- Fire testing of valves is one of the most critical qualification tests in the oil and gas industry — it determines whether a valve will maintain its ability to isolate process fluid after exposure to a hydrocarbon fire, when the consequences of valve failure are most severe.
- API 607 and API 6FA define the two main fire test protocols used in the industry, with distinct test methods, pass/fail criteria, and application scopes that engineers must understand to specify the correct fire-safe certification for their valve.
- This guide explains what fire-safe design means, how the test procedures differ between API 607 and API 6FA, what the test results actually tell you about valve performance in a real fire, and how to incorporate fire-safe requirements into your valve specifications.
Why Fire-Safe Valve Testing Matters
When a process plant fire occurs, the valves in the affected area are subjected to extreme heat — flame temperatures of 800–1000°C or higher in a hydrocarbon pool fire. Under these conditions, elastomeric seals in valve seats and stem packing are rapidly destroyed. Soft seats (PTFE, nylon, delrin) melt or burn. Body gaskets may fail. The question that fire-safe testing answers is: after these non-metallic materials are destroyed by fire exposure, can the valve still close and provide sufficient isolation to prevent the outflow of process fluid from making the fire worse?
This is a crucial point that is often misunderstood. Fire-safe testing does not certify that a valve is fireproof or that it will perform identically to its pre-fire condition after fire exposure. It certifies that the valve, after surviving a standardised fire test, can be closed (or remains closed if already shut) and leaks no more than a defined amount of fluid. The goal is to confirm that the valve can still function as an emergency isolation device even after its normal sealing materials have been destroyed.
Fire-safe valves typically achieve post-fire sealing through metal-to-metal contact between metallic body and seat components that survive the fire intact, even after the soft seat material burns away. The design philosophy — often called “fire-safe design” — requires that the valve have a secondary metal-to-metal seat or seating surface that comes into contact automatically when the soft seat is destroyed, providing at least partial isolation even in the worst case.
API 607: Fire Test for Quarter-Turn Valves
API 607 (Fire Test for Quarter-Turn Valves and Valves Equipped with Non-metallic Liners or Seat Seals) is the primary fire test standard for ball valves, butterfly valves, and plug valves. It defines a standardised test procedure that subjects the valve to a controlled hydrocarbon fire while the valve is in the closed position, then evaluates leakage after the fire and cooling period.
The API 607 test procedure involves: setting the test valve to the closed position and pressurising the upstream side with hydrocarbon fluid (kerosene or similar), then applying a burner flame to achieve a minimum flame temperature of 760°C (1400°F) at the valve surface for a minimum burn duration of 30 minutes. During the fire, external leakage from stem seals, body joints, and connections is measured. After the burn period, the valve is allowed to cool, then pressurised again to full rated pressure and external leakage is measured again. The valve is also operated (open and close) after the fire to demonstrate operability.
API 607 pass criteria require: external leakage during the fire period must not exceed 750 ml/minute per inch of nominal pipe size; external leakage after the fire (in the cooled condition) must not exceed 25 ml/minute per inch of nominal pipe size; and the valve must be operable after the test. These are not zero-leakage criteria — they permit controlled, limited leakage that would not significantly contribute to a fire, but they do not require hermetic sealing after fire exposure.
The current edition of API 607 also covers valves with non-metallic liners or seats even if they are not quarter-turn — a scope expansion from earlier editions that reflect the growing use of fully-lined and polymer-seated valves in process plant applications. Engineers should confirm they are referencing the correct edition when specifying API 607 compliance.
API 6FA: Fire Test for Valves in Wellhead and Pipeline Applications
API 6FA (Specification for Fire Test for Valves) is the fire test standard used specifically in conjunction with API 6D (Pipeline Valves) and API 6A (Wellhead Equipment). While API 607 targets quarter-turn valves in process plant service, API 6FA is the required fire test for pipeline ball valves, gate valves, and check valves in upstream and midstream oil and gas applications.
The API 6FA test procedure is similar in concept to API 607 but differs in important details: the required fire temperature is higher (at least 871°C / 1600°F at the valve surface), the burn duration is longer (minimum 30 minutes at the elevated temperature), the test fluid is hydrocarbon liquid, and the post-fire leakage criteria are expressed differently. API 6FA requires that the valve not leak more than a specified quantity of the test fluid through the bore seal (seats) or through the body/bonnet seal in the post-fire condition.
