‘Fitfor Purpose fire resistance’ - Whose responsibility is it?
15/03/2018 UK
Welcome toour Speaker presentation at the forthcoming Fire Australia 2108 Conferencein Brisbane, 1-3 May
Today the Australian Building Regulations (NationalConstruction Code) adopts the standard time temperature protocol of ISO834-1 /EN1363-1 as AS/NZS1530 pt4 for fire resistance testing of all building elementssuch as fire doors, fire stopping systems for penetrations, structuralelements, fire walls and partitions, in fact every material, component andproduct used in a building that is required to have a fire resistance rating.
What is oftenoverlooked is that this time temperature protocol for fire resistance testing(ISO834-1 / AS/NZS1530 pt4 aka the standard time temperature curve), wasdeveloped almost 100 years ago when buildings and contents were commonly madeof masonry, wood and fabric. At this time plastics and synthetic materials didnot exist (1). Further, buildings of this age were mostly not very tall or verylarge. Today our built environment is far more complex with small domesticdwellings, industrial and commercial buildings and super high rise,mega-interconnected transportation, retail, commercial structures withsignificant below ground environments. Across these buildings types we have alarge range of evacuation times and where these egress times are very long,designers and engineers need to look for alternative more innovative solutionsfor evacuation or protection of occupants such as reducing fire loads, liftevacuation or protect in place refuges. Today we also cannot ignore that manyof these facilities attract and congregate a large number of people, often inconfined areas which significantly increases the threat of terrorist attack.
Recent research(2) has identified that in most modern buildings the use of light weightpolymeric building materials, plastic contents, synthetic foams and fabricswith high calorific values can significantly increase fire loads resulting intime temperature fire profiles significantly different and in cases well abovethe original parameters of the existing, early 1900’s test protocol as adoptedin AS/NZS1530 pt4 (ISO834-1 / EN 1363-1) and as required by the BuildingRegulations for testing of all fire resistant building elements.
Undergroundenvironments can also exhibit very different fire profiles to those in aboveground built environments (3)(4) especially in confined underground publicareas like road and rail tunnels, underground shopping centers and car parkswhere a high fire load is present. Fire temperatures in these areas can exhibita very fast rise time and reach temperatures well above those in standard modelabove ground buildings. While we don’t have an Australian equivalent, BritishStandard BS8519:2010 and BS EN12485 clearly recognise underground public areassuch as car parks, loading bays and large basement storage as “Areas of SpecialRisk” with potential for fire temperatures to 1,200°C. In these environmentsmore stringent requirements for fire resistance maybe needed.
Worse still…
Almost all LifeSafety & Fire Fighting systems depend on the reliable function of electriccables during emergency. If these essential cables fail during a fire event,the critical equipment they enable also fails.
This could meanthat firemen’s lifts, fire sprinklers, hydrant pumps, smoke & heatextraction and pressurization fans, emergency communication, alarms andlighting systems stop working during evacuation putting occupants, emergencyresponse workers and property at risk. It is therefore concerning that theadopted Australian Standard for fire resistance testing of electrical wiringsystems (8) required to power all emergency life safety and firefightingsystems (AS/NZS3013:2005) has important omissions which are likely to resultwiring systems so tested and their connected equipment not providing theexpected performance reliability during fire emergencies. Specifically: Thefire test is mostly done in a small 1mtr by 1mtr pilot furnace where cablesamples are only mounted horizontally and supported by a cable tray. There isno vertical installation simulation. The test water spray is unrepresentativeof a fireman’s hose and the test allows for a 2 out of 3 pass criteria should the first sample fail.
Looking at globalbest practice for fire resistance testing of essential electrical wiringsystems, the American UL 2196 Ed.2 2017 test method (9) is more relevant. Thistest is done in a large representative 6.6 x 7 meter vertical furnace wherecables, fixings and accessories are all tested together in the mountingconfiguration they will be actually installed. The most demanding installationconfiguration is for vertical runs of cables, a common and unavoidableinstallation condition for all tall buildings. UL2196 requires that cables aretested at their rated voltage and with a minimum 5 samples across a range ofsmall to large sizes. All these circuits are mounted both horizontally andvertically in 3 meter (10 foot) lengths with bends and joints if needed. Thecables are energized and samples are subjected to the fire time temperatureprotocol of ASTM E-119-75 which is virtually identical with ISO 834-1 /EN1363-1. During testing the cables, fixings and supports experiencesignificant mechanical stresses caused by expansion and contraction. After 2hours at a final temperature of 1,020°C the cables are immediately subjected toa powerful fire hose stream test which not only imparts huge thermal stresseson the wiring system but also significant mechanical stresses.
