Analysis of Temperature Rise Characteristics in Metallic Pipe Firestop Systems with Different Pipe Thicknesses

The objective of this study was to quantitatively evaluate the effect of metallic pipe thickness on position-dependent temperature rise characteristics in vertical pipe firestop systems. Carbon steel (CS) pipes, stainless steel (SS) pipes, and a 0.5 mm galvanized steel spiral duct (GSD) were tested under the same 120 min standard fire exposure, and temperatures at key measurement positions were compared. Thinner metallic pipes produced higher temperature rises, with the clearest difference observed at the upper insulation. At 120 min, CS 3.0 and SS 2.8 reached approximately 200 and 195 °C, whereas CS 7.0 and SS 7.0 remained at approximately 106 and 114 °C, respectively. GSD 0.5 showed the highest initial rise rate at the pipe surface (~3.4 °C/min during 0–30 min). Regression analysis showed a clear relationship between cross-sectional area and upper-insulation temperature, with R2 values of 0.921 and 0.878 for CS and SS at 60 min and 0.999 and 0.865 at 120 min. Conversely, the ratio of room-temperature thermal conductivity to cross-sectional area did not consistently improve this relationship. These results indicate that pipe thickness and metallic cross-sectional area should be considered when determining approval ranges for metallic pipe firestop systems.