Signs of explosion safety of polymer dust that swells when heated

Introduction. Knowledge the maximum size of the dcr particles actively involved in the combustion of dust/air mixture makes it possible to classify the dispersed materials selected in the production according to the explosion hazard without fire tests. For flammable polymers, in particular polyethylene, dcr ≈ (150 ± 50) microns (Hertzberg et al., 1982). If such a polymer contains a bulging component that multiplies the particle size when heated (hereinafter referred to as the bulging polymer), its explosion hazard must be assessed experimentally, paying special attention to the analysis of the validity of the conclusions obtained.

Features of the object of analysis. A bulging polymer is considered, the dust of which, according to the results of a standard study in an 18.7-liter chamber, was classified as explosive with a maximum explosion pressure of about 600 kPa. The doubt about the validity of this conclusion is due to the need to double the energy of the ignition source (up to 5 kJ) to initiate an explosion of the polymer air suspension.

Signs of explosion safety and discussion of the results. A thorough analysis of the results of the study of a bulging polymer revealed two features: the accidental occurrence of explosive air suspension in a wide range of dust concentrations and the presence of two inflection points in the ascending section of the pressure dependence in the blast chamber on time in single experiments. These features, in their main parameters, coincided with those found in anthracite and melamine, which exhibit explosive properties when tested in a 20-liter chamber, but are nonexplosive according to the results of large-scale tests in a 1 m3 chamber with an ignition source of 10 kJ.

Conclusions. The explosion hazard of the considered dust of a bulging polymer is unlikely under normal atmo­spheric conditions. The explosions in the 18.7-liter test chamber are caused by the initial heating of the air suspension by the heat of the burning ignition source and partial dust burning in the chamber. The final conclusion should be made based on large-scale tests.

1. Eckhoff R.K. Dust explosions in the process industries. 3rd edition. Gulf Professional Publishing/Elsevier. Boston, 2003; 720. DOI: 10.1016/B978-075067602-1/50012-3

2. Teterin I.A., Kopylov P.S., Kopylov S.N., Leonchuk P.A. Method for determining the explosion pressure of a gas-air cloud during the release of liquefied natural gas into open space. Combustion and Explosion. 2025; 18(2-47):30-40. DOI: 10.30826/CE25180204. EDN GXHGGP. (rus).

3. Poletaev N.L. Maximum explosive particles size of iron air suspension. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2024; 33(3):5-10. DOI: 10.22227/0869-7493.2024.33.03.5-10. EDN ZOEVPA. (rus).

4. Poletaev N.L. Explosibility of nuclear graphite measured in a 1 m3 chamber. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2022; 31(2):15-21. DOI: 10.22227/0869-7493.2022.31.02.15-21. EDN XHNOXH. (rus).

5. Poletaev N.L. Explosion hazard of whey powder mixed with air. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2023; 32(1):51-56. DOI: 10.22227/0869-7493.2023.32.01.51-56. EDN UGDHRZ. (rus).

6. Bartknecht W. Explosionen, Ablauf und Schutzmaβnahmen. Berlin, Springer-Verlag, 1980; 259. URL: https://rusneb.ru/catalog/000200_000018_RU_NLR_INFOCOMM_116_5000063735/

7. Hertzberg M., Cashdollar K.L., Ng D.L., Conti R.S. Domains of flammability and thermal ignitability for pulverized coals and other dusts: Particle size dependences and microscopic residue analyses. Symposium (International) on Combustion. 1982; 19(1):1169-1180. DOI: 10.1016/s0082-0784(82)80293-2

8. Baratov A.N., Korolchenko A.Ya., Kravchuk G.N. Fire and explosion hazard of substances and materials and their extinguishing means : handbook in 2 vol. Book 2. Moscow, Khimiya, 1990. EDN UXZQDH. (rus).

9. Poletaev N.L. About criterion of dust explosibility. Fire Safety. 2018; 3:49-60. EDN XYUTLV. (rus).

10. Poletaev N.L., Sazonov M.S., Koptev M.Yu. Explosion hazard study of lead dust/air mixture. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2024; 33(4):5-12. DOI: 10.22227/0869-7493.2024.33.04.5-12. EDN ONWNUS. (rus).

11. Proust Ch., Accorsi A., Dupont L. Measuring the violence of dust explosions with the “20 l sphere” and with the standard “ISO 1 m3 vessel”. Systematic comparison and analysis of the discrepancies. Journal of Loss Prevention in the Process Industries. 2007; 20(4-6):599-606. DOI: 10.1016/j.jlp.2007.04.032

12. Poletaev N.L., Sazonov M.S., Koptev M.Yu. Anthracite dust explosion specificities in 20 L chamber. Pozharo­vzryvobezopasnost/Fire and Explosion Safety. 2024; 33(2):23-31. DOI: 10.22227/0869-7493.2024.33.02.23-31. EDN PYWDOT. (rus).

13. Portarapillo M., Sanchirico R., Di Benedetto A. On the pyrotechnic ignitors role in dust explosion testing: Comparison between 20 L and 1 m3 explosion vessels. Process Safety Progress. 2021; 40(4):289-295. DOI: 10.1002/prs.12249. EDN PZFPTL.

14. Krietsch A., Scheid M. Test on suitability of a new pyrotechnical igniter for determination of explosion characteristics of dust clouds in 20-l-sphere and 1-m3-vessel. Science and Technology Energetic Materials. 2011; 72(6):174-178. URL: tem/Vol.72/No.6.04.html

15. Cashdollar K.L., Chatrathi K. Minimum Explosible Dust Concentrations Measured in 20-L and 1-m3 Chambers. Combustion Science and Technology. 1993; 87(1-6):157-171. DOI: 10.1080/00102209208947213

16. Landsberg G.S. Elementary Textbook of Physics. Moscow, Nauka, 1967; I(414):576. URL: https://archive.org/­details/B-001-038-324-ALL/Landsberg_I/ (rus).

17. Dramićanin M. Luminescence Thermometry. Methods, Materials, and Applications. Chap. 1. Introduction to Measurements of Temperature. 2018; 1-12. DOI: 10.1016/B978-0-08-102029-6.00001-4

18. Taveau J.R., Going J.E., Hochgreb S., Lemkowitz S.M., Roekaerts D.J.E.M. Igniter-induced hybrids in the 20-l sphere. Journal of Loss Prevention Process Industries. 2017; 49:348-356. DOI: 10.1016/j.jlp.2017.07.014

19. Addai E.K., Clouthier M., Amyotte P., Safdar M., Krause U. Experimental investigation of limiting oxygen concentration of hybrid mixtures. Journal of Loss Prevention Process Industries. 2019; 57:120-130. DOI: 10.1016/j.jlp.2018.11.016

20. Friedrichova R., Karl J., Janovsky B. Preconditioning of Dust and Fluid in a 20 L Chamber During Ignition by a Chemical Ignitor. Fire. 2025; 8(9):336; DOI: 10.3390/fire8090336