L360N Seamless Tube Fire Protection Measures. Generally, at temperatures of 450~650°C, L360N seamless tubes will lose their load-bearing capacity, resulting in significant deformation and causing steel beams and columns to bend. The outcome is that the deformation is too great, rendering the tubes unusable. Seamless tubes have a耐火性 that can withstand fire for about 15 minutes. This duration is also related to the heat absorption reaction rate of prefabricated components.