About ISO Tanks

The ISO Tank Container, also known as the UN portable tank, tank container, ISOtainer, tanktainer, bulk storage container, shipping tank, or intermodal tank, is used for the transportation and storage of hazardous and non-hazardous chemicals, foodstuffs, and liquefied gases.

In the 1960s containers became the preferred way of moving goods around the world. The appeal was that every container conformed to sizes defined by the International Standards Organisation (ISO), 40’ x 8’ x 8’6” or 20’ x 8’ x 8’6”. (See Wiki article). Before long, the concept of fitting a stainless steel cylinder inside the standard 20’ frame was adopted and the ISO Tank was born. ISO Tanks became the standard for the transportation of liquids (including fuel), chemicals, gases, powders, and even some types of food, around the world.

Steve Darnell, the founder of Qualitank, began work for Trafpac in the 1970s. (Trafpac was one the first ISO Tank companies in the world.) Before long he was running his own tank repair business, and, over time, moved into the sale and hire of used ISO Tanks. Qualitank Services was incorporated in 1992.

An ISO Tank Container (sometimes called ‘Tanktainer’) is a stainless steel cylindrical vessel, usually made of 316 grade stainless steel, fixed to a mild steel frame, usually welded. The thickness of this container will vary depending on the purpose of the tank and will be rated for a specific working pressure. Beyond that, there are a bewildering array of variants.

Tanks are generally designed for a specific purpose or product and therefore there is no fixed construction that applies to all tanks. Because the product to be carried may heavy (have a specific gravity that restricts the volume that can be carried) and because there are limits to the weight that a loaded ISO Tank can be, the capacity of tanks varies greatly, typically from 21,000 Litres up to 27,000 Litres in a standard sized frame. (Smaller capacities will likely be in a smaller frame – 8′ high rather than 8’6″) Capacities beyond this are possible by extending the tank length so it sits outside of the standard frame and these tanks are known as ‘Swap Bodies’. Swap Body tank capacities can exceed 34,000 Litres.

One of our 31,000 Litre ‘Swap Body’ Tanks

The majority of tanks have means of heating the product inside the tank to allow the contents to flow more easily. Most commonly this heating is done by passing steam through pipes attached to the tank, which are surrounded by a layer of fibre glass insulation, which in turn is encased in either Glass Reinforced Plastic (GPR) or Aluminium. Some ISO tanks have an electrical heating system. Others have a refrigeration system to keep their contents cool. Occasionally a tank will have a rubber lining as the product being carried is highly corrosive. Some tanks have 2 or more compartments. Some tanks are designed to be pressurised for the transport of gasses. It is common for tanks to have no heating/cooling or insulation and are used for the transport of powders or liquids which flow easily at normal temperatures.

Tanks used for the transportation of dangerous goods must meet standards applicable to the mode of transport. ISO tanks are Intermodal (able to be carried by Road, Rail and Truck) and they must meet standards as defined by the relevant mode of transport. When the tank has been built it will be tested and issued with a certificate specifying which of the standards it meets. The tanks will have a full (hydraulic) test every 5 years and a partial retest (air pressure) at 2.5 years. The most common type of tank is UN type T11 which can carry more than 1000 types of dangerous goods. T11 tanks are tested to 6 bars of pressure and have a working pressure of 4 bar. (Qualitank keep a number of tanks available which have current valid test certificates.)

When sourcing our tanks we remove the identifying marks of the previous owner and apply our own numbering system based on internationally accepted code. This means that every single tank or container shipped around the world has its own unique number. Most of our tanks begin with the prefix QTSU….

Common Features of ISO Tanks

Isotainers will have a means of both filling and discharging the contents. The most common discharge is an outlet located on the bottom of the tank and will allow discharge under gravity. (Bottom discharge). Most tanks will have a means of pressurising the vessel to facilitate pumping the contents out. Some tanks will have a pipe going down from on top of the tank to the bottom inside the tank. This facilitates the pressurisation of the tank to allow discharge through this pipe (Top Discharge).

The bottom discharge outlets of UN type T11 tanks must have at least three independent closures that can stop the flow of any contents. 2 open/close valves and a screw on cap qualifies as the third closure.

Bottom Discharge

Man Lid

For inspection purposes there is an opening on top of the unit (man lid) that is 500mm or larger in diameter. Usually this is positioned inside an external fitting known as a spill box. The man lid is sealed with a high-quality gasket. The spill box is as it sounds, it is there to collect any spillage of the tank contents. Within the spill box is often an air valve that allows for the depressurisation of the tank, sometimes with a means of safely collecting or returning the gas back into the tank.  

Manlid with Swing Bolts

Air Valve

As ISO Tanks are designed to be pressurised there is an air inlet/outlet valve, usually at the top of the tank.

Air inlet with pressure gauge alongside. Also a blank over flange plate to allow extra fittings on tank.

Pressure/Vacuum Relief Valve

As a tank container is designed to be pressurised then there has to be a pressure relief valve which often also incorporates a vacuum relief in the one piece of equipment.

Pressure Relief Valve(s)

Data Plate and Test Certificate on an ISO Tank Container

To carry dangerous goods on the roads/railways/shipping each tank must be pressure tested, inspected and certified as suitable. On each there must be a data plate on which are stamped important details about the tank. Manufacturer, Serial Number, Year of Manufacture, Date of first test, Date of last test, the type of test (2.5 or 5 year), Tare Weight, and Maximum Gross Weight are some of the information recorded on the data plate.

Data Plate

Uses for an ISO tank container

Tank Containers are extremely configurable and may be built to safely carry a huge variety of loads, such as:

  • Alcoholic Beverages
  • Food Products
  • Hydrogen Peroxide
  • Mining chemicals
  • Nitric Acid
  • Oils
  • Resins
  • Solvents
  • Sulphuric Acid
  • Water
  • Many more

Why not contact us for more information?

A 25,000 litre ISO Tank we have repainted.