Purpose: The goal of the investigation was the qualification of the gasket material in accordance with the API Specification 6FB (dated December 2008): API Specification for Fire Test for End Connections. The API Specification 6FB describes the testing procedure and evaluation of the performance of API and connection when exposed to fire.


The Fire Test requires that any sealing and connection hold for 30 minutes in a flame condition and hold for a cool-down period. After the assembly is cooled down to room temperature the line is depressurized and then re-pressurized. During all facets of the test, the gasket must not exceed an API proscribed leak rate.

In the Fire Test, a 6" Class 300 flange is pressurized with a test pressure of 75% of 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 of the thermocouples must reach 760℃ within 2 minutes and the average of the calorimeter shall reach 650℃ within 15 minutes. The burn period shall last for 30 minutes. After the burn period, the connection is air-cooled down to 100℃ or less. After cooling down the flange is depressurized and the pressure is increased again to the test pressure and held for 5 minutes.


In the Fire Test API 6FB, the DeltaV-Seal was mounted in a 6" Class 300 flange with hydraulic spanners to a bolt load of 70.2 MPa witch means a total load of 842.4kN and a gasket surface stress of 92.7 MPa.

After that, the flange was pressurized with an internal pressure of 40 bar. The test medium was water. After 5 minutes flame impingement starts for a period of 30 minutes. During the burning period, the flame temperature was nearly constant. After 30 minutes of burning the flange was cooled down to a temperature less than 100℃ and the system was depressurized and the pressure was increased to 40 bar again.

Acceptance criteria:

The maximum leak rate is 1 ml/inch/min of mean gasket circumference.


During the burning period, a leak rate of 0.04 ml/inch/min could be measured.

During the complete pressurization with water, a leak rate of 0.01 ml/inch/min was measured.


It was concluded that the leak rate is far below the allowable leak rate and the DeltaV-Seal successfully passed the API 6FB Fire Test.

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