What causes a first-time UN 1093 consignment to be stopped before the crane cycle?
Acrylonitrile,
CAS 107-13-1, is a reactive unsaturated nitrile monomer transported under the proper shipping name Acrylonitrile, stabilised,
UN 1093,
Class 3,
Packing Group I. The liquid has a boiling point of
77.3 °C, a flash point below
0 °C, a vapour density of
1.83 relative to air, and an explosive range of approximately
3.0 vol% to
17.0 vol% in air. A first-time acrylonitrile import—documents, licences and the port entry checklist—comprises three interdependent control layers rather than a sequential paper exercise. Under the IMO International Maritime Dangerous Goods Code Dangerous Goods List, the shipment carries a
Class 3 primary hazard, a
Class 6.1 subsidiary risk, and a marine pollutant notation in most jurisdictions. The stabilised grade is typically inhibited with
35–50 ppm 4-methoxyphenol to prevent polymerisation during sea transit and terminal storage. The importer must also confirm the safety data sheet hazard statement profile before the shipper signs the dangerous goods declaration; discrepancies in the CLP Index No
608-003-00-8 classification or the Harmonized System code
2926.10.00 are a frequent cause of customs hold.
Port state control and terminal safety officers stop the consignment when the administrative record does not match the physical tank or container. The shipper’s dangerous goods declaration under the IMDG Code must state the proper shipping name, class, packing group, flash point, subsidiary risk, marine pollutant status, and the identity of the stabiliser. The certification statement must be signed by the shipper, not the freight forwarder, because a forwarder-issued declaration without the underlying shipper signature is a rejection point at many EU and Southeast Asian ports. The receiving terminal also verifies that the tank container data plate is in due date for the applicable UN portable tank test interval and that the cargo temperature has not exceeded the shipper’s maximum transit temperature during the voyage.
Core document set for first-time acrylonitrile import
| Document | Issuing party | Acceptance basis |
|---|
| Bill of lading / sea waybill | Carrier | Matches container or tank number, UN 1093, Class 3, PG I |
| Dangerous goods declaration | Shipper | IMDG Code chapter 5.4 and national dangerous goods transport regulation |
| Safety data sheet | Manufacturer / importer | REACH Annex II 2020/878 or GHS Rev 7, 16 sections |
| Packing list and tank tare certificate | Container packer / tank operator | CTU Code and tank data plate mass |
| Certificate of origin | Exporter / chamber of commerce | HS 2926.10.00 classification |
| Import licence / chemical permit | Competent authority | Destination-specific hazardous substance permit |
| Inhibitor certificate of analysis | Manufacturer / independent surveyor | 4-methoxyphenol concentration 35–50 ppm |
Before the vessel departs the load port, the importer should verify that the tank container is fitted with a vapour return connection and that the receiving terminal has reserved a berth with nitrogen supply. Acrylonitrile shore tanks are kept under inert gas. The tank container must not be opened for sampling if the terminal cannot provide a closed sampling loop. Sampling through the bottom outlet without a vapour-tight syringe or closed-loop sampler leads to vapour release and can render the port-entry permit void.
At the port gate, the tank container is photographed on all four sides. The photographs become part of the terminal’s dangerous goods acceptance record. Any placard that is missing, obscured, or generated on paper rather than as a fixed metal or polymer placard is a stop-cause. The UN number must be displayed on the tank container in accordance with the IMDG Code marking provisions. The tank container bottom outlet valve must be closed and locked, and the manlid or top hatch must be sealed with the seal number recorded on the gate inspection sheet.
Pre-Arrival Licensing and the Jurisdiction-Dependent Permit Stack
In the European Union, acrylonitrile is listed in Annex VI to Regulation (EC) No
1272/2008 under Index No
608-003-00-8. An importer placing the substance on the EU market in a quantity of
1 tonne per annum or more must be covered by a REACH registration dossier under Regulation (EC) No
1907/2006, Article
6, or by an only representative arrangement under Article
8. The customs declaration must use the HS code
2926.10.00 and the appropriate integrated tariff of the European Union product code. Some Member States add a restriction or additional storage requirement under Article
67 of REACH if the receiving storage facility does not hold a Seveso III major accident prevention licence under Directive
2012/18/EU, because acrylonitrile is listed for its acutely toxic and flammable properties.
