Dangerous goods expertise is needed

Monday, 15 August, 2005


Many companies use and store dangerous goods. These have the potential to cause serious accidents, frequently from causes not apparent to the inexperienced.

Persons experienced in assessing the health and safety risks of handling workplace hazardous substances may not have the expertise to identify, assess and control the hazards of dangerous goods. How are you placed to conduct the risk management required by the national standard? This will be mandatory in NSW this year and is required in other states.

If you store or handle dangerous goods, it will be mandatory to apply this process to your storage and handling. Many workplaces have conducted and are familiar with hazardous substances risk assessment, but most will not be familiar with a dangerous goods risk assessment.

What's the difference?

'Hazardous substances' are those which may present a risk during normal handling or use. A substance is classified as hazardous by mandatory criteria "based on its health effects". There are optional criteria based on eco-toxicological and physicochemical properties. Risk control measures for hazardous substances are frequently related to occupational exposure standards. Both short-term and long-term exposures must be considered for hazardous substances. Label directions are an important element of risk control for hazardous substances.

'Dangerous goods' are substances or items which may present an immediate safety hazard, such as fire, explosion or toxic cloud emission. The consequences are usually related to the amount of the dangerous goods and for personnel safety are frequently related to separation distances, integrity of containment, pressure relief and similar measures.

Some substances are classified as both 'hazardous substances' and 'dangerous goods', such as ethanol, while other substances fit only one classification, such as iodine (hazardous substance) and ammonium nitrate (dangerous good). Sometimes there are different concentration cut-offs - for example, ethanol 24% or less in water is not a dangerous good, but is a hazardous substance.

Classes of dangerous goods

There are nine classes of dangerous goods, labelled accordingly for transport and storage, and another two unlabelled classes (combustible liquids and goods too dangerous to transport). Generally the class indicates the hazard, but some of the classes are broken down into divisions indicating a different hazard within the class.

Where a significant subsidiary risk ('subrisk') applies, an additional class label is required. Within most classes/divisions the degree of hazard is categorised by 'Packing Group' which is assigned according to the degree of danger presented in transport:

  • Great danger - Packing Group I (PG I)
  • Medium danger - Packing Group II (PG II)
  • Minor danger - Packing Group III (PG III)

Except as indicated in the table on the following page, all dangerous goods are covered by legislation mandating the Australian Dangerous Goods (ADG) Code for road and rail transport. This legislation is common to all states and territories, based on model Commonwealth legislation. In the case of those dangerous goods when stored, handled or otherwise used, the National Standard [NOHSC:1015(2001)] Storage and Handling of Workplace Dangerous Goods has been adopted in slightly different ways by each state's legislation.

Class (and Division)

1 Explosives(1)

Packing Groups Apply

No (separate divisions)

2 Gases
2.1 Flammable gases
2.2 Non-flammable, non-toxic gases
2.3 Toxic gases

No
No
No
3 Flammable liquids Yes
4
4.1 Flammable solids
4.2 Substances liable to spontaneous combustion
4.3 Substances that in contact with water emit flammable gases

Yes
Yes
Yes
5
5.1 Oxidising substances(2)
5.2 Organic peroxides

Yes
Yes
6
6.1 Toxic substances
6.2 Infectious substances(3)

Yes
No
7 Radioactive material(3)
8 Corrosive substances
No (except for subrisk)
Yes
9 Miscellaneous dangerous substances and articles Yes
Combustible liquids(4) No, but two categories (C1, C2)
Goods too dangerous to transport(5) No

Notes
(1) Covered by explosives legislation and codes.
(2) Security sensitive ammonium nitrate is also covered by other legislation.
(3) Generally covered by separate legislation.
(4) Not required to be labelled for transport.
(5) May be generated and used on site.

Incompatibility

A common myth is that the segregation charts used for road transport can be used as complete guidance for segregation in storage. This ignores the fact that much larger quantities can be stored in a warehouse or tank than can be loaded onto a truck, with correspondingly greater potential consequences. It also ignores the proviso in the ADG Code that "it is necessary, in all cases, to consider whether goods which are not listed as being incompatible, are, in fact, compatible".

Another common myth is that all materials of the same Class are compatible with each other. This is particularly false for Class 5.1 and Class 8 where many substances will react dangerously with others of the same Class.

Nothing on the label?

As AS 1940 notes, "As there is no legal requirement to label combustible liquids as such, it is often difficult to ascertain whether liquid in a drum or other package is a C1 or C2 combustible liquid. Only rarely do material safety data sheets (MSDS) indicate that a liquid is combustible."

This difficulty has led to unsafe storage and handling of combustible liquids resulting in fires or contributing to the intensity of a fire. Some suppliers compound the issue by referring to products as 'non-flammable', implying that they will not burn when they are, in fact, combustible liquids.

Not in the MSDS?

Many processes use heat transfer oil which is in a sealed, recirculating system. It is quite often above its flashpoint and then must be classified as a flammable liquid (UN 3256). The supplier's MSDS will indicate that it is not classified as a flammable liquid for transport - this is because it is not transported while hot.

One of the particular hazards is that of fires starting in insulation which has been soaked in the oil, either by a leak or by poor practice. Hot liquids without a flashpoint or below flashpoint may also be dangerous goods, Class 9 (UN 3257) and their separation distance from on-site facilities may require temperature measurement or heat flux calculations to be included in the risk assessment.

Controlling the risk

While a single person may be burnt by the accidental ignition of a small amount of flammable liquid used in some process such as cleaning or in a laboratory, the potential exists for death and destruction on a large scale when industrial or commercial quantities and processes are involved.

More extensive preventive measures are called for and mitigation measures are required. Many of these are quite complex, involving such things as defining hazardous areas where the only electrical equipment permitted is specially designed to avoid igniting any flammable vapours, ensuring emergency venting is properly designed and installed etc.

Just apply the standard?

There are various Australian Standards covering storage and handling for many classes or types of dangerous goods. You might be excused for thinking that if you follow the one for your dangerous goods, all will be well. There are several problems with this approach, which can be illustrated with one of the most well known, AS 1940:2004 "The storage and handling of flammable and combustible liquids".

AS 1940 itself notes that "some flammable and combustible liquids have physical and chemical properties that require additional precautions [to those in this Standard]". Also noted is that: "It provides technical guidance that may assist...in accordance with the risk management requirements of NOHSC:1015."

Even if the liquid is a commonly used hydrocarbon or industrial solvent, the particular location, handling equipment etc may introduce hazards not addressed adequately by the Australian Standard. The National Code of Practice [NOHSC:2017 (2001)] which accompanies the National Standard contains the following statement about Australian Standards and similar references. "Following the provisions of [a standard] may not constitute full compliance with the relevant duties."

Sourcing expertise

Two groups of knowledge must be brought to bear, the local knowledge of what is being done or proposed and expertise in dangerous goods risk management. Usually only large organisations specialising in processing dangerous goods will have an in-house expert and his expertise may only involve the major product.

It will often be necessary to find a suitable consultant. A suitable consultant is one who has a track record of dangerous goods risk assessment, including goods and processes similar to yours. He or she should have appropriate accreditation from a body such as the Australasian Institute of Dangerous Goods Consultants. For processing, as distinct from simple storage, experience in hazard and operability studies (HAZOP) and relevant qualifications may be necessary.

The storage and handling of dangerous goods in commercial or industrial quantities introduces the risk of serious consequences.

Hazard identification and risk assessment and management must be conducted by people who will get it right, so the serious consequences are avoided.

The author, WV Peter Hunt, is a member of The Australasian Institute of Dangerous Goods Consultants. www.aidgc.com

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