The endurance limit should be reached simultaneously:

Endurance integrity

Loss of integrity sign: Penetrating cracks or penetrating pores appear on the surface of the pipeline

Thermal insulation resistance

Loss of insulation mark: The average temperature rise at the temperature measurement point on the back of the pipeline reaches 140 ℃, and the temperature rise at any point on the back of the pipeline reaches 180 ℃

6. Test conditions

6.1 Furnace temperature

6.1.1 Temperature rise curve: Measure the average temperature inside the furnace according to the thermocouple specified in 5.5.1.1, and monitor and control it according to the following relationship: T=315 lg (8t+1)

+In equation 20:

T - The average temperature inside the furnace, in degrees Celsius;

T - Time, in minutes.

标准时间-温度曲线