In the process of gasket material selection, many inquiries point to the term “fire-safe”. Lets briefly look at the two most commonly used gasket fire testing methods: API 6FA & API 607.
API 6FA: The American Petroleum Institute’s 6FA-re test is used to qualify valves for chemical process service.
The flange is assembled using proper bolt-up procedures and all parameters such as stress and torque are recorded. Thermocouples are mounted 1” away from the outside of the flange (Figure 1). The valve is enveloped in flame using four propane burners arranged symmetrically around the outside of the flange. The flame temperature should be 1400ºF to 1800ºF (average of the two thermocouples) for a burn period of 30 minutes from ignition. The temperature is maintained with no reading less than 1300ºF. An internal water pressure amounting to 75% of the flange rating is applied throughout the test and the leakage rate is continually measured. The test rig is then allowed to cool to 212°F in turbulent atmospheric air while continuing to measure leakage. The flange is disassembled and visual conditions such as material loss, sticking, and discoloration are noted.
Note : Klinger Top-Chem-2000 is a known PTFE based material that passes the API 6FA-re test. A PTFE material surviving 1472°F temperature for 30 minutes and 435-psig internal pressure with 0.0-ml/min leakage throughout the test makes this a valuable material for the chemical process industry.
API 607 Fourth Edition: This test is similar to the 6FA test, but with changes that reflect the conditions found in an oil refinery.
After the specified assembly procedure, the fixture is hydro-tested to 110% of the maximum flange rating e.g. 314 psi for ASTM 150#. Internal test pressure of this test is specified as 30 psi. The assembly is exposed to flames at a temperature of 1400ºF for a duration of 30 minutes. The assembly is then quenched with water and leakage is measured at 30, 50, 100, and 200 psig intervals. Maximum leakage rate is 100 ml/min throughout the test.
The extremely rapid heat-up/cool-down conditions cause distortions of the flange assembly, which the gasket material must compensate for.
Note : This test is best suited for composite gaskets. Klinger Quantum, Klingersil C-4433 and metal-reinforced Klingersil C-4439 are the three materials that have passed API 607 and are available in Canada through Robco.
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