Valve Fire Safety Testing: API 607, API 6FA, and Fire-Safe Design Requirements

Fire-safe valve design and testing is a critical requirement for valves installed in hydrocarbon service in refineries, offshore platforms, LNG facilities, and chemical plants. A fire-safe valve must be capable of providing an acceptable level of shutoff after exposure to fire conditions that destroy or damage non-metallic seat and seal materials. The purpose of this requirement is to ensure that a valve can limit hydrocarbon flow feeding a fire even after the fire has damaged the valve's soft sealing components. API 607 and API 6FA are the principal international standards governing fire testing of valves.

API 607 Fire Test Standard

API 607 (Fire Test for Soft-Seated Quarter-Turn Valves) establishes the test procedure and acceptance criteria for fire testing of soft-seated ball valves, butterfly valves, and plug valves. The test procedure involves mounting the valve in a test rig, pressurizing it with natural gas or equivalent hydrocarbon fluid, partially opening the valve to test in the most vulnerable position, then exposing the valve to fire using a calibrated burner that achieves a flame temperature of 760 to 1000 degrees Celsius for 30 minutes. After the burn test, the valve is cooled, closed, and pressure tested to verify the post-fire leakage rate is within the acceptance criterion.

• Test duration: 30 minutes at 760 to 1000 degrees Celsius flame temperature

• Test positions: valve tested in the partially open position (most vulnerable to seat damage)

• Post-fire leakage acceptance: maximum 400 ml/minute for valve DN 50 through DN 600

• External leakage: stem and body joint leakage also evaluated during and after fire test

• Functional test: valve must be operable (open and close) after cooling

API 6FA and Metal-Seated Valves

API 6FA (Fire Test for Valves) covers a broader range of valve types including gate valves, globe valves, check valves, and ball valves in both soft-seated and metal-seated configurations. The test procedure is similar to API 607 but includes additional requirements for stem seals, body-to-bonnet joints, and gasketed connections. Metal-seated valves that pass API 6FA testing demonstrate that their metal-to-metal seating provides adequate shutoff after fire even without the soft seat components. Many company specifications require API 6FA certification for all block valves in hydrocarbon service above a certain size or pressure rating.

Design Features for Fire Safety

Several design features are incorporated in fire-safe valves to improve post-fire sealing performance. Secondary metal-to-metal seats are machined behind the primary soft seats so that if the soft seats are destroyed, the metal surfaces provide backup sealing. Graphite stem packing inserts provide fire-resistant stem sealing that survives the destruction of PTFE or elastomeric packing components. Valve bodies are designed to prevent the accumulation of hydrocarbon liquid in cavities where it could continue to feed a fire. Anti-blowout stem designs prevent the valve stem from being ejected if the packing is destroyed, which would create an uncontrolled leak path.