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HomeMy WebLinkAboutExponent_MEC_10-26-20161 1607728.000 - 8562 Natick, MA 01760 (508) 652-8500 dust@exponent.com Table I: Summary of Sample and Test Conditions Project: Dust Testing (1607728.000) Sample Name: Fiberglass Date Tested: 10/26/2016 Type of Test: Minimum Explosible Concentration Test Sample Preparation: Tested as received Particle Size as Received / as Tested: 64% < 200 Mesh (75 µm) / 64% < 200 Mesh (75 µm) Moisture as Received / as Tested: 1% / 1% Ignition Source: 2.5-kJ Sobbe Igniter Test Chamber: Kühner 20-Liter Combustion Chamber Figure 1: Kühner 20-Liter Combustion Chamber Table II: Summary of Explosion Characteristics Minimum Explosible Concentration: MEC = 55 g/m3 2 1607728.000 - 8562 Testing Description Sample Fiberglass was tested by Exponent, Inc. in a Minimum Explosible Concentration Test in accordance with ASTM E1515-07 Standard Test Method for Minimum Explosible Concentration of Combustible Dusts using a Kühner 20-Liter Combustion Chamber shown in Figure 1. More details of the test procedure and testing equipment can be found in the ASTM E1515 standard available at <www.astm.org> and the Kühner manual available at <www.kuhner.com>. Testing Results Figure 2: Pressure rise as a function of dust concentration. Table III: Test results Dust: MEC FIBERGLASS Conc. Pm PR Explosible? [g/m3] [bar] [Yes/No] 45 0.4 1.4 No 45 0.4 1.4 No 55 1.1 2.1 Yes 55 1.1 2.1 Yes Based on these results and the ASTM E1515 criterion, the MEC for the sample in the form and conditions tested is 55 g/m3. Sample Preparation The sample preparation, particle size, and moisture are summarized in Table I. The results presented in this report are for the specific sample tested, in its as tested form. Particle size distribution and moisture content can affect the explosivity of a material. ASTM E1515 provides the following guidance about the selection of particle size for testing: 3 1607728.000 - 8562 9.2 Tests may be run on an as-received sample. However, due to the possible accumulation of fines at some location in a processing system, it is recommended that the test sample be at least 95 % minus 200 mesh (75 μm). NOTE 4—It may be desirable in some cases to conduct dust deflagration tests on materials as sampled from a process because process dust streams may contain a wide range of particle sizes or have a well-defined specific moisture content. Materials consisting of a mixture of chemicals may be selectively separated on sieves and certain fibrous materials which may not pass through a relatively coarse screen may produce dust deflagrations. When a material is tested in the as-received state, it should be recognized that the test results may not represent the most severe dust deflagration possible. Any process change resulting in a higher fraction of fines than normal or drier product than normal may increase the explosion severity." ASTM E1515 provides the following guidance about the selection of moisture content for testing. 9.5 The moisture content of the test sample should not exceed 5 % in order to avoid test results of a given dust being noticeably influenced." Testing Methodology In the test, the main chamber is partially evacuated and the dust storage chamber is pressurized. Dust is injected into the chamber and the igniter is activated. The pressure in the vessel is recorded as a function of time. Tests were performed at multiple dust concentrations in order to determine the minimum explosible concentration. Results from individual tests are shown in Figure 2 and Table III. As described in sections 12.7 and 12.8 of the ASTM E1515 standard and the Kühner manual, the raw explosion pressure in tests was corrected to account for the effects of the igniter and vessel walls on the maximum overpressure. The minimum explosible concentration (MEC) is defined as the lowest concentration for which the Pressure Ratio (PR) ≥ 2.0. PR = (Pex,a - ΔPignitor) / Pignition This criterion is equivalent to a Pm ≥ 1.0 when Pignition is nominally 1 bar(a). Use of Testing Results Testing results can be used as part of a process hazard analysis to determine if a material in a specific form is explosible. In October 2007, OSHA issued a Combustible Dust National Emphasis Program which lists OSHA regulations and NFPA standards that OSHA believes inspectors can rely on to issue citations. Building and Fire Codes also provide guidance on mitigating combustible dust hazards and, in some cases, reference NFPA standards. NFPA standards providing guidance on the prevention and mitigation of dust explosions include, but are not limited to:  NFPA 33 Standard for Spray Application Using Flammable or Combustible Materials  NFPA 61 Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities  NFPA 68 Standard on Explosion Protection by Deflagration Venting  NFPA 69 Standard on Explosion Prevention Systems  NFPA 120 Standard for Fire Prevention and Control in Coal Mines  NFPA 484 Standard for Combustible Metals  NFPA 652 Standard on the Fundamentals of Combustible Dust 4 1607728.000 - 8562  NFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids  NFPA 655 Standard for the Prevention of Sulfur Fires and Explosions  NFPA 664 Standard of Fires and Explosions in Wood Processing and Woodworking Facilities NFPA standards can be viewed and purchased at www.nfpa.org. Exponent can provide consulting services to help facilities identify and mitigate combustible dust hazards. Limitations Exponent performed a Minimum Explosible Concentration Test of a specific sample. The results presented in this report are for the specific sample tested, in its as tested form. Particle size distribution and moisture content can affect the explosivity of a material. The testing performed during this investigation may not adequately address the needs of other users of this report, and any re-use of this report or its findings, or conclusions presented herein are at the sole risk of the user. The results measured during this assessment are based on observations and information available at the time of the testing. No guarantee or warranty as to future testing results is expressed or implied.