ISO tanks work in sea freight for chemicals by serving as standardized, self-contained stainless steel pressure vessels mounted within a standard ISO frame, allowing them to be loaded directly onto container ships, rail flatcars, and road vehicles without transferring the liquid cargo. They hold between 14,000 and 26,000 litres, making them one of the most efficient and secure formats for bulk liquid chemical shipments by sea. The sections below answer the most common questions about ISO tank shipping for chemicals, from suitable products to regulatory requirements.
What types of chemicals are suitable for ISO tank shipping?
ISO tanks are suitable for a wide range of liquid and liquefied chemicals, including solvents, resins, acids, alkalis, food-grade liquids, industrial oils, and certain gases. The tank’s stainless steel interior and pressure-rated construction make it compatible with both hazardous and non-hazardous bulk liquids that would be impractical to ship in drums or flexitanks.
In practice, chemicals commonly transported in ISO tank containers include ethanol, glycols, fatty acids, caustic soda, hydrogen peroxide, and various polymer intermediates. The suitability of a specific chemical depends on several factors:
- Chemical compatibility with stainless steel or lined tank interiors
- Viscosity, highly viscous products may require heating during transit
- Vapour pressure, certain volatile substances require pressure-rated tanks
- Regulatory classification, whether the substance is classified as a dangerous good under IMDG rules
Chemicals that are too reactive with stainless steel, or that require specialist containment beyond standard tank specifications, may be better suited to lined tanks or alternative packaging formats.
How is an ISO tank loaded and sealed for ocean transport?
An ISO tank is loaded through a top manhole or bottom valve, depending on the chemical’s properties and the operator’s procedure. Once filled to the correct fill ratio, typically 80 to 95 percent of capacity to allow for thermal expansion, the valves and manhole cover are sealed, pressure-tested, and secured with tamper-evident seals before the tank is released for shipment.
The loading process follows a strict sequence to maintain safety and cargo integrity:
- The tank is inspected and cleaned or purged of the previous cargo
- All valves are checked for integrity and compatibility with the product
- The chemical is pumped or gravity-fed into the tank at a controlled rate
- The fill level is verified against the tank’s maximum gross mass rating
- All openings are sealed and documented with a tank certificate and dangerous goods declaration where applicable
- The tank is positioned on a chassis or flatbed and secured with twist-locks before sea loading
Shipping documentation, including a bill of lading, material safety data sheet, and any required customs or hazmat paperwork, must accompany the tank throughout its journey.
What’s the difference between an ISO tank and a flexitank or drum shipment?
The key distinction is containment structure and volume. An ISO tank is a rigid, reusable stainless steel vessel designed for repeated use with a wide range of chemicals, while a flexitank is a single-use bladder inserted into a standard dry container, and drums are individual sealed containers typically holding 200 litres each. Each format suits different cargo volumes, chemical types, and cost profiles.
ISO tank advantages
ISO tanks offer the highest volume per unit, up to 26,000 litres, with robust containment suitable for hazardous chemicals, heated transit, and pressure-rated cargo. They are reusable, traceable, and accepted by ports and terminals worldwide. The cost per litre transported is typically lower than drums for large volumes, and the risk of spillage from multiple container points is significantly reduced.
Flexitank and drum trade-offs
Flexitanks hold up to around 24,000 litres but are limited to non-hazardous, low-viscosity liquids and are single-use, generating more waste. They are a lower upfront cost option for food-grade or non-regulated liquids. Drums offer maximum flexibility for smaller quantities and mixed loads but create substantially higher handling, labour, and packaging costs at scale, and introduce more leak points per shipment. For hazardous chemical sea freight in bulk, ISO tanks are generally the safest and most economical choice.
How are temperature-sensitive chemicals kept stable during sea transit?
Temperature-sensitive chemicals are kept stable in ISO tank shipping through heated tanks equipped with steam coils, electric heating elements, or insulated jacketing that maintain the cargo within a specified temperature range throughout the voyage. This is particularly important for products that solidify, crystallise, or degrade outside a narrow temperature window.
