A fire test verifies the ability of a valve, or of a sealing system installed in a flanged connection, to retain a minimum containment function during a fire. It is neither a simple leak test nor an inspection performed on every individual product. Rather, it is a design qualification test of the assembly and the materials used, intended to demonstrate that a specific construction can contribute to plant safety.
During fire exposure, non-metallic components—including soft seats and gaskets, O-rings and polymeric materials—may degrade rapidly. The principle behind fire-safe design is not that the component must remain unchanged, but that it must maintain an acceptable level of internal and external tightness even after such degradation. This residual performance is essential to contain the process fluid and allow emergency measures to be implemented: isolation of the affected section, depressurisation, activation of firefighting systems and safe evacuation, for the time required to manage the event.
For soft- and metal-seated isolation valves, ISO 10497 and the applicable API references, such as API 607 and API 6FA, define the general test procedures. In a typical test, the valve is kept closed, filled and pressurised with water, then fully enveloped in flames for 30 minutes at indicative temperatures between 750 and 1,000 °C. Following exposure, several parameters are assessed: through-seat leakage, external leakage, the possible behaviour of the body cavity in double-seated valves, and the ability to operate the valve again after cooling.
The most important result is not the absolute absence of leakage—an unrealistic condition after severe thermal exposure. The criterion is that leakage remains within defined limits and that the valve retains a residual isolation and containment capability. This is the fundamental difference between a valve that simply complies with normal production tests and one with a fire-safe qualified design.
In this context, gaskets are fundamental elements of plant passive safety. A flanged connection or a valve may use robust metallic materials, but without adequate sealing technology the risk of process-fluid release during a fire increases significantly. Gasket selection must therefore consider not only pressure, temperature and chemical compatibility in normal operation, but also the ability to maintain its function when conditions become exceptional.
Graphite-based sealing solutions play a central role in this field. Spiral-wound gaskets with graphite filler, camprofile gaskets, expanded graphite sheet gaskets and graphite valve packings provide a reliable response to high temperatures and to the loss of performance of more heat-sensitive materials. Graphite retains thermal stability and conformability characteristics that make it particularly suitable for supporting the residual sealing performance required in fire-safe systems.
Carrara gaskets for valves and flanged connections are developed with this objective in mind: helping to preserve process containment when plant integrity is challenged by extreme conditions. Because in the event of a fire, sealing is not merely a technical performance—it is valuable time to protect people, the environment and the plant.
Carrara. Sealing safety when every second matters