Valuable assets with resale applications
Tank containers (ISO tanks) – or, to use the regulatory terminology, “UN Portable Tanks” – are mostly designed and constructed to the provisions of IMDG (International Maritime Dangerous Goods Code). IMDG governs the design e.g. tank shell thickness, pressure rating, openings and pressure relief device. IMDG designate a UN Portable Tank Instruction according to the tank design approval. The tank instruction is commonly referred to as a T-Code.
There are 25 T-Codes each providing variations in shell thickness, pressure, top or bottom openings, etc. Tanks might also be approved, or dual approved, to European Agreement RID-ADR. Tanks may also be designed to transport non-regulated substances (substances not classified as dangerous goods).
Design
Most tanks are designed for general-purpose tanks and meet the requirements of T-Code “T11”. This allows the tank to be used to transport a wide range of liquid substances. Capacities range from 14,000 to 26,000 litres, but the majority of the operator fleet are general purpose tanks are 24/25,000 litre, insulated and fitted with bottom outlets and steam heating.
Tanks are manufactured of stainless steel (liquefied gas tanks T50 tend to be carbon steel). The estimated service life is about 20-year service life.
The tank frame varies by manufacturer but all designs provide the similar functionality. Most tanks are fitted with a frame that includes top and bottom side rails. The end of the tank is attached to the frame by circular “collars”. Alternatively, some tanks are of a beam design where no top or bottom side rails are fitted.
Periodic inspection and test
When used for transport in accordance with IMDG, each tank is required to undergo a 5-year inspection and test and an additional intermediate inspection and test at 2.5-years. The test is witnessed by an authorised inspection body (AIB). The periodic test certificate is issued on completion and the tank data plate is stamped with the test date and mark. In addition, CSC (Convention for Safe Containers) examination applies.
Markings
Tanks display identification (BIC Code) markings and weights together with regulatory approvals e.g. UN Portable tank, T11, ISO code 2276 or 22K2. In addition, a consolidated data plate provides regulatory details and the tank specification.
Cleaning document
Cleaning should be undertaken at a qualified cleaning station that is licenced by the authorities to process waste effluent. Traders should ensure that they are in possession of a valid cleaning document. If it is necessary to enter the tank, health and safety regulations apply concerning the provision of a confined space entry permit.
Damage condition
Tanks are usually sold by operators and lease companies when the repair cost exceeds the depreciated value of the tank and taking into consideration obsolescence due to age, cubic capacity or type.
ITCO ACC (acceptable container condition) criteria is used to assess damage and repair.
Tanks in seemingly acceptable exterior appearance might be designated for disposal due to the condition of the tank interior shell. ACC requires remedial work to tank shell in the event the tank exhibits pitting, gouges and scrapes. Such repairs are usually of high cost.
Tanks in a pitted but leak-proof condition might be suitable, without repair, for static storage of non-dangerous substances.
Assets
Tank containers are valuable assets and if removed from international transport might be traded for domestic transport projects in places such as Africa, used for static storage, process vessels or in one case at least, converted into a trendy retail outlet.
The scrap value of stainless steel, which varies according to world market price, provides a disposal option. The stainless-steel tank vessel weights about 2 metric tonnes
Static storage
If the tank ceases to be used for transport and is confined only as a domestic static storage unit, IMDG does not apply but it is nevertheless necessary to comply with relevant National regulations.
If storing liquids classified as dangerous goods e.g. diesel or liquids that are pollutants, National regulations might require a secondary containment in case of leakage i.e. a bund wall and or a double wall tank. Check the specific requirements according to the liquid to be stored in the country of use.
If the tank is used at pressures from 0.5 bar, European Pressure Equipment Directive (PED) might apply.