Flame spread over polyethylene-insulated copper and stainless-steel wires at high pressure. (March 2021)

• Record Type: Journal Article
• Authors: Kobayashi, Yoshinari; Nakaya, Shinji; Tsue, Mitsuhiro; Takahashi, Shuhei
• Is Part Of: Fire safety journal. Volume 120(2021)
• Publication Date: 2021-03
• Subjects: Flame spread -- Polyethylene (PE)-insulated wire -- High-thermal-conductivity copper (Cu) rod -- Low-thermal-conductivity stainless-steel (SS) tube -- Ambient pressure -- Flame spread rate -- Dripping; Fire prevention -- Periodicals; Incendies -- Prévention -- Recherche -- Périodiques; Fire prevention -- Research; Periodicals; 628.92205
• DOI: 10.1016/j.firesaf.2020.103062
• Languages: English
• ISSNs: 0379-7112

Abstract

Abstract: This work studied flame spread over polyethylene (PE)-insulated wires at high pressure with an emphasis on the effect of ambient pressure. Laboratory simulated wires were used as a tested wire, which consisted of semi-transparent low-density PE (LDPE) tube as an insulation and copper (Cu) rod or stainless-steel (SS) tube as a core. Increasing ambient pressure produced much soot, leading to an intensively yellow luminous flame. Flame spread rate for Cu rod increased with ambient pressure, whereas that for SS tube decreased. A qualitative analysis via a simplified flame spread model shows that the flame heat flux increases with ambient pressure, but consequently the flame heating decreases due to the decreased flame heating length. Therefore, the flame spread rate for SS tube decreased with increasing ambient pressure. For Cu rod, however, the core heating is dominant enough to compensate the decreased flame heating, and thus the ambient pressure positively affected the flame spread. During the flame spread, melted insulations were often dripped down, but it reduced with increasing ambient pressure. For Cu rod, no dripping occurred when further increasing ambient pressure, which indicates that there is the dripping limit at a high-pressure region. These findings should contribute to electrical fire safety in elevated pressure environments. Highlights: Flame spread over polyethylene-insulated copper (Cu) and stainless-steel (SS) wires was studied at high pressure. Much soot was produced with increased ambient pressuredue to high flame temperature, resulting in a yellow luminous flame. Flame spread rate for Cu rod linearly increased with ambient pressure, whereas that for SS tube decreased. Increasing ambient pressure reduced the dripping of melted insulations regardless of core materials. The effects of ambient pressure on flame spread and dripping are discussed via a simplified flame spread model.