Fire-Safe Valve Testing — API 607 vs API 6FA Explained

In a hydrocarbon plant fire, valves in the fire zone must continue to perform two functions: (1) maintain external tightness to prevent additional fuel from feeding the fire through the valve body or stem, and (2) provide sufficient closure to maintain downstream isolation even if soft seats or seals have been damaged by the heat. Fire-safe valves are specifically designed and tested to demonstrate these capabilities after controlled fire exposure. In India, OISD 118 and most EPC project specifications for refineries, gas plants, and oil pipelines require fire-safe certification for all quarter-turn and isolation valves in hydrocarbon duty.

API 607 — Fire Testing of Quarter-Turn Valves

API 607 ('Fire Test for Quarter-Turn Valves and Valves Equipped with Non-Metallic Seats') is the standard for testing ball valves, butterfly valves, and plug valves. The test procedure involves mounting a valve with soft seats (PTFE, PEEK, etc.) in a test rig at operating pressure, exposing it to a propane-fed fire at a flame temperature of 871°C ± 55°C for 30 minutes, then conducting a post-fire hydrostatic leakage test. The test checks: seat leakage through the damaged soft seat (must be below API 607 Table 1 limit — a small controlled allowance through the metal backup seat), stem leakage (external, must be zero), and body leakage (must be zero). ISO 10497 is the international equivalent of API 607 and is accepted interchangeably by most project specifications.

API 6FA — Fire Testing for Gate, Globe, and Check Valves

API 6FA ('Specification for Fire Test for Valves') applies to gate valves, globe valves, and check valves — the multi-turn valve types not covered by API 607. These valve types rely on metal-to-metal seating (typically hardened stellite-faced seats and discs) rather than soft seats, so their fire performance is different. The API 6FA fire test still exposes the valve to 871°C for 30 minutes, but the acceptance criteria reflect metal seat performance: allowable seat leakage is per the API 6FA Table 1 (based on class IV to V leakage), and stem/body external leakage must be zero. For bi-directional gate valves, both seat directions are tested.

What Does a Fire-Safe Certificate Prove?

A fire-safe certificate per API 607 or 6FA proves that a specific valve TYPE and SIZE was tested and passed. It is a type test — not an individual valve test. This means a certificate for a 2" Class 300 ball valve does not cover a 4" Class 600 ball valve of the same model unless that larger size was also tested separately. When reviewing fire-safe documentation, procurement engineers should verify: (1) The certificate is for the same valve type, material, and pressure class as specified; (2) The test size brackets the valve being supplied — API 607 allows interpolation within a size range; (3) The certificate is from a recognized test facility (approved by API); (4) The certificate is not expired (API 607 6th Edition requires re-testing if design changes affect fire performance).

Fire-Safe Design Features in Ball Valves

• Metal backup seats: behind every soft seat (PTFE) ring, a metal seat ring provides a secondary seal when the soft seat burns away.
• Anti-blowout stem: a shoulder or step on the stem below the packing prevents the stem from being ejected if the packing burns out under pressure.
• Fire-safe stem packing: graphite (flexible graphite) packing rings are standard behind PTFE rings — graphite is fire-resistant and compresses under heat to maintain stem seal.
• Fire-safe body bolting: studs and nuts are specified as alloy steel (A193 B7 / A194 2H) not plated steel that can lose strength at 871°C.
• Cavity pressure relief: prevents body rupture if trapped liquid vaporises under fire conditions.

When is Fire-Safe Certification Required?