Tanks

Valuable assets with good resale applications

CTIA members have proven their ability to create innovative uses for many container types but resale tanks primarily continue to be used to store liquids.

Tank containers (ISO tanks) – or, more properly, to use the correct regulatory terminology, “portable tanks” - are typically designed and manufactured to the provisions of IMDG (International Maritime Dangerous Goods Code). According to the tank shell thickness, pressure rating, configuration of openings and pressure relief device, IMDG designate a portable tank instruction, commonly referred to as a T-code.

Design

Most general purpose tanks are designed to meet the requirements of “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 operator fleet general purpose tanks are of 24/25,000 litre, usually insulated and fitted with a steam heating system. Tanks are usually manufactured of stainless steel (liquefied gas tanks T50 tend to be carbon steel) and have the potential to provide many years of service beyond its initial use as tank transport unit.

Periodic inspection and test

When used for transport in accordance with IMDG and, if dual-regulated with RID-ADR (Europe) and CFR49 (USA), each tank is required to undergo, at 2.5 yearly intervals, a periodic inspection and test.

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. The 5 year test is carried out at test pressure e.g. 6 bar, the 2.5 year intermediate test at 25% of the working pressure, typically 1 bar. In addition CSC (Convention for Safe Containers) examination applies.

National regulations

If the tank ceases to be used for transport and is confined only as an inland static storage unit, IMDG does not apply but it is nevertheless necessary to comply with relevant National regulations. For example, if the tank container is used in a chemical plant as a process vessel or for storage, the national regulations required for plant equipment apply. Similarly, if used on a construction site.

National regulations such as European Pressure Equipment Directive (PED) include pressure vessel regulations. If the operations eg. filling, emptying or cleaning are from 0.5 bar, pressure vessel provisions, in addition to health and safety provisions, apply to the operation of the tank. Regulations might require a bund wall to contain leakages. National regulations apply to storage of fuel and any other substance classified as dangerous goods.

Markings

The tank will display markings showing that show its regulatory approval eg UN Portable tank, T11, RID/ADR, ISO code 2276 or 22K2. If the tank does not comply with the regulations displayed the markings should be removed. This also applies to any previous hazard placards or marks. The tank should be re-marked according to its current status and substance stored.

Since the tank container is designed to the high standards required for international transport of dangerous goods, it may be expected that the tank design would meet National regulations albeit, it might be necessary to undertake repairs and modifications and maintain the tank fit for its purpose.

Cleaning document

IMDG regulations for the transport of dangerous goods apply until the tank is cleaned and issued with a cleaning document. Cleaning should be undertaken at a qualified cleaning station that is licenced by the authorities to process waste effluent. Tank buyers 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

As with dry freight containers, tanks are often sold for commercial reasons. An international operator or lessor might have a commercial requirement to maintain a low fleet age profile, or the tank might be obsolete by its cubic capacity or equipment type accordingly to the company marketing plan. Other tanks are sold due to the cost of repairing damage compared to the financial depreciated book value.

Damage is determined by the ACC (acceptable container condition) damage criteria. Whereas this criteria is appropriate for the international transport of dangerous, the damage does not necessarily preclude alternative uses of the tank or alternative repair methods.

ACC requires remedial work to tank shell pitting, gouges and scrapes. The shell is approx. 4.5mm stainless steel and pitting or gouges of more than 0.1mm might be required remedial works, often at high cost. The condition however, might be suitable for static storage of non-dangerous substances.

Sales from international fleets provide an opportunity for regional buyers to undertake economical repairs and modifications consistent with a planned use to store non-dangerous liquids in static service.

Assets

Tank containers remain valuable assets even after their initial use as transport units. There are many possible uses for the tanks and once a few checks are made to ensure that the tanks meets relevant regulations in the region of use, continued safe service as a static liquid storage unit can be expected.