TT Talk - Implementing standards for flexitanks

The carriage of bulk liquids in general purpose (GP) containers is increasing in volume, with 650,000 shipments projected for 2014, up from about 100,000 in 2005. Attention has been focused on the two issues that plagued early designs - damage to container walls and cargo leakage - exacerbated by the proliferation of manufacturers and service providers. The diverse stakeholders have collaborated to improve standards, under the auspices of the Container Owners Association (COA).

While the flexitank - a bladder or bag used for the transport and/or storage of a non-regulated liquid inside a cargo transport unit - has been in existence for decades, the concept has enjoyed considerable success in recent years as a relatively light-weight form of packaging for liquids to be carried in standard GP containers. However, the risks relating to potential damage to container walls or failure of the bag have required greater scrutiny.

Flexitank manufacturers, trade organisations and regulators have been cognisant of these risks and have responded with publications aimed at improving safety and reliability.

TheContainer Owners Association's flexitank division put together a Code of Practice that covered both manufacturing and operational issues. On the manufacturing side, this has been developed, with the British Standards Institute (BSI), into a new Publicly Available Specification (PAS), which was published in June 2014.

Clarity of standard for manufacturing


BSI PAS 1008 Specification

for the performance and testing of a single-use flexitank provides a specification for testing materials, performance and labelling of the components in the flexitank system. It is applicable to single-layer and multilayer flexitanks that carry a commodity with a maximum mass of 24,000 kilo and volume of 24,000 litre.

PAS 1008 has usefully provided definitions for both the flexitank and the overall system. These can be stated as:

1. Flexitank - bladder with a loading/discharging valve to be installed inside a GP freight container as part of a flexitank system and used for holding a liquid commodity;

2. Flexitank system - system used for the transport of a liquid commodity, which comprises a flexitank, a restraining system, a GP freight container, and, where necessary, ancillary equipment.

“PAS 1008 provides a certifiable framework for high quality manufacture of these bladders in order to facilitate safe movement of liquids”

The overall aim of the PAS is to provide a certifiable framework for high quality manufacture of these bladders in order to facilitate safe movement of liquids without leakage and without causing permanent damage to freight containers. Each element of the standard, therefore, has associated minimum requirements and test regimes defined, specifically:

• the material properties of the flexitank film and, where fitted, the outer sleeve;

• the leak tightness of the loading/discharging valve(s);

• the flexitank system's resistance to a rail impact defined as a 2g (gravitational unit) retardation or acceleration force.

The test methods seek to ensure that the material used for the flexitank bladder cannot be easily punctured and that the assembled flexitank will not leak under normal operating conditions. The rail impact test specifically subjects the flexitank system to stresses to ensure that the flexitank does not fail or the system cause damage to the transporting container.

A secondary, but equally important, feature of the PAS sets requirements for the provision of Flexitank system information. Critical for safe and sound operations are the requirements to provide with the flexitank the specification and assembly drawings of the restraining system and any ancillary equipment used in the rail impact test. Compliance with and monitoring of these will counter the practice of substituting the restraining system (bulkhead) used during the rail impact test with one of a lesser capability.

Certification for operations

The PAS is a significant step forward in the reduction of risk associated with the carriage of bulk liquid cargoes in GP containers. However, it is not legally enforceable and may be viewed as simply a standalone guideline as to how a well specified and manufactured flexitank should be supplied. The effect of the PAS will only reach its potential as shippers and/or carriers consistently require certification against the specification and monitor compliance. Safety standards may only demonstrably improve with cargo management differentiation in favour of accredited flexitanks.

“Safety standards may only demonstrably improve with cargo management differentiation in favour of accredited flexitanks”

As it is written, the PAS needs to be accompanied by documentation concerning the safe operation and risk prevention aspect of the supply chain. This continues to be detailed in the COA's previous publication COA - Recommended code of practice for flexitanks, which identifies five main areas:

1. Container selection

2. Testing

3. Container and flexitank marking

4. Incident management and insurance

5. Training.

The COA code of practice and latterly the PAS have primarily focused attention on practices relating to the specification requirements and manufacturing of the flexitank. The code of practice also covered to some extent the operational aspects of carrying bulk liquids - and it is poor operational practices that generate a far greater risk to the supply chain. Further operational information is available in the ICHCA Briefing Pamphlet, Safe handling of flexitanks in General Purpose freight containers, and the IMO/ILO/UN ECE Code of Practice for packing cargo transport units (

CTU Code

) also includes packing instructions for flexitanks.

Manufacturers clearly need to step up to the mark to achieve compliance with PAS 1008 and the current COA code of practice. Submission of a material test report to the COA website - which few have done - evidences a level of adherence. Beyond that, the shipper and carrier stakeholders involved could usefully self-regulate to these baseline standards in order to increase confidence for those involved in transporting and handling flexitank systems.

We gratefully acknowledge the assistance in the preparation of this article of Bill Brassington of ETS Consulting.

We hope that you have found the above interesting. If you would like further information, or have any comments, please email us, or take this opportunity to forward to any colleagues who you may feel would be interested.

We look forward to hearing from you.

Peregrine Storrs-Fox

Risk Management Director, TT Club

Staff Author

TT Club