In the United States, acrylonitrile is an existing substance on the TSCA Inventory, and bulk import is subject to TSCA Section
13 certification through the customs broker’s Automated Commercial Environment entry. The importer must retain the positive or negative certification statement as required by
19 CFR 12.121. At the state level, a first-time importer must review the fire code storage permit and the local air district permit because acrylonitrile is a volatile organic compound and a listed toxic air contaminant in several jurisdictions. A licence application may be delayed when the SDS does not list the correct ACGIH TLV-TWA of
2 ppm for acrylonitrile or fails to state that skin absorption contributes to exposure.
Some Middle Eastern and Asian ports require an end-use declaration from the downstream polymer or synthetic fibre plant before dock receipt. Where the consignment is destined for an ABS resin or acrylic fibre line, the receiving factory’s environmental operating permit is included in the import licence file. Published data for this specific configuration is limited, but the documentary practice is enforced through the port customs inspection rather than through a uniform regional standard. The port authority may also require a local competent-authority acknowledgement for the storage of a
Class 3 /
Class 6.1 marine pollutant before the discharge permit is issued.
Discharge through an open vent is not acceptable. If the shore tank does not have a vapour balancing line, the terminal must use an alternative vapour management unit—typically a carbon adsorption skid or a thermal oxidiser permitted for acrylonitrile vapour. The transfer pump is started against a closed discharge valve and ramped to a maximum liquid velocity that keeps the tank container pressure below the data plate MAWP. During the first
15 minutes, the manifold is checked for leaks using a photoionisation detector calibrated for acrylonitrile with a response factor verified by the gas supplier. Vapour concentrations in the manifold area are kept below
2 ppm as an
8-hour TWA. If stagnant readings exceed
5 ppm, the transfer is interrupted and the line is depressurised to the shore tank.
The transfer rate is adjusted so that static electricity accumulation does not exceed the grounding system capacity. The tank container and shore pump are bonded before the hose is connected, and the resistance to earth is verified below
10 Ω. Hoses are purged with nitrogen before the first transfer. Residual oxygen in the hose must be below the lower explosive-limit safety margin specified in the terminal fire safety plan. The terminal work permit records the oxygen reading taken immediately before the manifold connection.
The checklist below is used by the dock supervisor during the pre-discharge gate inspection.
Port entry acceptance checklist for first-time acrylonitrile discharge
| Checkpoint | Acceptance criterion | Reference basis |
|---|
| Pre-arrival notification | Submitted to harbour master and terminal 72 h before ETA with DG declaration and tank certificate | Terminal dangerous goods procedure |
| Placards and marks | UN 1093 orange placards on all four sides; Class 3 primary, Class 6.1 subsidiary, marine pollutant mark | IMDG Code chapter 5.3 |
| Tank container data plate | UN portable tank type valid for PG I; periodic inspection stamp within applicable interval | IMDG Code chapter 4.2, ISO 1496-3 |
| Inert atmosphere | Nitrogen pad positive; oxygen below the concentration specified in the terminal fire safety plan | Terminal permit |
| Hose and gasket compatibility | PTFE-lined stainless steel or another manufacturer-approved arrangement; no EPDM, neoprene, or natural rubber gaskets | Manufacturer technical bulletin |
| Secondary containment | Transfer area bunded and drain valves closed; capacity not less than 110 % of the largest tank container or storage vessel in the spill zone | 40 CFR 112 / terminal fire code |
| Gas detection | Direct-reading detector with detection limit no greater than 0.5 ppm acrylonitrile and an alarm setpoint at 2 ppm | ACGIH TLV-TWA |
| Emergency stop | ESD interlock from ship to shore transfer pump; manual dead-man control at manifold | Terminal transfer procedure |
| Document set | Customs release, port entry permit, DG declaration, tank certificate, inhibitor analysis | National customs / port authority |
After the first discharge, the terminal operations record is retained for the permit file. A post-transfer line pig is not used for acrylonitrile unless the pig is compatible and the line is flushed with inhibited solvent within
24 hours. The shore tank sample is retained under refrigeration at
5 °C for
30 days and tested for water content and inhibitor depletion before the cargo is approved for downstream processing. The port entry checklist is closed only when the tank container bottom outlet valve is locked, the vapour return line is disconnected, and the tank container is gas-freed to the terminal’s safe level for road transport.
