Changes in design concentrations are among the revisions to be found in new standards on gaseous fire extinguishing systems. Bob Whiteley brings us up to date.
The BS ISO 14520 series of standards was first published in 2000, at which time BFPSA withdrew it Code of Practice for Gaseous Fire Extinguishing Systems, which had hitherto been the industry design guide and had formed the working document for the ISO committee.
ISO has revised and updated these standards in the interim, and these have now been published as British Standards at the end of 2005 (agent parts) and General Requirements (Part 1) early this year.
Agents
Three agents have been withdrawn: CEA 308 (FC2-1-8); CEA 410 (FC3-1-10); and FE241 (HCFC124). One agent has been added: NOVEC 1230 (FK5-1-12). The trade names for the various agents were included in the 2000 version but have been deleted in the current standard. For FM200 read HFC227ea, for Inergen read IG541, for Argonite read IG55, and for Argon/Argotec read IG100. While NAF S-III (HCFC Blend A) is included in the ISO Standard it remains banned within Europe. Due to changes made to the testing protocols the extinguishing and the resulting design concentrations have changed. These will be detailed later in this article.
Minor changes have been made to definitions, with clause 3.16 on maintenance being reworded and new clauses covering modular systems and safety factors being added.
As for safety, Informative Annex G has been added which details information on PBPK modelling (how the body reacts to toxins) for hydrocarbon agents – this model has also been used by the DTI Halon Alternatives Group for evaluation of these agents. The annex also covers guidance on the inert agents.
Fire extinguishment
The 2000 version of the standard based the design concentrations on wood crib and Heptane fire tests, but acknowledged that these may not be suitable for plastic fire hazards. The 2006 standard incorporates plastics (polymeric) fire tests and has changed the caution in clause 7.5.1.3 to cover grouped power or data cables as follows:
“It is recognised that the wood crib and polymeric sheet class A fire tests may not adequately indicate extinguishing concentrations suitable for the protection of certain plastic fuel hazards (e.g. electrical and electronic type hazards involving grouped power or data cables such as computer and control room under-floor voids, telecommunications facilities, etc). An extinguishing concentration not less than that determined in accordance with 7.5.1.3, or less than 95% of that determined from the Heptane fire test described in C.6.2, whichever is the greater, should be used under certain conditions.”
The requirement to maintain the extinguishing concentration for a sufficient period of time, to allow effective emergency action remains. However the latest version has changed its requirement from one where it concurred with NFPA 2001 – whereby the extinguishing concentration must be maintained at the height of the highest hazard (eg the top of a rack of computer equipment) – to a requirement to maintain 85% of the minimum design concentration at 10%, 50% and 90% of the enclosure height for 10 minutes.
Annexes
Some revisions have been made to the nominative Annex for cup burner extinguishing. The modifications cover the agent supply and heating, and the control of air flow. Annex C for fire extinguishing and nozzle coverage tests has been revised to incorporate the polymeric fire tests, with modified nozzle coverage test requirements. The normative Annex (E) covering fan integrity testing has detailed mixing in enclosures, to more clearly describe when and were continuous mixing can exist. It also provides more information regarding the identification and treatment of bias pressure – the pressure difference between the pre-test pressures inside and outside the enclosure. Additional calibration requirements for fan test equipment have been added, including a field calibration check. Other changes are:
– Hold time calculations now include those for lighter than air agents and for non standard enclosures.
– The contents of the report of a fan test have been specified in section E.4.
Informative Annex H is a new and covers flow calculation verification.
Part 2 to 15 provide data on the properties and data for the individual agents. Due to the changes in test requirements, the design concentrations have been revised following peer review of new fire test data. The tables below set out the key data for the extinguishing agents used in UK, as published in the 2000 version and for the 2005/6 version of BS ISO 14520.
The global fire engineering community has been committed since 1995 to the development of ISO 14520 as the ‘state of the art’ for gaseous fire systems. While no standard is perfect, the current version of BS ISO 14520 provides sound guidance for those specifying, providing and reviewing the vital clean agent fire protection systems widely used for protection of particularly electrical and electronic facilities. Members of BFPSA have been instrumental in the development of these standards from day one, and the association continues to actively support the ongoing developments in fire engineering technologies. This series of standards is also providing the basis for the pending European standard.
Bob Whiteley is engineering and standards manager at Tyco Fire & Integrated Solutions and chairman of BFPSA’s fire extinguishing executive committee.
