Loading operators should bond and ground the tank, pump, and piping in accordance with IEC TS 60079-32-1, and initial line velocity should remain below 1 m/s until the fill pipe outlet is submerged. After submergence, the flow rate may be increased but should not exceed the maximum velocity allowed by the terminal electrostatic management plan.

Incompatibility boundaries are as important as the filling calculation. ECH should not be loaded into a tank that previously carried acidic products without neutralisation and drying, because acid residues can initiate exothermic epoxide polymerisation. Tanks that have contained amines, ammonia, or alkali should be positively isolated and verified free of residue. Free water in the loading line or tank is a rejection criterion because ECH is partially miscible with water and can hydrolyse over time, producing chlorinated glycerol derivatives and increasing the acidity of the unstabilised liquid. Gaskets and seals should be PTFE, graphite, or another confirmed ECH-resistant material; EPDM and nitrile elastomers are not permitted in ECH service unless the specific compound is validated by immersion testing. The loading terminal should verify the tank certificate, pressure-relief device setpoint, cleanliness, and inert gas blanket before opening the liquid line. If those checks cannot be completed, the ECH transfer should not be started.