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An important cause of fire departure in industrial facilities is due to electrical origin and particularly to electrical cabinets. The investigation of such fires has been scarce up to now and has been investigated exclusively in the nuclear industry. The Institut de Radioprotection et de Sûreté Nucléaire (IRSN) conducted a large number of experiments involving electrical cabinets burning either under a calorimetric hood or inside a mechanically ventilated compartment to investigate this topic. Calorimetric hood experiments demonstrated that the most important parameter is the size of the vents of the cabinet and that the time to flashover depends on many factors and seems somewhat random with regard to the observable parameters. The influence of the compartment on the fire behavior depends on the temperature of the surrounding atmosphere of the cabinet and on the oxygen content in the compartment at the level of the inlet vent of the cabinet. The compartment strongly impacts the pyrolysis of the combustible, affecting the fire duration, but has a weak effect on the Heat Release Rate (HRR). Experiments were usually remarkably reproducible, opening the way to a phenomenological description of this type of fire. A semi-empirical model based on the coupled solution of ventilation limit and excess pyrolysate could then be developed. This model was introduced in a zone code, and an ad-hoc modeling of the fire extinction based on a critical surfacic mass loss rate is proposed. The major features of the compartment fire experiments such as characteristic HRR and fire duration could then be reproduced with acceptable error. The development of such a semi-empirical model is a common practice in fire safety engineering concerned with complex combustibles. © 2011 Elsevier Ltd. All rights reserved.

International audience; Introduction The study of electrical fires is a major concern for fire safety in the industry and more particularly for fire safety in nuclear facilities. To investigate this topic, IRSN conducted a large number of real-scale experiments involving open-door electrical cabinets burning firstly under a calorimetric hood and then inside a mechanically-ventilated compartment. The main challenges are to determine accurately the heat release rate of such a complex fire source in a vitiated atmosphere and to provide an experimental database for validating properly the combustible modelling, taking into account the oxygen depletion in an enclosure. After providing a detailed description of the fire scenarios and of the experimental apparatus, this paper focuses on the characteristic stages of the cabinet fire development, essentially based on the heat release rate time evolution of the fire. The effects of the confinement, of the outlet branch location, of the ventilation management and of the fire barrier on the fire source were then investigated. The reproducibility of electrical cabinet fires is also studied. A new model for complex fire source (applied in this study for open-door electrical cabinet fires) was then developed. This model was introduced in the zone code SYLVIA and the major features of the compartment fire experiments, such as characteristic heat release rate with effect of oxygen depletion and over-pressure peak were then calculated with a rather good agreement for this complex fire source (i.e. electrical cabinet). © 2015 Elsevier B.V. All rights reserved.

This article gives the results of the measurements of the Institut National de Metrologie (INM) LaseRad cavity reflectance. These measurements were performed at several laser wavelengths: 325 nm, 488 nm, 514 nm, 543 nm, 633 nm and 1550 nm. The comparison of our measurements at 633 nm with those carried out by Cambridge Research & Instrumentation, Inc. (USA) five years ago shows satisfactory agreement. The discrepancy between these two measurements is within the measurement uncertainties in the range of 5 × 10-5. The change in the reflectance with wavelength is not negligible. The reflectance varies from 2.8 × 10-4 to 1.10 × 10-4, according to the wavelength.

International audience; Electrical cabinet fires are a major concern in nuclear power plants due to the significant impact on plant safety. This paper investigates electrical cabinet fires in highly confined and mechanically ventilated compartments. In particular, it addresses the issue of experimentally determining the heat release rate of an electrical cabinet fire through realistic large-scale testing. The fire source is highly complex in nature due to the heterogeneity, stochastic geometry and location of the combustible materials within the electrical cabinet. After providing a detailed description of the experiments and apparatus, this paper focuses on the thermal modeling necessary to assess the heat release rate based on the energy balance in the fire compartment, the ventilation system and the electrical cabinet itself. The experimental method is then applied to a propane gas burner and an analytical cabinet containing PMMA tiles with homogeneous spatial distribution in order to validate the thermal model and heat measurements. Finally, the method is used to assess the heat release rate and combustion efficiency of an electrical cabinet. The various terms of the energy balance are described in detail to show the major role of the thermal inertia of both the electrical cabinet and the compartment walls. © 2012 Elsevier Ltd. All rights reserved.

A series of experiments is performed to determine the local burning rate of vertically oriented burning slabs of PMMA (poly(methyl methacrylate)) under steady-state conditions. The burning rate is essential for the determination of flame temperatures, flame lengths, and burnout, all critical parameters to establish fire growth. The experimental procedure consists of a postprocessing of digitized images obtained with three CCD cameras placed on the sides of the PMMA slabs. The cameras are used to establish the displacement of the regressing surface as a function of time. The PMMA/gas interface is characterized by a bubbling layer that scatters light, making the bubbles visible. The video images are processed by establishing a gray-level intensity threshold that defines the depth of the bubbling layer. The local burning rate is then computed from the time derivative of the surface regression. Local burning rates for PMMA slabs, 30 cm high, 3 cm thick, and 2.5, 5, 10, 15, and 20 cm in width are obtained. Three-dimensional effects appear for 2.5-cm-wide slabs. For wider slabs, the local burning rate along the centre line is found not to be width-dependent and to be in good agreement with literature data. Results show that the pyrolyzing surface divides vertically into four regions. In the lowest region (0 < x < 4 cm), the local burning rate increases with the distance from the leading edge, x. For 4 < x < 10 cm, the local burning rate follows a power-law decay. For slabs wider than 2.5 cm, the exponent approximates -0.35. This is higher than that predicted by the two-dimensional laminar boundary layer theory, i.e., -0.25. For 2.5-cm-wide slabs, the local burning rate decreases faster, with a power law dependency of -0.8. From x = 10 to 18 cm, the local burning rate is approximately constant, which is believed to correspond to the laminar/turbulent transition region. In the upper region, the flow becomes fully turbulent and the burning rate increases weakly with x. © 2007 The Combustion Institute.

At first, this paper gives a brief description of the cryogenic radiometer used as standard for radiometric measurements at the Institut National de Metrologie (INM). After, it describes the procedure used to calibrate transfer detectors, for the measurements in the field of optical fiber telecommunications. This absolute calibration was performed at the laser diode wavelength of 1550 nm. The first results for three different detectors calibrated by comparison to INM cryogenic radiometer for the above wavelength shows that the uncertainty of the calibration is less than 0.5% at 1 (sigma) level and is about twice as good as the uncertainty given by the former extrapolation method used at INM.