BRE FIRE CONFERENCE Research Conference 2015/12-BRE-Fire...•Recommended an “amendment to BS 7671 (2008)” to achieve ... 12 BRE Fire Conference 2015 -Assessing the impact on some elcrticial cable supports and fixings

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  • Part of the BRE Trust


    11th June 2015

  • Part of the BRE Trust

    Assessing the impact on some electrical cable supports and fixings

    BRE Fire Conference 201511th June 2015

    Ciara Holland and Martin ShippFire Safety Team, BRE Global

  • Introduction to BRE

  • Fire investigation work at BRE

    Learning lessons from fires performance of the building performance of fire safety systems behaviour of occupants improved regulations or guidance (AD B) Improved (or new) knowledge, information or data

    for fire safety engineering. Early warning system of topics to be addressed during

    updating of documentation; factory fires - large single-storey buildings, sandwich

    panels, cladding - changes in 2000 edition of AD B truss-rafter roofs - ODPM research programme

  • Fire investigation work at BRE

    BRE has well-established capability to assess the effects and implications of the fire (the lessons learned) not the cause. BRE provides FRSs and other agencies with scientific

    support; experimental and/or modelling work. Act as expert witnesses in Criminal Court, Coroners Court,

    Sheriff's Court, Fatal Accident Enquires, etc.

    Findings feed into Building Regulations guidance and other guidance, and/or into research and/or knowledge base.

    Gratefully acknowledge assistance of Fire and Rescue Service, and other agencies. Most of our fire visits are arranged through the Fire and Rescue Service.

  • Major fire investigations

    Woolworths, Manchester, May 1979 Stardust Disco, Dublin, February

    1981 King's Cross, London, November

    1987 Piper Alpha, July 1988 Windsor Castle, November 1992 The Channel Tunnel, November 1996 Ladbroke Grove Rail Crash, October

    1999 Yarls Wood Detention Centre,

    Bedfordshire, February 2002 Rosepark Care Home, Scotland,

    January 2004 Bethnal Green, London, July 2004

    Harrow Court, Stevenage, February 2005 Colindale, London, July 2006 Monica Wills House, Bristol, December 2006 Cutty Sark, June 2007 Penhallow Hotel, Newquay, August 2007 Atherstone on Stour, Warwickshire,

    November 2007 Royal Marsden Hospital, London, January

    2008 Lakanal House, London, July 2009 Peckham & Camberwell Timber Frames,

    London, November 2009 & January 2010 Shirley Towers, Southampton, April 2010 Freckleton House Fire, January 2012

  • ManchesterWoolworths 1979

    Stardust Disco 1981

    Kings Cross 1987

    Windsor Castle 1992

    The Channel Tunnel 1996

    Major fire investigations

    Lakanal House2009

    Atherstone on Stour 2007

  • Cable supports experimental programme

  • Common sights at fire scenes

  • Common sights at fire scenes

  • Harrow Court 2nd February 2005

    Two fire-fighters and one resident died.

    Fire-fighters trapped by fallen fire-alarm cable.

    Inquest in March 2007.

    HM Coroner issued several recommendations through a Rule 43 letter One to social housing providers regarding the

    support of fire alarm cables which should conform (as a minimum) to BS 5839 Part 1 : 2002; clause 26.2 (f:)

    Inquest into Harrow Court Findings. Rule 43 Harrow Court Letter. Published by Fire Brigades Union. Available at: Last accessed 10th October 2013.

  • Harrow Court Update to BS 5839-1

    Methods of cable support should be non-combustibleand such that circuit integrity will not be reduced below that afforded by the cable used, and should withstand a similar temperature and duration to that of the cable, while maintaining adequate support.

    NOTE 8 In effect, this recommendation precludes the use of plastic cable clips, cable ties or trunking, where these products are the sole means of cable support.

    NOTE 9 Experience has shown that collapse of cables, supported only by plastic cable trunking, can create a serious hazard for fire-fighters, who could become entangled in the cables.

    BS 5839-1:2002+A2:2008 Fire detection and fire alarm systems for buildings. Code of practice for system design, installation, commissioning and maintenance, British Standards Institution.

  • Atherstone-on-Stour 2nd November 2007

    Four fire-fighters died in a large highly-insulated warehouse fire.

    It was noted from witness statements that fire-fighters were being caught up in fallen cables during the incident.

    It is unclear whether the four fatalities were trapped by cables.