Heated ISO tanks, sometimes called steam-heated or electrically heated tanks, allow operators to set and monitor the internal temperature of the cargo. For sea freight, the heating system is typically connected to the vessel’s steam supply while on board, and to road or rail power sources during land legs of the journey.
Common temperature-sensitive chemicals transported this way include:
- Fatty acids and palm-based products that solidify below certain temperatures
- Phenol and other chemicals with high melting points
- Certain resins and polymer additives that increase in viscosity when cooled
- Food-grade oils requiring maintained fluidity for discharge
Insulated tanks without active heating are also used for products that simply need protection from extreme ambient temperature swings rather than precise thermal management. The choice between actively heated and passively insulated tanks depends on the chemical’s specific temperature sensitivity and the route’s climate profile.
What regulations apply to ISO tank shipments of hazardous chemicals?
ISO tank shipments of hazardous chemicals by sea are governed primarily by the International Maritime Dangerous Goods (IMDG) Code, which classifies substances by hazard type and sets requirements for tank specifications, labelling, documentation, and emergency procedures. Additional national and port-specific regulations may apply depending on the origin, transit, and destination countries.
Key regulatory frameworks that apply to chemical sea freight in ISO tanks include:
- IMDG Code: The global standard for maritime transport of dangerous goods, updated biennially and mandatory for all vessels on international voyages
- UN Portable Tank Instructions (T-codes): Specify the minimum tank design requirements for each chemical, including test pressure, shell thickness, and valve specifications
- ADR/RID regulations: Apply to the road and rail legs of intermodal journeys within Europe
- REACH and CLP regulations: Govern chemical classification and labelling within the European Union
- Customs and import/export controls: Vary by country and may require specific permits for certain substances
Shippers are responsible for correctly classifying the chemical, completing a Dangerous Goods Declaration, and ensuring the tank meets the required UN portable tank instruction for that substance. Non-compliance can result in cargo rejection at port, fines, or delays.
How do you choose the right ISO tank logistics provider for chemicals?
Choosing the right ISO tank logistics provider for chemicals comes down to three core criteria: specialist chemical handling expertise, ownership or direct access to compliant tank equipment, and a proven track record across your target shipping lanes. A provider without deep chemical knowledge may lack the regulatory competence and operational safeguards that hazardous or sensitive cargo demands.
When evaluating providers, consider the following factors:
- Tank fleet ownership: Providers with their own tanks offer greater control over equipment condition, cleaning standards, and availability
- Regulatory expertise: Look for ADR-certified drivers, IMDG compliance experience, and in-house customs knowledge
- Temperature control capability: Confirm they offer heated ISO tanks if your product requires thermal management
- Geographic coverage: Ensure they have established routes and local contacts in your origin and destination markets
- Quality certification: ISO 9001:2015 or equivalent certification signals a structured approach to quality and continuous improvement
- End-to-end service: Providers who manage storage, documentation, customs, and intermodal logistics under one roof reduce handover risk
It is also worth asking about tank cleaning and inspection protocols between loads, particularly if your product is sensitive to cross-contamination. A specialist provider will have documented cleaning procedures and be able to provide tank certificates confirming the previous cargo and cleaning status.
How KEMITO supports your ISO tank sea freight needs
KEMITO is a full-service chemical logistics provider with direct experience managing ISO tank shipments across EMEA and worldwide destinations. As a specialist in chemical distribution, storage, and transport, KEMITO offers a coordinated solution that covers every stage of the supply chain:
- Access to heated ISO tanks suited to temperature-sensitive chemical cargo
- ADR-certified drivers and in-house regulatory expertise for hazardous goods compliance
- Integrated customs and worldwide freight forwarding to manage documentation and cross-border requirements
- Flexible options from single-delivery ISO tank transport to fully outsourced distribution
- Distribution centres across Belgium, France, Italy, the Netherlands, Turkey, and the United Kingdom
Whether you are shipping a single ISO tank or managing a recurring bulk chemical supply chain, KEMITO brings the infrastructure and specialist knowledge to move your cargo safely and reliably. Contact KEMITO today to discuss your ISO tank shipping requirements.