Brandpreventieforum Forums Rook en WarmteAfvoerinstallatie Interactie tussen sprinkler en RWA

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  • palmpie
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    #1004 |

    Praktijk testen van de interactie tussen RWA en sprinkler

    The International Sprinkler, Smoke and Heat Vent, Draft Curtain Fire Test Project organized by the National Fire Protection Research Coundation (NFPRF) has brought together a group of industrial sponsors to study the interaction of sprinklers with roof vents and draft curtains of the type typically found in large warehouses, manufacturing facilities, and warehouse-like retail stores. The Technical Advisory Committee consisting of representatives of the sponsoring organizations and other interested parties planned and conducted thirty-nine large scale fire tests in the Large Scale Fire Test Facility at Underwriters Laboratories in Northbrook, Illinois. Thirty-four experiments were performed with a heptane spray burner, five were performed with racks of Group A Plastic commodity. The test parameters were chosen to address relatively large, open-area buildings with flat ceilings, adequate sprinkler systems and roof venting. In parallel with the large scale fire tests, a program was conducted at the National Institute of Standards and Technolgoy to develop a numerical field model incorporating the physical phenomena of the experiments. Bench scale experiments were performed to provide inputs for the Industrial Fire Simulator 2 (IFS2) model in terms of the thermal properties of the sprinklers and vent links, spray distribution, and commodity burn rate.

    Het rapport van de testen:


    -The tests and model simulations showed that when the fire was not ignited directly under
    a roof vent, venting had no significant effect on the sprinkler activation times, the number
    of activated sprinklers, the near-ceiling gas temperatures, or the quantity of combustibles

    -The tests and model simulations showed that when the fire was ignited directly under a roof
    vent, automatic vent activation usually occurred at about the same time as the first sprinkler
    activation, but the average activation time of the first ring of sprinklers was delayed. The
    length of the delay depended on the difference in activation times between the vent and the
    first sprinkler.

    -The tests and model simulations showed that when the fire was ignited directly under a roof
    vent that activated either before or at about the same time as the first sprinkler, the number
    of sprinkler activations decreased by as much as 50% compared to tests performed with the
    vent closed.

    -The tests and model simulations showed that when draft curtains were installed, up to twice
    as many sprinklers activated compared to tests performed without curtains.

    -In one rack storage test where the ignition of the fire took place near a draft curtain and the
    fuel array extended underneath the curtain, disruption of the sprinkler spray and delay in
    sprinkler operation caused by the draft curtain led to a fire that consumed more commodity
    compared to the other tests where the fires were ignited away from the draft curtains. This
    result was demonstrated by the model simulation, as well.

    -The significant cooling effect of sprinkler sprays on the near-ceiling gas flow often prevented
    the automatic operation of vents. This conclusion is based on thermocouple measurements
    within the vent cavity, the presence of drips of solder on the fusible links recovered from
    unopened vents, and several tests where vents remote from the fire and the sprinkler spray
    activated. In one cartoned plastic commodity experiment, a vent did not open when the fire
    was ignited directly beneath it. The model simulations could not predict this phenomenon.

    -Model simulations indicated that the cooling effect of sprinkler sprays reduced the total vent
    discharge rate from that assumed in design calculations for unsprinklered buildings.

    -Model simulations showed how the activation times of the the first and second sprinklers
    had a substantial impact on the overall number of activations in the plastic commodity tests.
    In the simulation of one test, it was shown that a delay of approximately one minute in the
    activation of the second sprinkler led to the activation of four times as many sprinklers as in
    a simulation of a test with no delay. It had been suggested that these different outcomes were
    due to the presence of draft curtains in the tests with the sprinkler delay, but the simulations
    showed that the curtains had no effect because they were over 9 m (30 ft) away from the
    ignition point.

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