Study of gases released under incomplete combustion using PCFC–FTIR

Abstract

In order to get new insights on cable behavior during real-scale fires, the gases released under incomplete combustion in pyrolysis combustion flow calorimeter were recorded for several PVC and halogen-free flame-retardant cables. Incomplete combustion was monitored by changing combustion temperature between 600 and 900°C. Gases were identified using PCFC-FTIR coupling. Quantitative assessment of different gases produced during combustion was also carried out. It appears that larger amounts of unburnt gases are produced for PVC cable at low temperature (\ 650°C). Moreover, CO release is observed for PVC cable up to 800°C while this gas disappears between 700 and 750°C for halogen-free flameretardant cables. Interestingly, the CO production is non-monotonous upon the temperature range investigated. These analyses would be useful to assess the risk of multiple re-ignitions during cable burning in real-scale fires, especially in confined compartments.

Electrical component ignition in a closed enclosure adjacent to a controlled fire

“…The T c,ig evaluation for the target type composed with the PVC cables (526 ± 21°C, Table 7) falls in the 500‐600°C range provided by Gong et al 15 that studied spontaneous ignition of similar cable type (ie, PVC external sheath and cross‐linked polyethylene [XLPE] insulation). Furthermore, the piloted ignition temperature was measured at around 300°C 16 for electric cables with a PVC external sheath. Accordingly, these outcomes confirm that the target type composed with the PVC cables spontaneously ignited.…”

Ignition and Charring of PVC-Based Electric Cables

“…It is obvious that the composition of the sheaths is different even if the same decomposition steps can be found. Relying on our previous paper [21], three decomposition steps can be identified in the range 250°C to 320°C, 400°C to 460°C and 700°C to 760°C but their intensity depends on the material. The first step can be assigned to the dechlorination of PVC as well as the decomposition/volatilization of the plasticizer.…”

“…The temperature of the third step (if any) corresponds to the decomposition of a mineral additive as calcium carbonate. In a previous article, we have shown that calcium carbonate is present in sheath from cable A14 but it reacts at much lower temperature with PVC to form CaCl 2 [21]. Therefore, we assume that calcium carbonate should be present in higher amount in sheaths from cables C16 and D28 and a fraction of unreacted calcium carbonate decomposes at around 750°C.…”

“…They are labelled by a letter (A, B, C, D) followed by their diameter in mm. Cable A14 has been studied in details in a previous article [21]. A picture of their section is shown in Fig.…”

“…Indeed, in our previous work on the cable A14, it was found that PVC accounts for only 41% of the weight of the sheath, other components were dioctyl phthalates, calcium carbonate and lead-based stabilizers. Therefore, the flammability of these cables strongly depends on plasticizer and not only on PVC matrix [21]. Gong et al have also obtained a high temperature at ignition (500°C) for a cable based on a PVC outer sheath [18].…”