Effect of sample orientation on fire hazard of non-metallic dust layers exposed to electric sparks

• Published in: Journal of loss prevention in the process industries Vol. 54; pp. 229 - 237
• Main Authors: Yuan, Chunmiao, Cai, Jingzhi, Amyotte, Paul, Li, Chang, Hao, Jiantao, Li, Gang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2018
• Subjects: Dust explosion; Dust layer; Electric spark; Fire hazard; Sample orientation; Dust explosion; Fire hazard; Electric spark; Dust layer; Sample orientation
• ISSN: 0950-4230
• DOI: 10.1016/j.jlp.2018.04.001

Surface flames are far stronger as dust explosion ignition sources than smoldering agglomerates, but surface fire seldom occurs with horizontally deposited non-metallic dust layers. In this paper, the effects of sample orientation on the fire hazard of four non-metallic dust layers were investigated using electric spark ignition. Layer surface inclination angle significantly influenced layer ignition sensitivity and fire hazard. For PMMA dust layers, flame spread velocity (FSV) reached 2.6 mm/s from 0.8 mm/s when the inclination angle was increased from 0° to 50°, while in wood dust layers, sustainable propagating combustion occurred when the inclination angle was increased to 40°. Also, the maximum temperature and FSV of surface fire in wood dust layers were far greater than these of smoldering fires, indicating a greater fire hazard for surface fire. Angle of inclination of combustible powder deposits should be considered when assessing fire and explosion hazard in real process industry situations. •MIEL values of non-metallic powders were far larger than their MIEC values.•Inclined deposits showed more rapid FSVs in PMMA dust layers.•Sustainable combustion occurs in inclined wood layers.•Surface layer fire showed greater fire hazard than smoldering fire in wood deposits.•Dust deposits with inclined surfaces had greater layer ignition sensitivity and fire hazard than horizontally oriented deposits.