Understanding Fire Rating

Understanding the fire rating requirements for structural members can be a confusing task for many industry professionals. In particular when there are so many foreign terms and concepts. Permax is dedicated to ensuring no question is left unanswered. From understanding what is fire rating, requirements of the NCC or even understanding the pros and cons of different application processes.

Cellulosic Vs. Hydrocarbon Fire

The inherent chemical composition in a material defines the way it reacts to heat and therefore fire, meaning all materials burn differently. Thus, it is necessary to define different standard heating conditions that represent the type of fire likely to develop in a particular built environment. Two commonly prescribed heating regimes used for compliance in the fire protection industry are cellulosic and hydrocarbon fire curves.

Cellulosic

A cellulosic fire is the most common type of fire event as it is fuelled by cellulosed based materials such as paper and timber, generally found in buildings. Passive fire protection for structural steel members which are placed in a cellulosic environment are required to undergo a standard fire resistance test in order to achieve compliance to the NCC. AS1530.4, which is the relevant fire testing standard for fire resistance tests for elements of construction.

Hydrocarbon

Compliance to the hydrocarbon fire curve is required for compartments or structures where flammable liquid such as oil and gas are present. Due to the flammability of this fuel source it requires structural elements to be tested to a harsher fire curve where 1050ᵒC is reached within the first 15 minutes.

Understanding Fire Rating

Passive Fire Protection

The purpose for providing a Fire Resistance Level (FRL) in a building is to ensure life-safety of occupants and fire fighters as well as protection of property. The three components of an FRL are – structural adequacy/integrity/insulation. These three components are described in more detail below.

In accordance to the prescriptive requirements of the BCA (Building Code of Australia), integrity and insulation are requirements of compartment separating elements such as walls and slabs, therefore load bearing structural elements such as beams and columns are only requiring to achieve structural adequacy. This is can be expressed as 120/–/– for example. If a member is required to achieve all three components of an FRL it can be described as 120/120/120.

 

Structural Adequacy

Structural adequacy is the ability for a structure to withhold the design loads placed on it under a fire load case without reaching failure.

 

Integrity

Integrity is preventing the passage of flame or hot gases from one compartment to the other.

 

Insulation

Insulation is limiting the temperature rise from the compartment exposed to a fire to the non-fire exposed compartment.

 

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Disclaimer: Permax is a supplier of various fire protection products that are manufactured in global locations. The Permax advisory notes are developed to assist the professions in the Australian construction industry with their passive fire protection design. If you are unsure about the content of the documents or if you have any project specific enquiries, please contact the Permax Technical Team for further assistance.

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You are about to download a file from the Permax site. Please note All technical advisory notes generated by Permax are based on research papers, indicative fire tests and any other existing evidence. These documents should not be used as an official evidence as design engineers should review the information and determine the reliability of the documents.

Permax constantly update the documentations based on the new fire testing outcomes and change of standards and regulations. To ensure the documents you read are up-to-date, please contact the Permax technical team.