In many processes, it may be necessary to minimize dangerous product leakage and maintain effective shutoff of a valve. Valves that satisfy this condition are known as fire-safe.
This term fire-safe is one of the least understood valve specifications. To date, there is no test protocol to establish whether a valve is fire-safe.
The common definition used for a fire-safe valve is when a valve is exposed to fire conditions, it will allow minimal leakage through the seat and stem, and continue to provide effective shutoff during or following a fire or exposure to excessive temperatures.
Gate and globe valves made from metals that do not melt during a catastrophic fire have also been classified as fire-safe.
Their design and construction assured metalto-metal seating before, during and after a fire. Butterfly valves are commonly manufactured with a “tandem” soft seat over metal to achieve a fire-safe application.
API 607 procedure dictates that a valve is enveloped in flames for 30 minutes while pressurized, after which it is force-cooled with water. The procedure is very clear on the minimum exterior temperatures, flame temperatures, the location of thermocouples, in how many minutes the valve should be cooled to ambient and so on.
This simulates a fire on a plant after which the fire is extinguished by emergency services. After and during the simulated fire, the seat leakage and body seals are to be measured and a final open/close functionality test is performed. If the results are within prescribed parameters, the valve will be considered Fire Safe and receive a conformity report.
This procedure can be applied to all kinds of valve, sealants, gaskets and appendages. The term Fire Safe is applicable for a wide range of valves, sealants and appendages. But for these different items, different procedures are relevant.
For example, the specific procedure for testing valves for Fire Safe conformity is the API-6FA. Its description reads: ‘It is the purpose of this document to establish the requirements for testing and evaluating the pressure-containing performance of API Specs 6A and 6D valves when exposed to fire.’ In relation to this, API-6FB. ‘
This specification was formulated to establish procedures for testing and evaluating the pressure-containing performance of API end connections when exposed to fire. Valves, wellhead seals, or other related equipment are not included in the scope of this document.’ API-589.
This procedure relates to testing only a part of a valve, namely the stem seal. The description of this spec reads: ‘Covers the requirements for testing valve stem packing and evaluating its performance when exposed to specifically defined fire conditions.
To my experience in O&G industry, no valve will be accepted without test certificate, specifically when it comes to shutdown valves, these shall be fire rated and there are several test protocols for the same, a few are given for reference.