Is diesel flammable or combustible?

Sep 28, 2020 Posted by Walter Ingles

If your organisation uses diesel fuel, it’s important for you to be aware of the dangerous properties associated with this substance such as its flammability. By understanding the chemical and physical properties of diesel fuel, it will allow you to implement controls to mitigate the hazards that diesel fuel may have upon your workplace. One property of diesel fuel that is often in question is whether it is flammable or combustible. To determine the answer to this question, we must know the different between flammable and combustible liquids and their flash points.

Flash point

The flashpoint of a flammable or combustible liquid is the lowest temperature at which the substances will give off sufficient flammable vapours to ignite in air.

Flammable liquids

The Australian Dangerous Goods Code outlines the definition for flammable liquids. This code states:

Flammable liquids are liquids, or mixtures of liquids, or liquids containing solids in solutionor suspension (for example, paints, varnishes, lacquers, etc., but not including substancesotherwise classified on account of their dangerous characteristics) which give off a flammablevapour at temperatures of not more than 60 °C, closed-cup test, or not more than 65.6 °C, open-cup test, normally referred to as the flash point. This class also includes:

  • Liquids offered for transport at temperatures at or above their flash point; and
  • Substances that are transported or offered for transport at elevated temperatures in a liquid state and which give off a flammable vapour at a temperature at or below the maximum transport temperature.

Combustible liquids

The Australian Standard that outlines the requirements for the storage and handling of flammable and combustible liquids provides us with a definition of combustible liquids: This standard states:

A combustible liquid is any liquid, other than a flammable liquid, that has a flash point, and has a fire point that is less than its boiling point. There are two different classes of combustible liquids. These include C1 & C2.

  • Class C1: A combustible liquid that has a closed cup flash point of greater than 60°C and no greater than 93°C.
  • Class C2: A combustible liquid that has a flash point greater than 93°C.

Therefore, flammable liquids are liquids that have a flash point below 60 °C and combustible liquids are liquids that have a flash point above 60 °C but below its boiling point. We can now use this information to determine whether diesel fuel is flammable or combustible.

Flammability of diesel fuel

Diesel fuel is any kind of liquid fuel that can be used in diesel engines. A diesel engine is an internal combustion engine which uses the heat produced from the compression of air to ignite the fuel that is injected into its cylinders. As there are a number of different kinds of diesel fuel, there is no straightforward answer as to whether they are flammable or combustible. The flash point of each diesel fuel must be checked to determine if it’s classified as a flammable liquid or combustible liquid. This information can be found by checking the safety data sheet for each diesel fuel. Diesel fuels normally have a flash point between 52 °C and 93 °C. Therefore those diesel fuels that have a flash point below 60 °C are classified as flammable liquids and those that have a flash point above 60°C are classified as combustible liquids.

Types of diesel fuels

There are many different kind of diesel fuels and they are derived from a number of different sources. The different types of diesel fuels include:

  • Petrodiesel - produced from crude oil
  • Synthetic diesel - produced from carbonaceous materials such as natural gas, biogas or coal
  • Biodiesel - produced from vegetable oils or animal fats
  • Hydrogenated oils and fats - produced by transforming the triglycerides in vegetable oils and animal fats into alkanes through refining and hydrogenation
  • DME (dimethyl ether) - synthetically produced gaseous diesel fuel that provides clean combustion

Of these different kinds of diesel fuels, petrodiesel is the most widely used. Most automotive diesel fuels are petrodiesel fuels.

Safe storage and handling of diesel fuels

No matter whether the diesel fuel that you are using is flammable or combustible, it must be stored in a safe and compliant manner. To protect your workplace from the hazards associated with diesel fuels, it’s important that you store your flammable liquids in full conformance to the Australian Standards.

The Australian Standard that outlines the requirements for the safe storage of diesel fuels is AS1940-2017 - the storage and handling of flammable and combustible liquids. The storage requirements outlined in this standard differ depending on the storage location. For outdoor locations diesel fuels can be stored safely in a bunded combustible liquids store. Smaller quantities of diesel fuel can be stored indoors. When diesel fuels are stored indoors, they must be stored in a compliant safety cabinet that meets the requirements of AS1940. Both the indoor safety cabinet and outdoor bunded combustible liquids store have complaint features such as spill containment sumps, ventilation provisions and safety signage to minimise the risks that diesel fuels pose upon people in your workplace.

Next steps

As some diesel fuels are classified as flammable liquid and others as combustible liquids, it’s very important that you store and handle all diesel fuels in a way that reduces the risk that they pose upon the people in your workplace.  If you would like more information on how to use a structured approach to managing the risk associated with flammable liquids, download our FREE eBook by clicking on the image below.     

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Walter Ingles

Walter Ingles Compliance Specialist

Walter is STOREMASTA’s Dangerous Goods Storage Specialist. He helps organisations reduce risk and improve efficiencies in the storage and management of dangerous goods and hazardous chemicals.

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