  • Atherstone-on-Stour Operational Bulletin

    Warwickshire Fire and Rescue Service issued an Operational Bulletin in March 2012 (OB 12/04):

    Hanging Cable Hazards from Surface Mounted Conduit and Trunking

    Based on experimental work carried out by BRE Global for the Fire Service.

    This work confirmed that plastic conduit or trunking surface mounted on ceilings and walls may fail at relatively low temperatures (150oC).

  • Shirley Towers 6th April 2010

    Two fire-fighters died.

    Trapped by fallen cables prior to an event of abnormal rapid fire development.

    Inquest in February 2013.

    HM Coroner issued recommendations in several Rule 43 letters. Reiterated the recommendations made by HM Coroner

    after the Harrow Court inquest. Further recommendation to have Building

    Regulations amended to ensure ALL [sic] cables, not just fire alarm cables, are supported by fire-resistant cable supports.

    Recommended an amendment to BS 7671 (2008) to achieve this.

  • Aims and objectives

  • Aims and objectives

    1. To assess the ability of a selection of commercially available cable supports for electrical installations to: maintain their integrity and, hold electrical cabling in place when exposed to temperatures typically encountered

    in compartment fires.

    2. To assess the performance of a range of commercially available fixings for cable supports in concrete substrates when exposed to elevated temperatures.

    3. Findings to inform Government.

  • Methodology

  • Experimental rig

    BS 476-33:1993, ISO 9705:1993

  • Experimental rig instrumentation

  • Supports in-situ

  • Experimental setup

    Standard 1.5mm flat twin and earth PVC sheathed cable

    Five types cable supports or clips

    Fixed with zinc-plated hardened steel 7 x 1 inch twinthread wood screws

    To fix into concrete lintels used same screws and plastic plugs

    Five supports of each type per lintel at 300 mm spacings

  • Cable supports experiments

    Experiment 1 0.7 MW wood crib

    Experiment 2 1.3 MW wood crib

    Heat release rate was not measured

    Wooden cribs chosen as follows a more typical fire growth curve than liquid pool fire

  • Results and findings

  • Results Experiment 1

    Lintel TypeAverage

    maximum temperature at lintel (C)

    Average temperature when cable observed to

    drop (C)

    Support 1

    Support 2

    Support 3

    Support 4

    Clip 5

    1 Timber 264 258 All intact All intact All intact All intact 4 failed

    2 Concrete 294 286 All intact All intact All intact All intact Allfailed3 Timber 255 243 All intact All intact All intact All intact Allfailed4 Concrete 204 No drop All intact All intact All intact All intact 4 failed

  • Photos after Experiment 1

  • Close up of Lintel 1

  • Results Experiment 2

    Lintel TypeAverage

    maximum temperature at lintel (C)

    Average temperature when cable observed to

    drop (C)

    Support 1

    Support 2

    Support 3

    Support 4

    Clip 5

    1 Timber 578 481 All intact All intact All intact All intact All failed

    2 Concrete 557212 (Clip 5) and 221(Clip

    2)Three failed *

    Three failed *

    Three failed *

    Three failed * All failed

    3 Timber 570 486 All intact All intact All intact All intact All failed

    4 Concrete 388 310 All intact All intact All intact All intact All failed

    *Due to fixing failure and not support

  • Photos after Experiment 2

  • Close up of Lintel 2

  • Concrete lintel after Experiment 2

  • Fixings experiment

    Number DetailFixing 1 Countersunk 6 mm x 45 mm concrete screw

    Fixing 2 Multipurpose twin thread countersunk zinc plated 4 mm x 40mm screw with 5 mm lightweight plastic wall plug

    Fixing 3 Hammer-in fixing 6 mm x 40 mm; nylon plug with drive screw

    Fixing 4 Multipurpose twin thread countersunk zinc plated 4 mm x 40mm screw with 6 mm medium weight nylon wall plug

    Fixing 5 Sleeve anchor M6 x 40 mm medium weight use

    Standard aerated 3.6N concrete blocks of dimensions 440mm by 215mm by 100mm deep.

    Each block was placed horizontally into an oven on top of two other concrete blocks (placed vertically) as supports to allow for the suspension of weights from the fixings.

    Steel bolts were used as weights, attached to the fixings using steel wire.

  • Fixings before installation






  • Exemplar block with fixings before experiment

  • Oven arrangement

  • Results from Fixings experiments

    Oven temperature


    Maximum temperature in block (C)

    Condition of each fixing

    Fixing 1 Fixing 2 Fixing 3 Fixing 4 Fixing 5

    100 58 Intact Intact Intact Intact Intact200 104 Intact Intact Intact Intact Intact