Signs of arc process during conduct of an expert study after fire of a copper contact plate of a car fuse block

Introduction. The data covered in the present article evidence that a problem of improvement of fire safety of motor vehicles is very important. The aim of the article is to develop a scientifically-based method of examination of copper contact plates of car fuse blocks, which could be employed during fire-technical examination in order to identify causes of their damages. Materials and methodology. Researches have been conducted with the use of JSM-6390LV scanning electron microscope equipped with an add-on device for energy dispersive spectroscopy. Surfaces of failure of parts of the copper contact plate of the car fuse block have been analyzed without prior sample preparation. Results and discussion. Based on analysis of practical data it has been proven that temperature of fire of a light motor vehicle in the range of 850-950 °C does not cause change in form of the copper contact plate of the car fuse block. It has been shown in a laboratory environment that contacts of the copper plate of the car fuse block have signs of overcurrent flow caused by high transient resistance. Transient resistance, in turn, is caused by inadmissible copper - zinc galvanic pair. The paper provides results of examination of parts of the copper contact plate of the car fuse block, which have different modes of failure. It has been proven that not only nominal value of current intensity shall be used for selection of car fuses, but also material of manufacture. Conclusion. A method of differentiation of failures caused by fire (high-temperature impact, arc process) of the copper contact plate of the car fuse block has been proposed. The arc process is characterized by such indicators as straight or beveled cut, craters, swelling, ball-like meltback, or mass-transfer. It has been determined that signs identified at surfaces of failure of the copper contact plate of the car fuse block are persistent and are not exposed to changes under natural conditions of storage. The information given in the article could be useful for specialists performing expert studies of car copper contact plates sampled from places of fires of motor vehicles, for identification of nature of their failures and, eventually, for identification of causes of fires of motor vehicles.

пожар, блок предохранителей, большое переходное сопротивление, сверхток, медь, цинк, растровая электронная микроскопия, диагностический признак, микрослед, пожарно-техническая экспертиза, недопустимая гальваническая пара, fire, fuse block, high transient resistance, overcurrent, copper, zinc, scanning electron microscopy, diagnostic signs, ultratrace, fire-technical examination, inadmissible copper-zinc galvanic pair

1. Брушлинский Н. Н., Соколов С. В., Вагнер П. Человечество и пожары.-М. :ООО“ИПЦ Маска”, 2007. -142 с.

2. Quintiere J. G. Fundamentals of fire phenomena.-England, Chichester : John Wiley and Sons Ltd, 2006. DOI: 10.10020470091150.fmatter.

3. Beyler C., Carpenter D., Dinenno P. Introduction to fire modeling. Fire Protection Handbook. - 20th ed. -Quincy : National Fire Protection Association, 2008.

4. Severy D., Blaisdell D., Kerkhoff J. Automotive collision fires SAE Technical Paper 741180, 1974. DOI: 10.4271741180.

5. Katsuhiro Okamoto, Norimichi Watanabe, Yasuaki Hagimoto, Tadaomi Chigira, Ryoji Masano, Hitoshi Miura, Satoshi Ochiai, Hideki Satoh, Yohsuke Tamura, Kimio Hayano, Yasumasa Maeda, Jinji Suzuki. Burning behavior of sedan passenger cars Fire Safety Journal. - 2009. - Vol. 44, No. 3. - P. 301-310. DOI: 10.1016j.firesaf.2008.07.001.

6. Недобитков А. И. Фрактография изломов медных проводников автомобильной электрической цепи Пожаровзрывобезопасность Fire and Explosion Safety. - 2016. - Т. 25, № 2. - C. 21-27. DOI: 10.18322PVB.2016.25.02.21-27.

7. Богатищев А.И. Комплексные исследования пожароопасных режимов в сетях электрооборудования автотранспортных средств : дис.…канд. техн. наук.-М. : Академия ГПС МЧС России, 2002. -269 с.

