Fire-Safe Ball Valves: API 607 Testing, Metal Seat Secondary Seal & ATEX Certification

In the oil and gas industry, a hydrocarbon fire can reach 750°C–1000°C within seconds. Soft-seated ball valves using PTFE or PEEK seats and elastomeric O-ring seals lose all sealing capability within minutes of fire exposure — the seats and seals burn away, leaving the valve unable to isolate flow. A fire-safe valve — tested and certified per API 607 or API 6FA — must demonstrate that even after complete burnout of all soft components, it maintains external leakage below acceptable limits through metal-to-metal secondary seats and graphite packing backup. This is not optional in upstream oil and gas — it is mandatory for all block valves in the wellhead area, production manifolds, and export pipelines.

API 607 vs API 6FA — Which Standard Applies?

API 607 (Fire Test for Quarter-Turn Valves and Valves Equipped with Nonmetallic Liners) applies to quarter-turn valves (ball valves, butterfly valves, plug valves) with resilient/elastomeric or thermoplastic seats. API 6FA (Fire Test for Valves — Flanged Valves) covers flanged end valves (ball, gate, globe, butterfly) regardless of size. API 607 (8th Edition, 2022) is the more commonly cited standard for ball valves in process service. BS EN ISO 10497 (Testing of Valves — Fire Type Testing Requirements) is the European equivalent and is aligned with API 607. Key point: specifying 'API 607 fire-safe certified' means the valve design (not just material) has been tested and certified — a valve with a metal seat but no third-party fire test certificate is not 'fire-safe certified'.

API 607 Fire Test Protocol

The API 607 fire test protocol: the valve is assembled in its normal configuration (with all elastomeric and PTFE seats, seals, and packing) and pressurized to rated working pressure; a calibrated burner surrounds the valve and maintains a temperature of 750°C–1000°C at the valve body surface for 30 minutes — this burns away all soft seats, O-rings, and stem packing; after the fire exposure, the burner is extinguished and the valve is cooled with water spray (simulating firewater deluge); the valve is then operability-tested (open and close cycle) and leak tested under pressure. External leakage during and after the fire must be below the API 607 Table 2 acceptance criteria (typically 0.03 ml/min for stem leakage in bore sizes ≤ DN50).

Metal Seat Secondary Seal Design

Fire-safe ball valves use a secondary metal seat that engages after the primary soft seat has been destroyed. The common design: a stainless steel or Stellite-faced spring-loaded seat ring that maintains contact with the ball after the soft PTFE seat is burned away. The spring force keeps the metal seat in contact with the ball even as thermal expansion and distortion occur during the fire. The metal-to-metal seat seal is not as tight as the primary PTFE seat (typically Grade D or E per BS EN 12266-1, allowing some small leakage through the valve in the fully closed position), but it provides the required safety function of reducing hydrocarbon release to well below a hazardous threshold. Trunnion-mounted ball valves with spring-loaded seat rings are the preferred fire-safe design for Class 600 and above.

Graphite Stem Packing for Fire Safety

The conventional PTFE stem packing in a ball valve burns away at approximately 350°C. After PTFE loss, there is no stem seal — external leakage from the valve body through the stem gland occurs freely. Fire-safe ball valves use graphite stem packing (expanded graphite rings, not rubber-impregnated) that survives temperatures up to 500°C in oxidising and 3000°C in non-oxidising environments. Graphite packing maintains stem sealing integrity during and after the fire exposure. The graphite packing must be pre-loaded to the correct compression load — insufficient preload causes leakage before fire; excessive preload causes high operating torque. Live-loaded (spring-loaded) packing assemblies maintain consistent packing compression over the valve service life, accommodating thermal cycling and graphite creep.

ATEX and IECEx Certification for Actuated Fire-Safe Valves

In hazardous areas (oil and gas production facilities, refineries, chemical plants) classified as Zone 0, Zone 1, or Zone 2 (explosive gas atmosphere), all electrical equipment — including valve actuators, solenoid valves, limit switches, and positioners — must be certified for use in the applicable zone. ATEX (ATmosphères EXplosibles) is the European certification scheme, required for equipment used within the EU/UK. IECEx is the international certification scheme recognised in many Middle East, Asian, and Australian jurisdictions. Both certify equipment categories: Category 1 (Zone 0 — continuous explosive atmosphere), Category 2 (Zone 1 — occasional explosive atmosphere), Category 3 (Zone 2 — infrequent explosive atmosphere). All electrical actuator components on fire-safe valves in upstream oil and gas must carry ATEX/IECEx Zone 1 (Category 2) or Zone 2 (Category 3) certification at minimum.

Fire-Safe Ball Valve Selection Checklist

• Confirm that the valve design is API 607 type-tested — request the test certificate number and independent laboratory (Factory Mutual, TÜV, BVQI)
• Specify metal seat secondary seal: spring-loaded SS 316 or Stellite 6 seat ring after PTFE primary seat
• Specify graphite stem packing with live-loaded (Belleville spring) assembly for consistent compression
• Specify trunnion-mounted design for Class 600 and above — floating ball valves have limited fire-safe capability at high pressure
• For actuated valves: specify ATEX/IECEx Zone 1 certification for all electrical components — solenoid valve, limit switches, positioner
• For spring-return pneumatic actuator: confirm fail-safe direction (fail-closed for isolation; fail-open for cooling duty)
• For SIL-rated ESD service: specify partial stroke test (PST) capability in the SMART positioner
• Request fire-safe test certificate with the valve delivery — not just 'designed to API 607', but 'tested and certified per API 607 with Type Test Certificate [number]'