Changes in design concentrations are among the revisions to be found in new standards on gaseous fire extinguishing systems. Bob Whiteley brings us up to date.
The BS ISO 14520 series of standards was first published in 2000, at which time BFPSA withdrew it Code of Practice for Gaseous Fire Extinguishing Systems, which had hitherto been the industry design guide and had formed the working document for the ISO committee.
ISO has revised and updated these standards in the interim, and these have now been published as British Standards at the end of 2005 (agent parts) and General Requirements (Part 1) early this year.
Agents
Three agents have been withdrawn: CEA 308 (FC2-1-8); CEA 410 (FC3-1-10); and FE241 (HCFC124). One agent has been added: NOVEC 1230 (FK5-1-12). The trade names for the various agents were included in the 2000 version but have been deleted in the current standard. For FM200 read HFC227ea, for Inergen read IG541, for Argonite read IG55, and for Argon/Argotec read IG100. While NAF S-III (HCFC Blend A) is included in the ISO Standard it remains banned within Europe. Due to changes made to the testing protocols the extinguishing and the resulting design concentrations have changed. These will be detailed later in this article.
Minor changes have been made to definitions, with clause 3.16 on maintenance being reworded and new clauses covering modular systems and safety factors being added.
As for safety, Informative Annex G has been added which details information on PBPK modelling (how the body reacts to toxins) for hydrocarbon agents – this model has also been used by the DTI Halon Alternatives Group for evaluation of these agents. The annex also covers guidance on the inert agents.
Fire extinguishment
The 2000 version of the standard based the design concentrations on wood crib and Heptane fire tests, but acknowledged that these may not be suitable for plastic fire hazards. The 2006 standard incorporates plastics (polymeric) fire tests and has changed the caution in clause 7.5.1.3 to cover grouped power or data cables as follows:
"It is recognised that the wood crib and polymeric sheet class A fire tests may not adequately indicate extinguishing concentrations suitable for the protection of certain plastic fuel hazards (e.g. electrical and electronic type hazards involving grouped power or data cables such as computer and control room under-floor voids, telecommunications facilities, etc). An extinguishing concentration not less than that determined in accordance with 7.5.1.3, or less than 95% of that determined from the Heptane fire test described in C.6.2, whichever is the greater, should be used under certain conditions."
The requirement to maintain the extinguishing concentration for a sufficient period of time, to allow effective emergency action remains. However the latest version has changed its requirement from one where it concurred with NFPA 2001 – whereby the extinguishing concentration must be maintained at the height of the highest hazard (eg the top of a rack of computer equipment) – to a requirement to maintain 85% of the minimum design concentration at 10%, 50% and 90% of the enclosure height for 10 minutes.
Annexes
Some revisions have been made to the nominative Annex for cup burner extinguishing. The modifications cover the agent supply and heating, and the control of air flow. Annex C for fire extinguishing and nozzle coverage tests has been revised to incorporate the polymeric fire tests, with modified nozzle coverage test requirements. The normative Annex (E) covering fan integrity testing has detailed mixing in enclosures, to more clearly describe when and were continuous mixing can exist. It also provides more information regarding the identification and treatment of bias pressure – the pressure difference between the pre-test pressures inside and outside the enclosure. Additional calibration requirements for fan test equipment have been added, including a field calibration check. Other changes are:
• Hold time calculations now include those for lighter than air agents and for non standard enclosures.
• The contents of the report of a fan test have been specified in section E.4.
Informative Annex H is a new and covers flow calculation verification.
Part 2 to 15 provide data on the properties and data for the individual agents. Due to the changes in test requirements, the design concentrations have been revised following peer review of new fire test data. The tables below set out the key data for the extinguishing agents used in UK, as published in the 2000 version and for the 2005/6 version of BS ISO 14520.
The global fire engineering community has been committed since 1995 to the development of ISO 14520 as the ‘state of the art’ for gaseous fire systems. While no standard is perfect, the current version of BS ISO 14520 provides sound guidance for those specifying, providing and reviewing the vital clean agent fire protection systems widely used for protection of particularly electrical and electronic facilities. Members of BFPSA have been instrumental in the development of these standards from day one, and the association continues to actively support the ongoing developments in fire engineering technologies. This series of standards is also providing the basis for the pending European standard.
Bob Whiteley is engineering and standards manager at Tyco Fire & Integrated Solutions and chairman of BFPSA’s fire extinguishing executive committee.