It is has beenwell established by companies involved with testing to UL2196, that firetesting the electrical integrity of cables in full scale is significantly moredemanding and representative than testing short lengths of horizontally mountedcircuits because the sheath and insulation of most flexible polymeric cableswill burn away in fire so that the cable supports holding the cables invertical installations can no longer support them. Bare Mineral Insulated(MIMS) cables do not have this problem. Whilst the time temperature regimes ofASTM E 119-75 (as used in UL2196) and ISO834-1 (as used in AS/NZS1530 pt4) maynot be fully representative for all built environments today using modernbuilding materials with high calorific values, nor for the potentiallyhigher/faster time temperature profiles of fires in ‘areas of special risk’,the American UL2196 fire test is certainly more representative of real lifeinstalled practice. UL2196 requires all the 5 samples in both horizontal andvertical configuration to pass and certification is given independently forhorizontal and vertical mounting. It is therefore is a much more robust firetest protocol. One good element of the Australian standard AS/NZS3013 is themechanical impact and cut through test criteria which gives designers theoption to specify a higher than minimum standard if the application requires.Ideally Australia might adopt the fire test protocol of UL2196 Ed2 2017together with the mechanical test and classification system of AS/NZS3013:2005for wiring systems enabling life safety and firefighting systems in criticalpublic infrastructure.
Today we have avery wide range of built environments, accordingly the current system ofadopting a “one size fits all” fire performance requirement for wiring systemssupporting Life Safety and firefighting equipment in all buildings, regardlessof the Required Safe Evacuation Time (RSET) may not be appropriate anymore.Currently there are no standards specifically addressing impact of possibleterrorist actions in this area but this should also be a factor in the designspecification of these essential wiring systems in large public buildings.
It is recognizedeconomic factors must also come into play and as it stands many of our currentproducts and test regimes, including those for essential electric cables, mayprovide an adequate level of protection in small or low rise buildings whereevacuation times are short. The concern is; are these same products andstandards going to provide the required reliability in performance and durationfor the new large high rise, underground and mega projects with large numbersof people and where long evacuation times are needed?
As it standsdesigning and constructing buildings is often focused on meeting the minimumcode rather than focusing on the different performances required by differentprojects. Often designers have budgetary constraints and whilst many arequalified to take a more holistic view to design optimization, unless theproject owners appreciate and accept the risk-cost-responsibility impact of‘Fit for Purpose’ design then a minimalist approach is often taken.Unfortunately many stakeholders consider that regulations and related standardsare “the requirements” and by complying they simply tick the box. Effectivelythis reduces the system of minimum building regulation and minimum standardsinto a prescriptive system just as has been identified in the UK post Grenfell(7). The situation is further compounded by our competitive bidding systemwhich ensures the cheapest product (and this often means the product with theslimmest of minimum compliance) wins the job.
It is correct tosay all Australian Standards and indeed The Building Regulations themselves areonly minimum requirements, so whilst it may be mandatory to meet this minimumcode it does not preclude the design of buildings and systems with higherperformances. Professional engineers who design the buildings and systems areaccountable for the use of ‘reasonable skill and care’ but often avoid theobligation of ‘Fit for Purpose’ design as their professional indemnityinsurance generally excludes this (6). In turn this means ‘Fitness for Purpose’mostly remains the obligation and liability of the project owner and/orbuilding contractor and as such there can be a critical gap in understanding. Asimilar finding on responsibility was recently identified in the UK as part ofthe Grenfell Fire Independent review (7).
With today’sknown terrorist risk ‘Fit for Purpose’ design of major public infrastructuremay need to include a rethink of existing essential wiring system installationpractices to ensure more robust and reliable performances of the very safetyequipment that is needed to facilitate effective mass public evacuation.
1) A ShortHistory Of The “Standard” (Cellulosic) and Hydrocarbon Time/Temperature Curves(2000)
Paul MatherTechnical Engineering Manager Fire & Insulation Products, InternationalCoatings Limited.
2) Fire Safety ofBuildings Based on Realistic Fire Time-Temperature Curves (2013). Ariyanayagam,Anthony Deloge & Mahendran, Mahen Queensland University of Technology.
3) Recentachievements regarding measuring of time-heat and time –temperature developmentin tunnels (2004). Haukur Ingason and Anders Lönnermark SP Swedish NationalTesting and Research Institute.
4) The MetroProject Final Report (2012/8) Ingason H., Kumm M., Nilsson D., Lonnermark A.,Claesson A., Li Y.Z., Fridolf K., Akerstedt R., Nyman H., Dittmer T., ForsenR., Janzon B., Meyer G., Bryntse A., Carlberg T., Newlove-Eriksson L., Palm A..
5) FenwickElliott Annual Review. (2014/2015) Understanding your design duty – “reasonableskill and care” vs. “fitness for purpose” – mutually incompatible orcomfortably coexistent?
6) ConsultAustralia “Australian Contract Law” (July 2012) Response to discussion paper.
7) Building aSafer Future: Independent Review of Building Regulations and Fire Safety (Dec2017). (UK. Follows Grenfell fire disaster: Interim Report)
8) AS/NZS3013:2005
9) UL2196 Ed 2:2017
About the author:
Richard Hosier is the Regional Manager in Asia/Pacific for the world’s largestmanufacturer of mineral cables the MICC Group: www.miccltd.com
Mr.Hosier has lectured at institutions and universities around the worldpublishing many technical papers on advanced fire safe cable design. He was thewinner of the Institute of Fire Protection Officers UK technical trophy awardin 2014 for his research into fire performance wiring systems and previouslyserved on 3 Australian and New Zealand technical standards committees for fire safewiring systems and cables.
Otherpublications by this author:
FireResistant Cables - 2017, Wiring Systems for Hospitals – 2015, Electric CablesFire Performance - 2014 Wiring Systems for Nuclear Power Stations - 2014,Wiring Systems for Road and Rail tunnels – 2014
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