The more severe temperature requirement in API 6FA reflects the higher consequence of failure in pipeline and wellhead applications — a pipeline valve failure in a fire scenario can result in uncontrolled release of large quantities of hydrocarbon, far exceeding the fuel release from a typical process plant valve failure. The additional severity in the test is justified by this higher consequence.
Valves tested and certified to API 6FA are marked accordingly, and this certification is required by most major pipeline operators and upstream operators worldwide as a minimum for block valves on hydrocarbon liquid and gas pipelines. API 6FA certification is a routine purchase specification requirement for pipeline projects — it is not optional for pipeline valve procurement.
BS 6755 Part 2 and ISO 10497: International Equivalents
BS 6755 Part 2 (Testing of valves — Specification for fire type-testing requirements) and ISO 10497 (Testing of valves — Fire type-testing requirements) are the British and international standard equivalents of the API fire tests. ISO 10497 is broadly aligned with API 607 for quarter-turn valves. Projects executed under European contractor leads or in jurisdictions where ISO standards are preferred may specify ISO 10497 or BS 6755 Part 2 rather than (or in addition to) the API standards. The test conditions and acceptance criteria are similar but not identical — equivalence between API 607 and ISO 10497 should be verified for specific projects rather than assumed.
Fire-Safe Design Elements in Valve Construction
Understanding what physical design features allow a valve to pass a fire test helps the engineer assess whether a valve’s fire-safe claim is genuine and durable. The key design elements that enable fire-safe performance are:
Secondary metal seats. In a fire-safe ball valve, the floating ball or trunnion-mounted ball has a secondary metallic contact face behind the primary soft seat insert. When the PTFE or other soft seat insert burns away, the ball moves slightly under system pressure to contact this metallic seat face, providing metal-to-metal sealing. The quality and precision of this secondary metal seat surface determines post-fire leakage performance. A valve with a poorly designed or poorly finished secondary metal seat will perform badly in a fire test even if its primary soft seat meets normal leakage requirements.
Graphite stem packing. Graphite is the material of choice for fire-safe stem packing because it does not burn or melt — it remains intact and maintains its sealing function at fire temperatures. Valves using PTFE or other polymer packing as the primary stem seal are not fire-safe because the packing will be destroyed in a fire, creating an external leakage path. Fire-safe valves use graphite packing (live-loaded with Belleville springs to maintain gland compression as the packing consolidates) as the primary or sole stem packing material.
Metallic body-to-bonnet gaskets. Spiral-wound metallic gaskets or metallic ring-type joints that will retain their sealing function even if the non-metallic filler component is damaged in a fire. Soft gasket materials (compressed fibre, rubber sheet) are not fire-safe.
Antistatic design. Fire-safe valve specifications typically also require antistatic (AS) design — an electrical bonding path between the ball/disc, stem, and body that prevents build-up of electrostatic charge from fluid flow. Antistatic devices (typically spring-loaded ball contacts or graphite-loaded springs) ensure that any static charge is safely dissipated rather than accumulating until it can create a spark.
Specifying Fire-Safe Valves: Practical Guidance
When writing a valve specification requiring fire-safe performance, the following elements should be clearly defined: the applicable fire test standard (API 607, API 6FA, ISO 10497, or BS 6755 Part 2 — or multiple standards if the project requires compliance with more than one); the requirement for the valve to be tested by an accredited third-party test house (not by the manufacturer testing its own product); the requirement for a test certificate and full test report to be provided with the valve documentation; and the requirement for antistatic design and graphite stem packing.
It is also important to understand that fire-safe certification is type certification — it applies to a valve design tested in a specific size, pressure class, and configuration. If the production valve differs in size, pressure rating, or construction details from the tested prototype, the certification may not apply. Confirming that the specific valve being procured is covered by the referenced fire test certificate is an important quality step, particularly for non-standard sizes or modified valve configurations.
Fire-safe valves are a non-negotiable requirement in most oil and gas, refinery, and chemical plant applications. They represent a specific engineering commitment — that when the worst happens, the valve will still do its job. Specifying them correctly, verifying the certification, and understanding what the test actually demonstrates are all part of doing that engineering commitment justice.