AbstractThe safety offered by the firefighters’ protective garment has been evaluated by a Thermal Protective Performance (TPP) Test. Current national and international standards recommend a maximum flux of 84 kW m2 ⁄ to be used as an assessment of the fabric, for extreme cases, which is based on a study conducted by Behnke in 1984.
Recently, fire tests, conducted on the modern compartments interior furnishing and construction layout, reported to record an average flux of 200 kW m2 ⁄ , after flashover or during backdraft. To evaluate the risk at this intensity, it is proposed to carry out the fabric test under a higher level of heat flux of 126 kW m2 ⁄ , which represents a typical heat flux at an initial phase of a fully developed fire. The proposed value of 126 kW m2 ⁄ is a step increment from 84 kW m2 ⁄ , beyond that, it is unrealistic to simulate the risk to firefighters.
A custom-built bench-scale setup is designed to vertically test a multi-layered firefighter garment (meta/para-aramid), comprised of the outer shell, moisture barrier and thermal liner. A subjective concept of “critical time” is introduced to examine the safety level with increasing heat flux. A firefighter educated with “critical time” can better evaluate the escape period to a changing fire incident during duty. The critical time subjected to incident flux levels of 40, 84 and 126 kW m2 ⁄ is estimated as 180, 25 and 15 seconds, respectively. The garment performance at 126 kW m2 ⁄ is improved by 32% with the utilization of auxiliary layers of meta-aramid.
The comprehensive analytical analysis showed that; (1) air gap in multiple layered assembly is optically thin; (2) for ∆T = 0 − 1500 ℃, enclosed cavity ranging from 1 – 7 mm is conduction dominant; (3) radiative attenuation in a smoke layer is 4.5 - 8.5%; (4) fabric-skin air gap should be treated as a convective media for the thermal manikin tests and (5) the fabric temporal-thermal properties reflect material decomposition and is essential for the numerical formulation.
At the thermal environment of 84 kW m2 ⁄ and above, moisture effects are insignificant in superficial burn estimates. It is observed that the numerical formulation for the benchtop test lacks spatial burn information. Therefore, a multi-physics numerical model is developed utilizing Gauss-Seidel serial coupling to approximate spatial temperature distribution analogous to thermal manikin experiments and is recommended for the firefighter’s protective garment numerical evaluation.
|Date of Award||Feb 2022|
|Sponsors||Korean Ministry of Public Safety and Security & Korean Conformity Laboratories|
|Supervisor||Seng-Kwan Choi (Supervisor) & Jianping Zhang (Supervisor)|
- High performance fabrics
- Fire resistant fabrics
- Thermal clothing system
- Bench scale
- Thermal manikin
- High temperature apparatus