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June 23, 2008

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Storage of hazardous substances- Bulk business

Intermediate Bulk Containers (IBCs) have become commonplace for the transport and storage of chemicals. However, recent research has shown that some IBCs may create unacceptable levels of risk in storage. As a result, new industry guidance has been issued. Douglas Leech explains what is involved.

Intermediate Bulk Containers (IBCs) are everywhere. They provide a simple and effective method of transporting and storing chemicals, and have proved to be flexible, cost-effective and, over the years, have developed a relatively good record for safety, and are subject to internationally-agreed certification procedures for transport.

There are three basic types of IBC. The first is the all-metal variety, made from stainless steel, mild steel and aluminium. The second type is completely made of plastic. And the third type, known as the composite IBC, is usually made of a rigid metal cage with an integral plastic inner receptacle, which, together, form a single unit that can be filled, stored, transported, or emptied.

What is an IBC?

An IBC means a rigid, or flexible portable packaging that:

• has a capacity of not more than 3m3 for solids and liquids of packing groups II and III;

• is designed for mechanical handling;

• is resistant to the stresses produced in handling and transport as determined by the tests specified in Chapter 6.5 of the ADR.3

Composite IBCs with plastic inner receptacles have a rigid outer structure encasing a plastic inner receptacle and are constructed so that the outer and inner assemblies are an integrated single unit to be filled, stored, transported, or emptied.

HSL research

As a result of investigations into large industrial fires, where the level of destruction could not be attributed to the inventory of flammable materials stored at the sites, the Health and Safety Executive commissioned research by the Health & Safety Laboratory (HSL) to determine the fire mechanism of these incidents.1

The HSL’s research has revealed concerns about the combustibility of plastic IBCs, and the potential for their contents to be released when exposed to even minor fires. Many IBCs have plastic components that are susceptible to ignition from even a brief exposure to a small and transient ignition source, such as a match, grass fires, or small ignited spillages. An IBC can fail rapidly in these circumstances.

As a response to this official research, new industry guidance for the safe storage of combustible liquids in IBCs2 has been issued jointly by the Chemical Business Association (CBA) and the Solvents Industry Association (SIA). In addition to the CBA, SIA and HSE, no fewer than 14 other industry organisations were consulted in the preparation of this guidance, which has now been fully endorsed by the HSE.

The guidance has been written in a way that allows safety specialists and trade organisations to use it as a basis for more specific advice, or for training purposes for their staff, clients, or members.

The IBC guidance has five specific objectives. It aims to:

• increase awareness of the dangers associated with the storage of packaged liquids – especially those stored in IBCs;

• help in the assessment and reduction of risks;

• advise on safe management practices in relation to IBCs;

• provide guidance on the standards for design and construction of areas used for storing packaged liquids at ambient temperature and pressure; and

• advise on the need for precautions, maintenance, training, and good housekeeping wherever packaged liquids are stored.

The fire risks

Flammability risks with IBCs in storage became apparent during the HSL’s research project. It showed that plastic or composite IBCs containing non-aqueous liquids typically fail rapidly when exposed to an engulfing fire.

After failure, IBCs release their contents within seconds, and spreading liquid released can quickly involve of more containers.

Where the liquids are combustible, large pools of free-burning liquid may be produced, and fire may spread very rapidly.

The new guidance covers all combustible liquids, including, for example, edible oils, as well as flammable liquids in Packaging Groups II and III, as defined by ADR 2007,3 and provides an assessment checklist in relation to fire risks.

Plastic vulnerability

IBCs have been shown to be especially vulnerable to fire even when not directly involved as the ignition source. Therefore any risk assessment needs to consider this in relation to the choice of a storage site, and to the containment of potentially large spillages. As outlined above, when exposed to the heat of a fire, plastic IBCs can soften and fail catastrophically, resulting in the rapid release of their contents. If IBCs are stacked, this could mean their contents may overflow any bund-wall or kerb.

Many IBCs have plastic components in their valves, which are unable to withstand the effects of a fire. Initially, the leakage may be slow, but eventually the valve may fail completely. Fitting more resistant metal outlet valves – or metal valve guards – to the valve housing can help protect against this eventuality.

Metal problems

Metal IBCs may also fail hydraulically or by ullage space explosion (ullage refers to the unfilled space in a container of liquid).

Studies show that an IBC with a metal pallet base has a greater resistance to fire, and that this type of base will delay the structural failure of the IBC. The fitment of pressure-relief valves will also reduce the risk of catastrophic failure in the event of fire.

Assessing the risk

The guidance provides a step-by-step approach to risk assessment in relation to these hazards and, in particular, the risk of fire. It then focuses on the management of these risks and the controls that can be introduced. These can include:

• minimising the quantity of liquids stored in IBCs;

• physical features – the location of storage, lift trucks, bunding, and storage racks;

• human factors, such as personnel selection and training; and

• organisational issues, such as supervision, maintenance, and audit procedures.

The guidance provides further advice on packaging, segregation, storage, and racking and stacking. It also provides guidelines for operational and monitoring procedures. These include effective stock control and stock rotation, as well as inspection regimes to ensure that IBCs remain fit for purpose.

Similarly, containment systems such as yards, bunds, drains, interceptors, and their control valves should be designed to minimise the impact of leaking IBCs. These controls must be regularly inspected and kept in good working order. Good housekeeping regimes will also help prevent build-up of combustible materials and degradation of packaging from standing water in outside storage areas.

Finally, a ‘No Smoking’ policy should be rigorously enforced, and is a mandatory requirement for enclosed workplaces.

Emergency procedures

The guidance also outlines appropriate emergency procedures and equipment that should be considered. Sites storing larger quantities of defined dangerous goods are required to prepare a formal emergency plan under the provisions of the Control of Major Accident Hazard Regulations (COMAH). Sites with smaller volumes should identify foreseeable emergency incidents, and prepare emergency procedures commensurate with the risks involved in their operations.

Specialised advice may be required when considering the selection and deployment of detection systems and fire-fighting equipment. The hazards, their degree, and quantities stored will determine the equipment required. It is also advisable to contact the local emergency services to ensure that they have the information they need to respond effectively to an emergency.

Information and training

Finally, the guidance underlines the importance of adequate information and training for employees. This includes agency or temporary staff, and, where young people are involved, more specific procedures may be required. The findings of all risk assessments should be communicated to all employees, who must have information relevant to their roles regarding the hazards, the need to exclude sources of ignition, and the actions to be taken in the event of an emergency, including specific training in emergency procedures, and how to deal with spillages and leaks.

Written procedures for controlling the risks from the storage of liquids will be required, and these should be used as the basis for training.

As a minimum, training should cover:

• the types of liquids stored, their properties, and hazards, with emphasis on combustible and flammable liquids;

• general procedures for safe handling, use of lift trucks, racking and stacking;

• recognition of abnormal situations;

• reporting of faults and incidents, including minor leaks and spills;

• use of protective clothing;

• housekeeping;

• emergency procedures, including raising the alarm, calling the fire brigade, and the use of appropriate fire-fighting equipment.

References

1 HSE (2007): ‘Fire performance of composite IBCs’

2 The full text of the IBC guidance can be downloaded from the CBA’s website here

3 ADR – the European Agreement for the International Carriage of Dangerous Goods by Road – ISBN 92-1-139112-1
 

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