Separation and Segregation of Dangerous Goods

Many of the chemicals we deal with each day are dangerous and need to be handled correctly and safely. Safe use of dangerous goods includes recognising when situations can arise where the consequence of a failure or error will result in danger to life, property or the environment. One of the methods used to minimise risk when dealing with dangerous goods is by separation and segregation.

Keywords: Hazard, storage facility, control, emergency plan, MSDS, material safety data

DANGEROUS GOODS

A dangerous good is any gas, liquid or solid that has been classified and is listed in the Australian Code for the Transport of Dangerous Goods or other international equivalent Codes. Typically they are chemicals that destroy or have the potential to destroy life, property or the environment. They are classified and labeled as a dangerous good belonging to one of the categories shown in Table 1.

Table 1 Classes of DAngerous Goods

Class	Category	Description
1	Explosives	Fragment violentyly
2	Gases	Are vapour or gas at atmospheric conditions
3	Flammable liquids	Liquids able to be ignited and burn
4	Flammable solids	Spontaneously combust or liberate flammable gases in contact iwth water
5	Oxidizers	Release oxygen and may combust
6	Poisonous	Cause death or injury to life if it enters into the body
7	Radioactive	Emits radiation
8	Corrosive	Cause damage to human tissue by chemical reaction
9	Miscellaneous	Hazardous materials not fitting into one of hte previous categories

Some of the categories are further broken down into sub- classes that better define the risks associated with the materials. For example gases are sub-classified as flammable (Class 2.1), non-flammable and non-toxic (Class 2.2) and poisonous (Class 2.3).Dangerous goods can also have multiple classifications. Once the primary classification is determined additional classifications are known as subsidiary risks. For example liquid air is classed as 2.2 (non-toxic gas) with a sub-class of 5.1 (oxidising agent).

Dangerous goods can also have multiple classifications. Once the primary classification is determined additional classifications are known as subsidiary risks. For example liquid air is classed as 2.2 (non-toxic gas) with a sub-class of 5.1 (oxidising agent).Because many dangerous goods are transported internationally the United Nations have established an internationally accepted numbering system to indicate dangerous goods. The UN Number must appear on all transport documentation.

Because many dangerous goods are transported internationally the United Nations have established an internationally accepted numbering system to indicate dangerous goods. The UN Number must appear on all transport documentation.To assist with emergency situations involving dangerous goods a special coding system known as the Hazchem Code has been developed. The code’s alphanumeric characters inform the emergency services of the immediate response actions needed to minimise hazards and restrict the spillage.

To assist with emergency situations involving dangerous goods a special coding system known as the Hazchem Code has been developed. The code’s alphanumeric characters inform the emergency services of the immediate response actions needed to minimise hazards and restrict the spillage.All this relevant information and a telephone number for emergency contact is displayed on the Hazchem Sign or label that accompanies transportation of the chemical. An example of a Hazchem sign is shown in Figure 1.

All this relevant information and a telephone number for emergency contact is displayed on the Hazchem Sign or label that accompanies transportation of the chemical. An example of a Hazchem sign is shown in Figure 1.

SAFE STORAGE PRACTICES

All hazardous substances must be stored 15 meters from boundary fences and from other buildings on-site. If a hazard does occur it is better to have a small problem removed from people than a large problem close to people.
A good philosophy to adopt when storing dangerous good is to only store the least quantity necessary for a short period of time and make arrangements to replenish stocks often. An alternate approach is to store the required quantity in several small containers. If one were to be spilt or ruptured only a small volume would be involved.

In situations where large amounts or multiple dangerous goods are required at a site the strategy of separation and segregation combined with containment is adopted.

Separation is the purposeful creation of a barrier between incompatible substances so they can never come together. Segregation is the spacing of incompatible substances from each other within the same location. Containment is the deliberate restriction of a hazard to a small geographic area.

The Material Safety Data Sheet (MSDS), which suppliers of chemicals must provide to all users, indicates the requirements for proper storage of the chemical. In addition various Codes, Standards and Regulations are available that specify separation and segregation requirements.

Usually separation is achieved by installing walls of suitable material between incompatible or hazardous chemicals. A typical example is the bunding around acid storage tanks. Another example is the locked drug and poisons cabinet in a doctor’s surgery.

Segregation is achieved by spacing incompatible chemicals a prescribed distance apart and preventing mixing of any spillage. An example is the storage shelves in a hardware store where packages of incompatible chemicals are separated onto individual shelves.

Containment is achieved by limiting any spillage or discharge to the boundaries of an enclosure. An example is the concrete floor in a mechanic’s workshop graded towards a drain so oil spills can be captured. Another example is the bunding around aboveground fuel tanks that limit spills and leaks to the immediate area of the tank.

PLAN TO CONTROL THE HAZARDS

In all cases where chemicals have associated risks and hazards there must be a plan in place to control the hazards. The best plans are those put together by the people that have to use a chemical and the people who supply the chemical. This permits practical solutions to be used that satisfy the dangerous characteristics of the chemical.

The plan must satisfy the hazards that arise from the most severe of occurrences. If when designing a plan it is evident that a major catastrophe is beyond control then it is necessary to redesign the facility and reduce the risk to one that is manageable with available resources and technology.

Plans must consider, amongst the site specific issues, materials of construction; washing down facilities for contaminated items and clothing; protection against heat and ignition sources; storage of emergency response equipment; fire protection requirements; the procedure to handle spillage and the procedure to handle major emergencies.

An additional important requirement is practice. Where your plan includes using in-house resources to confront a hazard the resources must be at constant readiness. This means regular practice in confronting the hazard. If a hazard does occur you want to be ready and prepared to confront it rather than e hoping things will be all right.
Mike Sondalini – Maintenance Engineer