8. Чешко И. Д. Экспертиза пожаров (объекты, методы, методики исследования).-2-е изд., стереотип. -СПб. : СПб ИПБ МВД РФ, 1997. -562 с.

9. Чешко И. Д., Мокряк А. Ю., Скодтаев С. В. Механизм формирования следов протекания сверхтоков по медному проводнику Вестник Санкт-Петербургского университета Государственной противопожарной службы МЧС России. -2015. -№ 1. -С. 41-46.

10. Мокряк А. Ю. Установление природы оплавлений медных проводников и латунных токоведущих изделий при экспертизе пожаров на объектах энергетики : дис.…канд. техн. наук.-М. : Академия ГПС МЧС России, 2018. -140 с.

11. Смелков Г. И., Чешко И. Д., Плотников В. Г. Экспериментальное моделирование пожароопасных аварийных режимов в электрических проводах Вестник Санкт-Петербургского университета Государственной противопожарной службыМЧСРоссии.-2017.-№ 3.-C. 121-128.

12. Недобитков А. И. Признаки электродугового процесса при экспертном исследовании после пожара плавкого элемента автомобильного предохранителя Пожаровзрывобезопасность Fire and Explosion Safety.-2017.-Т. 26,№ 11.-с. 21-30. DOI: 10.18322PVB.2017.26.11.21-30.

13. Смелков Г. И. Пожарная безопасность электропроводок.-М. :ООО“Кабель”, 2009.-328 с.

14. Babrauskas V. Arc beads from fires: Can ‘cause’ beads be distinguished from ‘victim’ beads by physical or chemical testing? Journal of Fire Protection Engineering. - 2004. - Vol. 14, No. 2. - Р. 125-147. DOI: 10.11771042391504036450.

15. Delplace M., Vos E. Electric short circuits help the investigator determine where the fire started Fire Technology. -1983.-Vol. 19, No. 3. -Р. 185-191. DOI: 10.1007bf02378698.

16. Wright S. A., Loud J. D., Blanchard R. A. Globules and beads: what do they indicate about small-diameter copper conductors that have been through a fire? Fire Technology.-2015.-Vol. 51, No. 5. -Р. 1051-1070. DOI: 10.1007s10694-014-0455-9.

17. Babrauskas V. Arc mapping: a critical review Fire Technology. - 2018. - Vol. 54, Issue 3. - P. 749-780. DOI: 10.1007s10694-018-0711-5.

18. Hoffmann D. J., Swonder E. M., Burr M. T. Arc faulting in household appliances subjected to a fire test Fire Technology. -2016.-Vol. 52, Issue 6. -P. 1659-1666. DOI: 10.1007s10694-015-0556-0.

19. Kuan-Heng Liu, Yung-Hui Shih, Guo-Ju Chen, Jaw-Min Chou. Microstructural study on oxygen permeated arc beads Journal of Nanomaterials. - 2015. - Article ID 373861. - 8 p. DOI: 10.11552015373861.

20. Lewis K. H., Templeton B. Morphological variation in copper arcs during post-arc fire heating Proceedings of 3rd International Symposium on Fire Investigation Science&Technology.-Sarasota :National Association of Fire Investigators, 2008. -P. 183-195.

21. Murray I., Ajersch F. New metallurgical techniques applied to fire investigation Fire & Materials ‘2009. -London : Interscience Communications Ltd., 2009. -P. 857-869.

22. Carey N. J. Developing a reliable systematic analysis for arc fault mapping : Ph. D. diss.-Strathclyde, United Kingdom : University of Strathclyde, 2009.

23. Roby R. J., McAllister J. Forensic investigation techniques for inspecting electrical conductors involved in fire Final Technical Report forAwardNo. 239052.-Columbia : Combustion Science&Engineering, Inc., 2012.

24. Экспертное исследование после пожара контактных узлов электрооборудования в целях выявления признаков больших переходных сопротивлений : метод. реком. К. Б. Лебедев, А.Ю.Мокряк, И. Д. Чешко. -М. : ВНИИПО, 2008. -29 с.