OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 10 Fire and Explosion Hazards

Section 163 Procedures and precautions

Subsection 163(1)


Subsection 163(2)

A hazardous location is by definition a location where a fire or explosion hazard may exist. If the hazard assessment required by section 7 determines that the potential for such a hazard does not exist, then the location is not a hazardous location. To ensure that this state continues, certain site requirements must be met:

(a) The quantity of flammable substance stored or used at the site must not be such that, if inadvertently released into the atmosphere, an explosive atmosphere (as defined) will be created. This quantity is dependent on such things as the type of substance, its explosive limits and other explosive properties, expected concentration if released, site environmental conditions, etc.

(b) Flammable substances must be prevented from unintentionally flowing into underground shafts. The 30 metre storage distance is intended to keep the substances far enough away to prevent this from happening.

(c) Flammable substances can give off vapours under the right conditions. If the substances are stored too close to the intake(s) of a ventilation system, vapours may be drawn into the air supply. This contamination could be harmful to workers or, under worst-case conditions, create an explosive atmosphere.

If flammable vapours enter an internal combustion engine, the engine runs faster, overheats, and can explode. A flashback from the engine could ignite the flammable substance outside the engine. Flammable vapours entering the firebox of a fired heater or furnace could similarly cause the equipment to overheat and explode.

(d) Only approved containers may be used to store portable quantities of flammable liquids. Containers manufactured on or after July 1, 2009 must be approved to

(i) CSA Standard B376-M1980 (R2008), Portable Containers for Gasoline and Other Petroleum Fuels;
(ii) NFPA Standard 30, Flammable and Combustible Liquids Code, 2006 edition; or
(iii) ULC Standard C30-1995, Containers Safety.

Such containers are specially designed for this purpose and bear the mark or label of a nationally accredited testing organization such as CSA, ULC, UL, etc. Liquids stored in these containers are unlikely to leak vapours into the air. Unapproved containers may not prevent leaks. Particular care must be taken when liquids are stored at temperatures above their flash point.

Containers manufactured prior to July 1, 2009 are acceptable if they were approved to an earlier edition of one of these referenced standards.

Subsection 163(2.1)

When transferred into or out of containers, flammable liquids can cause a static charge to build up on the container. This charge could create a difference in voltage potential between the containers, creating the possibility of an incendive spark igniting the vapours from the liquid. Effective control of static electricity can include actions such as grounding and bonding.

Metallic or conductive containers or vessels used to contain flammable or combustible liquid can be electrically bonded to one another and electrically grounded during the transfer of their contents. Bonding and grounding techniques prevent sparks from being created. Sparks are a potential source of ignition.

Making a low resistance electrical connection between two or more conductive containers is called “bonding”. Bonding ensures that the containers have the same electrical potential relative to one another. Without a difference in charge or “electrical potential”, a spark cannot be created that jumps from one container to another.

A container is grounded when a low resistance electrical connection is made between it and the earth (hence the term “earthing” or “grounding”). This ensures that the container has the same electrical charge as the earth. As with bonding, without a potential difference, no spark can be created. Figures 10.7 and 10.8 show examples of bonding and grounding situations.

Figure 10.7 Bonding and grounding during the transfer of flammable fluid from one conductive container to another

Figure 10.8 Filling a tanker with a flammable liquid

For proper electrical connections to be made, bonding and grounding conductors and the containers involved must all be conductive. This permits electrical charges to flow and disperse instead of building up and then jumping as a spark from one container to another. The use of non-conductive plastic containers to hold flammable liquids can be dangerous. When transferred into or out of such containers, flammable liquids can cause a static charge to build up on the container. This charge may result in a spark being created that ignites the liquid or its vapours.

For more information
Guidelines for the Control of Static Electricity in Industry
Department of Labour, New Zealand