The API Specification 6FB describes the testing procedure and evaluation of the performance of API end connections when exposed to fire.
The Fire Test according to API 6FB requires that any sealing end connection hold for 30 minutes in a flame condition and hold for a cool down period.
In the fire test a 6″ Class 300 flange is pressurized with a test pressure of 75% of the API rated working pressure. The test pressure is maintained during the burn and cool-down period. After 5 minutes a fire is established and the flame temperature is monitored. The average temperature of the thermocouples must reach 760 °C within 2 minutes and the average temperature of the calorimeter shall reach 650 °C within 15 minutes. The burn period shall last for 30 minutes. After the burn period the connection is air-cooled down to 100 °C or less. After cooling the flange is depressurized and the pressure is increased again to the test pressure and held for 5 minutes. The maximum leak rate is 1 ml/inch/min of mean gasket circumference. Dervos Valve’s fire-safe API 6FB valves have successfully cleared API 6FB test.