firesmiПожаровзрывобезопасность/Fire and Explosion SafetyPozharovzryvobezopasnost/Fire and Explosion Safety0869-74932587-6201ФГБОУ ВО «Национальный исследовательский Московский государственный строительный университет»10.22227/0869-7493.2022.31.01.14-20firesmi-1071Research ArticleПРОЦЕССЫ ГОРЕНИЯ, ДЕТОНАЦИИ И ВЗРЫВАCOMBUSTION, DETONATION AND EXPLOSION PROCESSESИсследование способности жесткого пенополиуретана противостоять зажиганию искрой дуговой электросваркиA research on rigid polyurethane foam resistibility to ignition from an electric arc welding sparkhttps://orcid.org/0000-0003-2586-8597ПолетаевН. Л.PoletaevN. L.

Полетаев Николай Львович, д-р техн. наук, ведущий научный сотрудник

РИНЦ ID: 1093620

143903, Московская обл., г. Балашиха, мкр. ВНИИПО, 12 

Nikolay L. Poletaev, Dr. Sci. (Eng.), Leading Researcher

ID RISC:1093620

VNIIPO, 12, Bala­shikha, Moscow Region, 143903 

nlpvniipo@mail.ruВсероссийский ордена «Знак Почета» научно-исследовательский институт противопожарной обороны Министерства Российской Федерации по делам гражданской обороны, чрезвычайным ситуациям и ликвидации последствий стихийных бедствийРоссияAll-Russian Research Institute for Fire Protection of Ministry of Russian Federation for Civil Defense, Emergencies and Elimination of Consequences of Natural DisastersRussian Federation2022150320223111420Copyright © Полетаев Н.Л., 20222022Полетаев Н.Л.Poletaev N.L.Данная работа распространяется под лицензией Creative Commons Attribution 4.0.This work is licensed under a Creative Commons Attribution 4.0 License.https://www.fire-smi.ru/jour/article/view/1071Введение

Введение. Производство пожарно-технической экспертизы предполагает, что искры дуговой электросварки (далее — искры) являются эффективными источниками зажигания. Однако вероятность зажигания искрой горючего материала зависит от времени контакта между ними. В данной работе экспериментально показано отсутствие зажигания искрами вертикальной гладкой стенки из горючего жесткого пенополиуреана (ППУ). Для объяснения данного факта рассчитали время контакта искры и стенки τint, которое сравнили с оценкой минимального времени контакта τmin, необходимого для зажигания стенки.

Образец и методика испытаний. Воздействию искр (мощность дуги до 6 кВт, ток до 160 А) подвергался участок стенки из ППУ, расположенной на расстоянии от 0,1 до 0,15 м от дуги. Отдельный опыт продолжался до выгорания электрода.

Результаты исследований и их обсуждение. Ни в одном из опытов воспламенить образец ППУ искрами не удалось. Искры отскакивали от образца ППУ и падали вниз. Характерные размеры застывших капель железа принадлежали диапазону от 0,2 до 3 мм.

Оценка τint

Оценка τint. Использовали модель упругого взаимодействия капли расплавленного железа с жесткой стенкой в предположении сохранения суммы потенциальной энергии капли, связанной с ее поверхностью, и кинетической энергией растекания капли при сплющивании. Наибольшее время контакта достигается для капель максимального диаметра (3 мм): τint ≈ 0,004 с.

Оценка τmin

Оценка τmin. Использовали экспериментальное моделирование процесса, при котором воздействие капли железа на ППУ заменяли регулируемым по времени воздействием пламени деревянного цилиндра диаметром 6 мм, горящего с торца. Получили τmin ≈ 0,3 с. Соотношение τint << τmin объясняет отсутствие воспламенения стенки из ППУ искрами дуговой электросварки.

Выводы

Выводы. Искры дуговой электросварки диаметром до 3 мм не воспламеняют вертикальную стенку из жесткого горючего пенополиуретана при боковом соударении. Отсутствие воспламенения объясняется малым временем контакта искры со стенкой.

 

 

Introduction

Introduction. A fire investigation assumes that electric arc welding sparks (hereinafter referred to as “sparks”) are effective sources of ignition. However, the spark ignition of a combustible material depends on the contact time. This work has experimentally proven that a smooth vertical wall, made of combustible rigid polyurethane foam (PUF), is not subjected to spark ignition. To explain this fact, the author calculated the time of contact between the spark and the wall τint, and compared it with the minimal estimated contact time τmin required to ignite the wall.

The sample and the testing procedure. Sparks (the arc power up to 6 kW, the current up to 160 A) reached the PUF wall located at a distance of 0.1–0.15 m from the arc. An everyone experiment was continued until the electrode was burned down.

Research results and discussion. Neither attempt to inflame the PUF sample by a spark was successful. Sparks bounced off the PUF sample and fell down. The characteristic dimensions of cooled iron droplets ranged from 0.2 to 3 mm.

An evaluation of τint

An evaluation of τint. The authors applied a model of elastic interaction between a drop of molten iron and a rigid wall, assuming that the sum of the potential energy of the drop, associated with its surface, and the kine­tic energy of a spreading drop, if flattened, is conserved. The longest contact time is achieved for drops, featuring the maximum diameter of 3 mm: τint ≈ 0.004 s.

Estimation τmin

Estimation τmin. The authors applied the experimental modeling of the process, whereby the effect of an iron drop on PUF was replaced by the time-controlled effect, produced by a wooden cylinder (6 mm in diameter), inflamed at one edge. τmin ≈ 0.3 s. The ratio τint << τmin explains the inability of electric arc welding sparks to ignite the PUF wall.

Conclusions

Conclusions. Electric arc welding sparks, having a diameter of up to 3 mm, cannot ignite a vertical wall, made of rigid combustible polyurethane foam, in case of a side impact. The lack of ignition is explained by the short-term contact between the spark and the surface of the polyurethane foam.

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The authors declare that there are no conflicts of interest present.