Fire-Safe Valve Design: Testing Standards API 607 and ISO 10497

Fire-safe valves are designed to minimize the release of flammable or hazardous fluids in the event of fire exposure. When a fire occurs in a process plant, the heat can degrade elastomeric and polymeric seat and seal materials that normally provide leak-tight performance, potentially releasing flammable process fluid and feeding the fire. Fire-safe valves incorporate secondary metal-to-metal sealing surfaces that engage when soft seats are destroyed, limiting leakage to defined acceptable levels and preventing escalation of fire incidents.

What Does Fire-Safe Mean?

A fire-safe valve is one that has been tested and certified to demonstrate that, after exposure to fire conditions that destroy its primary (soft) seating materials, it will continue to provide a defined maximum leakage rate through the seat and through the stem seal. The valve must also continue to be operable (open and close) after fire exposure. Fire safety does not mean zero leakage after fire, but rather controlled leakage within the limits specified by the test standard, sufficient to prevent major release escalation.

• Secondary metal-to-metal seat provides sealing after soft seat destruction

• Stem seal fire safety typically achieved via graphite packing or metal bellows

• Fire-safe certification requires passing a standardized fire test, not just design review

• Applicable to ball valves, butterfly valves, plug valves, and gate valves in flammable service

• Required by many national regulations and company engineering standards for hydrocarbon service

API 607 Standard

API 607 is the most widely referenced fire test standard for quarter-turn valves, developed by the American Petroleum Institute. The standard specifies a test procedure where the valve is subjected to fire exposure for 30 minutes at a temperature between 750 and 1000 degrees Celsius, followed by a cool-down period. Leakage through the seat and stem seal is measured before, during, and after the fire exposure. Maximum allowable leakage rates are defined based on valve size. API 607 has been incorporated by reference into many engineering standards and project specifications for oil and gas facilities.

• Fire test temperature: 750 to 1000 degrees Celsius for 30 minutes minimum

• Maximum seat leakage: defined per valve size in the standard, typically in cc per minute

• Stem seal leakage: measured separately and must meet the standard's requirements

• Post-fire operability: valve must be operable after fire exposure and cooling

• Test fluid: typically water or nitrogen, depending on the specific test phase

ISO 10497 Standard

ISO 10497 is the international fire testing standard for quarter-turn valves, developed by the International Organization for Standardization. It aligns closely with API 607 in test methodology but has some differences in acceptance criteria and test procedures. ISO 10497 is widely used for projects in Europe, Asia, and other regions following international standards. Both API 607 and ISO 10497 certification can be accepted on most international projects, though specific project specifications may require one or the other.

Valve Design Features for Fire Safety

Achieving fire-safe certification requires specific design features beyond standard valve construction. Ball valves typically use a trunnion-mounted design with spring-loaded seats that maintain contact with the ball even after the seat inserts are destroyed. A secondary metal seat ring behind the soft insert contacts the ball at high temperatures. Butterfly valves use a disc with metal edge seating surfaces and graphite or metallic stem seals. Plug valves incorporate metallic secondary seats on the plug face and body ports. All valves must use antistatic devices to prevent static electricity buildup that could ignite flammable fluids.